It is critical to find the OCV when using FOCV for MPPT in solar panels. To do this, the solar charger needs to be able to disable its input and then measure the OCV.

The next critical element is finding the K-factor. This is a ratio between 0 and 1 that is multiplied by the OCV to determine the input voltage operating point. Typically, this is found experimentally, and can vary depending on the solar panel and environmental conditions.

After the OCV and K-factor have been found, they are multiplied together and this is the MPP voltage. The solar charger needs to hold the input voltage no lower than this voltage to maximize the solar input.

The last key piece is a way to maintain the input voltage of the charger at the MPP voltage. In a solar charger, if this feature is absent you could crash the input voltage to the converter due to the solar panel current-voltage characteristic. It is necessary to hold the input voltage at the MPP voltage if the charger tries to draw more current than the solar panel can source.