EXTINGUISHING BATTERY THERMAL RUNAWAY

A system includes a stack of battery cells within a container. An interior space of the container is filled with a coolant in direct contact with the cells. There need be no intervening containers between the coolant in the interior space of the container, and the cells. A method can include detecting a thermal runaway event in one or more of the cells, and admitting some of the coolant at a first pressure into the one or more cells at a second pressure lower than the first pressure.