The invention relates to a device and a method for cooling an electricity storage means, in particular a high-capacity battery (110), said device comprising: cooling means (130) for cooling said storage means; a “low voltage” battery (120); means (130), supplied with power by the low voltage battery (120), for increasing the rate of cooling of the storage means (110). The invention also relates to a vehicle (100), especially a motor vehicle, comprising such a device, said vehicle comprising an electric power train (220).