2-Batteries

[[email protected]]

By all means a second battery should be installed in our electrically
driven modern sailplanes. After many years of quickly flipping my
3-position battery switch, and trying not to have my logger to
momentarily dropout, I have concluded that is best to use 2 single-pole
battery switches. That way one can have either or both batteries
connected at the same time.

I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
for Wing Deturbulator flight testing, and it was wired like that. You
will hear much more about that amazing new invention at the coming SSA
Convention.

Thermally,

Dick Johnson

[Gary Emerson]

wrote:
> By all means a second battery should be installed in our electrically
> driven modern sailplanes. After many years of quickly flipping my
> 3-position battery switch, and trying not to have my logger to
> momentarily dropout, I have concluded that is best to use 2 single-pole
> battery switches. That way one can have either or both batteries
> connected at the same time.
>
> I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> for Wing Deturbulator flight testing, and it was wired like that. You
> will hear much more about that amazing new invention at the coming SSA
> Convention.
>
> Thermally,
>
> Dick Johnson
>
Better yet is to use diodes so that both batteries will always be "on"
in parallel and you're always pulling from the best battery with no
fiddling required from the pilot. Relatively low voltage drop diodes
are available with 18 Amp forward capacity. For redundancy, I used two
in parallel on each battery. The diodes are available in the TO-220
package and it's easy to incorporate a small heat sink, but I have no
reason to believe they ever attained any temperature at all.

With two batteries connected with switches, if one battery does really
"die" then any time spent with both switches in the "on" position causes
the good battery to attempt to charge the "dead" battery to no avail, so
ultimately you're wasting what power you do have during this time. The
diodes eliminate any chance for cross charging...or discharging. Used
this system for several years, never experienced a single power issue.

[Udo]

> Better yet is to use diodes so that both batteries will always be "on"
> in parallel and you're always pulling from the best battery with no
> fiddling required from the pilot. Relatively low voltage drop diodes
> are available with 18 Amp forward capacity. For redundancy, I used two
> in parallel on each battery.

If it is always drawing from the best battery, what is the time
interval between switching.
What controls the switching. Please advise.
Udo

[Nyal Williams]

I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


At 19:48 25 December 2006, Udo wrote:
>
>> Better yet is to use diodes so that both batteries
>>will always be 'on'
>> in parallel and you're always pulling from the best
>>battery with no
>> fiddling required from the pilot. Relatively low
>>voltage drop diodes
>> are available with 18 Amp forward capacity. For redundancy,
>>I used two
>> in parallel on each battery.
>
>If it is always drawing from the best battery, what
>is the time
>interval between switching.
>What controls the switching. Please advise.
>Udo
>
>

[COLIN LAMB]

> Better yet is to use diodes so that both batteries will always be "on"
> in parallel and you're always pulling from the best battery with no
> fiddling required from the pilot. Relatively low voltage drop diodes
> are available with 18 Amp forward capacity. For redundancy, I used two
> in parallel on each battery.

>>If it is always drawing from the best battery, what is the time
>>interval between switching.
>>What controls the switching. Please advise.
>>Udo

There is no switching. As the higher voltage battery drops in value,
gradually a greater % will start drawing from the other. From that point,
they will discharge equally. Assuming there is slightly different capacity,
current will gradually increase from the battery with the greater capacity.

Most diodes have about a .6 volt drop, which may be significant. Therefore,
you will need diodes with a low threshold. Schottky diodes should be about
..3 volts drop. You can measure the actual drop using a digital
volt-ohmmeter. There is a diode test range and it will show the voltage
drop.

Colin Lamb

[Steve Paavola]

Gary Emerson wrote:
> wrote:
>> By all means a second battery should be installed in our electrically
>> driven modern sailplanes. After many years of quickly flipping my
>> 3-position battery switch, and trying not to have my logger to
>> momentarily dropout, I have concluded that is best to use 2 single-pole
>> battery switches. That way one can have either or both batteries
>> connected at the same time.
>>
>> I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
>> for Wing Deturbulator flight testing, and it was wired like that. You
>> will hear much more about that amazing new invention at the coming SSA
>> Convention.
>>
>> Thermally,
>>
>> Dick Johnson
>>
> Better yet is to use diodes so that both batteries will always be "on"
> in parallel and you're always pulling from the best battery with no
> fiddling required from the pilot. Relatively low voltage drop diodes
> are available with 18 Amp forward capacity. For redundancy, I used two
> in parallel on each battery. The diodes are available in the TO-220
> package and it's easy to incorporate a small heat sink, but I have no
> reason to believe they ever attained any temperature at all.
>
> With two batteries connected with switches, if one battery does really
> "die" then any time spent with both switches in the "on" position causes
> the good battery to attempt to charge the "dead" battery to no avail, so
> ultimately you're wasting what power you do have during this time. The
> diodes eliminate any chance for cross charging...or discharging. Used
> this system for several years, never experienced a single power issue.

If both batteries are on-line all the time, how do you know when one is
getting weak and needs to be replaced? Or do you replace both batteries
when voltage is marginal at the end of a flight?

I've been using the 2 toggle switch solution for years. I replace a
battery when it discharges within 5 hours. This means I've always got at
least 10 hours worth of battery (assuming I've recharged the batteries).

Steve

[COLIN LAMB]

"If both batteries are on-line all the time, how do you know when one is
getting weak and needs to be replaced? Or do you replace both batteries
when voltage is marginal at the end of a flight?"

Well, that is a problem. You do not know. Everything is automatic. If you
have one battery that has lost most of it's capacity, the good battery will
do all the work. The only way you will know is when the total capacity of
both batteries has been reduced. And, then, you will not know whether one
battery has done 50% of the work and they are both down in storage ability,
or one battery is still 90% and the other one is 10%.

So, you will have to determine the capacity of each battery separately. You
could test the battery capacity by switching either off during discharge, or
even by using 2 ammeters - but it is becoming more complex once we try to
extract more information. You can also determine the capacity during
charge.

Colin

[Gary Emerson]

Nyal Williams wrote:
> I'd like to see a full write-up with diagrams, photos,
> and names/addresses of places to buy parts. This would
> make a good article for Soaring.
>

Here is a sketch

http://www.mydatabus.com/public/emerson_gary/e/sketch.JPG

and a pic of my install...

http://www.mydatabus.com/public/emerson_gary/e/diodes.jpg

There is a aluminum bracket which is lightly mounted to the bulkhead.
The PC board just provides insulation and some support for the wires.

Each diode has a heat sink, but I don't really think it was necessary.

I don't have the part numbers handy, but I'll see if I can't find something.

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.

[Gary Emerson]

COLIN LAMB wrote:
> "If both batteries are on-line all the time, how do you know when one is
> getting weak and needs to be replaced? Or do you replace both batteries
> when voltage is marginal at the end of a flight?"
>
> Well, that is a problem. You do not know. Everything is automatic. If you
> have one battery that has lost most of it's capacity, the good battery will
> do all the work. The only way you will know is when the total capacity of
> both batteries has been reduced. And, then, you will not know whether one
> battery has done 50% of the work and they are both down in storage ability,
> or one battery is still 90% and the other one is 10%.
>
> So, you will have to determine the capacity of each battery separately. You
> could test the battery capacity by switching either off during discharge, or
> even by using 2 ammeters - but it is becoming more complex once we try to
> extract more information. You can also determine the capacity during
> charge.
>
> Colin
>
>

During any one flight, you don't need to know. What is a good idea is
to test the batteries if you think you are losing capacity. During the
week charge them up Monday and Tuesday, and Wednesday put a load on each
one and see how long it lasts. Ideally, you'd like the load to test the
batteries for as long as you'd normally fly. Say 4-6 hours unless you
are typically flying for longer. If either one can't go the 4-6 hour
distance and mainain a suitable voltage, then it's due for replacement.
After the Wednesday test, charge them back up so you're ready for the
weekend assuming they pass. I'd certainly do this in the spring and
before any big contest during the year. 7Ah batteries are cheap in the
grand scheme of things.

[Eric Greenwell]

wrote:
> By all means a second battery should be installed in our electrically
> driven modern sailplanes. After many years of quickly flipping my
> 3-position battery switch, and trying not to have my logger to
> momentarily dropout,

I thought all loggers just started again after a momentary power loss,
and continued the same flight file. It sounds like yours isn't behaving
properly, or are some brands a bit touchy?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

Thanks Gary for the writeup. I have been thinking of doing the exact
same for a glider I just bought. Can you please add the part number if
you recall them.

I suppose if one really wants to know about the condition of each
individual battery, you could put a voltmeter on a 3-way switch and see
the volatge on the "main" bus, and each of the batteries. This way you
could tell the difference between them.


Gary Emerson wrote:
> Nyal Williams wrote:
> > I'd like to see a full write-up with diagrams, photos,
> > and names/addresses of places to buy parts. This would
> > make a good article for Soaring.
> >
>
> Here is a sketch
>
> http://www.mydatabus.com/public/emerson_gary/e/sketch.JPG
>
> and a pic of my install...
>
> http://www.mydatabus.com/public/emerson_gary/e/diodes.jpg
>
> There is a aluminum bracket which is lightly mounted to the bulkhead.
> The PC board just provides insulation and some support for the wires.
>
> Each diode has a heat sink, but I don't really think it was necessary.
>
> I don't have the part numbers handy, but I'll see if I can't find something.
>
> With 18Amps of forward current capability (each), there isn't really any
> "need" for the two diodes in parallel, but for an extra $5 and a few
> extra minutes of wiring, if any one diode ever did fail "open" the other
> would still provide power. Most likely overkill.

[Marc Ramsey]

Eric Greenwell wrote:
> wrote:
>> By all means a second battery should be installed in our electrically
>> driven modern sailplanes. After many years of quickly flipping my
>> 3-position battery switch, and trying not to have my logger to
>> momentarily dropout,
>
> I thought all loggers just started again after a momentary power loss,
> and continued the same flight file. It sounds like yours isn't behaving
> properly, or are some brands a bit touchy?

There are some earlier approved flight recorder designs that will start
a new flight data file if the 12V power supply is interrupted
momentarily. The specifications were then changed to eliminate this
behavior from newer designs...

Marc

[Gary Emerson]

A quick Google of Schottky Diode and TO-220 yielded some sources.

I just tried the first one and then found this:

http://www.onsemi.com/PowerSolutions/product.do?id=MBR2515L

looks like even slightly better than what I had bought.

You'd lose about 0.3 volts during normal operation.

Datasheet at:

http://www.onsemi.com/pub/Collateral/MBR2515L-D.PDF

I'm sure some googling will find that someplace like DigiKey will have
these and will take small ordering quantities.

Is Paul Remde out there? Might be a nice "kit" to add to your line.
Kit includes 4 diodes, 4 heat sinks, 4 insulating washers some heat
shrink tubing, etc.??

Good luck.




Gary Emerson wrote:
> Nyal Williams wrote:
>
>> I'd like to see a full write-up with diagrams, photos,
>> and names/addresses of places to buy parts. This would
>> make a good article for Soaring.
>>
>
> Here is a sketch
>
> http://www.mydatabus.com/public/emerson_gary/e/sketch.JPG
>
> and a pic of my install...
>
> http://www.mydatabus.com/public/emerson_gary/e/diodes.jpg
>
> There is a aluminum bracket which is lightly mounted to the bulkhead.
> The PC board just provides insulation and some support for the wires.
>
> Each diode has a heat sink, but I don't really think it was necessary.
>
> I don't have the part numbers handy, but I'll see if I can't find
> something.
>
> With 18Amps of forward current capability (each), there isn't really any
> "need" for the two diodes in parallel, but for an extra $5 and a few
> extra minutes of wiring, if any one diode ever did fail "open" the other
> would still provide power. Most likely overkill.

