I have been flying with the set up for three seasons.
Since my power supply is adequate for all my instruments but for the radio
which is an old 1980 ATR 720 and it appears to work well if adequate power
is provided. I will go with Tom's suggestion of packing a larger battery.

The routine at a contest would be as follows.
We get our tasked. It will be entered. The radio and the L Nav is switched
off, the GPS and PDA will be on from this time on.
If you are in the middle of the pack it could take 25 minutes till launch.
Radio and L Nav is turned on at launch. Waiting for an other 25 minutes to
get started, maybe more plus a three hour task. Total over 4 hours.

Base on what I can figure the idle radio uses .4 amp, the L Nav, the PDA and
the GPS uses .35 amp combined, as per CAI. Borgelt uses ~.15 amp

I would say a normally charged 7 amp battery with the surface charge taken
off and reading about 12.7 volts to start with, it would not surprise me if
I would see 12 volt or slightly less on the meter after 4 hours.

As it is now all works well but at the end of the flight I should not forget
to
switch batteries and I been known to forget it. If the ground guys have a
good radio my radio will be ok for the normal operation even if I do not
switch batteries certainly air to air was never a problem unless I had the
radio turned off.
Udo

Eric Greenwell wrote:
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.


Using PowerFilm PT15-75 thin film flexible modules rated at 50ma, 15.4
volts, it would take 20 units to get 1 ampere. Cost $800 ($40@). These
would use 5 square feet plus of surface area. They are 10.6" x 3.9".
There were several of these or similar units on gliders at the SSA
convention. The edges were taped to mount them and at that size they
seemed to form well to the compound curve of the fuselage. Only two or
three on a glider which indicates to me that they were mostly for the
wow factor..
Randy