A system for explosively applying a fire-fighting foam is provided. The system includes a thermoelectric generator that is attached to a battery heat source. A temperature differential across the thermoelectric generator generates an electrical current having a temperature-dependent voltage. A detonator circuit is electrically connected to the thermoelectric generator. The detonator circuit measures the voltage of the electrical current. An explosive foam applicator is communicatively connected to the detonator circuit and includes a trigger mechanism that detonates a propelling charge in response to receiving a signal from the detonator circuit when the detonator circuit determines that the electrical current corresponds to temperature that is greater than or equal to a threshold temperature. The explosive foam applicator is oriented such that detonating the propelling the charge causes the explosive foam applicator to apply a foam to the battery heat source.