Most gliders are fitted with a single 12V7AH battery; some have 14V 7AH; some have a reserve....
Once you start adding GPS systems, horizons (which can draw 1.5A on start and 1A in a steady state), Mode C transponders etc then electrical endurance for these long flights (where you may be more reliant on additional instruments) does becomes a issue.
Let's go back to this bit for a moment. Filser's
TRT600 LAST draws about 0.2 A at 12 V.
If your AI draws 1 A, is it unreasonable to expect you to fit a transponder to fly in cloud? In fact, is it unreasonable to expect you to fit a transponder to fly at all?
As a power pilot, I'd rather you had a transponder and said nothing to ATC than vice versa. At least then they can tell me that you're there, rather than being told in the middle of a 300 mile IFR flight to look out for a glider that just reported going into cloud over Little Smallington.