Power bank circuit board
This tiny board is all you need to build your own power bank using 3.7V Lithium batteries. It charges as well as step the battery up to 5V to charge equipment like cellphones.
Below is a video that shows how to build a DIY unit. Using a solar panel with a step-down module like this ultra small voltage regulator can charge your batteries up easily as well.
Built-in charge and discharge
Charge status indication. Red light flashes when charging; Long red light when full
The step-up charging board can be connected to a lithium battery and connected in multiple sections of lithium batteries, as long as the voltage is 3.7-4.2V in parallel(only be connected in parallel, not in series)
It has protection functions, protect from over-charge / over-discharge/ over-load ( support charger and discharger at the same time )
Power bank circuit board product introduction:
5.BAT Discharging Stop Voltage:2.9V
6.Discharging Efficiency:85%(input 3.7V output 5V/1A)