"Eric Greenwell" wrote in message
news:0W6wj.4526$O64.2414@trndny03...
Bill Daniels wrote:
"Eric Greenwell" wrote in message
news:ja3wj.4512$O64.3149@trndny03...
ZZ wrote:

I agree. I usually install my PDA in the glider either fully charged or
nearly so. That's why I said 280ma minus 80ma is ABOUT 200ma.

Knowing this and the approximate draw by other equipment in the glider
should get me close enough to properly match a battery pack to expected
flight time.
It's more about "big enough", rather than "matching". Unless it involves
serious dollars or effort, put in one that's enough for possible future
additions, like a transponder and one of those brighter, panel-mounted
screens that are available now, and then make sure it's big enough to
run everything for serveral flights without charging. Need a 7 ah
battery but got room for an 18 ah unit? Go for it!

Yes, Eric. But keep an eye on the maximum weight of the "non-flying
parts". A heavy lead acid 18AH battery might put some gliders over that
limit.

Proper weight and balance is assumed, so that would fall under the
"serious dollars or effort" caveat; e.g., buying a lighter parachute or
dieting off the 8 pound difference between a 7 ah and 18 ah battery!

--
Eric Greenwell - Washington State, USA

All I asid was "keep an eye on non-flying parts weight". I'm sure you
aren't advocating ignoring it.

Well, In my case, getting below the Max Wt for non-flying parts required
removing two 12AH batteries and replacing them with one 7AH and replacing a
steel O2 bottle with an aluminum one and the heavy demand O2 regulator with
a light MH one. Since the steel O2 bottle was behind the wing, CG
considerations forced me to mount the 7AH on the floor ahead of the panel
instead of the usual position next to the wheel box. That was about $1500
and a months work. I already had a new, light parachute and I'm still
working on the diet.

The net result was reducing the fuselage weight by 22 Lbs. I'm just below
the allowed weight so adding an 18AH Lead Acid is not possible without
removing 18 pounds somewhere else. More likely is to make a 8 or 20 cell
pack using new LiFePO4 cells from A123 Systems which would provide 22AH at
about the same weight and size as the 7AH lead battery.

Bill D

I'd like to carry more drinking water and a more robust landout kit.
Everything is a tradeoff.