Multiple Battery Setup

[JohnDeRosa]

This came from a separate thread "Typo in Battery Article in Soaring"

On Feb 2, 10:11 am, Karl Kunz > wrote:
> John, also enjoyed your article and will try your technique on a couple of batteries I am unsure of. Also, since we have an EE on the line I wanted to ask about battery setups. My partner and I have installed some new toys in our ASW20 (transponder, etc) and are wondering what is the best way add more power. We are currently running a single 12v 9amp battery. Would it be better to add another 9amp battery or to go to a single higher capacity battery. If using two batteries, what is the best way to tie them together.
>
> -karl

I suggest multiple batteries for a couple of reasons;

Redundancy - you can have a failure either in the air or on the ground
so with two batteries you have a spare.
Expense - I replace one of my batteries (I own 4 and fly with 2) every
year so over the course of four years I replace them all (the older
units are given to the club). While two 9ah batteries are more
expensive than a single 12ah battery, my yearly replacement cost is
less of a single time bite to the budget.
Size - You are probably set up for the 9ah size and a larger 12ah may
not fit. However, someone mentioned a 12ah to me that has the same
footprint as the 9ah only taller. Anyone seen this?
Weight - Is 2x9ah heavier than 1x12ah? Is that important? Hmmmm.
Power - 2x9ah has more energy capability than 1x12ah

Now, how to connect them? What I recomment is three runs of 14-16
gauge Tefzel wire between the batteries and the panel. This gauge is
overkill but I don't want any voltage drop with a smaller gauge. 3
runs = a common ground, battery 1 and battery 2. I use red (battery)
and black (ground) heat shrink to mark each run. I use PowerPole
connectors - very robust and secure.

At the panel I use three switches to run the batteries in parallel.
Battery 1 on/off, battery 2 on/off and then the output of both to a
master switch and then to the avionics. The thinking of separate
battery switches is that you can disconnect a "bad" battery. I always
have all three switches turned on during flight - the need to be able
to turn off a bad battery hasn't arisen for me and I am unsure how I
would even know (everything dies? smoke?). I do, however, have a
voltmeter, so I turn on/off each battery to see how they are doing (on
the ground typically).

Some people wonder that with both batteries connected to one another
in parallel, is there an issue with one battery charging the other?
Certainly cross charging happens (no two batteries are identical) but
unless one battery is significantly discharged from another, this
cross charging would be slight. I always swap out both batteries
right off the chargers at the same time to minimize this. Some
solutions suggest installing diodes in series to prevent this cross
charging but diodes "steal" 0.5v-0.8v of your voltage and every volt
counts in a glider. So I don't use diodes. Does anyone else?

Finally - ABSOLUTELY CRITICAL - install a fuse on each battery right
at the terminals. Not a breaker, a fuse. Fuses are faster than
breakers. This fuse is more important than fuses/breakers in the
panel.

My $0.02. Let me know how your testing turns out.

- John DeRosa
http://aviation.derosaweb.net

[Karl Kunz]

John, you addressed all the issues we where concerned about. Thanks for some great info.

-karl

[rk]

On 3 helmi, 18:10, JohnDeRosa > wrote:

> At the panel I use three switches to run the batteries in parallel.
> Battery 1 on/off, battery 2 on/off and then the output of both to a
> master switch and then to the avionics. *The thinking of separate
> battery switches is that you can disconnect a "bad" battery. *I always
> have all three switches turned on during flight - the need to be able
> to turn off a bad battery hasn't arisen for me and I am unsure how I
> would even know (everything dies? *smoke?).

You would know that by total power loss of all your batteries. You
have essentially parallel connection with all your batteries during
flight. When one fails, it drains your good batteries empty. When your
radio or computer starts blinking it's too late. Best option is to use
simple selector switch to choose one battery at time, and keep other
batteries disconnected.

rk

[kirk.stant]

On Feb 5, 7:43*am, rk > wrote:
> On 3 helmi, 18:10, JohnDeRosa > wrote:
>
> > At the panel I use three switches to run the batteries in parallel.
> > Battery 1 on/off, battery 2 on/off and then the output of both to a
> > master switch and then to the avionics. *The thinking of separate
> > battery switches is that you can disconnect a "bad" battery. *I always
> > have all three switches turned on during flight - the need to be able
> > to turn off a bad battery hasn't arisen for me and I am unsure how I
> > would even know (everything dies? *smoke?).
>
> You would know that by total power loss of all your batteries. You
> have essentially parallel connection with all your batteries during
> flight. When one fails, it drains your good batteries empty. When your
> radio or computer starts blinking it's too late. Best option is to use
> simple selector switch to choose one battery at time, and keep other
> batteries disconnected.
>
> rk

I've been using a somewhat different approach. Two batteries, each
powering half the avionics. So batt 1 has the radio and nav computer
bus; batt 2 has the logger/PDA and backup vario bus. Instrument
"busses" hooked up via individual 3 position switches so that either
buss can be powered by either battery or disconnected. Normally, run
the batts/busses independent, but have had occasions when one batt
went low early, and just switched the bus it was on to the other
battery for all instruments for rest of flight.

