A battery charging system for a vehicle, capable of charging a vehicle battery pack properly in a short time even during driving a vehicle-mounted electrical load. The battery charging system includes the battery pack mounted in the vehicle, the vehicle-mounted electrical load that can be driven by a current from the battery pack, and a battery charge controller that controls charging of the battery pack. When the battery pack is charged by using an external battery charger during operation of the load, the battery charge controller requires the external battery charger to supply a sum current that is a sum of a current for charging the battery pack and a current for driving the load to the vehicle.