Electrical device and method for operating an electric device

The method involves discharging storage battery packs (110, 120) of an electrical device (100) having lowest temperature at predetermined time to operate a load (105). The packs to be discharged are selected based on temperature and internal resistance of the packs. The discharge of the packs is terminated when the temperature of the packs reaches a specified threshold value. The packs having lowest internal resistance are discharged if required electrical output exceeds a specified threshold value. An independent claim is also included for an electric device.