[John Galloway[_1_]]

Noone picking up on Dick Johnson's last paragraph??

http://sinhatech.com/SinhaFCSD-Progress-12132006.asp

John Galloway


At 15:42 25 December 2006, wrote:
> By all means a second battery should be installed
>in our electrically
>driven modern sailplanes. After many years of quickly
>flipping my
>3-position battery switch, and trying not to have my
>logger to
>momentarily dropout, I have concluded that is best
>to use 2 single-pole
>battery switches. That way one can have either or both
>batteries
>connected at the same time.
>
> I saw the light when Jim Hendrix brought his sailplane
>to Caddo Mills
>for Wing Deturbulator flight testing, and it was wired
>like that. You
>will hear much more about that amazing new invention
>at the coming SSA
>Convention.
>
> Thermally,
>
> Dick Johnson
>
>

[COLIN LAMB]

RE: Testing AH of batteries

Battery capacity is measured using a defined minimum voltage. That voltage
may or may not correspond to the minimum voltage your glider equipment will
operate on. If you use diodes, that minimum voltage will move slightly.
Capacity also depends upon a starting voltage - which is significantly
higher than 12 volts.

I often need to test batterys used in our search and rescue radios and have
found that I can test battery capacity quickly without a full discharge. I
charge the batteries, then let them sit for a day. Then, I put a load on
them and simply watch the decay of voltage over time. In a very short time,
you can make a graph that will indicate the trend of the battery and compare
with a new battery. A battery with reduced capacity will drop voltage much
more quickly.

You can determine the capacity of the battery during charge, too. Capacity
is the ability of the battery to resist change. That applies either way.
it means the battery will drop in voltage or charge more slowly. So, you
can simply time the charge of two batteries and learn the comparative
capacity of each.

Colin

[Lew Hartswick]

Gary Emerson wrote:
>
> With 18Amps of forward current capability (each), there isn't really any
> "need" for the two diodes in parallel, but for an extra $5 and a few
> extra minutes of wiring, if any one diode ever did fail "open" the other
> would still provide power. Most likely overkill.
Yes because most often (probably at least 90% of the time) a diode
fails "short"
Therefore you may be reducing the reliability. :-)
...lew...

[[email protected]]

John Galloway wrote:
> Noone picking up on Dick Johnson's last paragraph??
>
> http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
>
> John Galloway
>
>
The results are interesting, but way do the testing on a Std. Cirrus?
To be taken seriously put them on a modern ship and test them. I
can't believe Dick did the testing on the Std. Cirrus and did not at
least put them on his Ventus for some additional comparisons.

[Mike[_8_]]

If the numbers are real, that Standard Cirrus is now a 41-1+
sailplane-and that IS a serious improvement. $16K for a 41-1sailplane
is great, and a boon for a lot of people that do not have $40K-60K for
that type of sailplane performance. Looks like some older sailplanes
could be hanging out with a new crowd.

Mike



wrote:
> John Galloway wrote:
> > Noone picking up on Dick Johnson's last paragraph??
> >
> > http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
> >
> > John Galloway
> >
> >
> The results are interesting, but way do the testing on a Std. Cirrus?
> To be taken seriously put them on a modern ship and test them. I
> can't believe Dick did the testing on the Std. Cirrus and did not at
> least put them on his Ventus for some additional comparisons.

[[email protected]]

With the diode solution, when the system is turned on the battery with
the highest voltage will provide the current. As the battery draws
down the second battery will come on line. From that time on both
batteries will be providing power to the circuits. The strongest
battery will provide the most current but both batteries will be
stabilized at a common voltage. Therefore BOTH batteries will require
re-charging after being used for any substantial period of time.

Regarding the 3 position switch. The simple solution is to put a
capacitor between ground and the output side of the switch. The
capacitor must be large enought to provide the current needed during
the switch switching time. This should not be a very large capacitor
for our purposes.

Brian Utley
Gary Emerson wrote:
> COLIN LAMB wrote:
> > "If both batteries are on-line all the time, how do you know when one is
> > getting weak and needs to be replaced? Or do you replace both batteries
> > when voltage is marginal at the end of a flight?"
> >
> > Well, that is a problem. You do not know. Everything is automatic. If you
> > have one battery that has lost most of it's capacity, the good battery will
> > do all the work. The only way you will know is when the total capacity of
> > both batteries has been reduced. And, then, you will not know whether one
> > battery has done 50% of the work and they are both down in storage ability,
> > or one battery is still 90% and the other one is 10%.
> >
> > So, you will have to determine the capacity of each battery separately. You
> > could test the battery capacity by switching either off during discharge, or
> > even by using 2 ammeters - but it is becoming more complex once we try to
> > extract more information. You can also determine the capacity during
> > charge.
> >
> > Colin
> >
> >
>
> During any one flight, you don't need to know. What is a good idea is
> to test the batteries if you think you are losing capacity. During the
> week charge them up Monday and Tuesday, and Wednesday put a load on each
> one and see how long it lasts. Ideally, you'd like the load to test the
> batteries for as long as you'd normally fly. Say 4-6 hours unless you
> are typically flying for longer. If either one can't go the 4-6 hour
> distance and mainain a suitable voltage, then it's due for replacement.
> After the Wednesday test, charge them back up so you're ready for the
> weekend assuming they pass. I'd certainly do this in the spring and
> before any big contest during the year. 7Ah batteries are cheap in the
> grand scheme of things.

[[email protected]]

This is great discussion. I was doing a bit of research myself (it has
been over 10 years since I did any HW design, so am pretty rusty).

Another option that sounds even better is to use the new chips designed
for exactly this to control DirectFETs. That way the voltage drop and
power waste will be significantly reduced with very little additional
cost. The chips I were looking at were IR5001S:
http://www.irf.com/product-info/datasheets/data/ir5001s.pdf or LT4351:
http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1142,C1079,P21 73


I have used DirectFET stuff in robotics and found them to be very
reliable and very simple to design with.

My biggest problem is all these components are only available in
surface mount these days and I have never tried to build a circuit
using them.

[Ian[_1_]]

On Tue, 26 Dec 2006 01:39:44 +0000, Steve Paavola wrote:

> Gary Emerson wrote:

>> wrote:
>> Better yet is to use diodes so that both batteries will always be "on"
>> in parallel and you're always pulling from the best battery with no
>> fiddling required from the pilot. Relatively low voltage drop diodes
>> are available with 18 Amp forward capacity.

> If both batteries are on-line all the time, how do you know when one is
> getting weak and needs to be replaced? Or do you replace both batteries
> when voltage is marginal at the end of a flight?

I used two small diodes to provide a "fail safe" supply to the
Volkslogger, but the radio, vario, transponder etc get theirs via a 2 way
toggle switch.

Then when one battery dies in flight, I will notice and switch to the next
one manually. But in the meantime the logger always draws current from the
highest voltage battery and hence no interruption to the trace.

The diodes are equivalents of IN 5817 "Shottky rectifying diodes". They
are cheap and tiny. At the low currents drawn by the logger, the forward
voltage drop is very small (less than 0.2V). No cooling is required. I
soldered them directly in line with the wires from the fuse holder to the
toggle switch, without a circuit board.

I test the voltage on each battery during my pre-flight by setting the
Volkslogger on its battery voltage function and disconnecting the
batteries one at a time. (If the electric vario had a battery voltage
function, I could switch it between the batteries and measure their
voltage in flight.)

The weak link in this setup is the toggle switch which has to be sized to
handle a significant DC current.

(The u/c warning buzzer is now also running off a 2 diode "fail safe"
supply - but there is another story behind that ...).


Regards


Ian

[COLIN LAMB]

"Regarding the 3 position switch. The simple solution is to put a
capacitor between ground and the output side of the switch. The
capacitor must be large enought to provide the current needed during
the switch switching time. This should not be a very large capacitor
for our purposes."

This brings up another issue. Switches may be rated for ac or dc (or both).
Many of the switches sold at the local electronics supply house are not
rated for dc. And, some may be less reliable than others. Many are not
rated for the current you want to run through them. That means likely a
failure. It could also be worse, with a possible fire.

When you get to rotary switches, contacts may be configured to make before
break, which means the rotor will contact the new contacts before
disconnecting from the old. This is another subject.

Colin

[Doug Haluza]

This is how I finally set up my glider--with two main battery switches.
But if you want to run this way without bouncing the logger, the two
switches should be on for the whole flight. You don't want to run one
battery down like a fuel tank, then switch when it is empty. If you do,
you will get a big current spike when you switch them both on. At best,
this wastes energy from the new battery by dumping it into the dead
one. You can also burn-out your switch, weld the contacts, or blow a
fuse.

What you want to do is run two identical batteries, bought at the same
time from the same production batch. Then always charge and run them
together. They should age together, and share the load properly this
way. You only want to use the two switches in opposite positions to
separate the batteries for testing, or if one battery fails.

wrote:
> By all means a second battery should be installed in our electrically
> driven modern sailplanes. After many years of quickly flipping my
> 3-position battery switch, and trying not to have my logger to
> momentarily dropout, I have concluded that is best to use 2 single-pole
> battery switches. That way one can have either or both batteries
> connected at the same time.
>
> I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> for Wing Deturbulator flight testing, and it was wired like that. You
> will hear much more about that amazing new invention at the coming SSA
> Convention.
>
> Thermally,
>
> Dick Johnson

[Doug Haluza]

Steve Paavola wrote:
>
> If both batteries are on-line all the time, how do you know when one is
> getting weak and needs to be replaced? Or do you replace both batteries
> when voltage is marginal at the end of a flight?
>
> I've been using the 2 toggle switch solution for years. I replace a
> battery when it discharges within 5 hours. This means I've always got at
> least 10 hours worth of battery (assuming I've recharged the batteries).
>
It doesn't really matter, when one goes bad, you should replace both.
Not only will a new battery not load share properly with an old one, if
one battery in the set failed, the other can't be far behind.

The same thing goes for your two bulb light fixture at home. If you
only change one bulb at a time, you will just be changing bulbs twice
as often.

[Paul Remde]

Hi,

I agree that it would be a nice product to offer. Larry Goddard reads this
group, hopefully he'll come up with a good solid product to offer. I'll
copy him on this note as well.

