I'm with others on battery fires, you don't extinguish them, at best you contain them and minimize collateral damage.

The energy is already there in multiple forms (it's the worst hybrid of a chemical, electrical and metal fire all at once), and unlike a regular fire getting it under combustion temperature won't even stop it for long, as there's still a massive chemical potential and damaged containment between it.

Honestly the best you can have for a contingency plan once ignition has occurred is to have something sufficiently long and insulated that will let you relatively safely drag it the fuck outside in the early stages and just hope for the best.