Tray Surfer has it with the ice-bins! It's important that the ice isalso submerged in water ,to maximise heat transfer. Water will
not extinguish a lithium fire, neither will oxygen starvation.....this is important.
A lithium battery fire is self-sustaining it has it's own oxygen supply.
Water and ice will cool it , hopefully you can get it cild-enough to stop the thermal-runaway (works a bit like underground coal-mine or peat-fires...both burn quite happily without external oxygen.
I wondered if a Co2 extinguisher, inverted , so it sprays liquid Co2 onto a battery, may well be very effective at instantlt freezing a burning battery.
Reverting to yhe original scenario......if the terrain is that hostile, you're a goner anyway....keep 'er flying and look on the map for a divert...at least, if there is a fire and you do ultimately lose control, your body will be recovered quicker.
