What size power bank can you take on a plane in the UK?

Anything rated at 100 watt-hours or less travels in hand luggage with no approval needed, and that covers essentially every consumer power bank. Between 100Wh and 160Wh you need the airline's permission in advance. Above 160Wh it cannot be carried on a passenger aircraft at all. The limit is set in watt-hours, not the milliamp-hour figure printed on the front of the case. On a standard 3.7V cell, 100Wh works out at roughly 27,000mAh.

How many power banks can I take on a flight?

Two per person. This limit was introduced on 27 March 2026 and applies whatever the size of the power banks, so a slim 5,000mAh bank counts as one in exactly the same way a large one does. If you carry a magnetic bank stuck to your phone as well as two in your bag, you are over the limit.

Can you charge a power bank on a plane?

No. Since 27 March 2026 power banks must not be recharged on board the aircraft, and that includes charging them from an in-seat power socket or USB port. The Civil Aviation Authority's own passenger checklist puts it plainly: do not charge your power bank on any flight. Charge it at the gate instead, before you board.

Can a power bank go in checked luggage?

Never. A power bank counts as a spare lithium battery and must travel in the cabin with you, because a fire in the hold is far harder to deal with than one in the cabin. The case people forget is the gate: if your cabin bag is taken at the aircraft door to be put in the hold, take the power bank out before you hand it over.

How do I work out the watt-hours of my power bank?

Multiply the voltage by the capacity in amp-hours. For a figure given in milliamp-hours, the formula is volts times milliamp-hours divided by 1,000. A 10,000mAh bank on a 3.7V cell is 37Wh. The important caveat is that not every bank uses a 3.7V cell — 3.6V and 3.85V are both common — so the watt-hour figure printed on the case is the one that counts, and the formula is only for when the case does not show it.

What happens if my power bank is damaged or swollen?

It must not be carried on an aircraft at all, in any bag. A battery showing damage, swelling or signs of overheating should be taken out of use entirely rather than just left out of your luggage. If a power bank, vape, phone or tablet starts to get hot during a flight, switch it off, stop charging and tell the cabin crew immediately.

Tech Tips 09 November 2026

Flying with a power bank: the UK rules that changed in 2026

Hand luggage only, two per person, and since March you may not recharge one on board. The limit is in watt-hours, not the mAh on the front — here is the arithmetic.

By Kwasi Acheampong6 min readUpdated November 2026

A white magnetic power bank seen from the back, its printed label reading rated capacity 5000mAh, 18.5Wh — the watt-hour figure airlines go by.

The short version

Power banks go in hand luggage only, you may carry two per person, each must be protected against short circuit when it is not in use, and since 27 March 2026 you must not recharge one on board — including from the seat socket. The size limit is measured in watt-hours, not milliamp-hours: under 100Wh needs no permission, 100–160Wh needs the airline's approval, and above 160Wh cannot fly. On a standard 3.7V cell, 100Wh is about 27,000mAh.

The rules changed this year and the change was not well advertised. If the last time you thought about this was a holiday in 2024, two of the five points above are new.

What actually changed in March 2026

The International Civil Aviation Organization issued an addendum to its Technical Instructions for the Safe Transport of Dangerous Goods by Air, and the UK Civil Aviation Authority adopted it with effect from 27 March 2026. It separates power banks out from ordinary spare batteries for the first time and attaches specific restrictions to them.

Two of those restrictions are genuinely new, and they are the two that catch people out.

A maximum of two power banks per person. Size does not come into it. A slim 5,000mAh bank counts for one in exactly the way a heavy 20,000mAh one does. If you travel with two in your bag and a magnetic bank stuck to the back of your phone, you are carrying three.

No recharging on board. You may not top a power bank up during the flight, and that explicitly includes plugging it into the seat's own power outlet or USB port. The CAA's passenger checklist does not qualify this: do not charge your power bank on any flight. The guidance also says a power bank should not be used to charge other devices in the air, so the practical position is that a power bank is something you carry, not something you use between doors closed and doors open. Charge the phone and the bank at the gate.

Watt-hours, not milliamp-hours

This is the part that causes the most confusion at a check-in desk, and it is entirely avoidable.

