We're not going to explain what a power bank is. We know you know, and if you don't, you can work it out. What we will explain is why they're useful to have in the car and which ones are worthwhile.
Why do I need a power bank in my car?
Yes, you can charge devices via the USB plugs seen in almost all cars these days. But what happens if the car has a breakdown, such as that common ailment: a flat battery and you need to charge your phone? This is where a power bank comes in useful.
Which power bank is best?
For having in a car, the ideal power bank can do a lot more than just charge. The best picks offer other functions such as a tyre inflator perhaps, or even a portable jump starter for the car itself.
In terms of capacity, you'll want at least 5,000mAh. This is roughly what's required to fully charge one phone and plenty for top-ups.
The best power banks
Editoru2019s pick
The best power bank for a car is one that can jump-start the car too. The GBX45 from battery specialists NOCO is CAR's recommendation. It's the smallest of the Boost X range but given it's American, the tiddler is more than enough for Brits. The GBX45 is capable of jump-starting petrol engines up to 6.5-litres and diesel engines up to 4.0-litres.
And yet it's only about 20cm x 13cm and weighs a mere 1.25kg. It's a tough power bank too, with an IP65 rating. It also features a 100-lumen flashlight. In terms of battery capacity for charging devices, it is 5,000mAh. The GBX45 itself can be recharged via USB in less than an hour.
Runner up
CAR's silver medallist power bank is a little tyre inflator. It's about the size of a pint glass, weighs half a kilo and can top up a car tyre in a couple of minutes. It comes with two adaptors for other inflatables, and features auto-shutoff to prevent overinflation. The inflator can be recharged via USB and can of course charge devices. The battery capacity is 5,200mAh.
Best value
Finally, for an actual power bank, we recommend Anker's PowerCore Slim. It's small and light, measuring 15cm x 6.8cm x 1.4cm and weighs just over 200g. Yet with 10,000mAh, it has twice the capacity of the jump starter and tyre inflator above - it's enough for about two phone charges. It has USB, micro USB and USB-C ports.
Best solar power bank
This is for people who like to get properly out and about away from urban zones. Both the power bank and the solar panel are rugged, with the power bank being IP65 rated, yet both weigh less than 300g. The power bank has the largest capacity here at 12,000mAh - enough for about three smartphone charges, with USB and USB-C.
The solar panel is a 5 Watt unit and can charge a device directly. It makes use of something called MPPT (maximum power point tracker) technology that can still draw solar power even during cloudy conditions and low light.
Best wireless power bank
The PowerCore 3 is a bit thicker than the PowerCore Slim and a little heavier, but the trade-off is wireless charging capability (allowing you to charge up to three devices simultaneously) and more powerful 18 Watt charging (10 Watts on the PowerCore Slim). Battery capacity is the same at 10,000mAh, but an extra feature we like is the built-in phone stand.
Read next:
Sealey Compact Rechargeable Tyre Inflator & Powerbank review