I also use the built-in voltmeters in various instruments (AR-4201,
SN10) to monitor the health of the batteries during flight.

Seems to work OK for the past 12 years...

Kirk
66

[John Godfrey (QT)[_2_]]

On Feb 3, 8:10*am, JohnDeRosa > wrote:
> This came from a separate thread "Typo in Battery Article in Soaring"
>
> On Feb 2, 10:11 am, Karl Kunz > wrote:
>
> > John, also enjoyed your article and will try your technique on a couple of batteries I am unsure of. *Also, since we have an EE on the line I wanted to ask about battery setups. My partner and I have installed some new toys in our ASW20 (transponder, etc) and are wondering what is the best way add more power. We are currently running a single 12v 9amp battery. Would it be better to add another 9amp battery or to go to a single higher capacity battery. If using two batteries, what is the best way to tie them together.
>
> > -karl
>
> I suggest multiple batteries for a couple of reasons;
>
> Redundancy - you can have a failure either in the air or on the ground
> so with two batteries you have a spare.
> Expense - I replace one of my batteries (I own 4 and fly with 2) every
> year so over the course of four years I replace them all (the older
> units are given to the club). *While two 9ah batteries are more
> expensive than a single 12ah battery, my yearly replacement cost is
> less of a single time bite to the budget.
> Size - You are probably set up for the 9ah size and a larger 12ah may
> not fit. *However, someone mentioned a 12ah to me that has the same
> footprint as the 9ah only taller. *Anyone seen this?
> Weight - Is 2x9ah heavier than 1x12ah? *Is that important? *Hmmmm.
> Power - 2x9ah has more energy capability than 1x12ah
>
> Now, how to connect them? * What I recomment is three runs of 14-16
> gauge Tefzel wire between the batteries and the panel. *This gauge is
> overkill but I don't want any voltage drop with a smaller gauge. *3
> runs = a common ground, battery 1 and battery 2. *I use red (battery)
> and black (ground) heat shrink to mark each run. *I use PowerPole
> connectors - very robust and secure.
>
> At the panel I use three switches to run the batteries in parallel.
> Battery 1 on/off, battery 2 on/off and then the output of both to a
> master switch and then to the avionics. *The thinking of separate
> battery switches is that you can disconnect a "bad" battery. *I always
> have all three switches turned on during flight - the need to be able
> to turn off a bad battery hasn't arisen for me and I am unsure how I
> would even know (everything dies? *smoke?). *I do, however, have a
> voltmeter, so I turn on/off each battery to see how they are doing (on
> the ground typically).
>
> Some people wonder that with both batteries connected to one another
> in parallel, is there an issue with one battery charging the other?
> Certainly cross charging happens (no two batteries are identical) but
> unless one battery is significantly discharged from another, this
> cross charging would be slight. *I always swap out both batteries
> right off the chargers at the same time to minimize this. *Some
> solutions suggest installing diodes in series to prevent this cross
> charging but diodes "steal" 0.5v-0.8v of your voltage and every volt
> counts in a glider. *So I don't use diodes. *Does anyone else?
>
> Finally - ABSOLUTELY CRITICAL - install a fuse on each battery right
> at the terminals. *Not a breaker, a fuse. *Fuses are faster than
> breakers. *This fuse is more important than fuses/breakers in the
> panel.
>
> My $0.02. *Let me know how your testing turns out.
>
> - John DeRosahttp://aviation.derosaweb.net

I've been using very low loss Schottky diodes (95SQ015 - Vf stays at
about 0.2v @ 1A last I checked) to run all my batteries (sometimes 4)
in parallel. Increased AH capacity from parallel operation offsets Vf
and provides isolation of a misbehaving battery. Absolutely fuse at
the battery terminals with fuse sized appropriately for the size/
length of conductor. Comments welcome.
QT

[Bart[_4_]]

On Feb 3, 8:10*am, JohnDeRosa > wrote:
> right off the chargers at the same time to minimize this. *Some
> solutions suggest installing diodes in series to prevent this cross
> charging but diodes "steal" 0.5v-0.8v of your voltage and every volt
> counts in a glider.

Ideal diode, such as LTC4358, would eliminate the voltage drop at the
cost of higher complexity.

