Abstract: A backup power system is provided for fluorescent lamps which energizes one of the lamps when normal A.C. mains power is not available. The circuit operates with a standard fluorescent fixture which contains two or more fluorescent lamps. When A.C. mains current is available, both lamps are operational so that the lighting fixture produces a maximum brightness. The A.C. mains current also trickle charges a low-voltage battery contained in the lighting fixture. When mains current is not available, the battery maintains only one of the lamps lighted. Consequently, although the lighting fixture produces a reduced output, the battery life is extended. In one embodiment both fluorescent lamps are powered directly from the AC line. When A.C. power is not available, a relay disconnects the A.C. line from both lamps and connects one lamp to a DC/AC inverter which is powered by the internal battery.