Solar charging question

On 1/17/2011 12:42 PM, Ed wrote:
Again, thank you Eric for your thoughtful replies. I think I may have
found just what I need. I'll post the details in case someone else
might benefit.

If you go tohttp://www.powerstream.com/DC-input-chargers.htm and
click on the PST-BC1212-15DCDC Charger you can see this option.

It looks like a good choice for your situation. Did they say how much
current it drew from the source battery when it wasn't charging the
glider battery?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Jan 17, 1:32*pm, Eric Greenwell wrote:

It looks like a good choice for your situation. Did they say how much
current it drew from the source battery when it wasn't charging the
glider battery?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

I didn't ask, and it doesn't seem to be available on the website.
Since it's generating a constant float I imagine that it is not
inconsequential. I'll find out when it arrives. I'm not an electrical
engineer, but my guess is that the converter will shut down at some
low voltage like 11.9 v and drop the source battery out of the
picture. That's why I wonder if I need to keep the solar charger in
the mix. The question then becomes should I have the 5W solar panel in
parallel with the main aircraft battery to take over the topping of
the battery (output side of the converter), or should I try to keep
the source battery above the lower limit using the solar. The unit is
also flexible enough that if the source power is interrupted it will
figure out where things stand and pick up the charge at the right
place. There's an interesting charge state digram on the website that
shows this. I may need to think about a timer that only allows the
source battery to be available for a certain amount each day so that
it lasts longer.

"Eric Greenwell" wrote

I don't know the Grob 103 details, but most self-launchers do have an
alternator. If not, finding a way to mount an alternator in what is
usually a very cramped location, and making it sturdy enough to keep the
two-stroke engine from vibrating it to pieces, and integrating it into the
electrical system would be a major project.

The recharge current is limited by the battery size, and the 28 Ah battery
means a limit around 5 or 6 amps. Since the current drops off as the
battery charges, replacing 6 Ah means an engine run of at least 1.5 hours.
Nobody wants to put an hour and a half on their engine to top off a
battery - the noise alone is enough to seek other solutions!

I see your points, but still am not sure that some increased charging system
could not provide a good answer.

Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. One of the small
alternators from something like a small tractor could be mounted, and a
larger battery installed, probably a wet cell, or other type that could
handle more charging current. If not able to fill the larger battery in a
20 minute run to altitude, it would be darn close, and the larger capacity
would have more than enough to run your electronics all day, even at only
1/2 or 2/3rds capacity. I agree about not running an engine a long time,
just to charge, but if you ran the battery down one day on a marathon
flight, a little run would keep your electrons zinging around the
microcircuits!
--
Jim in NC

On 1/17/2011 3:30 PM, Ed wrote:
On Jan 17, 1:32 pm, Eric wrote:

It looks like a good choice for your situation. Did they say how much
current it drew from the source battery when it wasn't charging the
glider battery?


I didn't ask, and it doesn't seem to be available on the website.
Since it's generating a constant float I imagine that it is not
inconsequential. I'll find out when it arrives. I'm not an electrical
engineer, but my guess is that the converter will shut down at some
low voltage like 11.9 v and drop the source battery out of the
picture. That's why I wonder if I need to keep the solar charger in
the mix. The question then becomes should I have the 5W solar panel in
parallel with the main aircraft battery to take over the topping of
the battery (output side of the converter), or should I try to keep
the source battery above the lower limit using the solar. The unit is
also flexible enough that if the source power is interrupted it will
figure out where things stand and pick up the charge at the right
place. There's an interesting charge state digram on the website that
shows this. I may need to think about a timer that only allows the
source battery to be available for a certain amount each day so that
it lasts longer.

The self-discharge rate on the typical SLA is low enough, you could
forget about more charging for a month, once it was fully charged.
Unless, of course, your temperatures average over 90-100 F. But,
putting that little 0.3A panel on would keep it topped off.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Jan 18, 3:17*pm, "Morgans" wrote:
Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. *One of the small
alternators from something like a small tractor

After suffering for years with motorcycles that could barely light a
decent headlight, it was fantastic to get my current bike, a 1995 BMW
R1100.

It has an 800W alternator. That's a lot of amps at 12V!

I don't know how many of those amps it can put into the battery. It
has power outlets for both rider and passenger intended to plug
electrically heated clothing in to for winter riding. (not necessary
in NZ, so I've never investigated properly)

On Jan 17, 6:17*pm, "Morgans" wrote:
"Eric Greenwell" wrote



I don't know the Grob 103 details, but most self-launchers do have an
alternator. If not, finding a way to mount an alternator in what is
usually a very cramped location, and making it sturdy enough to keep the
two-stroke engine from vibrating it to pieces, and integrating it into the
electrical system would be a major project.

The recharge current is limited by the battery size, and the 28 Ah battery
means a limit around 5 or 6 amps. Since the current drops off as the
battery charges, replacing 6 Ah means an engine run of at least 1.5 hours.
Nobody wants to put an hour and a half on their engine to top off a
battery - the noise alone is enough to seek other solutions!

I see your points, but still am not sure that some increased charging system
could not provide a good answer.

Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. *One of the small
alternators from something like a small tractor could be mounted, and a
larger battery installed, probably a wet cell, or other type that could
handle more charging current. *If not able to fill the larger battery in a
20 minute run to altitude, it would be darn close, and the larger capacity
would have more than enough to run your electronics all day, even at only
1/2 or 2/3rds capacity. *I agree about not running an engine a long time,
just to charge, but if you ran the battery down one day on a marathon
flight, a little run would keep your electrons zinging around the
microcircuits!
--
Jim in NC

Last time I checked we were talking about an aircraft and associated
weight and balance, saftey and regulatory concerns. Adding a larger
generator and a flooded battery is not something more practical people
would even consider to solve a problem that can practically be solved
with a larger solar panel or a DC-DC charger.

Darryl

On Jan 17, 3:30*pm, Ed wrote:
On Jan 17, 1:32*pm, Eric Greenwell wrote:

It looks like a good choice for your situation. Did they say how much
current it drew from the source battery when it wasn't charging the
glider battery?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

I didn't ask, and it doesn't seem to be available on the website.
Since it's generating a constant float I imagine that it is not
inconsequential. I'll find out when it arrives. I'm not an electrical
engineer, but my guess is that the converter will shut down at some
low voltage like 11.9 v and drop the source battery out of the
picture. That's why I wonder if I need to keep the solar charger in
the mix. The question then becomes should I have the 5W solar panel in
parallel with the main aircraft battery to take over the topping of
the battery (output side of the converter), or should I try to keep
the source battery above the lower limit using the solar. The unit is
also flexible enough that if the source power is interrupted it will
figure out where things stand and pick up the charge at the right
place. There's an interesting charge state digram on the website that
shows this. I may need to think about a timer that only allows the
source battery to be available for a certain amount each day so that
it lasts longer.

These devices are really designed to charge a 12V wheelchair from a
car electrical system - typically including while the car is running
and as such often have a low voltage disconnect (LVD) to prevent the
car battery becoming so flat that it can't crank the starter to start
the car again and that may mean you can't get a full charge out of the
"donor" battery. It all depends on the LVD set point and I have no
idea what Powerstream do in this case - although they talk about a 10V
low voltage alarm, it that is also the LVD set point then that seems
great for this application. I've seen some attempts to do this with
similar systems and undersizing of the donor battery has caused some
problems even with a low LVD set pount. I'd personally be thinking of
a larger VRLA battery (2-3X the glider battery capacity) - maybe on a
small hand cart.

I would not run the small solar panel in parallel with this charger or
on the donor battery. Just let the the charger just see the VRLA
battery it is charging. Such a small solar panel is pretty useless as
you have already found out, may interfere with the other charger if
used on the recipient battery (depending if it has isolation diodes
etc.) and is just overall more unecessary complexity to deal with. As
Eric points out self discharge of a VRLA battery is usually extremely
low.

Darryl

On Jan 18, 9:06*am, Darryl Ramm wrote:
On Jan 17, 3:30*pm, Ed wrote:





On Jan 17, 1:32*pm, Eric Greenwell wrote:

It looks like a good choice for your situation. Did they say how much
current it drew from the source battery when it wasn't charging the
glider battery?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

I didn't ask, and it doesn't seem to be available on the website.
Since it's generating a constant float I imagine that it is not
inconsequential. I'll find out when it arrives. I'm not an electrical
engineer, but my guess is that the converter will shut down at some
low voltage like 11.9 v and drop the source battery out of the
picture. That's why I wonder if I need to keep the solar charger in
the mix. The question then becomes should I have the 5W solar panel in
parallel with the main aircraft battery to take over the topping of
the battery (output side of the converter), or should I try to keep
the source battery above the lower limit using the solar. The unit is
also flexible enough that if the source power is interrupted it will
figure out where things stand and pick up the charge at the right
place. There's an interesting charge state digram on the website that
shows this. I may need to think about a timer that only allows the
source battery to be available for a certain amount each day so that
it lasts longer.

These devices are really designed to charge a 12V wheelchair from a
car electrical system - typically including while the car is running
and as such often have a low voltage disconnect (LVD) to prevent the
car battery becoming so flat that it can't crank the starter to start
the car again and that may mean you can't get a full charge out of the
"donor" battery. It all depends on the LVD set point and I have no
idea what Powerstream do in this case - although they talk about a 10V
low voltage alarm, it that is also the LVD set point then that seems
great for this application. I've seen some attempts to do this with
similar systems and undersizing of the donor battery has caused some
problems even with a low LVD set pount. I'd personally be thinking of
a *larger VRLA battery (2-3X the glider battery capacity) - maybe on a
small hand cart.

I would not run the small solar panel in parallel with this charger or
on the donor battery. Just let the the charger just see the VRLA
battery it is charging. Such a small solar panel is pretty useless as
you have already found out, may interfere with the other charger if
used on the recipient battery (depending if it has isolation diodes
etc.) and is just overall more unecessary complexity to deal with. As
Eric points out self discharge of a VRLA battery is usually extremely
low.

Darryl- Hide quoted text -

- Show quoted text -

Darryl -

Thank you, this additional perspective is very helpful. The idea of
additonally having an input to charge from the car is a great idea.
Whatever it takes to get flying!!

Old but good thread.

Found these Imac B6 and Imac B6AC of ebay. This may be a good alternative to consider given that the Multiplex charger mentioned about is now apparently discontinued (I believe). The B6 model only runs off 12V, the B6 AC runs on either 115vac or 12v. It looks like Imax came out with the new plastic enclosure so the previous models are going for $35...

http://www.ebay.com/itm/iMAX-B6-AC-B...ht_2631wt_1206

In addition to charging multiple type of batteries (including Pb), the charge can be used to run a discharge test.