Bart

[JohnDeRosa]

> I've been using very low loss Schottky diodes (95SQ015 - Vf stays at
> about 0.2v @ 1A last I checked)
> QT

> Ideal diode, such as LTC4358, would eliminate the voltage drop at the
> cost of higher complexity.
>
> Bart

First, a teaching moment for those non-techies about using diodes to
isolate two battery setups so that a bad battery won't suck the life
out of the good battery, see
http://aviation.derosaweb.net/presentations/Soaring_Electronics_Made_Easier_Wiring_2007.pdf
(page 21-25) for some explanations.

While I know about Schottky diodes and their low forward voltage drop
(0.2v which seems like the best of the diode worlds) but I had not
heard of the Ideal Diode which seems custom made for our application
of two battery sources and if one dies the other takes over. Good to
5A. What's not to like? But what is the critical forward voltage
drop? I read;

"The internal MOSFET turns on and the amplifier tries to regulate the
voltage drop across the IN and OUT connections to 25mV. If the load
current causes more than 25mV of drop, the MOSFET is driven fully on
and the voltage drop is equal to RDS(ON) x ILOAD."

25mv? GREAT NEWS!
RDS(ON) x ILOAD = 20milli-ohm x 5A = 0.1 volt. Better than a
Schottky. WHOOP!
(BTW: the small m for milli instead of big M for mega tripped me
up)

But then in the Specs Table I read;

ÄVSD Source-Drain Regulation Voltage (VIN - VOUT) 1mA < IIN < 100mA
l 25 mV (Typ)
ÄVSD Body Diode Forward Voltage Drop IIN = 5A, MOSFET Off l 0.8 V
(Typ)

So aren't we back to a silicon diode like forward drop? OK, when the
MOSFET is ON then we are back to the 0.1 volt. Interesting.

Lousy SM packaging for our application though. Bart - How are you
mounting it? Pictures?

[Bart[_4_]]

On Feb 5, 8:47*pm, JohnDeRosa > wrote:
> But then in the Specs Table I read;
>
> * *ÄVSD Source-Drain Regulation Voltage (VIN - VOUT) 1mA < IIN < 100mA
> l 25 mV (Typ)
> * *ÄVSD Body Diode Forward Voltage Drop IIN = 5A, MOSFET Off l 0.8 V
> (Typ)
>
> So aren't we back to a silicon diode like forward drop? *OK, when the
> MOSFET is ON then we are back to the 0.1 volt. * Interesting.

The 0.8V voltage drop is for the "body diode" of the internal MOSFET:
http://en.wikipedia.org/wiki/Power_MOSFET#Body_diode
In other words, that's the drop you will get if the controller dies,
or if the input voltage drops below 9V.

> Lousy SM packaging for our application though. *Bart - How are you
> mounting it? *Pictures?

I have never used one in a glider. If I were to, I would put the two
chips on a small PCB and cover it with heatshrink. Something like
this: http://i00.i.aliimg.com/img/pb/905/834/400/400834905_364.jpg

Actually, if I find time, I can make a prototype within a week or two.
Then Karl can test it if he wants to :-)

Bart

[Karl Kunz]

I would certainly be willing to give it a try.

[Karl Kunz]

I would certainly be willing to give it a try. Would 5amps be adequate for this? Are these diodes fail operational, i.e. if it fails will I continue to get power from the effected battery.

[Dave Nadler]

You don't need to use an ideal diode part like LTC4358.
You can use a reverse-connected MOSFET as an ideal
diode for battery paralleling and/or reverse-polarity
protection. Here's an explanation:
http://www.geofex.com/article_folders/mosswitch/mosswitch.htm

In my never-ending quest to make glider-pilot-proof
equipment, I'm using FDC610PZ in a new project.
I've recently noticed this part featured in some
LTC appnotes so apparently others think this a
suitable part for this application.

Choosing MOSFETs, watch the body diode max current on
inrush current (not specified for all MOSFETs).

Remember to keep the smoke inside the chips,
Best Regards, Dave "YO electric"

[Dave Nadler]

PS: This configuration is not an ideal diode;
does not prevent crossfeed as an ideal would...

[brianDG303[_2_]]

On Feb 6, 8:38*am, Dave Nadler > wrote:
> PS: This configuration is not an ideal diode;
> does not prevent crossfeed as an ideal would...

Question, if you want to keep it pretty simple and just have two
batteries, for example a big 12 volt 15AH like a 12150 and a smaller
back-up like a 4AH Li-Ion. Then this is wired to an A B switch and
you only use the Li-Ion for emergencies. OK, finally the question.
When you switch from A to B doesn't the computer restart? I have
heard of a capacitor you can connect somehow to provide enough voltage
to keep everything from dropping off like, but now we aren't keeping
it simple anymore.

