In order to supply power to other devices without external power supply, the mobile power supply needs batteries for energy storage. Most mobile power supplies use lithium ion batteries (Li ion) or lithium ion polymer batteries (Li Po), a small number of mobile power supplies use nickel metal hydride batteries (Ni MH), and some mobile power supplies used primary batteries in the early stage.

The energy density of lithium ion battery (Li ion) or lithium ion polymer battery (Li Po) is higher, that is, lighter and finer, whether in terms of weight or volume. In addition, lithium ion / ion polymer batteries are also more efficient in the process of charging and discharging (less energy / electricity is wasted). But the price is also higher among these batteries, and because overcharge or over discharge can easily damage the battery, it is necessary to have more precise electronic circuits to control charge and discharge. Due to the spontaneous combustion of lithium ion / ion polymer battery at high temperature, safety and stability have become important requirements. Reliable safety protection circuit is needed to prevent any overheating.

The lithium-ion battery has a hard shell, but the lithium-ion polymer battery does not, so the lithium-ion battery will be slightly heavier in theory. Because there is no hard shell, the lithium-ion polymer battery is easy to be made into a specific size to match the appearance. However, the volume of the lithium-ion polymer battery will expand slightly and become larger after being fully charged. Space needs to be reserved in the design to avoid danger caused by excessive pressure in the battery.