Quote:
Originally Posted by adciv
This is a NiMH battery pack, it shouldn't catch fire spontaneously again after the damage it has sustained.
Top end = connector end
Bottom end = end opposite connector
Well, the batteries went into thermal runaway. Cause TBD. Unfortunately this is one of the failure modes shared with Lithium Batteries (see 787 for more details). The cells at the bottom appear to have swelled and cracked. The cells on top look to have burst and were probably the source of the smoke.
Does the controller still work?
What happened to the insulation & wire on the cells at the bottom of the battery?
Was it dropped recently?
Any idea how old the battery is?
At this point, the cause seems most likely due to a cell to cell short internal to the battery pack. This would lead to thermal runaway in the cells causing the deformation and smoking. Placing it in the pack was probably the straw that broke the camels back in the internal insulation.
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At this point, the battery has been disposed of. As far as i could determine, the battery was intact, not new, but it had not been used too much. I will test the controller on monday, and figure out if it had anything to do with it. Before
The incident it showed no signs of damage except for a scratch here and there on the plastic insulation. It may have been dropped,but if it was, it wasnt by me. As of after the incident, much of the insulation had burned away around the tops and bottoms of the cells inside. all wires were in good condition. Until the cause is determined we have locked up all the batteries of this exact kind. As for its age, we bought them last year.
To be clear, the battery that did this is not the battery that powers the vex microcontroller, rather the one that powers the handheld radio controller.