Cheers,
Brian

[Dave Nadler]

On Monday, February 6, 2012 1:25:06 PM UTC-5, brianDG303 wrote:
> When you switch from A to B doesn't the computer restart?
If you have an ILEC SN10 this is not a problem
(if the power cycles off and on, no information is lost).

> I have
> heard of a capacitor you can connect somehow to provide enough voltage
> to keep everything from dropping off like, but now we aren't keeping
> it simple anymore.

And you will get big inrush current when you connect the
battery to charge the capacitor, and maybe you will blow
fuses and/or damage our switch...

Hope that helps,
Best Regards, Dave "YO electric"

[jcarlyle]

I vote for simplicity - a fuse at each battery, a panel switch for
each battery, a fuse for each instrument, a switch for each
instrument, and a voltmeter (discrete or in an instrument). If its a
long flight for a badge or record, use a separate flight data logger
powered from an independent battery, and turn off instruments you
don't need. No circuit breakers, no diodes, no FETs - save that energy
for the avionics.

Fly with one battery until its voltage goes below 11.0, then switch to
the other battery. Switch the battery you fly with first the beginning
of next flight. You'll then know the performance ability of each
battery during the season, because you'll know how long it supplied
your exact flight needs, at what temperature, at most one flight ago.
And of course, charge the overnight batteries after the flight.

Automation is fine, but battery management is so simple why waste
electrical energy? I bet there isn't a glider pilot out there who
doesn't look at his battery voltage at least several times during each
flight, and who doesn't understand switches...

-John

[Craig[_2_]]

On Feb 6, 11:10*am, jcarlyle > wrote:
> I vote for simplicity - a fuse at each battery, a panel switch for
> each battery, a fuse for each instrument, a switch for each
> instrument, and a voltmeter (discrete or in an instrument). If its a
> long flight for a badge or record, use a separate flight data logger
> powered from an independent battery, and turn off instruments you
> don't need. No circuit breakers, no diodes, no FETs - save that energy
> for the avionics.
>
> Fly with one battery until its voltage goes below 11.0, then switch to
> the other battery. Switch the battery you fly with first the beginning
> of next flight. You'll then know the performance ability of each
> battery during the season, because you'll know how long it supplied
> your exact flight needs, at what temperature, at most one flight ago.
> And of course, charge the overnight batteries after the flight.
>
> Automation is fine, but battery management is so simple why waste
> electrical energy? I bet there isn't a glider pilot out there who
> doesn't look at his battery voltage at least several times during each
> flight, and who doesn't understand switches...
>
> -John

I agree John. One switch for each battery. During switch over to the
stronger battery, both switches are "on" for a brief moment. No loss
of power to the flight recorder and no loss of capacity.

Cheers,
Craig

[Herbert kilian]

On Feb 6, 1:10*pm, jcarlyle > wrote:
> I vote for simplicity - a fuse at each battery, a panel switch for
> each battery, a fuse for each instrument, a switch for each
> instrument, and a voltmeter (discrete or in an instrument). If its a
> long flight for a badge or record, use a separate flight data logger
> powered from an independent battery, and turn off instruments you
> don't need. No circuit breakers, no diodes, no FETs - save that energy
> for the avionics.
>
> Fly with one battery until its voltage goes below 11.0, then switch to
> the other battery. Switch the battery you fly with first the beginning
> of next flight. You'll then know the performance ability of each
> battery during the season, because you'll know how long it supplied
> your exact flight needs, at what temperature, at most one flight ago.
> And of course, charge the overnight batteries after the flight.
>
> Automation is fine, but battery management is so simple why waste
> electrical energy? I bet there isn't a glider pilot out there who
> doesn't look at his battery voltage at least several times during each
> flight, and who doesn't understand switches...
>
> -John

John Carlyle is right and it pains me to say this but the whole
parallel battery business is nonsense. In the first place, select
batteries that last by themselves over a long day of flying. Have two
of those installed and follow John C's advice above. Except, you
don't have to switch since you don't run your primary battery down.
In fact, I only charge my battery #1 before each flight and top off
the reserve every couple of weeks (all NiMH batteries). I carry a
third large battery that only drives my transponder.

[Andy[_1_]]

On Feb 6, 12:10*pm, jcarlyle > wrote:
> I bet there isn't a glider pilot out there who
> doesn't look at his battery voltage at least several times during each
> flight, and who doesn't understand switches...


I'll take your bet on understanding switches. How many glider pilots
do you think understand the difference between the AC and DC rating of
a switch and select one with an approprate DC rating? How many know
why the ratings are very different? How many glider pilots know the
inrush current of their installed avionics? How many know if the the
load has a significant inductive component?

