The FAA guidance places ordinary rechargeable lithium-ion batteries within a 100 Wh limit. Larger spare batteries in the 101–160 Wh range need airline approval and are limited to two. These are passenger provisions, not a general authorization for every battery or route.

Spare lithium batteries, including power banks, belong in carry-on baggage. If a cabin bag is taken at the gate for the hold, remove them and keep them with you. Protect terminals from short circuits and accidental contact with metal objects.

When only milliamp-hours are shown, use nominal battery voltage: Wh = mAh × V ÷ 1,000. For example, 20,000 mAh at 3.7 V equals 74 Wh. This is an arithmetic example, not certification of an unidentified product; do not substitute a USB output voltage.

Check the actual marked rating, battery condition, airline approval process and all operating carriers. Airline restrictions can be stricter, and international itineraries may add local rules. Do not assume that being allowed to carry a battery also permits using it throughout the flight.

Keep the specification label legible and obtain any required approval before departure. If a battery overheats, swells, smokes or burns on board, notify the crew immediately. Large camping power stations need a separate transport plan, not a guess at the airport.

Editorial note: manufacturer specifications are not independent test results. Source links are references, not purchase recommendations.