The circuit’s built-in power supply has been kept very simple. The single-cell Li-ion battery (BAT) provides a nominal voltage on 3.7 V. The power supply also drives a “luxury” white LED light source ...

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 ...

This takes our AA power and changes it into the 5Vs we need for charging USB." It can be done with a Minty Boost kit, a premade circuit off of ebay, or grabbing one from a cheap USB charger.