A solar cell cannot be considered as an ideal source of current or tension. Depending on the illumination, it has a characteristic curve where the current is maximum with a voltage equal to zero and where the voltage is maximum without any load and thus no current. Between those points, there exist a point where the power available is maximum (MPP).

In order to get the highest amount of energy from the solar cells, a so called Maximum Power Point Tracker (MPPT) is required. A MPPT is basically a DC/DC converter with variable and adjustable gain. It contains electronics that will monitor the current and the voltage of the cells and battery. By changing the gain, it will ensure the best use of the solar cells energy.

The current version of the MPPT has a weight of 22.5 grams and can convert up to 90W with an efficiency of up to 97%.