What is power bank?
Power bank, mobile charger (power bank, power bank, urine bag, nanny; English: Power bank) is a kind of personal portable, which can store electrical energy, mainly for consumer electronic products such as handheld mobile devices ( For example, portable chargers for charging wireless phones and notebook computers are especially used in situations where there is no external power supply. Its main components include: a battery used as electric energy storage, a circuit to stabilize the output voltage (DC-DC converter), and most of the mobile power supplies have a charger to charge the built-in battery.
The power bank has three basic functions, including energy storage, charging and power supply. Other functions, such as safety protection, battery status detection and display, etc., are added to meet the needs of different designs, uses and convenient operation.
Energy storage：
In order to power other devices without an external power supply, the mobile power supply needs to have a battery for energy storage. Most mobile power sources use lithium-ion batteries (Li-ion) or lithium-ion polymer batteries (Li-PO). A small number of mobile power sources use nickel-metal hydride batteries (Ni-MH). There are also some early mobile power sources. Use the battery once.
Charging：
Lithium-ion batteries (Li-ion) or lithium-ion polymer batteries (Li-PO) have the highest energy density in terms of weight or volume, that is, the lightest and smallest. In addition, lithium-ion/ion polymer batteries are more efficient during charging and discharging (less energy/electricity is wasted). But the price is also the highest among these batteries, and because overcharge or overdischarge can easily cause permanent damage to the battery, a more sophisticated electronic circuit is required to control the charge and discharge. Since lithium ion/ion polymer batteries will spontaneously ignite at high temperatures, safety and stability have become extremely important requirements. A reliable safety protection circuit is required to prevent any over-temperature conditions.
Power supply：
Lithium-ion batteries have a hard shell, while lithium-ion polymer batteries do not. Therefore, lithium-ion batteries are theoretically slightly heavier. Since lithium-ion polymer batteries do not have a hard shell, they can be made into a specific size to match the appearance. The volume of the polymer battery will expand slightly after being fully charged. It is necessary to reserve space in the design to avoid danger caused by excessive pressure in the battery.
