A battery for when the phone runs low
A power bank is a battery in a case with a USB socket or a cable, carried so a phone never runs flat away from a plug. It is the answer to a long day out, a festival, a long journey, a phone whose battery has started to fade, and a power cut. Choosing one comes down to three things: how much it holds, how fast it charges, and how it fits the way you carry things. The power banks here today include magnetic ones that click onto the back of the phone, power banks with their cables built in and a display showing what is left, and solar ones for the outdoors.
The kinds of power bank
How much it holds, and how fast
The mAh on a power bank is measured at its cells, at about 3.7 volts. Some is lost raising that to USB voltage and in the phone, and roughly two-thirds of the number ends up in the phone's battery. So a 10,000mAh power bank gives a phone with a 4,000mAh battery about one and a half charges, and a 20,000mAh one about three. Power banks are also filed by size, from 5,000mAh and 10,000mAh to 20,000mAh and over.
For fast charging, a power bank needs the same as a wall charger: USB Power Delivery on a USB-C socket. A 20W PD output fast-charges most phones. The guide to power banks explains the sums.
Questions people ask about power banks
Can I take a power bank on a plane?
Power banks travel in your hand luggage, never in a checked bag, and the UK Civil Aviation Authority allows two per passenger. They must not be recharged on board, and each should sit in a pouch or its packaging so its sockets cannot touch keys or coins. The limits are in watt-hours: under 100Wh is allowed in the cabin, 100Wh to 160Wh needs the airline's approval, and over 160Wh is not allowed in passenger baggage. Check your airline's own rules as well, as some are stricter.
How do I use a power bank safely?
Never charge a swollen, damaged or hot power bank. Stop using one that bulges, cracks, smells odd, smokes or gets too hot to hold, and do not take it apart. Charge it uncovered on a hard surface, not on a bed or inside a bag, and unplug it once it is full: Electrical Safety First advises against charging power banks overnight or while you are out. An old power bank goes to a battery recycling point, never the household bin.
How long does delivery take?
Delivery is included in every price and tracked to your door. Each product page says when it usually arrives.
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