The number printed largest on a power bank is almost always its capacity in milliamp-hours — 10,000mAh, 20,000mAh. Aviation rules are not written in milliamp-hours. They are written in watt-hours, which measures energy rather than charge, and which is the figure that actually relates to how much there is to burn.

The conversion the CAA gives is straightforward: volts multiplied by amp-hours. For a capacity in milliamp-hours, multiply by the voltage and divide by 1,000.

Lithium cells in a power bank are usually rated at 3.7V nominal, so:

5,000mAh × 3.7V ÷ 1,000 = 18.5Wh
10,000mAh × 3.7V ÷ 1,000 = 37Wh
20,000mAh × 3.7V ÷ 1,000 = 74Wh

Work the 100Wh limit backwards and it lands at roughly 27,000mAh. That is why 26,800mAh turns up so often as a capacity: it is the largest round number that comfortably clears the threshold, and it is marketed accordingly.

One honest caveat, because it matters. Not every cell is 3.7V. Some manufacturers build on 3.6V cells and some on 3.85V, and the arithmetic moves with it — the same 26,800mAh built on 3.85V cells comes out above 100Wh. So the figure printed on the case is the one that counts, and the formula above is for when the case does not show it. Any power bank worth buying prints its watt-hour rating. If you are looking at one that does not, that is itself worth knowing before you get to an airport.

Where our range sits

We sell power banks between 5,000mAh and 20,000mAh, which on the standard arithmetic is 18.5Wh to 74Wh. Every one of them is inside the 100Wh limit, and the largest is still a quarter clear of it. Nothing we sell requires airline approval and nothing we sell is close to the line.

That is not a boast — it is true of most of this market, and it is the reason the limit rarely bites. It is worth stating anyway, because the question we get asked is "will this be a problem at the airport", and for anything in this range the answer is no.

We would still tell you to read the watt-hour figure on the case rather than trust our arithmetic. It is printed there for exactly this reason.

Protecting it properly

The requirement is that each power bank is individually protected against short circuit when it is not in use. In practice any of these satisfies it:

its original retail packaging
a separate pouch or plastic bag, one bank per bag
tape over the terminals

The point is that the contacts cannot touch keys, coins or another battery. A power bank loose in a bag with a handful of metal is the specific scenario the rule exists to prevent.

You may also be asked to keep power banks out of the overhead locker and in the seat pocket or the bag under the seat in front of you, so that a problem is noticed immediately rather than above your head. Some airlines require this and some go further than the minimum in other ways, which is why the CAA's advice ends where ours does: always check with your airline before you fly.

The gate trap

The most common way a perfectly legal power bank ends up somewhere it should not be is nobody's fault in particular.

You board with a cabin bag. The flight is full, the lockers fill up, and the crew take your bag at the aircraft door to put it in the hold. If the power bank is still inside, it has just travelled in checked luggage.

Take it out first. Same for vapes, spare batteries, and anything else with a lithium cell in it. It takes five seconds and it is the single most useful habit in this whole article.

When a power bank should stop flying — and stop being used

A battery showing damage, swelling or any sign of overheating must not be carried on an aircraft. Not in the cabin, not in the hold, not at all.

A swollen power bank is not a power bank with a cosmetic problem. The casing is being pushed apart from the inside by gas, which means the cell has already failed. The honest advice is that it should not be going in your bag and it should not be going back in a drawer either — it should be recycled properly, at a shop or recycling centre that takes batteries.

If something starts getting hot in the air — a power bank, a vape, a phone, a tablet — switch it off, stop charging it and tell the cabin crew straight away. They are trained for it and they would far rather hear about it early.

The whole thing, in six lines

Hand luggage. Never the hold, and take it out if your bag goes down at the gate.
Two per person, whatever the size.
Each one protected against short circuit — box, pouch, or tape on the terminals.
Do not recharge it on board, including from the seat socket.
Under 100Wh needs no approval. Read the watt-hours on the case, not the mAh on the front.
Damaged or swollen: it does not fly, and it should not be used again.

Rules in this article are the UK Civil Aviation Authority's, in force from 27 March 2026, following the ICAO Technical Instructions addendum. Individual airlines may impose stricter conditions than the minimum, so check yours before you travel.