BATTERY PACK

A battery pack to be mounted on a hybrid system includes a battery module to supply electricity to a motor generator of the hybrid system, a control circuit configured or programmed to control the battery module, and a housing to accommodate the battery module and the control circuit. The battery module includes a plurality of battery cells, and a cell case to accommodate the plurality of battery cells the control circuit is configured or programmed to include a Battery Management Unit (BMU) configured or programmed to monitor and control an entire state of the battery pack, and a Cell Management Unit (CMU) configured or programmed to monitor a state of each of the plurality of battery cells and send information to the BMU. The CMU is mounted on the cell case in the battery module.