I received three new Lithium Polymer batteries yesterday to replace three suspect batteries for my electric gliders. These are 22.2V 4400mAh (That’s 60 sec @ 4000 Watts). They were sent by airfreight.
On the weekend I had a LiPol battery fire in one of my gliders. Luckily it was my biggest one so it has heaps of space, plenty of ram air for cooling and enough room to have separate battery power for critical controls well away from motor and battery heat. I got it down in one piece, but I lost my rudder servo and the secondary battery (NiCad) which runs secondary controls was crispy but still delivered power. Another 30sec and I would have lost the whole thing.
I’ve seen LiPols deliberately set alight on YouTube, but nothing like this…funny thing though, was that I was filming the flight from directly in front of the glider for a YouTube clip (as I’ve done before), but do you think it recorded properly…nope! It would have recorded everything and I would have had evidence. Damn!
My surprise in all of this is that LiPol batteries burn like you wouldn’t believe…I mean, when I pulled the canopy off to get the battery out, there was a ball of fire (and the worst smelling white smoke imaginable). I had to burry the battery in a hole and cover it with sand to put it out.
I tested the charge on the new batteries when they arrived, and they were about 85-95% full.
When you touch the wire contacts of this much potential difference, the wires weld together and stay connected (I’ve done it by mistake when soldering connectors onto the leads). What prevents this from occurring is just two pieces of heat-shrink…something that can easily be missing. Now I received 3 packs, imagine if I had ordered 10 or 20 packs and just one packs’ wires connected accidentally because the person sending them was not diligent …I don’t think it would extinguish in a hurry, especially if there’s a tonne of other burnable stuff in the container.
I still remember ValuJet lost an aircraft over Florida because of oxygen generator canisters were not shipped correctly.
I think sending these things by air isn’t such a good idea. Road freight takes only a few days more and is a little cheaper.