Lipo or NiMh

[RogueTwoRobots]

That was battle damage though, ram a piece of metal through a lipo pack and that will happen
But if you think of the number of robots running lipos now (across all weight classes), we've never had a fire just from misuse. A few folk have had packs/cells that have swollen up, but no fires that I can think of, contrary to the belief when everyone started using them that we would all be treated to regular pyrotechnics masterclasses.

[psychostorm]

Doesn't count. No base to hold the battery in at the time.

[RogueTwoRobots]

I believe the battery was held in, it was one of the front prongs being slammed into it by a hit from 720's drum that pierced the pack.