BATTERY CHARGING/DISCHARGING SYSTEM

A battery charging/discharging system in which cost reduction is achieved by decreasing the number of components constituting the system. The battery charging/discharging system performs charging control of an auxiliary battery provided separately from a main battery in which a master is connected with a slave mounting the auxiliary battery thereon such that they can communicate with each other, and the slave controls permission/prohibition of charging operation of the auxiliary battery based on the decision results as to whether the master is in sleep state or not.