The faster phones become, the less able their batteries seem to be at keeping up. We want a high-end phone that lasts at very least a full working day, and until we get one power banks can provide welcome relief.
Confusingly for consumers, not all power banks are created equal. The Zendure A2 sitting at the top of our best power banks list is there because it offers a great balance of portability, affordability, capacity and efficiency, and has an ultra-tough design and passthrough charging.
But there are power banks in our round-up that are technically superior, with LCD screens, faster and mutliple inputs and outputs, support for USB-C, AC outlets, higher capacity, waterproofing and so forth. We’ll help you to wade through this mess to find the best power bank for your precise needs.
What’s the best power bank you can buy?
Want more help deciding which is best for you? Read our buying advice for the Best Power Banks
How to choose the best power bank for you
You might assume all power banks are much the same thing, but you would be wrong. You can get compact power banks that will charge your phone once, slightly larger portable chargers that might offer two or three charges, or high-capacity banks that can charge your phone in excess of 10 times.
Working out how many times a power bank will charge your phone depends on more than the mAh rating on the packaging. No power bank is 100 percent energy-efficient, with every portable charger losing power through voltage conversion and heat generated.
The industry standard for energy efficiency is between 60- and 70 percent, but some of the best can offer 90 percent efficiency.
We’re seeing an increasing number of power banks with support for Quick Charge 4.0 and USB-C, and in some cases these are supported on the input as well as the output, making them as fast to refill as they are to charge your phone. Power banks may offer these in place of or alongside full-size USB, Micro-USB and Lightning ports.
We’re starting to see power banks that feature an AC/DC outlet (a plug socket for non-USB devices). Unfortunately many offer only a US two-pin plug, so you may need to carry an adaptor.
Another type of power bank builds in solar panels. You might think living in the UK our grey climate would rule out the use of such a device, but even in cloudy conditions these devices can draw some solar power.
Design is important when it comes to choosing a power bank, and some batteries are more compact than others at the same capacity. You can also buy those protected from the elements, but be sure to check whether they are waterproof or simply rainproof.
Nearly all power banks use LEDs to show you how much power remains in the device. This is fine for smaller-capacity devices, but when each LED represents several charges for your phone it can be difficult to see where you are. We favour banks with built-in LCDs.
Passthrough charging is a great feature to have – the ability to charge a connected smartphone at the same time as the device itself.
Auto-on and auto-off is another sought after feature, though sometimes a bank can support this and your phone won’t. It means you can plug in a device and the power bank will begin charging without you pressing any buttons. When charging is complete it will put itself into standby mode to conserve energy.
Some power banks also come with an LED torch, activated by double-pressing the power button.
Get the fastest charging rates
The input rating is key when it comes to recharging the bank – the higher is this figure the more quickly it will charge. You’ll see a figure in Amps, and you multiply this number by the voltage (5V for USB) to find the rating in Watts.
Don’t expect to get a USB mains charger in the box – you can use that which was supplied with your phone or tablet. Note that a power bank with a 2A (10W) input will not recharge its own battery any faster than one with a 1A (5W) input when used with an underspecified USB charger.
The reverse is also true when it comes to charging your devices – a phone that supports only a 1A (5W) input won’t charge faster from a 2A (10W) output.
The output rating refers to how quickly a power bank will charge your devices. In most cases you’ll find 1A (5W), 2A (10W) or 2.5A (12.5W) outputs.
You can use any output to charge any USB device – it will draw only the power it needs. However, you might find some tablets will refuse to charge from lower-specified outputs.
Increasingly power banks feature clever technology called PowerIQ or similar. This allows the bank to recognise the type of device you have connected and deliver the optimum amount of power.
If a power bank has several outputs the maximum total output capacity is key, since it may not be able to simultaneously support each at full power.
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See our pick of the Best Power Bank Deals and Best power banks for Nintendo Switch. Plus: How to charge your smartphone or tablet faster.