Lithium Li-ion 18650 3.7V 4.2V Battery Charging Board with DC-DC 4.3 to 27V 2A Step Up Boost Module

This circuit is a dream come true. Just connect a 18650 and power whatever that uses 5-12v. (adjustable) Can charge while load stays, so perfect for emergency lights that will stay on after power goes. Higher voltages than 12 are possible but have very little current (less than 150mA).