Lithium batteries are not like regular AA batteries. They need very specific condition to charge safely. For ANY project where you plan on charging a lithium battery you need an appropriate charge controller.
What could you use this for? How about combining this circuit with one of our DC to USB circuits and making a recharging pack for your gadget? Or adding a solar panel along with a DC to USB circuit to make a solar powered charger? Then you could power your gadgets or projects through the mystical power of the sun!
Charge module: Linear charging Current: 1A Charge precision: 1.5% Input voltage: 4.5V-5.5V Full charge voltage: 4.2V Led indicators: red is charging, blue is full charged Input interface: micro USB Work temperature: -10℃ to +85℃ Inverse polarity: NO Weight: 5g Size: 25 x 19 x 10mm