This is a light weight, high energy density polymer lithium battery. It outputs a nominal 3.8v at 5100mAh, including built-in protection against over voltage, over current, and minimum voltage. It comes terminated with a standard 2-pin JST connector-2.0 mm spacing between pins.
Please do not attempt to charge these with anything but a specialized Lithium Polymer charger.
Recommended chargers for 3.8V polymer lithium battery:
LiPo Rider Pro
Solar Charger Shield V2
Excellent long-term self-discharge rates
UL,MSDS,CE, Rosh, UN38.3 compliance