On 3/17/19 9:54 PM, Eric Greenwell wrote:
kinsell wrote on 3/16/2019 9:46 PM:


Many of us are flying with multi-cell LiFePO4 batteries that have
internal wiring and are not filled with resin.Â* Is that a problem?
Or is the location of the batteries in this specific glider such that
the resin is advisable?Â* A battery fire anywhere in a glider (even
without a fuel tank) is catastrophic. OTOH I havn't heard of any
fires with this type of battery.Â* It's the lithium-polymer battery
pack (also much larger, with many more cells) in the FES systems that
has had fires.


Well, the service bulletin talks about an LFP that burned.Â* There was
a fire in an EB-28 in Finland last year with a 10 A-H LFP.Â* Here's a
video of an LFP burning:

https://www.pilotsofamerica.com/comm...-fires.102016/


There have been claims that LFP's don't burn, but that's simply not true.

The Aerovoltz battery that burned did not have a BMS; in fact, none of
the Aerovoltz batteries have a BMS (battery management system). I would
not want to use one, even though the short engine runs typical of
self-launchers means problems would be less likely than in airplanes.
The Earth-X batteries all have a BMS, seem better characterized, and I
would trust them a lot more.


Yes, EarthX is well regarded in the homebuilt powerplane world. Dual
redundant BMS boards to make you feel good. Here's a greatpicture of one:

http://www.avidfoxflyers.com/index.p...ttery-warning/

If you poke around, there's a nice video from the Director of
Engineering at EarthX, he talks about the requirement to have a
gas-tight battery box vented to the outside, to use only a three-phase
alternator to charge it, and to add a crowbar circuit to prevent
over-voltage. Wonder how many glider pilots go to all this trouble?

I think I'll stick to SLA, just press the button and the engine starts
in about a second.


-Dave

P.S. That StewartB in the original thread was a real hoot. Said he
worried more about getting mad cow disease than having trouble with his
EarthX battery. Until his battery went bad. Don't know if he still
eats hamburgers or not.