System unit for battery control

A system unit to the battery control unit is provided which is inserted into a battery pack and allows system a battery ECU to maintain its monitoring and control operation, without using an auxiliary battery, even if a battery pack switch which is set to be turned on when a battery is in use, is turned off. A system unit to the battery controller 1 detects a state of a battery 3, which is used to drive a vehicle 20, and monitors the state of the battery 3 based on the information acquired by calculation, to a circuit device, which surrounds the battery 3, according to a result of the to control monitoring, wherein the system unit includes the battery controller 1, an internal power source 5, which is connected directly in parallel with the battery 3 and feeds the system unit to the battery control current, and by means of a software process an on / off state of a battery pack switch by means of a microcontroller 7 detects which is operated by the internal power source. 5 The system unit to the battery controller 1 is in a high-low-consumption mode when the battery pack switch 2 is turned off, or the system unit to the battery controller 1 controls a battery disconnection switch 4 to remain switched on, corresponding to the traveling state of the vehicle 20th