Why, you afraid it'll make it catch more fire?
It’s often a waste of water, because the burning metal can extract the oxygen it needs to burn and reignite from the very water being used to put out the fire!
Dropping the burning hulk into a car-sized tank of water will predictably bring the fire to an end, since total immersion of the big battery compartment in water will quickly and efficiently remove heat from the equation by conduction and not let it creep back up to ignition temperature.
No, but well, if the water is not working to extinguish the flames, then pouring water on a malfunctioning, high voltage electrical source is probably not going to accomplish anything particularly good or safe...