Here is a tried and tested sample circuit of a Li-Ion battery charger that can be used to charge any 3.7V Li-Ion battery using a 5VDC (USB, Solar Panel…) power supply. At the heart of the circuit is ...

Fig. 1 depicts the system block diagram of the solar window charger, whereas Fig. 4 shows the tried-and-true circuit diagram. Fig. 1 As stated above, the Li-ion battery charger circuit is built around ...