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Power Banks

Power Bank

Power banks are popular for charging smartphones and mobile tablet devices. A power bank is a portable device that can supply power from its built-in batteries through a USB port. They usually recharge with USB power supply. Technically, a power bank consists of rechargeable Lithium-ion or Lithium-Polymer batteries installed in a protective casing, guided by a printed circuit board (PCB) which provides various protective and safety measures. Due to its general purpose, power banks are also gaining popularity as a branding and promotional tool. Different brands and promotional companies use it as a promotional tool and provide a customized product.

Many power banks use the common 18650 size lithium-ion battery which may or may not be user-replaceable.


  • Capacity in Wh: Total power capacity measured by multiplying mAh by voltage.
  • Capacity in mAh: mAh stands for Milli Ampere-hour and measures the amount of power flow that can be supplied by a certain power bank at a specific voltage. Many manufacturers rate their products at 3.7 V, the voltage of cell(s) inside. Since USB outputs at 5 V, calculations at this voltage will yield a lower mAh number. For example, a battery pack advertised with a 3000 mAh capacity (at 3.7 V) will produce 2220 mAh at 5 V. Power losses due to the efficiency of the charging circuitry also occur.
  • Simultaneous charging and discharging: need to specify if the power bank can be used while it is charging.
  • The number of output USB ports: This specifies the number of devices that can be charged simultaneously.
  • Output current rating: This specifies the current rating that it can charge maximum. The higher the number, the better the power bank. This can vary from output port to output port.
  • Input Current Rating: Input current rating is the amount of current the power bank is able to draw at its maximum level while getting charged.
  • Safety Protections: Over Voltage Protection, Over Charge Protection, Over Current Protection, Over Heat Protection, Short-Circuit Protections and Over Discharge Protections are the common safety measures observed with standard power banks.
  • LED Indications: The Led glows as per indicating the amount of charging ability left with the power bank.

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