Battery charging apparatus

The battery charging apparatus has an auxiliary battery 1, a first charging circuit 20 for charging the auxiliary battery 1 with a first charging current derived from an externally connected commercial power source AC, and a second charging circuit 30 for charging the load battery LB with a second charging current that is higher than the first charging current and is derived from power from the auxiliary battery 1, which is charged by the first charging circuit 20. The first charging circuit 20 is connected to allow power supply to the auxiliary battery 1 and the second charging circuit 30. This makes charging circuit switching unnecessary and eliminates the need for components such as high-power switching devices. The charging apparatus has the positive features that stability and reliability are improved, and the load battery can be charged with the auxiliary battery 1 in a shorter time than using commercial power.