I must admit that I'm not sure I like the automatic switching approach - I
guess I just like to be in control of which battery is being used. The idea
of 2 battery switches and diodes to stop flow seems OK to me, but I'm not
sure it is necessary. I have always used 1 single 3 position switch (Batt
1/Off/Batt 2). I have never had a problem making a fast switch from battery
A to battery B. I wonder if there is a perceived need for something that
really isn't necessary. But I'm not an expert on batteries or diodes.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com


"Gary Emerson" > wrote in message
. net...
>A quick Google of Schottky Diode and TO-220 yielded some sources.
>
> I just tried the first one and then found this:
>
> http://www.onsemi.com/PowerSolutions/product.do?id=MBR2515L
>
> looks like even slightly better than what I had bought.
>
> You'd lose about 0.3 volts during normal operation.
>
> Datasheet at:
>
> http://www.onsemi.com/pub/Collateral/MBR2515L-D.PDF
>
> I'm sure some googling will find that someplace like DigiKey will have
> these and will take small ordering quantities.
>
> Is Paul Remde out there? Might be a nice "kit" to add to your line. Kit
> includes 4 diodes, 4 heat sinks, 4 insulating washers some heat shrink
> tubing, etc.??
>
> Good luck.
>
>
>
>
> Gary Emerson wrote:
>> Nyal Williams wrote:
>>
>>> I'd like to see a full write-up with diagrams, photos,
>>> and names/addresses of places to buy parts. This would
>>> make a good article for Soaring.
>>>
>>
>> Here is a sketch
>>
>> http://www.mydatabus.com/public/emerson_gary/e/sketch.JPG
>>
>> and a pic of my install...
>>
>> http://www.mydatabus.com/public/emerson_gary/e/diodes.jpg
>>
>> There is a aluminum bracket which is lightly mounted to the bulkhead. The
>> PC board just provides insulation and some support for the wires.
>>
>> Each diode has a heat sink, but I don't really think it was necessary.
>>
>> I don't have the part numbers handy, but I'll see if I can't find
>> something.
>>
>> With 18Amps of forward current capability (each), there isn't really any
>> "need" for the two diodes in parallel, but for an extra $5 and a few
>> extra minutes of wiring, if any one diode ever did fail "open" the other
>> would still provide power. Most likely overkill.

[Greg Arnold]

Paul Remde wrote:
> Hi,
>
> I agree that it would be a nice product to offer. Larry Goddard reads this
> group, hopefully he'll come up with a good solid product to offer. I'll
> copy him on this note as well.
>
> I must admit that I'm not sure I like the automatic switching approach - I
> guess I just like to be in control of which battery is being used. The idea
> of 2 battery switches and diodes to stop flow seems OK to me, but I'm not
> sure it is necessary. I have always used 1 single 3 position switch (Batt
> 1/Off/Batt 2). I have never had a problem making a fast switch from battery
> A to battery B. I wonder if there is a perceived need for something that
> really isn't necessary. But I'm not an expert on batteries or diodes.
>
> Good Soaring,
>
> Paul Remde
> Cumulus Soaring, Inc.
> http://www.cumulus-soaring.com

I have the same setup as Paul, and it works fine. However, I have a 302
-- when I had a Volkslogger, this setup would create two separate IGC
files when you switched from one battery to the other.

[Nyal Williams]

Seems to me that in order to take care of the Volkslogger,
the ideal switch would be a 3-positionswitch: 1.
Battery A; 2. Battery A&B in parallel; 3. Battery B.
Switching rapidly from 1. through 2. to 3. would prevent
interruption in power without raising voltage or otherwise
causing damage, and position 2. could be used when
and if both batteries are somewhat low.

Does such a switch exist that provides such an overlap?


At 18:12 27 December 2006, Greg Arnold wrote:
>Paul Remde wrote:
>> Hi,
>>
>> I agree that it would be a nice product to offer.
>> Larry Goddard reads this
>> group, hopefully he'll come up with a good solid product
>>to offer. I'll
>> copy him on this note as well.
>>
>> I must admit that I'm not sure I like the automatic
>>switching approach - I
>> guess I just like to be in control of which battery
>>is being used. The idea
>> of 2 battery switches and diodes to stop flow seems
>>OK to me, but I'm not
>> sure it is necessary. I have always used 1 single
>>3 position switch (Batt
>> 1/Off/Batt 2). I have never had a problem making
>>a fast switch from battery
>> A to battery B. I wonder if there is a perceived
>>need for something that
>> really isn't necessary. But I'm not an expert on
>>batteries or diodes.
>>
>> Good Soaring,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>
>I have the same setup as Paul, and it works fine.
>However, I have a 302
>-- when I had a Volkslogger, this setup would create
>two separate IGC
>files when you switched from one battery to the other.
>

[Marc Ramsey]

Greg Arnold wrote:
> I have the same setup as Paul, and it works fine. However, I have a 302
> -- when I had a Volkslogger, this setup would create two separate IGC
> files when you switched from one battery to the other.

The 302 has an internal capacitor across the power supply lines, the
Volkslogger does not. Volkslogger owners can solve this problem by
adding an external capacitor, as is suggested in the manual...

Marc

[Udo]

> I have the same setup as Paul, and it works fine. However, I have a 302
> -- when I had a Volkslogger, this setup would create two separate IGC
> files when you switched from one battery to the other.

I agree as well.
I used to switched an L nav on each flight with no problem.
Now that I use a 10.5 amp/h battery I rarely switch.
Hence I only have to take out one battery for charging.
I would use the same battery for about 5 flights and then rotate.
Udo

[Lew Hartswick]

Nyal Williams wrote:
> Seems to me that in order to take care of the Volkslogger,
> the ideal switch would be a 3-positionswitch: 1.
> Battery A; 2. Battery A&B in parallel; 3. Battery B.
> Switching rapidly from 1. through 2. to 3. would prevent
> interruption in power without raising voltage or otherwise
> causing damage, and position 2. could be used when
> and if both batteries are somewhat low.
>
> Does such a switch exist that provides such an overlap?
>
Sure it's called "make before break" some one already
has mentioned it.
...lew...

[Gary Emerson]

Lew Hartswick wrote:
> Gary Emerson wrote:
>
>>
>> With 18Amps of forward current capability (each), there isn't really
>> any "need" for the two diodes in parallel, but for an extra $5 and a
>> few extra minutes of wiring, if any one diode ever did fail "open" the
>> other would still provide power. Most likely overkill.
>
> Yes because most often (probably at least 90% of the time) a diode
> fails "short"
> Therefore you may be reducing the reliability. :-)
> ...lew...

Fail "short" won't leave you without power on a flight. Fail "open"
might...

[OxAero]

Gary,

I developed a circuit card with isolation diodes for two batteries and
a pair of efficient voltage regulators, one for high current devices
(radio and transponder) and the other for the rest. As Dick indicated
the panel has two SPST switches for two batteries. The diodes drop .3
Volts, but the regulators operate down to low voltages. There is a
price to pay for operating the regulators. But, I felt that
considering that I use 12 Ah batteries, I had plenty of capacity and I
was more interested in supplying regulated power to my instruments.

The problem was that the large regulator couldn't handle the start up
load from the transponder. So, my quick fix was to bypass that
regulator with the second switch. I expect to revisit the project some
day and finish it properly.

Jim Hendrix


Gary Emerson wrote:
> wrote:
> > By all means a second battery should be installed in our electrically
> > driven modern sailplanes. After many years of quickly flipping my
> > 3-position battery switch, and trying not to have my logger to
> > momentarily dropout, I have concluded that is best to use 2 single-pole
> > battery switches. That way one can have either or both batteries
> > connected at the same time.
> >
> > I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> > for Wing Deturbulator flight testing, and it was wired like that. You
> > will hear much more about that amazing new invention at the coming SSA
> > Convention.
> >
> > Thermally,
> >
> > Dick Johnson
> >
> Better yet is to use diodes so that both batteries will always be "on"
> in parallel and you're always pulling from the best battery with no
> fiddling required from the pilot. Relatively low voltage drop diodes
> are available with 18 Amp forward capacity. For redundancy, I used two
> in parallel on each battery. The diodes are available in the TO-220
> package and it's easy to incorporate a small heat sink, but I have no
> reason to believe they ever attained any temperature at all.
>
> With two batteries connected with switches, if one battery does really
> "die" then any time spent with both switches in the "on" position causes
> the good battery to attempt to charge the "dead" battery to no avail, so
> ultimately you're wasting what power you do have during this time. The
> diodes eliminate any chance for cross charging...or discharging. Used
> this system for several years, never experienced a single power issue.

[Tinwings]

Being the incurably curious type, I decided to test this theory. I
took two known good 7Ah 12V SLA batteries and discharged one to 8 volts
(resting) with a 12V light bulb. The other battery I topped off with a
charger to 13.6 volts. I connected the two using less than two feet of
18 gauge wire and a ordinary toggle switch. Using a 60 Mhz bandwith
oscilloscope and a hall-effect type current probe I looked at the
resulting waveform when I closed the switch; a nice square edged rise
to about 3 amps, tapering down to 2.5 amps in a few seconds. Because I
didn't know what the frequency response of this current probe was, I
inserted a precision .001 ohm current shunt in line (very high
frequency response) and used the scope to watch the voltage drop across
it. The results were identical; no current spike, no inrush of current
- just a nice square edged waveform rising to about 3 amps. This simply
isn't going to weld contacts, burn out switches or blow (properly
sized) fuses. As for "wasting energy" by dumping from the good battery
into the dead battery when switching over - just do the math. Even if
the two batteries were connected for as much as 5 seconds while
switching from one to the other (two switch or "make before break"
switch arrangement), you will be using less than one thousanth of the
good battery's capacity to charge the "dead" battery.

RF

Doug Haluza wrote:
> This is how I finally set up my glider--with two main battery switches.
> But if you want to run this way without bouncing the logger, the two
> switches should be on for the whole flight. You don't want to run one
> battery down like a fuel tank, then switch when it is empty. If you do,
> you will get a big current spike when you switch them both on. At best,
> this wastes energy from the new battery by dumping it into the dead
> one. You can also burn-out your switch, weld the contacts, or blow a
> fuse.
>
> What you want to do is run two identical batteries, bought at the same
> time from the same production batch. Then always charge and run them
> together. They should age together, and share the load properly this
> way. You only want to use the two switches in opposite positions to
> separate the batteries for testing, or if one battery fails.
>
> wrote:
> > By all means a second battery should be installed in our electrically
> > driven modern sailplanes. After many years of quickly flipping my
> > 3-position battery switch, and trying not to have my logger to
> > momentarily dropout, I have concluded that is best to use 2 single-pole
> > battery switches. That way one can have either or both batteries
> > connected at the same time.
> >
> > I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> > for Wing Deturbulator flight testing, and it was wired like that. You
> > will hear much more about that amazing new invention at the coming SSA
> > Convention.
> >
> > Thermally,
> >
> > Dick Johnson

[5Z]

On Dec 29, 6:25 pm, "Tinwings" > wrote:
> Being the incurably curious type, I decided to test this theory.
-- snip --
> ...you will be using less than one thousanth of the good battery's
> capacity to charge the "dead" battery.

Holy cow!! Blasphemy!!!!

We can't have people posting empirical evidence complete with a
complete description of the experiment messing up our continuing
propagation of "old wives' tales" in this group.

Seriously, thanks for doing the experiment and reporting the results
here. Perhaps now we can close out the power switch discussion once
and for all. Naaaah, I'm sure it will come back.

-Tom

[[email protected][_1_]]

Excellent! Beat to the punch... I was reading this thead and thinking
I'd just go measure this to quiet concerns about inrush currents.
I've.been operating my glider with 2 x 12 Ah batteries with seperate
spst master switches on each battery. I'll run one battery at a time
but both will be on for a short while when switching batteries. I've
never had a problem with switches and currents and never expected that
I would.

