How to Check Power Bank Capacity

Power bank capacity is the first element to consider when you are to buy a power bank. How to check real power bank capacity becomes a question since there is a large capacity range in current market of power bank. You can buy power bank 2600mAh, 10400mAh, 20000mAh or even more powerful power bank according to your needs. But the following steps will help you check the real capacity of your power bank.

Check your power bank capacity approximately

If you just need to get how many mAh your power bank has approximately, formula below would meet your needs.

Power bank real capacity = claimed power bank capacity * battery efficiency

Let’s take a 2600mAh power bank as an example. As the most decent power banks are about 90% efficient, and then the actual capacity of the power bank is around:

Claimed power bank capacity (2600mAh) * battery efficiency (90%) = 2340mAh

How long to charge 2600mAh power bank first time.

Check your power bank capacity accurately

If you need check out how many mAh your power bank really has, you will need the following tools which you can get from eBay or any other online shop at very low price:

1. a power bank
2. USB current voltage meter
3. USB AC charger (or any USB power source)
4. timer/clock/stop watch or anything you can use to count time

Let’s again take the 2600mAh power bank as example:

Fully discharge your power bank and follow steps below:

1. plug the USB AC charger into a power plug, then connect the USB current voltage meter to USB AC charger;
2. charge the power bank via USB current voltage meter and start the timer;
3. take note of the amp in the beginning and wait for the power bank to be fully charged;
4. take note of the amp when the charging stops.

We can get 3 numbers from the experiment: amp in the beginning (0.7A), amp at the end (0.34A) and charging time (3h 53m 05s). So we can calculate that the capacity of the 2600mAh is:

Average amps (0.52A) * charging time (3.88h) = 2019mAh.

How many times can a 14000mAh power bank full charge your phone?

Above are 2 methods to check power bank capacity. You can also join our discussion about power bank capacity calculation and how to tell fake power bank capacity here. Remember to let me know if you have any questions or suggestions.