I assume you are talking about charging your glider battery from a
storage battery, which you charge with a solar panel during the day.
This would probably work with the solar charger I mentioned, but I
offer no guarantees (there is nothing obviously wrong). I would NOT use
this without a charge controller, however. I would experiment with
output voltages to find which one was most efficient. To do this you
will need to measure both discharge current from the storage battery
and charge current into the battery you are charging. You probably can
use 18V safely. Be sure to measure voltages at both batteries to sure
something isn't going wrong (the battery under charge shouldn't measure
more than 15V unless it is cold (I did this when it was 26 deg and it
measured over 15V).

Tom Seim
DG-400
Richland, WA