This is the Dual USB 5V 1A 2.1A Digital LCD 18650 Lithium Battery Charging Module Accessories, 18650 Circuit board shell.
Meet the individual needs of your DIY, but you must understand basic electronic assembly. The motherboard comes with protection Charging, overcharge protection, over-discharge protection, overcurrent protection. Intelligent output device after charging full, automatically stop charging, to prevent mobile phones overcharge. Output voltage and current stable, will not harm user devices.

Specifications and features:

1. USB Output: 5V 2.1A / 5V 1A(Dual USB interface)
2. Charging display: intelligent digital display
3. Batteries Type: liquid lithium-ion batteries (18650) 3.7 lithium-ion battery only
4. Product Size: 57mm x 28mm
5. Screen size: 27mm x 17mm
6. Charging voltage input: 5V-6V 1A
7. Step up voltage output: 5V 1A/2.1A (Dual output, Total 2.5A)
8. Protection circuit: Overcharge protection:4.250V Overcharge protection release: 4.100V
9. Protection circuit: Over discharge protection:2.900V Over discharge protection release: 3.000V
10. Idle time before LCD switch off: 60secs