A power delivery system includes a power supply unit, a secondary power unit, a controller, and a monitor. The power supply unit is configured to receive primary power and provide operating DC power to a DC load. The secondary power unit is configured to store energy from the primary power. The controller is configured to control the secondary power unit during a testing period such that the secondary power unit uses the stored energy to provide secondary DC power to the load instead of the operating DC power. The monitor is configured to monitor the operation of the secondary power unit during the testing period and provide a signal indicative of whether the secondary power unit operated within defined parameters during the testing period.