The 18650 is a rechargeable Lithium Ion battery for general use. It has a nominal voltage of 3.7 volts and a capacity of 2800 milliamp-hours. These batteries have tested higher, but we warrant them for the rated capacity which is 2800mAh.
18650 lithium ion batteries are extremely powerful and can deliver quite a kick. If you are combining these to create higher voltages you will need a battery management system.