How Do Power Banks Work?

With modern batteries usually not holding enough juice for the regular person now a days the market has come up with a solution, power banks. Power banks are extremely helpful for any USB-charged devices with phones being one of the top uses almost every portable device that uses a USB style charging cable can be plugged into power bank. But you may ask, how do power banks really work?

Other names common names for power banks are battery pack, battery bank, power station, or mobile chargers. We are going to refer to it as a power bank here.

How Do Power Banks Work?

How does a power banks work?

Types of power banks

1. There are a couple different versions of power banks with the most common one being the Universal Power Bank, usually just a square cube that can hold a variable amount of power bank charge depending on the quality of the power bank and voltage it holds.

2. Solar-Charged Power Bank. The name is pretty self-explanatory. It is usually a Universal Power Bank with three or so mini solar panels that self-charge the batter when placed in sunlight. Solar charging itself is not a fast way to charge a battery. Depending on the battery it can take a couple of days for a Solar Power Bank to charge. Usually this type of power bank will have

3. The third popular style of power banks is the battery power phone case. This can be handy until you need to charge another device or you change the type of phone you have.

Let’s Get Technical

A power bank is, to oversimplify, a complex battery. It sits inside a case or phone case with a specialized circuitry to control the power flow, this specialized technology allows the power bank to smartly charge the device by not over-charging and only charging when it needs to be to.

Power banks are measured in mAh which stands for milli Ampere hour. This is how battery “fuel” is measured. An example is an iPhone X battery charge 2,716 mAh and an iPad Pro 12.9 has a battery capacity of 9,720 mAh. So, if you’re in the market looking for for quality power banks for your iPad I would not recommend one that can’t fully charge your device. And that is not the only consideration you should take into account when buying a power bank. Actually, an amount of charge is lost when you charge your device. This is often a small amount, but, in some cases, with poor power banks, the amount can be significant. As for most products, the higher price the higher quality.

Here is a video (below) to help explain this visually. 

How well do power banks work?

Every power bank has a certain conversation rate for charging devices. High-end power banks can have conversation rates of 90%. A power bank’s conversation rate also depends on the battery’s material used in the production. Lithium-polymer rechargeable batteries have a work output conversion rate around 85% – 95% and lithium-ion possess an output conversion between 75% – 90%.

Now you can use the formula power = voltage x current to calculate how much charge a battery has. Using 3.7 V as voltage due to power banks using that as the output. 

If the battery power is marked 4,000 mAh then the power of a 4,000 mAh power bank should be 4 x 3.7 = 14.8 W. Calculate by our battery’s conversion rate of 80% the real total power supply is approximately 11.8 W. Take a 1500 mAh smart phone for example, the demand power is 3.7 * 1.5 = 5.55 W, then it can charge the phone two times. So if you want to charge your tablet, you need a larger capacity power bank. The power bank capacity should be more than 8000 mAh and can provide high current 2 A output charging requirements.

Well that explains how universal power banks work but not solar power banks.

How Do Solar Power Banks Work?

As you can guess from the name, they are powered by solar panels. Solar panels work by converting the sun’s energy into electricity to power the battery. However, this process is slow due to the small size of the solar panel readily available on many power banks and the big mAh capacity on batteries. To fill up an entire 25,000 mAh battery it may take up to a week staying out in the sun. However, using them wisely together with general electricity, they are a valuable gadget for many fishing men, campers, hikers and hunters. 

Interested in a portable Solar Power Bank? Here is a guide to buying a Solar Power Bank that have been heavily reviewed. 



To sum all of this up, modern problems require modern solutions. Short battery lives can be a nuisance and sometimes, dangerous if you need to call 911 and your phone is dead. Learning how power banks work will help you buy one that suits your needs. Do you need to charge your iPad or charge your iPhone? Will you be out camping or will you be be around outlets to readily charge your battery? Hopefully this will help you make a smart power bank purchase.

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