Patent ID: 8384351

Claim:
A battery system comprising: a battery unit in which battery arms are connected in parallel; and a charge/discharge control device that controls a charge/discharge current of the battery unit, wherein each of the battery arms comprises: a battery composed of one or more battery cells connected in series; a switch connected in series to the battery; and a battery monitoring device that, in a case of having detected abnormality of the battery, opens the switch to thereby isolate the battery arm including the abnormal battery, and sends a switch opening signal indicating that the switch has been opened to the charge/discharge control device, the charge/discharge control device comprises: a current detector for detecting the charge/discharge current flowing between the charge/discharge control device and the battery unit; a current control unit for controlling a magnitude of the charge/discharge current; and a voltage detector for detecting an input voltage of the battery unit; and in a case where the charge/discharge control device receives one more of the switch opening signals from the battery unit, the current control unit controls the charge/discharge current to gradually reduce a charge/discharge power of the battery unit in a stepwise manner in response to a number of the received switch opening signals based on a detected value of the current detector and a detected value of the voltage detector.