It's only a switch after all.

Andy

[jcarlyle]

Andy wrote:
> On Feb 6, 12:10 pm, jcarlyle > wrote:
> > I bet there isn't a glider pilot out there who
> > doesn't look at his battery voltage at least several times during each
> > flight, and who doesn't understand switches...
>
>
> I'll take your bet on understanding switches. How many glider pilots
> do you think understand the difference between the AC and DC rating of
> a switch and select one with an approprate DC rating? How many know
> why the ratings are very different? How many glider pilots know the
> inrush current of their installed avionics? How many know if the the
> load has a significant inductive component?
>
> It's only a switch after all.
>
> Andy

Andy,

Mea culpa - in my attempt to tread a fine line between brevity and
excruciating detail I omitted the phrase "how to use" between the
words "understand" and "switches" in the last sentence of my post. I
also omitted giving precise instructions on how to switch over from
the supplying battery to the unused battery, and I didn't explain the
need to size the batteries to avionics current draw, expected
temperatures, battery age, etc.

Others kindly added some of the information I omitted regarding the
last two points, thus furthering the conversation. It would have been
nice if you'd done the same, rather than attempt to pick a fight. But,
I guess you're not one of those people who share.

I'm not going to provide answers the questions you raised, even though
I could. I'll just say that for those who are interested in this
topic, if you don't understand the questions Andy raised, then don't
attempt to select components and wire your glider yourself. Rather,
use this thread as a rough guide, get professional advice (Radio Shack
doesn't count, spend a few bucks at an avionics firm), and avoid the
horror of fire in the air.

-John

[Bart[_4_]]

On Feb 6, 8:23*am, Dave Nadler > wrote:
> You don't need to use an ideal diode part like LTC4358.
> You can use a reverse-connected MOSFET as an ideal
> diode for battery paralleling and/or reverse-polarity
> protection. Here's an explanation:http://www.geofex.com/article_folders/mosswitch/mosswitch.htm

I get the "reverse polarity" part. But how is it supposed to help with
connecting batteries in parallel? The weaker battery will still pull
the strong one down - at least SPICE says so.

On an unrelated note, I enjoyed your presentation in Reno.

Bart

[Peter Purdie[_3_]]

The 'split services' approach is much better than running
everything off 1 battery, and then switching to another. The
standard 7AH gel cell is rated at the 20hour discharge current -
about 300mA. Any higher current and the total energy available
decreases. (and that 7AH is a new battery at room temperature,
not a 2 year old one freezing at 18,000ft).

If you have room, paralleling batteries works well, so long as
you have another independent battery to run essential services
if the main one drops below 11V (for me vario/flight director
only, and radio when 5 minutes out on final glide).

At 16:27 05 February 2012, kirk.stant wrote:
>On Feb 5, 7:43=A0am, rk wrote:
>> On 3 helmi, 18:10, JohnDeRosa wrote:
>>
>> > At the panel I use three switches to run the batteries in
parallel.
>> > Battery 1 on/off, battery 2 on/off and then the output of
both to a
>> > master switch and then to the avionics. =A0The thinking of
separate
>> > battery switches is that you can disconnect a "bad"
battery. =A0I
>alway=
>s
>> > have all three switches turned on during flight - the need
to be able
>> > to turn off a bad battery hasn't arisen for me and I am
unsure how I
>> > would even know (everything dies? =A0smoke?).
>>
>> You would know that by total power loss of all your batteries.
You
>> have essentially parallel connection with all your batteries
during
>> flight. When one fails, it drains your good batteries empty.
When your
>> radio or computer starts blinking it's too late. Best option is
to use
>> simple selector switch to choose one battery at time, and
keep other
>> batteries disconnected.
>>
>> rk
>
>I've been using a somewhat different approach. Two batteries,
each
>powering half the avionics. So batt 1 has the radio and nav
computer
>bus; batt 2 has the logger/PDA and backup vario bus.
Instrument
>"busses" hooked up via individual 3 position switches so that
either
>buss can be powered by either battery or disconnected.
Normally, run
>the batts/busses independent, but have had occasions when
one batt
>went low early, and just switched the bus it was on to the other
>battery for all instruments for rest of flight.
>
>I also use the built-in voltmeters in various instruments (AR-
4201,
>SN10) to monitor the health of the batteries during flight.
>
>Seems to work OK for the past 12 years...
>
>Kirk
>66
>

[rk]

On 7 helmi, 09:45, Peter Purdie > wrote:
> * The 'split services' approach is much better than running
> everything off 1 battery, and then switching to another. *The
> standard 7AH gel cell is rated at the 20hour discharge current -
> about 300mA. *Any higher current and the total energy available
> decreases. (and that 7AH is a new battery at room temperature,
> not a 2 year old one freezing at 18,000ft).
>
> If you have room, paralleling batteries works well, so long as
> you have another independent battery to run essential services
> if the main one drops below 11V (for me vario/flight director
> only, and radio when 5 minutes out on final glide).

