BATTERY CHARGE/DISCHARGE TESTING DEVICE AND BATTERY DISCHARGE POWER CONTROL METHOD

The battery charge/discharge testing device includes a sub-charge/discharge unit connected to a main charge/discharge unit through bus lines, wherein when an output voltage of a built-in battery in the sub-charge/discharge unit is in a voltage range capable of supplying power, sub-power supply control is executed to supply discharge power of a built-in battery between the bus lines through a full-bridge circuit in a sub-DC/DC conversion unit by duty-ratio controlling ON/OFF of switching elements of the full-bridge circuit so that the voltage between the bus lines becomes a first predetermined voltage value. When the voltage exceeds the first predetermined voltage value during the sub-power supply control, the control is stopped, and constant current charge control is executed to charge the built-in battery through the full-bridge circuit by using, as a power supply, discharge power of the test battery supplied between the bus lines by duty-ratio controlling ON/OFF of the switching elements.