[FTC]: Tetrix Battery Pack Internal Short Circuit

[charrisTTI]

The students were taking their parts and robot chassis out of the storage container yesterday, when one of them called out to me, "Hey our battery pack is smoking!".

We disconnected the battery pack from the robot and took it outside until the "fireworks" were over. Both the black and red wires were cool, except that the black wire had come unsoldered from the tab on the battery. The fuse was not blown. Only the first cell at the negative end of the stack got hot. It appears that the metal tab attached to the end of last battery, to which the black wire is soldered, cut through the heat shrink insulation and the plastic covering of the adjacent battery. The case (-) of the adjacent battery is connected to the terminal (+) of the last battery, so when the tab connected to the case, there was a direct short across the last cell.

(see attached picture)