FlexMax80 FM80-150VDC Charge Controller FLEXmax MPPT Charge Controllers are the only choice when you demand a high performance, efficient and versatile charge controller for your advanced power system. The FLEXmax Charge Controllers are the revolution. Developed by OutBack Power, its features include support for a wide range of nominal battery voltages and the ability to step-down a higher voltage solar array to recharge a lower voltage battery bank. A built-in, backlit 80 character-display shows the current status and logged system performance data for the last 128 days at the touch of a button.