Blocking diode The SPV array is connected to the battery. During sunny hours, the panels generate electricity to charge the battery. But when there is no sunlight or at night, the current will try to flow in the opposite direction, i.e. from the cell to the array. This could damage the array. Therefore, to avoid this reverse flow. Stand-alone system In this system, power is supplied to the load without using any public grid or connection to any other system, and can operate.