This really should not need an experment to prove it... (but its fun
and who would believe anything on ras without it?). While AGM batteries
have very low internal resistance when fully charged, like all lead
acid batteries the internal resistance increases as they discharge due
to the reduction in electrolyte conductivity (the sulfuric acid is
turning into water as the sulfate ions form lead sulfate on the
plates). Internal resistance might go from ~0.002 ohm fully charged to
maybe an 0.1 to an ohm or so if you really discharge things (your
mileage will vary widely). You won't find the internal resistance specs
anywhere except at full charge, but you can infer them from the
standard manufacturers discharge curves (usually voltage vs. log time
at various discharge currents). That fall off in voltage measured in
those discharge curves is actually telling a lot about the internal
resistance increasing as the battery discharges. The internal
resistance increasing inside the battery causes the external measured
voltage under load to decrease - this dominates the voltage measured
under load much more than the cell chemical potential decreasing due to
the weaker electrolyte concentration. The battery voltage is not
getting lower as much as it is getting harder to pull whatever is in
the battery out. And for our switch story, it is luckilly also harder
to push charge back into the flat battery.

So while a fully charged lead acid battery and especially (for their
size) AGM batteries can sink huge currents into a short circuit the
other battery just does not look like a short circuit if it is
discharged, and if it is not very discharged then the small voltage
differences (fractions of a volt) don't generate a large current even
with fairly small total internal resistance of both batteries.

I run my glider with two 12 Ah batteries and two seperate master
switches because I like to be able to see what is going on and I like
the redundancy and to be able to control things. I don't like the diode
idea since in normal operation you can't see if you have a weak battery
(like when you make a mistake and don't fully charge one battery - I'm
more worried about operator error (me) like that than by one of the
batteries actually being sick. I just think I'm more likely to spot a
mistake like that with the batteries not wired in parallel with diodes.

BTW in the test described below the current starting at 3 amps and
dropping to 2.5 amps is casued by surface charge -- surface chemsiry
effects of the electrolyte in the very porous surface of the plates. It
it also the reason why a "12 volt" lead acid battery measure up over 13
volts, if you burn of the surface charge you'll find the true open
circuit cell voltage is around 12.5 volts (depends slightly on battery
chemsitry and temperature). Surface charge is why a damaged old battery
can sometimes charge up over 12 volts but rapidly fall and why just
pulling a battery off charge and measuring it's open circuit voltage
without either waiting (many hours) or deliberately drawing current to
burn off the surface charge is next to useless. But it is always
amusing watching people do this at the gliderport... (see the surface
charge effect slides in the link below, they show the surface charge
being discharged and the battery voltage allowed to relax back again
prior to a proper open circuit voltage measurement to estimate the
state of charge - a measurement that even if properly made tells you
*nothing* about the actual battery capacity).

I was asked to give a talk at one of our PASCO seminars on glider
batteries. I'm not sure how useful the slides will be by themselves but
they are available here
http://www.pacificsoaring.org/articles/Darryl%20Ramm%20Battery%20Care%20and%20Maintenance %20PASCO%202006.pdf

Anyhow again thanks for the measurements


Darryl Ramm
DG-303 6DX


Tinwings wrote:
> Being the incurably curious type, I decided to test this theory. I
> took two known good 7Ah 12V SLA batteries and discharged one to 8 volts
> (resting) with a 12V light bulb. The other battery I topped off with a
> charger to 13.6 volts. I connected the two using less than two feet of
> 18 gauge wire and a ordinary toggle switch. Using a 60 Mhz bandwith
> oscilloscope and a hall-effect type current probe I looked at the
> resulting waveform when I closed the switch; a nice square edged rise
> to about 3 amps, tapering down to 2.5 amps in a few seconds. Because I
> didn't know what the frequency response of this current probe was, I
> inserted a precision .001 ohm current shunt in line (very high
> frequency response) and used the scope to watch the voltage drop across
> it. The results were identical; no current spike, no inrush of current
> - just a nice square edged waveform rising to about 3 amps. This simply
> isn't going to weld contacts, burn out switches or blow (properly
> sized) fuses. As for "wasting energy" by dumping from the good battery
> into the dead battery when switching over - just do the math. Even if
> the two batteries were connected for as much as 5 seconds while
> switching from one to the other (two switch or "make before break"
> switch arrangement), you will be using less than one thousanth of the
> good battery's capacity to charge the "dead" battery.
>
> RF
>
> Doug Haluza wrote:
> > This is how I finally set up my glider--with two main battery switches.
> > But if you want to run this way without bouncing the logger, the two
> > switches should be on for the whole flight. You don't want to run one
> > battery down like a fuel tank, then switch when it is empty. If you do,
> > you will get a big current spike when you switch them both on. At best,
> > this wastes energy from the new battery by dumping it into the dead
> > one. You can also burn-out your switch, weld the contacts, or blow a
> > fuse.
> >
> > What you want to do is run two identical batteries, bought at the same
> > time from the same production batch. Then always charge and run them
> > together. They should age together, and share the load properly this
> > way. You only want to use the two switches in opposite positions to
> > separate the batteries for testing, or if one battery fails.
> >
> > wrote:
> > > By all means a second battery should be installed in our electrically
> > > driven modern sailplanes. After many years of quickly flipping my
> > > 3-position battery switch, and trying not to have my logger to
> > > momentarily dropout, I have concluded that is best to use 2 single-pole
> > > battery switches. That way one can have either or both batteries
> > > connected at the same time.
> > >
> > > I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> > > for Wing Deturbulator flight testing, and it was wired like that. You
> > > will hear much more about that amazing new invention at the coming SSA
> > > Convention.
> > >
> > > Thermally,
> > >
> > > Dick Johnson

[[email protected][_1_]]

Two significant things missing from the comments below are

1. Measured battery capacity depends significantly on discharge current

2. Measured battery capacity dependssignificantly on temperature (esp.
for lead acid batteries)

These two things cause most of the confusion I see glider pilots having
understanding battery run time

For #1. A 12 Ah battery is not 12 amps for one hour, far from it. For
lead acid batteries the standard is to measure the discharge over a 20
hour period. That is at a constant discharge current of 0.05 x C (where
C is the capacity in Ah).

If you draw higher current from a battery you get less total energy
out, the extra energy has gone into ohms law heating in the internal
resistance (I squared R). The internal resistance is only the simplest
model of what is going on, there are other effects that increase losses
as the current increases significantly.

Understanding the dependency of the measured battery capacity on the
discharge current/capacity ratio also explains things like why a single
12 Ah battery can provide more capacity than 2 x 7Ah batteries
discharged one after the other. A higher current/capacity ratio is
being drawn from the 7Ah batteries.

If you want to measure how many amps x hours you really will get our of
a battery then you need to measure it near the actual discharge current
it will have (and near the actual temperature it will be at). The
reason that (as mentioned in the posting) that discharge curves measure
down to different voltages depending on the current/capacity ratio the
measuremnt is made at is due to internal resistance. Higher discharge
currents cause more of an internal voltage drop across the internal
resistance so the external voltage you measure the discharge down to
has to be lower. The easiest way to get the correct cut off voltage is
to look at a discharge graph on a manufactueres spec sheet.

While the measuremnt cut-off voltage (usually around 10 to 10.5 volts
for typical glider battery measurements) may be too low for some older
electronics it is likely to be high enough to power modern
avionics/toys found in gliders (I know some of the older transponders
and radios that really prefer to run at ~14 volt alternator voltrages
may have issues).

For those more interested in capacity measurements and discharge curves
should Google Peukert's equation that describves a useful emperical
relationship between discharge currents and battery capacity.The
"Peukert number" for a battery describes how immune its capacity is to
changes in the discharge current. You have to calcualte this number
yourself from meaurements, manufacters won't usually quote it.

Battery capacity measuremnts usually start with a fully charged
battery. Using a trusted charger and leaving the thing on charge for a
long time is a good way to do this in practice. The open circuit
voltate when you take the battery off charge will measure above 12.5
volts or so but that is an aberation caused by surface charge. You will
see the voltage rapidly drop of (usually in seconds to tens of seconds
depending on the measurement current) as you measure voltage under
load. In practice this surface charge represents no significant battery
capacity. In the measurement mentioned below there should really be no
need to let batteries sit for a day or so before a discharge test.

BTW as mentioned below even a partial discharge cycle can show up
problems. Again it is internal resistance that is likely dominating the
measurements. Cells that are sick or damanged or just old often have
higher internal resistance than a healthy cell and will cause the
voltage to drop quickly. For those reasons discharge tests at currents
much higher than you will operate the batteries can be useful since the
higher currents will show up internal restance problems quickly
(resistive power losses are proportional to the square of the current)
-- even if the measuremnts don't mean much for calculating expected
battery life under any particular load.

For #2 Temperature effects, that is a longer topic, but be the standard
is to measure lead acid batteries at 20 C. AGM battery capacities
approximately halve down to around -20 to -25C where the electrolyte
can start to freeze. And yet again internal resistance (decreasing
conductivity of the electrolyte vs temperature) explains a lot of this
behavior. I show a few capacity vs. temp curves in the slide talks I
linked to in another reply in this thread. One of the curves shows the
rapid voltage drop of a cell freezing as it discharges (some thing to
worry about on that next really long and cold wave flight :-)

Cheers


Darryl Ramm
DG-303 6DX


COLIN LAMB wrote:
> RE: Testing AH of batteries
>
> Battery capacity is measured using a defined minimum voltage. That voltage
> may or may not correspond to the minimum voltage your glider equipment will
> operate on. If you use diodes, that minimum voltage will move slightly.
> Capacity also depends upon a starting voltage - which is significantly
> higher than 12 volts.
>
> I often need to test batterys used in our search and rescue radios and have
> found that I can test battery capacity quickly without a full discharge. I
> charge the batteries, then let them sit for a day. Then, I put a load on
> them and simply watch the decay of voltage over time. In a very short time,
> you can make a graph that will indicate the trend of the battery and compare
> with a new battery. A battery with reduced capacity will drop voltage much
> more quickly.
>
> You can determine the capacity of the battery during charge, too. Capacity
> is the ability of the battery to resist change. That applies either way.
> it means the battery will drop in voltage or charge more slowly. So, you
> can simply time the charge of two batteries and learn the comparative
> capacity of each.
>
> Colin

[Tony Verhulst]

wrote:
> <Nice presentation snipped>
> ... One of the curves shows the
> rapid voltage drop of a cell freezing as it discharges (some thing to
> worry about on that next really long and cold wave flight :-)

If we had properly designed heater elements surrounding the battery,
powered by the battery itself, could we expect more "useful capacity"
from the battery on those cold flights? Useful capacity being defined as
the amount of current delivered to the avionics.

Tony V.

[kirk.stant]

A question for the group from someone who admits to knowing little
about batteries:

My glider is setup with two 12v9ah (the new "same size as the 7.5ah"
ones) batteries, with each normally powering half my electronics; i.e
one batt is powering the radio and SN10/GPS, while the other runs the
logger/GPS, PDA, and backup vario. Each is connected via a 3-way
master switch, so either battery can power either or both "busses".

This setup does not allow both batteries to be connected to the same
"bus" at the same time. On the rare time I've had to switch due to old
or insufficiently charged batteries, I've had no trouble with the
traces from the loggers.

My question is, is this better, equal, or worse (from the standpoint of
battery usage/efficiency) than the more common "use one batt until it
dies, then switch" 2-battery setup.

TIA,

Kirk
66

[QT]

One reason to run the batteries in parallel is that the slower the rate
at which you discharge a battery, the more total power you can get from
it. I.e. if you discharge a battery at 1 amp it will not deliver as
many amp hours than if you discarge it at 0.5 amps. This is somewhat
offset by the need ( or good idea) to isolate the batteries with low
loss zener diodes. The 0.25 volt drop of the zeners means that in
effect you can only discharge you batteries to 11.25 rather than to 11
volts - which sacrifices some capacity. You have to get out the data
sheets for the diodes and batteries to see if this is a good tradeoff.

