UNINTERRUPTIBLE POWER SUPPLY (UPS), POWER SUPPLY SYSTEM AND BATTERY CAPACITY TEST METHOD

This application provides an uninterruptible power supply (UPS), a power supply system, and a battery capacity test method, to accurately detect a total battery capacity of the system, so that during a capacity test and when mains supply is abnormal, battery backup time of the power supply system is sufficient. The UPS is separately connected to a load and at least two battery packs. The UPS includes a test unit, configured to: perform a separate capacity test on each battery pack in the at least two battery packs, and obtain a battery capacity of the battery pack, where when the battery capacity of each battery pack is measured, another battery pack other than the battery pack does not discharge and has backup power. The UPS further includes a determining unit, configured to determine a total battery capacity of the at least two battery packs based on the battery capacity of each battery pack.