Power bank


Powerbank charging a smartphone.

Powerbanks are popular for charging smartphones and mobile tablet devices. A powerbank 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 powerbank consists of rechargeable Lithium-ion or Lithium-Polymer batteries installed in a protective casing, guided by a printed circuit board (PCB) which ensures 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 powerbanks use the common 18650 size lithium-ion battery which may or may not be user-replaceable.


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

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