I believe that using one battery switch rather than multiple spst
switches is a bad idea because the single switch becomes a single point
of failure. Having 15 batteries is of no value if the switch breaks.

[Eric Greenwell]

Tony Verhulst wrote:
> wrote:
> > <Nice presentation snipped>
>> ... One of the curves shows the
>> rapid voltage drop of a cell freezing as it discharges (some thing to
>> worry about on that next really long and cold wave flight :-)
>
> If we had properly designed heater elements surrounding the battery,
> powered by the battery itself, could we expect more "useful capacity"
> from the battery on those cold flights? Useful capacity being defined as
> the amount of current delivered to the avionics.

Yes, if the battery is well insulated so the heating doesn't require
much current, and if it is relatively warm before you launch (usually
the case), so current isn't required to warm it initially. Installing a
warm battery just before flying is one way, or an obsessed pilot could
connect external power to the heater to warm the battery (to, for
example, 90 deg F) before the flight, so no power is required for
heating during the flight.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected][_1_]]

Tony

You would start by insulating the battery well. It should only take
about an inch of foam insulation (R7) to get the heat leak down to a
watt or so but it needs to be carefully made.Startting with a warm
battery, good insulation and a little self heating from the battery
during discharge should get you a long way. Of course the battery
likely won't fit into its mount with all that insulation. After doing
all that adding a heater may make sense but you need to know what you
are doing with a termperature regulation circuit, and good luck finding
somebody who will sign off the work. And yes the expectation for an
insulated battery should be that the cost of running the heater is
well worth it in terms of getting more capacity out of the battery. It
would take two heater plates or nichrome wire on the battery end (or
sides) that parallel the internal plates. It is those two outward most
facing cells that probably conduct most heat into/out of the battery
(in a well insulated battery the terminals and cables may be a
significant leak as as well).

Before looking a the complexity of a heater I'd look at a solar panel
of the glider. They work great cold.

If you need to go to the effort of adding a heater it may also be time
to investigate alteratives to lead acid batteries (which may also need
heaters).

Lead acid batteries have a pretty large thermal mass and the AGM
bateries cores tend to relatively well insulated because there is
little electrolyte or metal contact with the case so in practice they
probably don't get as cold as ambient on typical flights, especially if
like my batteries they sit up on a parcel shelf packed with stuff
around them. I've been curious about the temperature issues and have
thought about drilling thermocouples into the inside of AGM batteries
for some tests but I've never got around to it (just for ground
measuremnts I'd not want to fly with it).

Darryl Ramm

Tony Verhulst wrote:
> wrote:
> > <Nice presentation snipped>
> > ... One of the curves shows the
> > rapid voltage drop of a cell freezing as it discharges (some thing to
> > worry about on that next really long and cold wave flight :-)
>
> If we had properly designed heater elements surrounding the battery,
> powered by the battery itself, could we expect more "useful capacity"
> from the battery on those cold flights? Useful capacity being defined as
> the amount of current delivered to the avionics.
>
> Tony V.

[Eric Greenwell]

OxAero wrote:

> The problem was that the large regulator couldn't handle the start up
> load from the transponder. So, my quick fix was to bypass that
> regulator with the second switch. I expect to revisit the project some
> day and finish it properly.

If you are using a transponder like the Becker ATC 4401, the bypass is
the best setup. The Becker, like many other modern transponders and
radios, has a wide range input voltage regulator (9-32 volts for the
Becker), so regulating it's input voltage has no advantage. As you
discovered, it may even prevent the equipment from working properly, as
it is designed to operate from a battery, not a regulated supply.

I suggest you determine exactly which instrument(s) really benefit from
input voltage regulation and put only those on the regulator. Most of
the newer equipment we use was specifically designed for battery use, so
adding a regulator just increases the things that can fail.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Martin Gregorie[_1_]]

COLIN LAMB wrote:
> Most diodes have about a .6 volt drop, which may be significant. Therefore,
> you will need diodes with a low threshold. Schottky diodes should be about
> .3 volts drop. You can measure the actual drop using a digital
> volt-ohmmeter. There is a diode test range and it will show the voltage
> drop.
>
I'm flying with the diode setup. The best diodes I was able to find in
the UK were Fairchild MBR1035 Schottky diodes. These handle 35 amps and
come in TO-220 packages. Their spec quotes a 0.57 v drop, which seems
about right: with 2 x GPS II+, EW-D logger, SDI C4 and B.40 varios all
on the C4's internal voltmeter shows 11.6 v on two fully charged 7 AH cells.

I need to fit a radio and am thinking of fitting a Filser ATR-500. Can
anybody tell me if that will be OK on the end of the diodes or would I
be better to discard the diodes and use one battery to drive the ATR-500
and the other to run the GPS, logger, and varios?

Another reason I'm wondering about rewiring to separate the batteries is
that if we get landed with transponders I assume I'd be better off using
one for radio and transponder and reserving the other for the
GPS/logger/vario setup. Comments?

The other choice of radio would be a Microair 760. I assume that, as its
rated for 12-14v it would be quite unhappy on the end of the diodes and
just barely usable on a separate battery. I see that Maxim sell a range
of solid state voltage boosters (there is a model that can output 14v at
2 amps). Has anybody tried using one of these to drive a Microair radio?
If so, how well did it work?




> Colin Lamb
>
>


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_1_]]

wrote:
> This is great discussion. I was doing a bit of research myself (it has
> been over 10 years since I did any HW design, so am pretty rusty).
>
> Another option that sounds even better is to use the new chips designed
> for exactly this to control DirectFETs. That way the voltage drop and
> power waste will be significantly reduced with very little additional
> cost. The chips I were looking at were IR5001S:
> http://www.irf.com/product-info/datasheets/data/ir5001s.pdf or LT4351:
> http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1142,C1079,P21 73
>
>
> I have used DirectFET stuff in robotics and found them to be very
> reliable and very simple to design with.
>
> My biggest problem is all these components are only available in
> surface mount these days and I have never tried to build a circuit
> using them.
>
That should be easy enough to do with a pair of suitable power MOSFETs
and an LM358 dual op-amp to control the MOSFETs. If I don't split my
supply (see earlier post) I'm thinking about making this type of circuit
this because the voltage drop in the MOSFET will be very small.

Size isn't an issue - suitable MOSFETs are in TO-220 type packages and
the LM358 is an 8 pin DIP package.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_1_]]

Steve Paavola wrote:
>
> If both batteries are on-line all the time, how do you know when one is
> getting weak and needs to be replaced? Or do you replace both batteries
> when voltage is marginal at the end of a flight?
>
You can get fairly inexpensive automatic peak detecting battery
cycler/charger units ($60-$100 at a guess - around GBP 69.00 in the UK)
that will measure the capacity during a discharge cycle. These units
will charge lead-acid, NiCd, NiMH and Li-poly with settable charge and
discharge currents. You can run them off 12v DC (mains or batteries)
they'll charge 12v lead acid and 14 cell NiCd batteries.

Check your local friendly RC model supply shop if you're interested in
this type of charger.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[[email protected][_1_]]

The Filsner is unlikely to have a problem through the diode setup you
have now. (not that I like the diode setup but it should work - BTW you
should be able to find lower voltage drop diodes).

For the Microair I would not read too much into a nominal voltage spec.
It is hard to tell wether the manufacturer is quoting a real absolute
voltage range or the nominal voltage. On the other hand I'd not want to
inflict anybody with a Microair radio (oops I can feel the flames
already). They have a very bad reputation where I fly. The several I've
seen installed have had problems, especially apparent heat related
problems with the displays getting garbled and then finally the whole
radio going out to lunch (and I'm not talking really hot days). Other
brands seems to be much more reliable. Why not go with Becker?

Personally I'd stay away from trying to get too fancy with regulators
etc. I want the supply to be as dumb and simple as possible. Just
batteries and circuit breaker or fuse and master switches. As few
connectors or solder joints as possible. And I personally I like
running one battery at a time - I want to see the health of each
battery and know about how much capacity I have in both batteries and
know I can switch in a reserve if I run a battery down -- which I may
not notice until it is too late. Like many of us in the Western USA I
fly over pretty desolate areas and I really want to know roughly what
battery capacity in reserve.

If you are goigg to install a transponder, have lots of avionics toys,
expect long cold flights it may well be you need to look at moving up
to larger capacity batteries or installing solar panels.

Darryl Ramm


Martin Gregorie wrote:
> COLIN LAMB wrote:
> > Most diodes have about a .6 volt drop, which may be significant. Therefore,
> > you will need diodes with a low threshold. Schottky diodes should be about
> > .3 volts drop. You can measure the actual drop using a digital
> > volt-ohmmeter. There is a diode test range and it will show the voltage
> > drop.
> >
> I'm flying with the diode setup. The best diodes I was able to find in
> the UK were Fairchild MBR1035 Schottky diodes. These handle 35 amps and
> come in TO-220 packages. Their spec quotes a 0.57 v drop, which seems
> about right: with 2 x GPS II+, EW-D logger, SDI C4 and B.40 varios all
> on the C4's internal voltmeter shows 11.6 v on two fully charged 7 AH cells.
>
> I need to fit a radio and am thinking of fitting a Filser ATR-500. Can
> anybody tell me if that will be OK on the end of the diodes or would I
> be better to discard the diodes and use one battery to drive the ATR-500
> and the other to run the GPS, logger, and varios?
>
> Another reason I'm wondering about rewiring to separate the batteries is
> that if we get landed with transponders I assume I'd be better off using
> one for radio and transponder and reserving the other for the
> GPS/logger/vario setup. Comments?
>
> The other choice of radio would be a Microair 760. I assume that, as its
> rated for 12-14v it would be quite unhappy on the end of the diodes and
> just barely usable on a separate battery. I see that Maxim sell a range
> of solid state voltage boosters (there is a model that can output 14v at
> 2 amps). Has anybody tried using one of these to drive a Microair radio?
> If so, how well did it work?
>
>
>
>
> > Colin Lamb
> >
> >
>
>
> --
> martin@ | Martin Gregorie
> gregorie. | Essex, UK
> org |

[Gary Emerson]

OxAero wrote:
> Gary,
>
> I developed a circuit card with isolation diodes for two batteries and
> a pair of efficient voltage regulators, one for high current devices
> (radio and transponder) and the other for the rest. As Dick indicated
> the panel has two SPST switches for two batteries. The diodes drop .3
> Volts, but the regulators operate down to low voltages. There is a
> price to pay for operating the regulators. But, I felt that
> considering that I use 12 Ah batteries, I had plenty of capacity and I
> was more interested in supplying regulated power to my instruments.
>
> The problem was that the large regulator couldn't handle the start up
> load from the transponder. So, my quick fix was to bypass that
> regulator with the second switch. I expect to revisit the project some
> day and finish it properly.
>
> Jim Hendrix
>
>
> Gary Emerson wrote:
>
wrote:
>>
>>> By all means a second battery should be installed in our electrically
>>>driven modern sailplanes. After many years of quickly flipping my
>>>3-position battery switch, and trying not to have my logger to
>>>momentarily dropout, I have concluded that is best to use 2 single-pole
>>>battery switches. That way one can have either or both batteries
>>>connected at the same time.
>>>
>>> I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
>>>for Wing Deturbulator flight testing, and it was wired like that. You
>>>will hear much more about that amazing new invention at the coming SSA
>>>Convention.
>>>
>>> Thermally,
>>>
>>> Dick Johnson
>>>
>>
>>Better yet is to use diodes so that both batteries will always be "on"
>>in parallel and you're always pulling from the best battery with no
>>fiddling required from the pilot. Relatively low voltage drop diodes
>>are available with 18 Amp forward capacity. For redundancy, I used two
>>in parallel on each battery. The diodes are available in the TO-220
>>package and it's easy to incorporate a small heat sink, but I have no
>>reason to believe they ever attained any temperature at all.
>>
>>With two batteries connected with switches, if one battery does really
>>"die" then any time spent with both switches in the "on" position causes
>>the good battery to attempt to charge the "dead" battery to no avail, so
>>ultimately you're wasting what power you do have during this time. The
>>diodes eliminate any chance for cross charging...or discharging. Used
>>this system for several years, never experienced a single power issue.
>
>

Just curious what made you want to add a regulator? Pulling off a
battery should be pretty regulated supply in the first place. Shouldn't it?

