Admittedly, power banks are an awesome invention of the times.They are portable, inexpensive, and store back-up charge for our mobile phonepower off. In the wake of the technology renovation, consumers have moreoptions in color, style, capacity and function etc.

But sincethe average Joe does not have a degree in electrical engineering, people always have misconception aboutthe capacity of power bank, like 10,000mAh of charge could fully recharge a2000mAh Smartphone 5 times which never happen in our real world. In a nutshell,the actual mAh capacity of a powerbank is smaller because the 3.7 V nominal voltage of its battery has to beboosted to 5 V, and this will results in about 10% losses. Also, power bankcapacity is affected by many factors such as ambient temperature, chargingcurrent, even the health of your phone's batteries, and efficiency of yourphone's charge regulating circuitry.

For rough calculation of the total charge time, kindly usethis formula below:

Real capacity * conversation rate * phone battery health /phone capacity=Total charge times

Example: 10,000mAh *0.85 * 0.8 / 2000mAh = 3.4 chargetimes(0.5-1 times plus minus)

Here is something you need to know before purchase a powerbank

1. Conversation rate

   Conversation rate is theremaining percentage of the battery after the battery lost in heat or PCBAoperation. power bank needs to boost the voltage of its internalbattery to 5 volts, and a special voltage boosting circuit is used for thepurpose. However, this circuit is where some of the energy is lost, and thelosses may exceed 10%, depending on the circuit's efficiency. Generally, theconversation rate is between 75%-85%. If the conversation rate is lower than75%, you’d better stop buying cause it must use poor components or fakecapacity; and if it’s mark 90% or more, it only just a advertised.

2. Phone battery health

   In short, besides of thelosses of power bank, Further losses occur inside the Smartphoneitself, within the circuitry that regulates the voltage fed to itsbattery. That’s also the reason why your phone can last longer when it’snewly bought after 3-6months we used it.

3. PCBA

   PCBA or PCB’A meansPrinted Circuit Board+Assembly, a very important essential component and controlall the operation flow inside the power bank, a good quality PCBA will allowthe power bank to charge more and have better durability.

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5. 18650power bank and Li-polymer power bank

   The common typebattery is 18650 cell and better type will be Li-polymer

- 18650size and dimension are fixed. Li-Polymer size and dimension are flexible.

- 18650 are cheaper.Li-Polymer more expensive

- 18650 have higher selfdischarge rate. Li-Polymer has a very low self discharge rate

- 18650 battery’sdurability will drop faster.  Li-Polymer battery capacity more durable