Power banks are not just a simple battery: they use sophisticated electronics circuit to manage itself being charged, and then charging other devices.The management of the battery charging and discharging is key to the way the power bank works. All power banks use rechargeable batteries based around lithium technology. Lithium-Ion and Lithium-Polymer batteries are most commonly used for power banks.These two kind of technologies have slightly different propertie. Both forms of power bank work well, but it is a balance between cost and performance.

Lithium-ion:   it offers a higher energy density. They can store more electrical charge in a given size or volume, and are cheaper to manufacture, and does not exhibit what’s called the memory effect, but they may have issues with ageing.

Lithium-polymer : it is generally more robust and flexible, especially when it comes to the size and shape of their build and they tend to last longer. They are also lightweight and have a lower chance of suffering from electrolyte leakage.  Lithium-polymer power banks do not suffer from ageing so much. However they are more costly to manufacture.

Older power banks had capacities of 3,000 to 5,000mAH only. Recent years the battery capacities have increased significantly to provide longer times between charge. While some of the latest ones available can offer huge capacities of 30,000 mAH.


There are two main forms to define a power bank lifetime.
Charge discharge cycles:   Any rechargeable battery will gradually wear out. Normally the lifetime of a battery is quoted in terms of the number of charge discharge cycles it can undergo before its performance falls by a given degree. Some cheaper power banks may only have a life of 500 or so charge discharge cycles, but better ones will have lifetimes of many more charge discharge cycles.

Self discharge time:   All battery cells, whether rechargeable or primary have a certain level of self discharge. For rechargeable batteries these days with their own control circuitry, a small amount of power is required to keep these circuits alive. A good power bank can hold charge for up to 6 months with only a small loss of charge, but lower quality ones may only retain a useful charge for about a month.