[Gary Emerson]

Martin Gregorie wrote:
> wrote:
>
>> This is great discussion. I was doing a bit of research myself (it has
>> been over 10 years since I did any HW design, so am pretty rusty).
>>
>> Another option that sounds even better is to use the new chips designed
>> for exactly this to control DirectFETs. That way the voltage drop and
>> power waste will be significantly reduced with very little additional
>> cost. The chips I were looking at were IR5001S:
>> http://www.irf.com/product-info/datasheets/data/ir5001s.pdf or LT4351:
>> http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1142,C1079,P21 73
>>
>>
>>
>> I have used DirectFET stuff in robotics and found them to be very
>> reliable and very simple to design with.
>>
>> My biggest problem is all these components are only available in
>> surface mount these days and I have never tried to build a circuit
>> using them.
>>
> That should be easy enough to do with a pair of suitable power MOSFETs
> and an LM358 dual op-amp to control the MOSFETs. If I don't split my
> supply (see earlier post) I'm thinking about making this type of circuit
> this because the voltage drop in the MOSFET will be very small.
>
> Size isn't an issue - suitable MOSFETs are in TO-220 type packages and
> the LM358 is an 8 pin DIP package.
>
>
How much lower thatn 0.3V drop will the MOSFETs get you?

[Gary Emerson]

Tinwings wrote:
> Being the incurably curious type, I decided to test this theory. I
> took two known good 7Ah 12V SLA batteries and discharged one to 8 volts
> (resting) with a 12V light bulb. The other battery I topped off with a
> charger to 13.6 volts. I connected the two using less than two feet of
> 18 gauge wire and a ordinary toggle switch. Using a 60 Mhz bandwith
> oscilloscope and a hall-effect type current probe I looked at the
> resulting waveform when I closed the switch; a nice square edged rise
> to about 3 amps, tapering down to 2.5 amps in a few seconds. Because I
> didn't know what the frequency response of this current probe was, I
> inserted a precision .001 ohm current shunt in line (very high
> frequency response) and used the scope to watch the voltage drop across
> it. The results were identical; no current spike, no inrush of current
> - just a nice square edged waveform rising to about 3 amps. This simply
> isn't going to weld contacts, burn out switches or blow (properly
> sized) fuses. As for "wasting energy" by dumping from the good battery
> into the dead battery when switching over - just do the math. Even if
> the two batteries were connected for as much as 5 seconds while
> switching from one to the other (two switch or "make before break"
> switch arrangement), you will be using less than one thousanth of the
> good battery's capacity to charge the "dead" battery.

If the batteries are both "good", but not charged equally, then the last
part is true. If a battery happens to go "bad" and won't take a charge
then the situation is different. Then the "bad" battery will just suck
down the extra power from the good battery and that power will not be
recovered.

[Gary Emerson]

Gary Emerson wrote:
> Tinwings wrote:
>
>> Being the incurably curious type, I decided to test this theory. I
>> took two known good 7Ah 12V SLA batteries and discharged one to 8 volts
>> (resting) with a 12V light bulb. The other battery I topped off with a
>> charger to 13.6 volts. I connected the two using less than two feet of
>> 18 gauge wire and a ordinary toggle switch. Using a 60 Mhz bandwith
>> oscilloscope and a hall-effect type current probe I looked at the
>> resulting waveform when I closed the switch; a nice square edged rise
>> to about 3 amps, tapering down to 2.5 amps in a few seconds. Because I
>> didn't know what the frequency response of this current probe was, I
>> inserted a precision .001 ohm current shunt in line (very high
>> frequency response) and used the scope to watch the voltage drop across
>> it. The results were identical; no current spike, no inrush of current
>> - just a nice square edged waveform rising to about 3 amps. This simply
>> isn't going to weld contacts, burn out switches or blow (properly
>> sized) fuses. As for "wasting energy" by dumping from the good battery
>> into the dead battery when switching over - just do the math. Even if
>> the two batteries were connected for as much as 5 seconds while
>> switching from one to the other (two switch or "make before break"
>> switch arrangement), you will be using less than one thousanth of the
>> good battery's capacity to charge the "dead" battery.
>
>
> If the batteries are both "good", but not charged equally, then the last
> part is true. If a battery happens to go "bad" and won't take a charge
> then the situation is different. Then the "bad" battery will just suck
> down the extra power from the good battery and that power will not be
> recovered.
Sorry, didn't read your post fully. You were only talking about the
very short period when the batteries are still connected while switching
from A to B. The nice thing about the diode setup is you'll never have
to fiddle with a battery switch again.

[[email protected][_1_]]

The previous poster was making measuremnts that disproved the argument
that there is a loss while temporarilly having both masters on while
switching batteries.Whichever way you slice that it is just not an
issue that causes any significant power loss, It is totally
insignificant, you lose much more power though ohmic loses in fuses
and circuit breakers.

Of course that relies on the operator not to accidently leave two
master switches both on all the time (without taking the diode
approach).

Darryl

Gary Emerson wrote:
> Tinwings wrote:
> > Being the incurably curious type, I decided to test this theory. I
> > took two known good 7Ah 12V SLA batteries and discharged one to 8 volts
> > (resting) with a 12V light bulb. The other battery I topped off with a
> > charger to 13.6 volts. I connected the two using less than two feet of
> > 18 gauge wire and a ordinary toggle switch. Using a 60 Mhz bandwith
> > oscilloscope and a hall-effect type current probe I looked at the
> > resulting waveform when I closed the switch; a nice square edged rise
> > to about 3 amps, tapering down to 2.5 amps in a few seconds. Because I
> > didn't know what the frequency response of this current probe was, I
> > inserted a precision .001 ohm current shunt in line (very high
> > frequency response) and used the scope to watch the voltage drop across
> > it. The results were identical; no current spike, no inrush of current
> > - just a nice square edged waveform rising to about 3 amps. This simply
> > isn't going to weld contacts, burn out switches or blow (properly
> > sized) fuses. As for "wasting energy" by dumping from the good battery
> > into the dead battery when switching over - just do the math. Even if
> > the two batteries were connected for as much as 5 seconds while
> > switching from one to the other (two switch or "make before break"
> > switch arrangement), you will be using less than one thousanth of the
> > good battery's capacity to charge the "dead" battery.
>
> If the batteries are both "good", but not charged equally, then the last
> part is true. If a battery happens to go "bad" and won't take a charge
> then the situation is different. Then the "bad" battery will just suck
> down the extra power from the good battery and that power will not be
> recovered.

[Martin Gregorie[_1_]]

wrote:
>
> The Filsner is unlikely to have a problem through the diode setup you
> have now. (not that I like the diode setup but it should work - BTW you
> should be able to find lower voltage drop diodes).
>
Thanks for that advice.

> For the Microair I would not read too much into a nominal voltage spec.
> It is hard to tell wether the manufacturer is quoting a real absolute
> voltage range or the nominal voltage. On the other hand I'd not want to
> inflict anybody with a Microair radio (oops I can feel the flames
> already).
>
I'd noticed that they get generally slagged off and have a reputation
for low output and intolerance for depleted batteries. I tend to think
there must be something behind those stories except that I've never seen
one being flogged off second hand.

Are they really so bad that folks are slinging them in the garbage
rather than risking their reputation by selling them on? ;-)

> If you are goigg to install a transponder, have lots of avionics toys,
> expect long cold flights it may well be you need to look at moving up
> to larger capacity batteries or installing solar panels.
>
That's not an option. I fly a Standard Libelle and already have two 7 AH
gel cells installed: there's not a cat's chance in hell of fitting
anything significantly bigger.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_1_]]

Gary Emerson wrote:
> Martin Gregorie wrote:
>> wrote:
>>
>>> This is great discussion. I was doing a bit of research myself (it has
>>> been over 10 years since I did any HW design, so am pretty rusty).
>>>
>>> Another option that sounds even better is to use the new chips designed
>>> for exactly this to control DirectFETs. That way the voltage drop and
>>> power waste will be significantly reduced with very little additional
>>> cost. The chips I were looking at were IR5001S:
>>> http://www.irf.com/product-info/datasheets/data/ir5001s.pdf or LT4351:
>>> http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1142,C1079,P21 73
>>>
>>>
>>>
>>> I have used DirectFET stuff in robotics and found them to be very
>>> reliable and very simple to design with.
>>>
>>> My biggest problem is all these components are only available in
>>> surface mount these days and I have never tried to build a circuit
>>> using them.
>>>
>> That should be easy enough to do with a pair of suitable power MOSFETs
>> and an LM358 dual op-amp to control the MOSFETs. If I don't split my
>> supply (see earlier post) I'm thinking about making this type of
>> circuit this because the voltage drop in the MOSFET will be very small.
>>
>> Size isn't an issue - suitable MOSFETs are in TO-220 type packages and
>> the LM358 is an 8 pin DIP package.
>>
>>
> How much lower thatn 0.3V drop will the MOSFETs get you?
>
The forward resistance is around 0.015 ohms (HUF75337P3, 62A, 55V, TO220
package), so at 5amps that's a 75 mV drop. That looks like a worthwhile
improvement.

The MBR1035 was the lowest drop type (0.6v drop) I could find at RS
Components or Maplins, the only two decent retail outlets in the UK.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Richard[_1_]]

I have had a Microair 760 Rev N, radio in my glider for two years with
no problems. I believe that the key is the Rev N or later. There are
tech notes and fixes on the problems you detailed with earlier
revisions. For those with the earlier revs, Erie Aviation is a
Microair Service Center and may be able to help.

I sell Microair and also Becker for an addtional $450.

