Toasted Lipo!?!?!?!?!

[Hickoryhead]

OK I messed something up. I puffed a Lipo. I am kind of stumped. It’s on my GEVO. I had (being the key word) 2 Lipo’s ran in serious. They were both 6000 mah 2s2p. I was letting a 7 year old play with it. He was not jumping the throttle or any thing. Just simple nice and slow run. Then out of the blue it stopped in its tracks. I walked over thinking gearing. I pulled the top off and could see the problem. Wow lipo’s get hot. The other battery was cold. The motor and MM were cool. That one battery was hot enough to not touch. What’s up with it? Any thoughts?