To improve the performance of a power supply apparatus by a method wherein a plurality of batteries are connected to compose a battery assembly, a plurality of the batteries are connected selectively in parallel to a control circuit group with selection switches, the states of the respective electric energies stored in a plurality of the batteries are decided and the connection operations of the selection switches are controlled in accordance with the decision.
Selection switches 25d and 25g which are connected to both the positive side and negative side of a battery 13c are closed and the battery 13c are connected in parallel to a control stabilizer circuit and a power of 12V is directly supplied to control circuits, etc. This state is maintained as long as the capacity of this battery is larger than the capacities of other batteries. If smaller, the power supply is switched from this battery to the other one. Therefore, the batteries having large remaining capacities are also used as batteries for control circuits as well and the capacities of the respective batteries are inspected every predetermined time interval to switch the battery for the control circuit, so that the nonuniformity of the remaining capacities of the respective batteries can be avoided and the respective batteries can be uniformly discharged for the operation. As a result, the performance of a power supply apparatus can be improved.
YAMAKOSHI KAZUNARI
OKAYAMA SHINJI
FUKAZAWA TAMOTSU
TOKYO R & D KK