Abstract: A battery pack suppresses temperature rise of secondary battery during charging and discharging. The battery pack includes a plurality of batteries stacked up, a case enclosing the plurality of batteries, a heat collector disposed near the battery positioned in the center of the plurality of batteries, a heat radiator placed at one side of the case, and a first heat transfer unit placed for connecting the heat collector and heat radiator. Further, the battery pack includes a heat transfer plate placed at the other side of the case, and a second heat transfer unit placed between the heat collector and heat transfer plate.

Abstract: A control circuit measures the battery voltage, intermediate voltage and discharge current of a rechargeable battery comprising a plurality of cells connected in series, at prescribed time intervals, and detects values for these parameters based on running averages for a prescribed number of measurement operations, while also detecting the battery temperature. If the battery temperature becomes equal to or greater than a prescribed temperature, or if the discharge current is an excessive current equal to or greater than a prescribed value, or if the battery voltage is equal to or less than a prescribed value, or if it is judged, from detection of the intermediate voltage that the balance between cell capacities has declined, then the control circuit halts discharge from the rechargeable battery by switching an FET to OFF.