Photovoltaic Cell Battery Charger / Solar Cell Li-Ion Battery Trickle Charger with MPPC

This is a tiny module that allows users to charge small Li-ion batteries, CR2032 or equivalent, from a low power source such as a small photovoltaic cell. The project consists of the LTC3105 step-up DC-DC converter chip which features Maximum Power Point Control (MPPC) and 250mV start-up voltage which enables operational directly from low power, high impedance alternative power sources such as photovoltaic cells. A user-programmable MPPC set point maximizes the energy that can be extracted from any power source. Burst Mode operation, with a proprietary self-adjusting peak current, optimizes converter efficiency and output voltage ripple overall operating conditions. The circuit works with single-cell or dual-cell in parallel. The operating supply of this project is as low as 225mV and a maximum of 5V. Input supply should not exceed 5V DC. The module is programmed to output 4.1V which is important to charge the Li-On battery. Jumper J1 should be open for normal operation, close to disable the output.