Richard
www.craggyaero.com

wrote:
> The Filsner is unlikely to have a problem through the diode setup you
> have now. (not that I like the diode setup but it should work - BTW you
> should be able to find lower voltage drop diodes).
>
> For the Microair I would not read too much into a nominal voltage spec.
> It is hard to tell wether the manufacturer is quoting a real absolute
> voltage range or the nominal voltage. On the other hand I'd not want to
> inflict anybody with a Microair radio (oops I can feel the flames
> already). They have a very bad reputation where I fly. The several I've
> seen installed have had problems, especially apparent heat related
> problems with the displays getting garbled and then finally the whole
> radio going out to lunch (and I'm not talking really hot days). Other
> brands seems to be much more reliable. Why not go with Becker?
>
> Personally I'd stay away from trying to get too fancy with regulators
> etc. I want the supply to be as dumb and simple as possible. Just
> batteries and circuit breaker or fuse and master switches. As few
> connectors or solder joints as possible. And I personally I like
> running one battery at a time - I want to see the health of each
> battery and know about how much capacity I have in both batteries and
> know I can switch in a reserve if I run a battery down -- which I may
> not notice until it is too late. Like many of us in the Western USA I
> fly over pretty desolate areas and I really want to know roughly what
> battery capacity in reserve.
>
> If you are goigg to install a transponder, have lots of avionics toys,
> expect long cold flights it may well be you need to look at moving up
> to larger capacity batteries or installing solar panels.
>
> Darryl Ramm
>
>
> Martin Gregorie wrote:
> > COLIN LAMB wrote:
> > > Most diodes have about a .6 volt drop, which may be significant. Therefore,
> > > you will need diodes with a low threshold. Schottky diodes should be about
> > > .3 volts drop. You can measure the actual drop using a digital
> > > volt-ohmmeter. There is a diode test range and it will show the voltage
> > > drop.
> > >
> > I'm flying with the diode setup. The best diodes I was able to find in
> > the UK were Fairchild MBR1035 Schottky diodes. These handle 35 amps and
> > come in TO-220 packages. Their spec quotes a 0.57 v drop, which seems
> > about right: with 2 x GPS II+, EW-D logger, SDI C4 and B.40 varios all
> > on the C4's internal voltmeter shows 11.6 v on two fully charged 7 AH cells.
> >
> > I need to fit a radio and am thinking of fitting a Filser ATR-500. Can
> > anybody tell me if that will be OK on the end of the diodes or would I
> > be better to discard the diodes and use one battery to drive the ATR-500
> > and the other to run the GPS, logger, and varios?
> >
> > Another reason I'm wondering about rewiring to separate the batteries is
> > that if we get landed with transponders I assume I'd be better off using
> > one for radio and transponder and reserving the other for the
> > GPS/logger/vario setup. Comments?
> >
> > The other choice of radio would be a Microair 760. I assume that, as its
> > rated for 12-14v it would be quite unhappy on the end of the diodes and
> > just barely usable on a separate battery. I see that Maxim sell a range
> > of solid state voltage boosters (there is a model that can output 14v at
> > 2 amps). Has anybody tried using one of these to drive a Microair radio?
> > If so, how well did it work?
> >
> >
> >
> >
> > > Colin Lamb
> > >
> > >
> >
> >
> > --
> > martin@ | Martin Gregorie
> > gregorie. | Essex, UK
> > org |

[COLIN LAMB]

>This setup does not allow both batteries to be connected to the same
>"bus" at the same time. On the rare time I've had to switch due to old
>or insufficiently charged batteries, I've had no trouble with the
>races from the loggers.

>My question is, is this better, equal, or worse (from the standpoint of
>battery usage/efficiency) than the more common "use one batt until it
>dies, then switch" 2-battery setup.


I think you have a simple, efficient method of using your batteries.

The only time having both batteries on at the same time is an advantage is
when they are both so depleted that neither one alone will operate the
equipment, or the current draw is so great that the capacity will increase
by dividing the work. Your system has the advantage that it works and you
have specific information from the work performed by each battery.

There is a slight potential problem with having two batteries in parallel.
That is if one has a shorted cell. In that case, the good battery will try
to charge the bad battery, wasting energy. That could be solved by the
diodes, but they waste energy, also.

There is a great deal of merit to keeping something as simple as possible
and remembering that if it works, don't fix it.

Colin

[[email protected]]

Mike,

The web link gives my interpretation of Dick's preliminary data. He
will speak for himself in Memphis.

Many will not agree with my methods. I'll be more specific soon.
possibly before Memphis, but using my data from two years of flying
deturbulated wings, not Dick's data. I'll give my interpretation of
his data after the convention. I'm not an aerodynamicist, so you will
be excused for not believing me. On the other hand, new things often
don't fit in old boxes, so an open mind may be required for
understanding the true potential of this new technology.

Jim Hendrix
(The Johnson deturbulator flight tests were sponsored by Dallas Glider
Association.)

On Dec 26, 11:41 am, "Mike" > wrote:
> If the numbers are real, that Standard Cirrus is now a 41-1+
> sailplane-and that IS a serious improvement. $16K for a 41-1sailplane
> is great, and a boon for a lot of people that do not have $40K-60K for
> that type of sailplane performance. Looks like some older sailplanes
> could be hanging out with a new crowd.
>
> Mike
>
>
>
> wrote:
> > John Galloway wrote:
> > > Noone picking up on Dick Johnson's last paragraph??
>
> > >http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
>
> > > John Galloway
>
> > The results are interesting, but way do the testing on a Std. Cirrus?
> > To be taken seriously put them on a modern ship and test them. I
> > can't believe Dick did the testing on the Std. Cirrus and did not at
> > least put them on his Ventus for some additional comparisons.- Hide quoted text -- Show quoted text -

[[email protected]]

John,

You use what you have.

Jim Hendrix
(The Johnson deturbulator flight tests were sponsored by Dallas Glider
Association.)

On Dec 26, 11:01 am, wrote:
> John Galloway wrote:
> > Noone picking up on Dick Johnson's last paragraph??
>
> >http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
>
> > John GallowayThe results are interesting, but way do the testing on a Std. Cirrus?
> To be taken seriously put them on a modern ship and test them. I
> can't believe Dick did the testing on the Std. Cirrus and did not at
> least put them on his Ventus for some additional comparisons.

[OxAero]

Nyal,

You can get a PDF of a schmatic I used for my Standard Cirrus panel at
http://www.oxaero.com/GliderPowerBoard-Hendrix.pdf.

It's a bit over the top, but you may get some ideas. If you run a
transponder and use a voltage regulator, you will need more than 1.25 A
capacity.

Jim Hendrix

On Dec 25, 2:09 pm, Nyal Williams
> wrote:
> I'd like to see a full write-up with diagrams, photos,
> and names/addresses of places to buy parts. This would
> make a good article for Soaring.
>
> At 19:48 25 December 2006, Udo wrote:
>
>
>
>
>
> >> Better yet is to use diodes so that both batteries
> >>will always be 'on'
> >> in parallel and you're always pulling from the best
> >>battery with no
> >> fiddling required from the pilot. Relatively low
> >>voltage drop diodes
> >> are available with 18 Amp forward capacity. For redundancy,
> >>I used two
> >> in parallel on each battery.
>
> >If it is always drawing from the best battery, what
> >is the time
> >interval between switching.
> >What controls the switching. Please advise.
> >Udo- Hide quoted text -- Show quoted text -

[OxAero]

Link to schematic: http://www.oxaero.com/GliderPowerBoard-Hendrix.pdf
Jim Hendrix

On Dec 29, 7:02 pm, "OxAero" > wrote:
> Gary,
>
> I developed a circuit card with isolation diodes for two batteries and
> a pair of efficient voltage regulators, one for high current devices
> (radio and transponder) and the other for the rest. As Dick indicated
> the panel has two SPST switches for two batteries. The diodes drop .3
> Volts, but the regulators operate down to low voltages. There is a
> price to pay for operating the regulators. But, I felt that
> considering that I use 12 Ah batteries, I had plenty of capacity and I
> was more interested in supplying regulated power to my instruments.
>
> The problem was that the large regulator couldn't handle the start up
> load from the transponder. So, my quick fix was to bypass that
> regulator with the second switch. I expect to revisit the project some
> day and finish it properly.
>
> Jim Hendrix
>
>
>
> Gary Emerson wrote:
> > wrote:
> > > By all means a second battery should be installed in our electrically
> > > driven modern sailplanes. After many years of quickly flipping my
> > > 3-position battery switch, and trying not to have my logger to
> > > momentarily dropout, I have concluded that is best to use 2 single-pole
> > > battery switches. That way one can have either or both batteries
> > > connected at the same time.
>
> > > I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> > > for Wing Deturbulator flight testing, and it was wired like that. You
> > > will hear much more about that amazing new invention at the coming SSA
> > > Convention.
>
> > > Thermally,
>
> > > Dick Johnson
>
> > Better yet is to use diodes so that both batteries will always be "on"
> > in parallel and you're always pulling from the best battery with no
> > fiddling required from the pilot. Relatively low voltage drop diodes
> > are available with 18 Amp forward capacity. For redundancy, I used two
> > in parallel on each battery. The diodes are available in the TO-220
> > package and it's easy to incorporate a small heat sink, but I have no
> > reason to believe they ever attained any temperature at all.
>
> > With two batteries connected with switches, if one battery does really
> > "die" then any time spent with both switches in the "on" position causes
> > the good battery to attempt to charge the "dead" battery to no avail, so
> > ultimately you're wasting what power you do have during this time. The
> > diodes eliminate any chance for cross charging...or discharging. Used
> > this system for several years, never experienced a single power issue.- Hide quoted text -- Show quoted text -

[[email protected][_1_]]

I just don't get it. Why do you need the extra stage of regulation -
what device is having problems running at typical "12 volt" battery
voltages?

I have the same compuer (C302) as you, fly often in a club ships with
B40 varios and I've never noticed any problems with either at during
battery discharge. I've not heard of problems with the TruTrack T&B
either. Are you doing this because the Microair 760 is voltage
sensitive?

If you believe the efficiency figures for the regulators you quote you
are paying a cost around a 20% reduction in capactity for something I'm
not sure you need. I expect it may be less than this but still it seems
like an unneeded throwing away of capacity and increase in complexity
for no real benefit. It might be interesting to measure the actual
capacity penalty you are paying.

Though I don't use diodes with my two main batteries/master switches, I
do understand the why/how/advantages and disadvantages for doing so. I
do not get the why/how/advantages for adding voltage regulation.


Darryl Ramm


OxAero wrote:
> Link to schematic: http://www.oxaero.com/GliderPowerBoard-Hendrix.pdf
> Jim Hendrix
>
> On Dec 29, 7:02 pm, "OxAero" > wrote:
> > Gary,
> >
> > I developed a circuit card with isolation diodes for two batteries and
> > a pair of efficient voltage regulators, one for high current devices
> > (radio and transponder) and the other for the rest. As Dick indicated
> > the panel has two SPST switches for two batteries. The diodes drop .3
> > Volts, but the regulators operate down to low voltages. There is a
> > price to pay for operating the regulators. But, I felt that
> > considering that I use 12 Ah batteries, I had plenty of capacity and I
> > was more interested in supplying regulated power to my instruments.
> >
> > The problem was that the large regulator couldn't handle the start up
> > load from the transponder. So, my quick fix was to bypass that
> > regulator with the second switch. I expect to revisit the project some
> > day and finish it properly.
> >
> > Jim Hendrix
> >
> >
> >
> > Gary Emerson wrote:
> > > wrote:
> > > > By all means a second battery should be installed in our electrically
> > > > driven modern sailplanes. After many years of quickly flipping my
> > > > 3-position battery switch, and trying not to have my logger to
> > > > momentarily dropout, I have concluded that is best to use 2 single-pole
> > > > battery switches. That way one can have either or both batteries
> > > > connected at the same time.
> >
> > > > I saw the light when Jim Hendrix brought his sailplane to Caddo Mills
> > > > for Wing Deturbulator flight testing, and it was wired like that. You
> > > > will hear much more about that amazing new invention at the coming SSA
> > > > Convention.
> >
> > > > Thermally,
> >
> > > > Dick Johnson
> >
> > > Better yet is to use diodes so that both batteries will always be "on"
> > > in parallel and you're always pulling from the best battery with no
> > > fiddling required from the pilot. Relatively low voltage drop diodes
> > > are available with 18 Amp forward capacity. For redundancy, I used two
> > > in parallel on each battery. The diodes are available in the TO-220
> > > package and it's easy to incorporate a small heat sink, but I have no
> > > reason to believe they ever attained any temperature at all.
> >
> > > With two batteries connected with switches, if one battery does really
> > > "die" then any time spent with both switches in the "on" position causes
> > > the good battery to attempt to charge the "dead" battery to no avail, so
> > > ultimately you're wasting what power you do have during this time. The
> > > diodes eliminate any chance for cross charging...or discharging. Used
> > > this system for several years, never experienced a single power issue.- Hide quoted text -- Show quoted text -

[John Galloway[_1_]]

Jim,

Of what you quoted (below) only the sentence 'Noone
picking up on Dick Johnson's last paragraph??' was
written by me. I was trying to attract attention to
Dick Johnson's hint that he had tested the Sinha deturbulators
- the progress of which I have followed with great
interest on your website.