I see the point of using parallel batteries to achieve lower current
draw per battery, though you have basically no way to know or control
the current draw from each battery.

The main benefit of using one battery at time is that you allways know
exactly how good your batteries are. I use two batteries, usually one
battery is just enough for day's flying, if it's cold I might have to
use second one for an hour or two. After flight I charge it overnight
and next day use the second battery as my primary. This way cycles are
evenly split between batteries and running them empty on regular basis
gives me pretty good idea how healthy they are (bad batteries develop
symptoms long before they actual fail). Only failure I have had during
flight was parallel connected batteries with one of them failing and
draining the other one empty in two minutes. After that I have flown
no 5 years with three way selector switch, without a single glitch.
This is the way they do electrical systems in Schempp, Schleicher etc.
No need to invent wheel again, IMO.

Of course running batteries empty might shorten their life a bit, but
replacement cost is next to nothing (for 7 Ah lead gel). One more
thing, switching batteries doesn't power off my acionics. They have
some capacitors built into them too.

[Andy[_1_]]

On Feb 6, 3:45*pm, jcarlyle > wrote:

>
> Others kindly added some of the information I omitted regarding the
> last two points, thus furthering the conversation. It would have been
> nice if you'd done the same, rather than attempt to pick a fight. But,
> I guess you're not one of those people who share.
>

I never considered taking a bet to be the same as picking a fight.
Each to his own I suppose.

To further the conversation - When selecting a glider main battery
switch please ensure that the DC rating is appropriate for the current
being switched. Some switches may not even be marked with a DC
rating. Why does it matter? The AC rating relies on the fact that
any arc induced as the contacts are opened will be quenched as the
alternating current passes through zero. No such quenching can happen
in a DC circuit and the arcing may reduce contact life or even sustain
long enough for the switch to burn.

Andy

[Dave Nadler]

On Monday, February 6, 2012 11:10:18 PM UTC-5, Bart wrote:
> I get the "reverse polarity" part. But how is it supposed to help with
> connecting batteries in parallel? The weaker battery will still pull
> the strong one down - at least SPICE says so.

Right, as noted in the "PS" above.

> On an unrelated note, I enjoyed your presentation in Reno.

Thanks ! Which one ?

See ya, Dave "YO electric"

[Bart[_4_]]

On Feb 7, 5:41*am, Dave Nadler > wrote:
> > On an unrelated note, I enjoyed your presentation in Reno.
> Thanks ! Which one ?

Actually, both. But I was thinking of the "electric flight" one when I
made the comment above. Speaking of which - in Antares, is it possible
to use all those batteries to power avionics? I would imagine that
long after they are depleted as far as powered flight is concerned,
there should be enough juice for radios, varios, transponder etc.

Bart

[Mike the Strike]

On Feb 7, 8:32*pm, Bart > wrote:
> On Feb 7, 5:41*am, Dave Nadler > wrote:
>
> > > On an unrelated note, I enjoyed your presentation in Reno.
> > Thanks ! Which one ?
>
> Actually, both. But I was thinking of the "electric flight" one when I
> made the comment above. Speaking of which - in Antares, is it possible
> to use all those batteries to power avionics? I would imagine that
> long after they are depleted as far as powered flight is concerned,
> there should be enough juice for radios, varios, transponder etc.
>
> Bart

This is the route the Front Electric Sustainer guys have gone - using
the large high-voltage LiPo pack with a DC/DC converter with just a
small 12 V battery for stabilization. A neat solution.

Mike

[Dave Nadler]

On Tuesday, February 7, 2012 10:32:02 PM UTC-5, Bart wrote:
> > Thanks ! Which one ?
> Actually, both.

I guess you missed the third one ;-)

> ... Speaking of which - in Antares, is it possible
> to use all those batteries to power avionics? I would imagine that
> long after they are depleted as far as powered flight is concerned,
> there should be enough juice for radios, varios, transponder etc.

Antares has no separate battery for avionics,
just the big battery in the wings (which also
powers the hydraulic system).

See ya, Dave "YO electric"

[RAS56]

This came from a separate thread "Typo in Battery Article in Soaring"

My $0.02. Let me know how your testing turns out.

- John DeRosa
http://aviation.derosaweb.net


Hi John,

I enjoyed your article and just completed 2 test runs using the rig you detailed..I was mildly surprised to find 2 identical batteries with identical manufacture dates vary significantly on the results.

