Battery control system for a lithium ion battery and assembled battery control system

A lithium ion battery control system includes a degradation rate calculating unit 202, a degradation rate storage unit 203, a degradation rate comparing unit 204, a charging and discharging control circuit 205, and a rechargeable battery. The degradation rate calculating unit 202 calculates a degradation rate when receiving a trigger for starting the check of the degradation rate of the battery. The degradation rate comparing unit 204 receives a present degradation rate from the degradation rate calculating unit 202 and a previous degradation rate from the degradation rate storage unit 203 and compares both degradation rates. As a result, when the present degradation rate is greater than the previous degradation rate by a predetermined value, a charging and discharging condition is limited.