Make your own battery bank with this 5V Boost Step Up and Charging Module.
Specifications
Battery Type
Li-ion
Li-Po
Current
Charging Current - 1A(max)
Output Current - 1A(max)
Efficiency
85%(input 3.7V output 5V/1A)
Input Voltage
3.7V ~ 5.5V
BAT Discharging Stop Voltage:2.9V
Output Voltage
5V