"GM" wrote

it's still winter with lousy weather in the northern hemisphere, so it
is time to warm up an old discussion. I searched the forum for threads
reg. Lithium-Polymer Batteries and there have been none for a while.
Here are the questions:
- Does anyone have real life experience with LiPo's in a glider? (real
gliders, that is - not models)

The only way I would use LiPo's in a glider would be in a fire proof, burn
though, melt through- enclosure. Like a ceramic pot with a lid, for one
good example.

- Can I combine two 7.4V packs in series to get a 14.8V unit or is
there a risk with that?

Not if they are of the same manufacture, capacity and age. If they are too
much different, one of them will be over stressed and may catch fire.

- How would one charge a combo like this? Each unit by itself and then
hook them together or with one charger while hooked together?

Together is fine if the above conditions stated by me exist. Most people
say that if the batteries are not discharged and charged at too high of a
rate, a balancer is not necessary, or at least not absolutely necessary.

The prices have dropped to a very affordable level; so have the
chargers/balancers. The weight savings are considerable. My 12V/7.5Ah
standard sealed gel-cell weighs 2.35kg (5.17lbs) and it lasts a few
days. I found two 7.4V/5.0Ah units on e-bay that weigh in at 0.3kg
each (0.6kg or 1.32 lbs in total)

By the time you use a ceramic pot container, any weight savings is probably
gone. Having a battery catch fire in a cockpit and generating it's own
oxygen to fuel the fire would be about the worst nightmare I could imagine.
How probable is it to have this happen? Not all that great, but that one
chance is .....shudder.....bad!
--
Jim in NC