Lithium ion batteries and chargers. The typical nominal voltage of lithium ion battery is 3.6 or 3.7V, and the cut off voltage is 4.1 or 4.2V. Use only Li-ion mode of a smart charger to charge these batteries.

Generally speaking, there are two types of lithium ion batteries: high capacity or high discharge rate. High capacity cells are generally low in discharge rate, ideal for electronics that do not draw high current, but prefer to a long running time, such as flash, RC radio. Panasonic NCR18650B and Samsung 35E cells can be used for these applications. High discharge rate cells typically come with a lower capacity, but can discharge much faster than high capacity cells, making them ideal for power tools and power source in RC vehicles. Samsung 25R and Sony VTC4 cells are recommended in these scenarios.

Be aware of some extremely high capacity 18650 cells sold on eBay and other unreliable eCommerce websites. Presently technology has not been able to break through the energy density limit of lithium ion chemistry. Sony (Murata), the inventor of lithium ion battery, and Panasonic, the partner of Tesla, are the two brands can always be trusted.