Spare lithium batteries and power banks go in carry-on baggage, not in checked luggage. Under FAA PackSafe guidance, lithium-ion batteries up to 100 Wh are generally allowed, batteries from 100 to 160 Wh need airline approval, and batteries above 160 Wh are not allowed for passengers. That guidance applies to US flights and is consistent with widely used international dangerous-goods rules. Your airline can be stricter, so check its rules before you fly.
Work out watt-hours before you pack
Watt-hours are volts multiplied by amp-hours. Many power banks and batteries print the Wh figure on the label, and if it is there, use it. If the label gives only mAh, divide by 1,000 to get amp-hours, then multiply by the voltage printed on the label. The 3.7 V used in the table below is an example, so replace it with the voltage on your own product.
| Battery | Calculation | Result for carry-on |
|---|---|---|
| Example battery, 10 Ah at 3.7 V | 3.7 × 10 = 37 Wh | Generally allowed up to 100 Wh |
| Power bank labelled 27,000 mAh at 3.7 V | 27 Ah × 3.7 = 99.9 Wh | Just under 100 Wh |
| Power bank labelled 40,000 mAh at 3.7 V | 40 Ah × 3.7 = 148 Wh | In the 100 to 160 Wh range, so airline approval is needed |
The 27,000 mAh example sits just under the line, which is exactly where a rounded or mistyped figure causes trouble. The 40,000 mAh example falls in the approval range even though the number of milliamp-hours looks like a simple capacity figure. Check the label of each power bank before you pack it, because the same capacity can be sold with different voltages.
Check each item in the bag
The Wh limits apply to each battery, so a bag is checked item by item, and the largest item sets the question for the whole trip. The table takes three power banks, each with a label giving only mAh and a voltage of 3.7 V. The figures are illustrative.
| Power bank | Calculation | Outcome under the guidance |
|---|---|---|
| A: 20,000 mAh | 20 Ah × 3.7 V = 74 Wh | Generally allowed |
| B: 27,000 mAh | 27 Ah × 3.7 V = 99.9 Wh | Generally allowed |
| C: 30,000 mAh | 30 Ah × 3.7 V = 111 Wh | Needs airline approval |
Item C is the one that changes the plan. Its figure is 11 Wh over the 100 Wh line, so it needs the airline’s approval before you fly, while items A and B do not. Checking each item this way takes a few minutes at home and avoids finding the problem at the gate. Count the batteries you are carrying, not only the largest one, and check the airline’s own limit on the number as well as the size.
Check the rating before you buy
A rating is easiest to check on the shelf or the product page, before you pay. Look for a Wh figure on the box or in the specification sheet. If the listing gives only mAh and a voltage, work out the Wh figure yourself using the table above before you decide. If the listing gives both, use the Wh figure, because it already includes the voltage. Do not add the two numbers together or convert one into the other from memory. If the listing gives neither, ask the seller in writing for the rating, and keep the answer with the receipt. An item with an unclear rating is one you can decide against before it reaches your bag.
Installed batteries and spares are treated differently
A device with its battery installed is treated differently from a spare battery or a power bank in your bag. The phone, laptop or camera you bought abroad may follow a different rule from the spare battery you carry with it, and the airline is the place to confirm which one applies. Do not assume that a device carried with its battery follows the same rule as a loose battery. If you are unsure which category a device falls into, ask the airline in advance and keep a note of the answer, rather than settling it at the gate.
Keep the battery information with the purchase
When you buy a device or a power bank abroad, keep the box, or a copy of the product page, showing the Wh rating, together with the receipt. If a security officer or airline agent asks about a battery, the label and the receipt answer the question faster than a search for the model. A power bank bought at the end of a trip is not a special case, but it still needs its Wh figure in your hand.
Keep refund purchases within reach at departure
Several refund schemes check goods at departure, and the carry-on rule and the refund rule point the same way. Germany’s refund process asks you to keep the goods in your carry-on, because customs examines them before stamping the paperwork. Australia’s Tourist Refund Scheme requires you to present the goods in person at the facility. Japan’s refund method, which applies to purchases made on or after 1 November 2026, depends on customs confirming at departure that the goods are being taken out of Japan.
Where a scheme asks you to keep the goods in your carry-on, as Germany does, a device bought for a refund travels with you, where you can take it out at the desk. A power bank has to travel that way anyway. Keep its battery information with the receipt so that the battery and the paperwork can be checked together. Our German refund guide and the documents guide list the paperwork each scheme asks for.
Checks before you fly
- Work out the Wh figure for every battery and power bank in the bag, using the label first.
- Put spare batteries and power banks in carry-on, not in checked luggage.
- Look up the airline’s own rule for anything between 100 and 160 Wh, and ask whether approval is needed in advance.
- Keep the receipt and the Wh rating with each new device, and keep any refund goods where you can reach them.
The tourist refund calculator estimates what a refund could return on a receipt, but it does not tell you whether a battery can fly. If the device also carries duty or import tax on the way home, the full landed-cost calculator covers that part of the comparison.