SLUSDV2A May 2020 – May 2021 BQ25798
BQ25798 has a 3.6 to 24V wide input voltage range, allowing it to interface with 6V, 9V and 12V photovoltaic panels. Two critical parameters of the PV panel are the open circuit voltage, VOC, and the maximum power point voltage, VMPP. The open-circuit voltage should not exceed the 24V recommended operating condition of VIN1 or VIN2. BQ25798 has a small-PV maximum power point tracking algorithm (see Section 22.214.171.124) to simplify the interface to the solar panel while maintaining high effiiency.
The ratio of maximum power point voltage to open circuit voltage can change over differing conditions such as temperature and irradiance, but the ratio of VMPP / VOC as provided in the PV panel manufacturer's datasheet provides a good estimate to use when configuraing VOC_PCT. For a panel with VOC = 10.0 Vand VMPP = 8.0 V, the calculated maximum power point ratio is 8.0 V / 10.0 V = 80.0%. A setting of VOC_PCT = 4 (81.25%) is a good starting configuration for this panel. Users may wish to characterize their PV panel's operation over their specific application conditions of temperature, irradiance, humidity and other parameters in order to adjust this setting if necessary.