A battery safety arrangement for a motor vehicle

There is disclosed a battery safety arrangement for a motor vehicle, the arrangement being operable to extinguish a battery fire and comprising. The arrangement comprises a battery unit (1) having a housing (2) defining an interior volume (3) containing at least one electric cell (4) and a separate internal pressure vessel (5). The pressure vessel (5) is exposed to the internal temperature of the interior volume (3) and contains a volume of compressed extinguishing medium at a pressure which is dependant on said internal temperature. The pressure vessel (5) is initially closed by a closure arrangement (9) which is configured to open upon an increase in said pressure corresponding to an increase in said internal temperature above a threshold temperature value to thereby release said extinguishing medium from said pressure vessel (5) for flow into said interior volume (3) of the housing (2).