The complete guide to Power Banks


It has happened to all of us. We’re away from a power source and our phone is about to die. Luckily for us, we had a power bank. So what exactly is a power bank and how does it work. We’ll give you a complete guide to everything you need to know before and after buying a power bank.

So, What exactly is a power bank?

Think of a power bank as a portable battery that you charge in a manner similar to your phone or laptop. Power banks vary in size, color, shape, capacity, and input & output charging rates.

In the following guide, we’ll dive through all the details of a power bank

1) The size, shape and color

Power banks vary in size, shape, and color. When it comes to the size, the battery technology hasn’t advanced very far in the last couple of years and so, the battery inside the power bank is usually directly proportional to its capacity. So, usually, the bigger or heavier the power bank, the higher the capacity. However, always read on the battery capacity indicated on the product packaging.

When it comes to the shape and color, it’s really up to your preference and shouldn’t have any effect on the performance of the device.

2) The Power bank capacity. What is mAh and why is it important?

The power bank capacity is measured in mAh (Milli-amp hour) which is a unit that measures electric power over time. Generally, the more mAh, the longer the battery capacity or battery life is. Standard nowadays are the 2600 mAh, 4000 mAh, 5200 mAh, 10000 mAh, 20100 mAh, and 26800 mAh.

To help you better understand those capacities, look at the following table that includes some of the major cellular phones available nowadays along with their internal battery capacity

Phone Model Battery Capacity
Samsung Galaxy S8 3000 mAh
Samsung Galaxy S8+ 3500 mAh
Samsung Galaxy S7 3000 mAh
iPhone 6 2915 mAh
iPhone 6s 1715 mAh
iPhone 6s Plus 2750 mAh
iPhone 7 1960 mAh
iPhone 7 Plus 2900 mAh
Google Pixel XL 3450 mAh
LG V20 3200 mAh
HTC 10 3000 mAh

3) The input & output charging rates

The battery charging rate is measured in Amperes or Amps or the letter A. This is a unit of electrical current. For power banks, this unit measures how fast a battery can charge or be charged. 1 Ampere = 1000 Milliamps

Battery input charging rate

Usually indicated on the product itself or packaging and shows how fast you would be able to charge the battery itself. The higher the number of Amps or A the faster you could charge the battery. The standard now is 0.5A, 1A, 1.5A, 2A.
But how long will it take to charge your power bank? Well, it depends on the capacity of the power bank and the input charging rate.

Let’s do some simple math
Charging time = Battery Capacity in Amps / Input Charging Rate in Amps
So, for example, if you bought a 5200mAh battery (which would be 5.2Ah if you divide by 1000 to convert units), and it had an input charging rate of 1.5 Amps:

It would take you approximately:
5.2 / 1.5 = 3.46 hours to charge from empty to completely full capacity

Battery output charging rate (discharging the power bank or charging your phone)

Also indicated on the product itself, the output charging rate is also indicated in amps and follows the same guidelines above.
So, how long will it take to charge my completely dead-charge phone to full capacity? Click here or scroll below to find out

4) How to charge a power bank for the first time

It is always advised to charge your power bank fully for the first time. Most power banks have an indicator to show you the charging status and capacity. You should charge your power bank to full capacity before using it for the first time. Once it is charged, you should use it until it is completely empty. This should only be necessary for a brand new power bank and might not be necessary for some models.

5) How long will it take to charge my phone?

The answer depends on the power bank output charge rate in amps, the battery capacity of your phone in amp-hour, and the input charge rate of your phone also in amps
Let’s do some simple math. First, from the power bank output charging rate and the phone input charging rate, pick the lesser of the two and let’s call that C
Charging time = Phone Battery Capacity in Amps / C
So, for example, if you bought a Samsung Galaxy S8 with a 3000mAh battery (which would be 3Ah), and it had an input charging rate of 2 Amps, and also bought a power bank with an output charging rate of 1.5 Amps:

First, we choose the lesser of the two charging rates, which would be 1.5 Amps. Then, It would take you approximately:
3Ah / 1.5 = 2 hours to charge from empty to completely full capacity

Please be advised that using a higher charging rate than your phone manufacturer recommends could result in permanent damage to your phone. Always consult your device manufacturer before buying third party accessories.

Please note, the above calculation assumes the phone is powered off while charging and is only accurate theoretically. Additionally, please note that some device manufacturers invented faster charging technologies (such as quick-charge) which use a non conventional method to charge your phone. Those methods do not follow the above calculation

6) How many full phone charges will i get?

Well, it depends on your phone battery capacity and the power bank capacity.
Assuming zero power wasted during charging, dividing the power bank capacity by the battery capacity of your phone will give you the number you seek.

For example, if you bought an iPhone 7 which has a battery capacity of 1960 mAh, and also bought a 10000 mAh power bank, you should theoretically get:
10000 mAh / 1960 mAh = 5.1 Full Phone Charges

We hope this guide was informative and would like to thank you for reading it.