US Patent 10153522 Battery pack

In a battery pack having one or more battery modules, each battery module includes a plurality of cylindrical batteries, and a battery holder for holding the plurality of cylindrical batteries and forming a space between itself and an adjacent member, the space being at least partially open to the outside and the battery pack further includes a heater mounted in the space, for heating the plurality of cylindrical batteries via the battery holder, and an elastic member for urging the heater onto the battery holder, and closing an opening of the space to thereby form a first space closed from the outside.