NOVELTY - A system has an array (10) of photo voltaic (PV) cells (1-1 to q-n) that are connected in banks (1n-a to qn-a,2n-b to qn-b) to provide a predetermined level of output voltage when exposed to predetermined level of light energy. A sensor is connected to the output terminals (V+,V-) of the array to sense when output voltage level drops the predetermined level. A switch (S1-a to S4-a,S1-b to S4-b,S5-S6) responds to the sensor to switch banks from parallel to series connections to boost the output voltage level as the exposure to light energy drops below the predetermined level.    USE - System for controlling the output of an array of photo voltaic cells for a battery charger.    ADVANTAGE - The system boosts or enhances the output of the PV cell array when the incident light energy levels incident on the array drop below the predetermined level. The system can extend the usefulness of the PV cell array to continue to produce voltage and operate when exposed to lower light energy levels.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for    (1) method of controlling the output of a array of photo sensitive devices formed of banks of series connected devices to provide a voltage output of a predetermined level when exposed to a predetermined level of light energy and the banks of devices are connected together in parallel to provide a predetermined level of current capacity to a load;    (2) microprocessor controlled system for regulating the output of an array of photovoltaic cells when the exposure of the array to radiant light energy falls below a predetermined light energy level and the corresponding output voltage from the array is reduced below a predetermined level    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a PV cell array containing the switching elements in a normal operating condition under normal light levels.    Switch (S1-a to S4-a,S1-b to S4-b,S5-S6)    PV cell (1-1 to q-n)    Output terminals (V+,V-)    Banks (1n-a to qn-a,2n-b to qn-b)    PV cell array (10)