John Galloway



At 23:02 31 December 2006, wrote:
>John,
>
>You use what you have.
>
>Jim Hendrix
>(The Johnson deturbulator flight tests were sponsored
>by Dallas Glider
>Association.)
>
>On Dec 26, 11:01 am, wrote:
>> John Galloway wrote:
>> > Noone picking up on Dick Johnson's last paragraph??
>>
>> >http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
>>
>> > John GallowayThe results are interesting, but way
>>>do the testing on a Std. Cirrus?
>> To be taken seriously put them on a modern ship and
>>test them. I
>> can't believe Dick did the testing on the Std. Cirrus
>>and did not at
>> least put them on his Ventus for some additional comparisons.
>
>

[John Galloway[_1_]]

Jim,

Of what you quoted (below) only the sentence 'Noone
picking up on Dick Johnson's last paragraph??' was
written by me. I was trying to attract attention to
Dick Johnson's hint that he had tested the Sinha deturbulators
- the progress of which I have followed with great
interest on your website.

John Galloway



At 23:02 31 December 2006, wrote:
>John,
>
>You use what you have.
>
>Jim Hendrix
>(The Johnson deturbulator flight tests were sponsored
>by Dallas Glider
>Association.)
>
>On Dec 26, 11:01 am, wrote:
>> John Galloway wrote:
>> > Noone picking up on Dick Johnson's last paragraph??
>>
>> >http://sinhatech.com/SinhaFCSD-Progress-12132006.asp
>>
>> > John GallowayThe results are interesting, but way
>>>do the testing on a Std. Cirrus?
>> To be taken seriously put them on a modern ship and
>>test them. I
>> can't believe Dick did the testing on the Std. Cirrus
>>and did not at
>> least put them on his Ventus for some additional comparisons.
>
>

[Ian]

John Galloway wrote:

> I was trying to attract attention to
> Dick Johnson's hint that he had tested the Sinha deturbulators
> - the progress of which I have followed with great
> interest on your website.

I have been intrigued by reports here which suggest that Dick Johnson
can take a glider which has been extensively developed and tested by
manufacturers (and, in some cases, Akafliegs or Idaflieg), shift the
turbulators by a couple of inches and report huge performance
increases.

Are his results reproduceable? Have they been independently verified?

Ian

[ContestID67]

I wish it were so. While most loggers can handle a momentary power
loss, not all can. I spoke at the last convention on this and related
avionics wiring issues. I contacted each manufacturer and as of Feb,
2006, I compiled the information below. I need to add the EW
MicroRecorder. I will be speaking on Saturday at the Memphis
convention if you are interested in more details.

2:00PM 3:00PM John DeRosa
Understanding Soaring Recorders and Computers
Convention Center Ballroom C

3:15PM 4:15PM John DeRosa
Aviation Electrical And Electronic Wiring Basics
Convention Center Ballroom C

- John DeRosa "67R"
======================
Cambridge
During a power Interruption, will IGC file be maintained?: Yes
How long of a power interruption can be survived?: 2 hours with aux
battery, otherwise <no response>
Start new log file?: 5 mins before starting new log file
Require secondary power source?: CAA-117 auxillary battery
Other information maintained?: Yes
Minimum operational voltage?: 8vdc is guaranteed but 6vdc is possible

Garrecht Volkslogger
During a power Interruption, will IGC file be maintained?: No, new file
How long of a power interruption can be survived?: 0.1 sec
Start new log file?: Yes
Require secondary power source?: Yes
Other information maintained?: Yes
Minimum operational voltage?: 7vdc

LX Navigation
During a power Interruption, will IGC file be maintained?: Yes
How long of a power interruption can be survived?: Approximately 1 min
Start new log file?: 1 min before starting new log file.
Require secondary power source?: No
Other information maintained?: Yes
Minimum operational voltage?: 8vdc

New Techologies
During a power Interruption, will IGC file be maintained?: Yes
How long of a power interruption can be survived?: few seconds
Start new log file?: 5 mins before starting new log file
Require secondary power source?: No
Other information maintained?: Yes
Minimum operational voltage?: 8.9vdc

Borgelt
During a power Interruption, will IGC file be maintained?: Yes
How long of a power interruption can be survived?: hours to weeks
Start new log file?: <no response>
Require secondary power source?: Internal "super" capacitor
Other information maintained?: Yes
Minimum operational voltage?: 10.0vdc




Eric Greenwell wrote:
>
> I thought all loggers just started again after a momentary power loss,
> and continued the same flight file. It sounds like yours isn't behaving
> properly, or are some brands a bit touchy?
>

[jcarlyle]

I use a Cambridge Model 25 GPS. Can either Tim or John supply power
interruption data for this "legacy" model data logger? Thanks!

-John

Tim Newport-Peace wrote:
> ContestID67 > writes
> >Cambridge
> >During a power Interruption, will IGC file be maintained?: Yes
> >How long of a power interruption can be survived?: 2 hours with aux
> >battery, otherwise <no response>
> >Start new log file?: 5 mins before starting new log file
> >Require secondary power source?: CAA-117 auxillary battery
> >Other information maintained?: Yes
> >Minimum operational voltage?: 8vdc is guaranteed but 6vdc is possible
> >
> John, that is specific to the 302. The answers are somewhat different
> for the legacy models.

[5Z]

On Jan 1, 5:28 pm, "ContestID67" > wrote:
> Garrecht Volkslogger
> During a power Interruption, will IGC file be maintained?: No, new file
> How long of a power interruption can be survived?: 0.1 sec
> Start new log file?: Yes
> Require secondary power source?: Yes
> Other information maintained?: Yes
> Minimum operational voltage?: 7vdc

I have heard stories that the Volkslogger will also create a new
declaration on power up. That is, it sets the timestamp of the
declaration that is currently stored to be the time of power on. Any
idea this happens? Though, since one is already splicing together two
logs, the declaration of the previous log should be good enough.

The CAI 302, on the other hand, will not update the declaration (with
the timestamp of when it was made) until it starts a new log. This is
after about 5 minutes of "inactivity". I sent a concern to CAI a while
ago about this, as there could be a situation where a pilot will decide
to make a new declaration during a quick relight. If no OO is
available to do a paper declaration, then only the electronic one can
be used - and it's possible it won't take. (Consider a self-launcher
at an unattended airport).

....No matter how had one thinks during the design, the application will
always be different...
-Tom

[Tom Gardner[_1_]]

T o d d P a t t i s t > wrote in
:

> Marc Ramsey > wrote:
>
>>The 302 has an internal capacitor across the power supply lines, the
>>Volkslogger does not. Volkslogger owners can solve this problem by
>>adding an external capacitor, as is suggested in the manual...
>
> IIRC, the Volkslogger recommended capacitor size was 22,000
> microfarads. That's a fairly large cap (physically and
> electrically), and it holds the VL on for only a second or
> so. It's enough to switch batteries, but don't delay. It
> also can cause problems on initial power-on when it first
> charges up if your fuse is not large enough. The inrush
> current is pretty high.

The inrush current issue can probably be solved by a circuit thus:


-------batteries---------------------------------logger---
| -ve and +ve | |
| switches | |
| and fuse ------------- |
| | | |
| ---- _ |
| /\ | | |
| Diode / \ | | Resistor |
| ---- |_| R |
| | | |
| ------------- |
| | |
| Capacitor --- +ve |
| 22mF --- -ve |
| | |
----------------------------------------------------------


When the switch is first closed the voltage across the capacitor
is zero and the diode is reverse biassed. Hence there is negligible
current through the diode and current flow into the capacitor
is limited to a peak of V/R amps.

After the capacitor is fully charged and the switch is opened,
current will flow through the forward biassed diode into the
logger with a voltage drop of ~0.6V (silicon diode) or ~0.3V
(schottkydiode).

Choose a diode with:
- reverse voltage greater than the battery voltage
- forward current greater than the peak logger current

Choose the resistor to limit the inrush peak current flow.

[Andy[_1_]]

Tom Gardner wrote:
> Choose a diode....

It's hard to read your schematic but it looks as though there is
nothing stopping the capacitor trying to power everything connected to
the same bus. Don't you need another blocking diode so the cap only
feeds the logger?

Andy

[Tom Gardner]

Andy wrote:
> Tom Gardner wrote:
> > Choose a diode....
>
> It's hard to read your schematic

Sorry about the ASCII schematic; it looks less bad when used with a
fixed-width font.

> but it looks as though there is
> nothing stopping the capacitor trying to power everything connected to
> the same bus.

That's correct. The schematic is sufficient only to show how how to
limit the inrush current.

> Don't you need another blocking diode so the cap only
> feeds the logger?

If that's the case then another (forward biased) diode would be
required between the battery +ve and the rest of the circuit in my
schematic.

[Peter[_4_]]

test
"Ian" > wrote in message
...
> On Tue, 26 Dec 2006 01:39:44 +0000, Steve Paavola wrote:
>
>> Gary Emerson wrote:
>
>>> wrote:
>>> Better yet is to use diodes so that both batteries will always be "on"
>>> in parallel and you're always pulling from the best battery with no
>>> fiddling required from the pilot. Relatively low voltage drop diodes
>>> are available with 18 Amp forward capacity.
>
>> If both batteries are on-line all the time, how do you know when one is
>> getting weak and needs to be replaced? Or do you replace both batteries
>> when voltage is marginal at the end of a flight?
>
> I used two small diodes to provide a "fail safe" supply to the
> Volkslogger, but the radio, vario, transponder etc get theirs via a 2 way
> toggle switch.
>
> Then when one battery dies in flight, I will notice and switch to the next
> one manually. But in the meantime the logger always draws current from the
> highest voltage battery and hence no interruption to the trace.
>
> The diodes are equivalents of IN 5817 "Shottky rectifying diodes". They
> are cheap and tiny. At the low currents drawn by the logger, the forward
> voltage drop is very small (less than 0.2V). No cooling is required. I
> soldered them directly in line with the wires from the fuse holder to the
> toggle switch, without a circuit board.
>
> I test the voltage on each battery during my pre-flight by setting the
> Volkslogger on its battery voltage function and disconnecting the
> batteries one at a time. (If the electric vario had a battery voltage
> function, I could switch it between the batteries and measure their
> voltage in flight.)
>
> The weak link in this setup is the toggle switch which has to be sized to
> handle a significant DC current.
>
> (The u/c warning buzzer is now also running off a 2 diode "fail safe"
> supply - but there is another story behind that ...).
>
>
> Regards
>
>
> Ian
>
>