The point is batteries can burn, explode, catch fire... (even if there has never been a problem before) Keep that in mind if you change batteries and want to take a long flight on unproven batteries. From the MD500 POH, the only event you land immediately (even if over a forest according to factory pilots) is a battery run away (the only red button on the warning panel), I had one of those while flying. Ended up getting stalked by mountain lion. My batteries are double fused and each instrument has a breaker.


On Friday, March 23, 2018 at 5:00:00 PM UTC-7, BobW wrote:
On 3/23/2018 5:35 PM, Jonathan St. Cloud wrote:
I have no idea why is was "bad". I just knew that every time I took glider
out of box fuse was melted. We checked the trailer top solar chargers with
controllers, they were fine as was solar charger and controller in glider.
One bad one out of bunch, replaced it no further problems.


On Friday, March 23, 2018 at 12:28:46 PM UTC-7, wrote:
Can you explain what was "bad" with this battery, and can such a problem
develop eventually in a good battery? I'm puzzled what would cause the
fuse at the battery to blow when there wasn't a short circuit
downstream.

On Friday, March 23, 2018 at 12:56:41 PM UTC-4, Jonathan St. Cloud
wrote:
Not a direct reply, but I took delivery of a brand new glider from
Schleicher that had one (out of four) bad LFP battery. All the
batteries are fused at the battery with circuit breaker on panel for
each instrument. Kept blowing fuses. Schleicher told me they had not
heard of a battery going bad, but quickly refunded monies to purchase a
new battery. No problems with new battery... Snip
Since this thread has drifted already...

...on the subject of "explaining battery 'badness'," ~2012 I encountered a
wet-cell SLA starter battery in a friend's car; it/she was suffering from
'intermittent/sudden deadness,' in the 'car won't start/suddenly quits
running' sense of things. Got lucky while troubleshooting, and noted the
battery's voltage suddenly halve (12.6-6.3V as I recall)...to eventually
return to 12.6V. Ultimately confirmed it started/ran-fine when DVM-showing
12.6V, and was 'quite silent' when the battery showed 6.3V (big surprise)..
Since the battery was ~1yr-old from A-zone, I advised her to return it for a
new one (and don't take, "But it checks out OK on our tester," as an
acceptable - though quite possibly true - return-outcome).

Return accomplished; problem hasn't recurred in the years since then.

An EE brother said he'd never heard of such a failure (nor had AE-degreed I).

If it happens, it must be possible. 'Weird internal shorts,' weird internal
opens,' I wouldn't bet agin' either of 'em being possible...

Bob W.

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