A Power Bank You Can Actually Fly With

Carry-on only, never checked — and the number that matters is watt-hours, not mAh.

TSA guidance is that portable chargers and power banks with lithium-ion cells go in carry-on baggage and not in checked bags, and the FAA asks that spare batteries stay accessible in the cabin and protected from damage and short circuits. Airline policies vary on top of that, so check TSA and your airline before you travel rather than relying on any guide, including this one.

A note on this guide: this rests on published TSA and FAA guidance and on how lithium cells are rated, not on testing done here. Rules change and airlines differ — verify for your own trip. See how we test.

The problem, as it appears

A power bank bought on capacity, packed in a checked bag because it is heavy, and either removed at check-in or — worse — discovered in a bag that has already gone.

Or the subtler version: a bank that satisfies the rules perfectly and has no legible marking, so it becomes a conversation at a security check because nobody can confirm what it is.

Why the obvious approach disappoints

Buying on mAh. It is the number on the front of the box and it is not what limits are written in.

mAh is charge; watt-hours are energy. A capacity in mAh means nothing without a voltage attached, which is why two banks with identical mAh figures can be rated differently. Airline and regulatory limits are written in Wh, so that is the number to know.

The conversion is simple:

Watt-hours = (mAh × nominal voltage) ÷ 1000

Lithium-ion cells are typically 3.7 V nominal, so a 20,000 mAh bank is roughly 74 Wh. Most banks print the Wh figure somewhere on the casing.

Expecting the printed capacity to arrive in your phone. It does not. Stepping cell voltage up to USB output wastes energy as heat, so the number of full charges is meaningfully below the arithmetic. A 10,000 mAh bank does not deliver 10,000 mAh to a device.

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What actually matters

1. That the marking is legible

The single most practical property, and nobody checks it before buying.

Security staff cannot verify a rating they cannot read. A bank with the Wh figure printed clearly and durably on the casing is the one that does not slow you down; a bank with the figure on a peel-off sticker that came away in a bag is the one that does.

2. Capacity matched to the actual day

Most people carry more than they need. The question is not "how big can I get" but "how long is the day between reliable sockets".

3. Keeping it accessible and protected

The FAA point about accessibility is practical rather than bureaucratic: a battery in the cabin can be dealt with if it misbehaves, and one in the hold cannot.

"Protected from short circuits" means terminals not loose against keys and coins. In a bag with other metal, a pouch is the whole answer.

4. What else the socket is doing

A charger and a bank do different jobs and people carry duplicates. A single multi-port charger handles the overnight refill for everything, including the bank.

The options, and who each suits

10,000 mAh for a normal travel day with a phone and earbuds. Light, unobtrusive, sufficient.

20,000 mAh for long-haul, laptop top-ups, or sharing. Heavier, and closer to the limits that require checking.

Two smaller banks if redundancy matters more than weight — one can be charging while the other is in use.

None, if the trip is short and sockets are reliable. A charger and a cable weigh far less, and the bank that stays in a drawer at home was the right decision.

The mistake to avoid

Putting it in the checked bag because it is heavy. That is the one thing the rules are unambiguous about, and the bag is usually already gone when it is discovered.

The second mistake is treating any product labelled "TSA-approved" as settled. TSA does not approve power banks — the rules are about lithium content and where the battery travels, and a marketing phrase on a listing is not a substitute for the current guidance. Check TSA's own page for power chargers and your airline before the trip.

The same "keep the phone alive" logic applies away from airports, where the failure mode is a car you are trying not to flatten — keeping your phone alive during a breakdown.