Battery #1 took 4:13 to run down to 11.5 volts, at about 5:45 it hit the "knee" at 10.5V described in the article and started dropping rapidly.

Battery #2 lasted almost an hour longer...5:10 to hit 11.5, then longer than 6:30 to get below 10.5V.

Both batteries were 12V 7.5 AH SLA.

Now I have a limited exposure to longer duration flights, heck I've not got my Silver duration yet, but I'm concluding from this test that, as long I stay off the XMIT button, I've got enough juice to keep electrons flowing as long as needed. My panel consists now of a Borgelt B-400 (soon to be Lx7) and an Oudie which I power off the ship. I've got a PowerFLARM brick on order and use a Lx Nano which I don't connect to the glider's electrical system. Hopefully, I have enough battery to power my expansion plans...your thoughts appreciated here.

A few questions? I've got an older Dittel radio (ship is an ASW 19b) that may be as old as the glider. The manual for the radio says it needs 13.5V to operate...obviously, it's getting nowhere near that. Last season, I had comm issues with other gliders or ATC facilities having trouble hearing my transmissions. Receive works fine for me. I was going to put the ship in a radio shop to test the transceiver, but now this whole electrical discussion has me wondering if the older radio is just needing more juice than a 12V battery can provide? Especially as I get 2, 3, 4 hours into a flight. Could that be a cause of the transmission difficulties? If so, do the newer radios work better on lower voltages?

Also, any anecdotal experience with battery manufacturers? I have a couple of "generic" SLA batteries that I picked up cheap...but now after my testing am wondering if brands like "Powersonic" or others might push my curves further to the right till hitting 11.5V...does price=quality in the battery world?

As to wiring, I jerked all the hardware/auto supply junk out and did the Tefzel wire as you suggested. Every component is fused, including the batteries. I decided to put in an A/B battery switch and a separate Master. Switching between batteries has never been a problem for the Oudie...probably b/c of its internal battery.

The one electrical failure I've had so far was not hardware related but human...I had flung the drinking tube to my Camelback back over my shoulder to get it out of the way one flight...when I retrieved it, it took some
tugging to get it back. I figured it had hung up on the parachute harness or seat back...Actually, it had snagged on the wiring leading to TQD connector on the battery. Tugging it (unknown to me at the time) disco'ed the TQD and killed everything. At the time I was 45 miles from home and my mechanical vario was inop...it would not have been fun for a newbie to struggle back home with no vario! Fortunately, flipping the A/B over to "B" got me onto #2 and home to a happy ending! The lesson I learned on this was...now I put a couple of winds of electrical tape around each of the TQD connections after assembly before securing them behind the seatback. Murphy struck, glad I had a backup!

Thanks again for the article, good off season project info!

Regards,

Rob S.
ZAP

[Bart[_4_]]

On Feb 8, 6:47*am, Dave Nadler > wrote:
> > > Thanks ! Which one ?
> > Actually, both.
> I guess you missed the third one ;-)

Electric flight and POWER Flarm. What was the third one?

B.

[JohnDeRosa]

On Feb 8, 10:33*pm, RAS56 > wrote:

> I enjoyed your article and just completed 2 test runs using the rig you
> detailed..

Glad you enjoyed the article, I've gotten lots of positive feedback.

>I was mildly surprised to find 2 identical batteries with
> identical manufacture dates vary significantly on the results.

The good news is that both batteries each lasted a "long" time. If
older batteries then you might put this down to one battery has been
used more often than the other as based on your recovery story you
don't run them in parallel.

> Hopefully, I have enough battery to power my
> expansion plans...your thoughts appreciated here.

I will evasively say, "time will tell". Obviously, adding more
devices to your bus is going to run down your batteries faster. How
long? Sorry too many variables. A FLARM transmitts and anything that
Transmitts (transceiver, transponder) is THE variable and can be
massive power hogs so keep those on a separate battery (my thinking is
changing in this regard) from the other stuff like GPS, PDA, vario and
recorder...those really important things for soaring pilots (which
don't transmit)! If you loose the "T" (transmit) battery, you can
still get home on the other "S" (soaring) battery. Think about
getting a bigger T battery next round.

> I've got an older Dittel radio (ship is an ASW 19b)
> that may be as old as the glider. The manual for the radio says it needs
> 13.5V to operate...Could that be a cause of the transmission
> difficulties? If so, do the newer radios work better on lower voltages?

