Maximum Battery Power Point (MPP) For Solar Inverters

Solar cells can operate over a wide range of voltages and currents. By continuously increasing the resistive load on the irradiated cell from zero (short circuit event) to a very high value (open circuit event), it can be determined that MPP.MPP is the operating point at which V x I reaches its maximum value and that the maximum power can be achieved at that irradiation intensity. The output power is zero when a short circuit (PV voltage equals zero) or open circuit (PV current equals zero) event occurs.
High quality monocrystalline silicon solar cells can produce an open circuit voltage of 0.60 volts at their temperature of 25°C. With full light and an air temperature of 25°C, the temperature of a given cell may be close to 45°C, which drops the open circuit voltage to about 0.55 V. As the temperature increases, the open circuit voltage continues to drop until the PV module shorts.
Maximum power at a battery temperature of 45°C is typically generated at 80% open circuit voltage and 90% short circuit current. The short circuit current of the battery is almost proportional to the illuminance, and the open circuit voltage may only be reduced by 10% when the illuminance is reduced by 80%. A lower quality battery will lower its voltage faster when the current is increased, reducing the available power output from 70% to 50%, or even as little as 25%.