Flying With a Handheld and a Power Bank

Find the watt-hour figure on the bank before you pack it, and treat 100 Wh as the number that matters. It is printed on the case, usually in small text near the certification marks, and it is not the capacity in mAh that the marketing uses.

A note on this guide: aviation rules vary by airline and by country and they have been changing. This explains how the limits are structured and how to work out your own figure — it is not authorisation, and your airline is the authority. See how we test.

The problem, as it appears

You have a handheld, a power bank to keep it alive on a long flight, and a vague sense that there are rules about batteries. The bank says 20,000 mAh. The airline's page says something about 100 Wh.

Those are different units and nothing on the packaging makes the relationship obvious, which is how people arrive at security genuinely unsure whether the thing in their bag is allowed.

Why the mAh figure disappoints

Because milliamp-hours are not a measure of energy on their own.

A capacity in mAh only means something alongside a voltage — the same 10,000 mAh at 3.7 volts and at 7.4 volts are different amounts of stored energy. Aviation limits are written in watt-hours because that is the figure corresponding to how much energy is available to be released if a cell fails.

Marketing uses mAh because the number is bigger and sounds better. Regulators use Wh because it is the number that describes the risk.

What actually matters

The conversion, and the mistake people make in it

Watt-hours are amp-hours multiplied by volts. So:

20,000 mAh = 20 Ah. At a cell voltage of 3.7 V, that is 20 × 3.7 ≈ 74 Wh.

The common error is using 5 V — the USB output voltage — instead of the cell voltage. That gives 100 Wh for the same bank and makes a compliant item look borderline. The cells inside are lithium-ion at roughly 3.6 to 3.7 V nominal, and that is the figure the rating is based on.

Most banks print the Wh figure directly. When they do, use it and skip the arithmetic entirely.

The three bands

The framework applied by most carriers works in three steps:

• Up to 100 Wh — carry-on, no approval needed. Almost every consumer power bank sits here.
• 100 to 160 Wh — carry-on with airline approval, usually a limited number.
• Above 160 Wh — generally not permitted in passenger baggage at all.

A 20,000 mAh bank at around 74 Wh is comfortably inside the first band. The banks that get people into trouble are the large ones sold for laptops and camping.

Cabin, never the hold

Spare batteries and power banks go in the cabin. This is consistent, it is enforced, and the reason is straightforward: a fire in the cabin can be reached and dealt with, and one in the hold cannot.

This applies to the spare battery specifically. The handheld with its battery installed is a device rather than a spare, and is treated differently.

The rules have been getting stricter, not looser

Worth saying plainly because it is the part that dates fastest. Several carriers have added rules about using or charging power banks during flight, and about stowing them where they can be seen rather than in an overhead locker.

Check your airline near departure. This is one of the few topics where last year's answer is genuinely unreliable.

Terminals and protection

Loose spare cells need their terminals protected against short circuits — original packaging, a case, or tape over the contacts. A sealed power bank with a plastic housing already satisfies this; a bare 18650 rattling around in a bag does not.

The options, and who each suits

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A power bank comfortably under 100 Wh suits essentially every handheld user, and the figure to check is the one printed on the case rather than the one on the box.

A case that keeps the handheld and its cable together suits the security tray more than the flight — a device that comes out cleanly and goes back in cleanly is one you are less likely to leave behind.

A compact travel strip suits the destination rather than the aircraft, where one hotel socket has to serve several things.

A USB-C video adapter suits playing on a hotel television, and is the smallest item that changes a trip.

The mistake to avoid

Assuming the mAh number is the regulated one. It is the number on the front of the box and it is not what any airline is asking about, so people either worry about a compliant bank or — less often and more seriously — carry a non-compliant one believing it is fine. Ten seconds finding the Wh figure settles it.

The second mistake is packing the power bank in a checked bag because it is heavy and the carry-on is full. That is the one rule in this area that is close to universal, and it is the one most likely to result in the item being removed rather than a conversation.