Udo Rumpf wrote:

If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
what rating would I need during flight, if after 4 hrs I wanted to have
a usable, not full, charge in my 12 Volt battery.
Right now, my as good as new battery is useless after 4 hours.


This suggests you are drawing about 1.5 amps from your battery, which is
very high, even for a glider with a transponder. Is that right? Can you
reduce the drain safely by turning something off?

and what size would the panel be?

It would have be about a 1 amp maximum output panel just to be sure of
getting 0.5 amps on average, which would leave ~2 amphours to the battery
after a 4 hour flight. About 1+ hours of use would remain at your 1.5 amp
drain. That's a rather large solar panel to mount on glider, or a rather
expensive one.

If you are really drawing 1.5 amps and can't reduce it, I'd suggest first
putting in another (or bigger) battery. Cheaper and easier, I think.

Eric,
As per manuals I draw about 1.1 amps without talking on the radio
I can fly for about 4 hours and I drop to 12 volts from fully charged
7 amp/h battery. Add an other 1.4 amps for transmit.
Regards
Udo