PowerBankExpert.com is reader-supported. If you purchase products via the links on our site, we might earn affiliate commissions.

What is a power bank? Power banks explained

What is a power bank? Power banks explained

A power bank is a portable battery designed to recharge electronic gadgets when you don’t have access to a regular wall charger. Ranging in size from slim, pocket-sized devices up to larger, high-capacity power banks – they can be used to charge cell phones, tablets, cameras, portable speakers, gaming consoles, or even laptops.

So the concept of a power bank is pretty simple: a rechargeable battery that can be used to charge other devices. However, even if they seem pretty basic, power banks can have some pretty complex technologies built-in.

For example, in order to reduce the risk of malfunctioning, a lot of safety features are added: overcharge protection, over-discharge protection, short circuit protection, etc.

Other types of technologies frequently seen in power banks are pass-through charging, wireless charging, and fast charging technologies such as Qualcomm Quick Charge, Power Delivery, or PowerIQ. Some newer models are even featuring futuristic battery techs such as GaN or Graphene technology.

How does a power bank work?

Since power banks are basically regular batteries with some extra features, they work just like any other rechargeable batteries. They first store energy up to their maximum capacity and then release it when connected to a different device that needs recharging. That’s the basic gist of it.

Of course, in terms of circuitry, they can be quite complex devices. Besides charging and recharging they also have other features such as safety features, power indicators, quick charging technologies, etc.

What are the different types of power banks?

Power banks come in many different shapes and sizes to suit different budgets and power needs. There are portable chargers that can be used for just about every device. Most people buy power banks to use them for their cell phones, tablets, or laptops. But some portable chargers can also be used for devices such as drones, mini-fridges, or even CPAP machines.

New portable charger models are coming out every day with improved charging technologies. Some power banks even work by harnessing solar energy while others double as a protective case that also charges your phone. In terms of shape, the most popular ones are cylindrical or rectangular, similar to a smartphone or a deck of playing cards.

How to charge a power bank

All power banks come with a power input port. The type of port can be different based on the model but micro USB was the most popular one until recently. However, micro USB is slowly being replaced by USB type C ports, which seems to be the new standard for the coming years. So, if you’re looking to buy a new power bank, our advice is to look for one with has a USB type C input port.

The most efficient way to charge a power bank is to use a wall charger that can deliver a high power output. Using a low-quality wall charger that only delivers 2A for example, can extend the recharging time for several hours. For this reason, we have put together a list of the best GaN chargers and a different one of the best chargers with Quick Charge 3.0 and 4.0.

Other ways to charge a power bank is using your laptop USB port, a car cigarette lighter, or using a solar charger such as the Anker 21W. However, all these methods are slower and you should avoid them unless you can’t access a wall charger.

Make sure to also read our guide on how to use a power bank for the first time.

How long does it take to charge a power bank?

This is largely dictated by the size of your power bank’s capacity. The larger the capacity of the power bank you decide to purchase, the longer it may take to charge. But other factors can influence the charging speed too, such as the charging technology used. For example, power banks with fast charging features or those built based on the new graphene or GaN technologies will charge much faster than usual.

As a rule of thumb, for a power bank of 10000mAh, the average recharging time is around 4-6h. The fastest ones can charge in under 1h but expect to pay a premium price for that. And the slowest ones might take as much as 8h to recharge. It’s best to avoid them if you can find faster-charging options at a similar price point.

How many times can a power bank charge my device?

This comes down to the capacity of your device and the power bank/portable charger. A power bank is measured by its capacity, which is rated in mAh (milliampere-hour). Generally, the higher the mAh rating of your power bank or portable charger, the more power it will have to recharge your devices. A good rule of thumb is to look at the mAh rating of the devices you want to charge, and purchase a power bank that has an equal rating (preferably higher).

For example, the iPhone 11 has a 3110mAh rated battery. The XCentz Wingman has a mAh capacity of 5000mAh. This would safely charge your phone back to 100% battery. However it is not an exact science, there are factors to consider such as the power bank’s efficiency rating and the condition of the battery in the device you are charging. Read more about the real battery capacity of a power bank.

The following set of figures can be used as a rough guide to what kind of recharging capacity a power bank may give you.

Device Charge Times Example

Power Bank RatingMobile PhoneTablet
2500mAhApprox. 1 full chargeApprox. 25%
5200mAhApprox. 2 full chargesApprox. 50%
10000mAh4 full chargesAt least 100% full charge

On ou product review pages such as the RAVPower 20000mAh PD 60W, we even have an automatic calculator that can tell you exactly how many times that specific power bank can charge your specific smartphone model:


Charging capacity calculator

Use the search bar below and find out exactly how many times can the RAVPower PD Pioneer 20000mAh charge your smartphone battery

If you don’t know which power bank you want, then you can use our general mAh calculator.

We’re discussing also this subject in more detail here: How many mAh do you need to charge your phone?

Is a Power Bank and a Portable Charger the same thing?

YES! They are basically one and the same thing 😊

Different terms such as power bank, portable charger, portable phone charger, external battery, external battery pack, etc. all refer to the same type of device. If it’s a battery that you can use to power a device with its own battery without using a wall socket, it’s a power bank.

Read more about these two terms and about their popularity in our dedicated article: Power Bank or Portable Charger?

What type of batteries do power banks use?

Power banks generally come with either Lithium-Polymer (Li-Po) and Lithium-Ion (Li-Ion) batteries. Of the two Li-Ion power banks are more popular.

In terms of differences between these two types:

  • Lithium-Polymer batteries have a higher energy density but they tend to have a shorter lifespan and are also more expensive to manufacture. They’re also less prone to explosion.
  • Lithium-Ion batteries, on the other hand,  have a slightly lower energy density but they can withstand more charge/discharge cycles and are generally less expensive.

For a more in-depth look at this subject, check out our article: Lithium-ion vs Lithium-polymer power banks. Which is better?

Are you allowed to take power banks on flights?

Yes, you can take power banks and other batteried on flights, however, some conditions apply:

  • you can only take them in your cabin luggage
  • the battery should be 100 Wh or under
  • batteries that are between 100 Wh and 160 Wh need a special permit
  • ideally, the output should be clearly labeled on the device

Read our detailed article for more information about power banks on flights.

Power bank reviews

If you’re interested in comparing different power bank models, head on to our power bank review section. Otherwise, you can check out our curated list of what we believe to be the current 10 best power banks.