Solar charging question

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!!