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How we test power banks

Here's how we find a good power bank that will keep your smart device up and running when you need it most.

phone power bank chargers

Our power bank reviews will help you find the best model to keep your smart device going when you're out and about. We assess their size, ease of use and charging capabilities, so you can be confident you're making the right decision when it's time to buy. Here's how we do it.

How we choose what we test

We look for readily available power banks with a power rating of at least 10,000mAh, up to around 30,000mAh. However, we do test smaller and larger capacity models from time to time if they're from a popular brand. 

We also try to find power banks that can charge multiple devices at once, models that can charge devices other than smartphones such as tablets, laptops or portable games consoles and some with fast-charge capabilities.

In addition to this, we looked for models with USB-C connectivity (though this is only available on some products).

How we score power banks

Our overall score consists of:

  • capacity performance (70%)
  • ease of use (15%)
  • display (15%)

We also look at how well the power bank can charge multiple devices if applicable, but this does not contribute to the overall score.

How we test power banks

We rate and/or assess the following aspects of each power bank.

Usable capacity (USB-A power banks): Each product is connected to a Maynuo M9712 DC electronic load reference instrument. This instrument is set to draw the maximum supported current from the power bank's fastest charging USB-A port. The output is sent to a PC and logged in a spreadsheet, with the data graphed to show the capacity drain over time. This test gives us the total milliamp hours that the battery supports.

Usable capacity (USB-C only power banks): We calculate what 80% of the battery capacity of our test phone is, then we use the power bank to charge the test phone to 80%, multiple times, until the power bank is fully discharged. Finally, we multiply the number of charges (including partial charges) by the 80% phone battery capacity value to give the usable capacity of the power bank.

Multiple device score: This refers to the power bank's ability to charge multiple devices at once, if more than one port is available. Higher scoring models showed a limited drop in charging performance when two or more devices were plugged in. In 2022 this method was altered to be a general performance test observed over the course of 30 minutes. This aspect of the test is not directly comparable to models tested prior to 2022.

Ease of use: This is based on port labelling (were the inputs clearly labelled, e.g. USB-A, USB-C and fast charge) and the quality of the instruction manual.

Display: This takes into account the position of the display on the unit and how easy it is to see and understand at a glance.

Charge time: We completely drain a smartphone and note the time required to charge the device to 80%. We run this test three times.

Power bank charge time: We drain a power bank to the point where it will not charge a smartphone, then record how long it takes to recharge.

Powering a laptop: Some USB-C enabled power banks can power USB-C enabled laptops using a USB-C to USB-C connection. This means the laptop battery will last longer, as the power bank is essentially operating as a second battery. Charging is different to powering, as it replenishes the battery during use or when it's off. Power banks in this test can't charge laptops, but some can power laptops. If the laptop didn't indicate that it was on battery power, then we determined that the power bank on test couldn't power it.

Powering a Nintendo Switch: This is the same as the USB-C laptop test, but with a Nintendo Switch.

Pocketability: This is a broad guide based on our experience handling the devices – does the device fit in your jeans pocket, jacket pocket, or a bag?

We care about accuracy. See something that's not quite right in this article? Let us know or read more about fact-checking at CHOICE.