Certainly old radios (meant for airplanes with generators) did want a
nice warm 13.5VDC. I have seen these frankenstein combinations of a
12V and 1.5V battery to get that much voltage. Newer radios like the
Microaire work down to 10.7VDC. Older radios are also more power
hungry so when you transmit the voltage might droop (nice to have a
voltmeter on board to test with). Have you always had transmit
problems or just recently? If always then voltage could be your
problem. Have someone drive to the other end of the runway and test
with a handheld (anything works when you are 5 feet away from each
other). As radios are expensive, send it in for a bench test before
replacing. I recommend http://www.erieaviation.com.

> does price=quality in the battery world?

You would think so wouldn't you. But I really don't know. Not
enough data points. Sorry.

> As to wiring, I jerked all the hardware/auto supply junk out and did the
> Tefzel wire as you suggested. Every component is fused, including the
> batteries.

Tefzel! Fuses! You are my hero! Send me before/after pictures.

> Thanks again for the article, good off season project info!

You are very welcome!

- John

[Dave Nadler]

On Thursday, February 9, 2012 5:37:29 PM UTC-5, JohnDeRosa wrote:
> ... A FLARM transmitts and anything that
> Transmitts (transceiver, transponder) is THE variable and can be
> massive power hogs...

Please, FLARM takes very little power !
For PowerFLARM, keep the backlight turned down to minimize draw...

Thanks,
Best Regards, Dave "YO electric"

[JohnDeRosa]

On Feb 9, 8:37*pm, Dave Nadler > wrote:
> On Thursday, February 9, 2012 5:37:29 PM UTC-5, JohnDeRosa wrote:
> > ... A FLARM transmitts and anything that
> > Transmitts (transceiver, transponder) is THE variable and can be
> > massive power hogs...
>
> Please, FLARM takes very little power !
> For PowerFLARM, keep the backlight turned down to minimize draw...
>
> Thanks,
> Best Regards, Dave "YO electric"

Please excuse anything demeaning to the FLARM. The only power
requirement specifications I have found are in the PowerFLARM manual
which says, "Supplied power must be 12 V DC nominal at 500mA". 0.5A
is nothing to sneeze at but is probably the instantaneous maximum.
Does someone have some real world power requirement information for
the various (US) FLARMS? I have not found an online FLARM or
PowerFLARM Brick manual (sources?). Thanks.

[cernauta]

On Thu, 9 Feb 2012 14:37:29 -0800 (PST), JohnDeRosa
> wrote:

>. A FLARM transmitts and anything that
>Transmitts (transceiver, transponder) is THE variable and can be
>massive power hogs so keep those on a separate battery

A Flarm transmits at only 50mW power. The power consumption is
negligible, always less than 100mA, and it includes a GPS engine
capable of NMEA communication.
A radio in receive-only mode, will use more power than a Flarm.

And, if I were low on battery, Flarm is still the latest "switch-off"
option, considering the benefits for safety.

aldo cernezzi
www.voloavela.it

[Martin Gregorie[_5_]]

On Thu, 09 Feb 2012 04:33:04 +0000, RAS56 wrote:

> I enjoyed your article and just completed 2 test runs using the rig you
> detailed..I was mildly surprised to find 2 identical batteries with
> identical manufacture dates vary significantly on the results.
>
> Battery #1 took 4:13 to run down to 11.5 volts, at about 5:45 it hit the
> "knee" at 10.5V described in the article and started dropping rapidly.
>
> Battery #2 lasted almost an hour longer...5:10 to hit 11.5, then longer
> than 6:30 to get below 10.5V.
>
> Both batteries were 12V 7.5 AH SLA.
>
I just did the same: bought a pair of Yuasa 12v 7Ah SLAs, call them D and
E, because A, B and C dropped off their charge curves when tested during
the week before last. A and B had also been bought together in 2008 and
had both been measured at a bit over 6500 mAh then, but both were under
4000 mAh this time.

I put them both the new batteries on my three phase mains charger to top
them off as soon as they arrived. E took over an hour longer to top off.
Then I measured them with a Pro Peak Prodigy II charger/cycler. E ran the
device while I measured D. Then both went back on the mains charger and
this time D ran the device while it measured E.

Results: D was measured at 7003 mAh and E at 7510 mAh

I was a little surprised at the difference since, with both batteries
being the same model there's every change they're from the same batch.

The Prodigy II isn't what you'd call a heavy duty discharger and self
limited itself to 0.4A despite me being optimistic and asking for a 0.7A
rate. IIRC it has a 5 watt discharge limit. I As this somewhat less
current than we'd expect to use during a flight and all batteries show
lower capacity the faster you discharge them and the colder they are. IOW
this over-estimated the in-flight capacity due to the lower current and
higher temperature during my test, but thats fine: I do the same tests at
about the same time of year and am only interested in the relative drop
in capacity from one year to the next.


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