Oops!

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Jacampb2
Mad Scientist
Posts: 1562
Joined: Sat Apr 19, 2008 11:57 pm
Location: Beaverton 48612

Oops!

Post by Jacampb2 »

So, to continue on with my RC problem, a guy at work gave me two RC airplanes that he had crashed and didn't want. I got one of them back together and went to charge the li-po batteries. Both were 3S batteries, and they both had balanced slow chargers. The smaller of the two batteries charged up fine and I used that to crash the plane for my first time. The second battery would not charge on the balanced charger, so I got the bright idea to throw it on the programmable charger that I got with all the other RC stuff. This in itself is not an issue, the programmable charger is designed to do li-po batteries, its just not a balanced charger. I was powering the programmable charger with a big automotive 12V charger out in my pole barn. The charger and the li-po were on top of the automotive charger. Lesson learned: If it won't charge on the balanced charger, DO NOT take the brute force approach of putting it on the big charger. At least don't walk away...

I put it on the charger and then left for work last night. I remembered to check it this afternoon when I woke up. Below is what I found. I think that one of the three cells were bad/shorted in the pack. I think that the unbalanced charger just proceeded to charge the other two to ~12.5 Vdc, about a 33% over charge. The programmable charger had a port for a temperature sensor. I really should have used one, it might have avoided this.

Image

Final death toll-- I can't find any remains of the battery at all. It was immolated. The multimeter that was sitting on top of the big charger is pretty charred. It may still work, but I couldn't get the selector switch to turn on my initial try. The big 12V charger is almost certainly a total loss. Not only did the top melt in and all the controls are destroyed, but it seems to have kept burning down inside the charger. I'm hoping to salvage the big transformer, but I'm not holding my breath. At first I thought the programmable charger was a write off too, but I pulled the charred plastic off it and hooked it up to my good DC supply and it fired right up and ran. It needs a new fan and some kind of end caps, but it looks like it will still charge batteries.

The funny thing is, I had a premonition when I put the li-po on the charger. I had 4 NiMh stick packs sitting on the top of the charger with everything else, and I thought, I better move those just in case something goes wrong... I should have set up a camera to catch the carnage :) Luckily no one was hurt and there is no huge loss here.

Later,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
ttocs
the Floor Sweeping Hack with Golden Ears
Posts: 14783
Joined: Fri Dec 19, 2008 9:53 pm

Re: Oops!

Post by ttocs »

dude charging lipos is no joke you do NOT walk away from the charger and now you know why. They make a special bag that you can put them in that will not catch fire otherwise I know most people would find a nice thick ceramic pot or two to put them in. There was a guy in my club in az that died in a fire in his garage we suspected because of lipo fire. He was known to be a heavy sleeper and take naps in his work shop. I had that same charger and its not a bad one. I think there is a spot to add a temp sensor to it and I think we all see the benifit of that.
what else can I say I am a grumpy asshole most of the time.
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