What the standard defines
UN 38.3 is a series of tests a lithium cell or battery must pass before it may be transported: reduced pressure, thermal cycling, vibration, shock, external short circuit, impact or crush, overcharge and forced discharge. A maker that ships batteries internationally has a test summary for each model, and larger sellers publish it.
Alongside the tests sit the carriage rules themselves, which are written in watt-hours — the reason this site converts every milliamp-hour figure before comparing two power banks.
What it does not promise
It is a transport condition, not a performance statement. A battery that passed says nothing about its usable capacity, its cycle life, its behaviour in cold weather, or the quality of its battery management system.
Nor does it settle what you personally may carry. Airline and carrier rules differ, they change, and they distinguish between batteries in a device, spare batteries and batteries in checked baggage. The carrier’s own current rules are the reference.
What it works with
Every battery product on this site falls under these rules somewhere between the factory and the buyer. Where a maker publishes a watt-hour figure, the product page reports it; where only milliamp-hours are given, the product page says so and gives the conversion with the cell voltage it assumed.
What people ask before they order
Why do airlines ask for watt-hours rather than milliamp-hours?
Because carriage limits are written in watt-hours. A bank sold in milliamp-hours has to be converted first, and the conversion needs the cell voltage — which is why this site prints watt-hours beside every capacity.
Does UN 38.3 mean a battery is good?
No. It means it survived a defined series of transport tests — altitude, thermal cycling, vibration, shock, external short circuit and others. It says nothing about capacity, cycle life or how it behaves in your installation.
Last reviewed 16 September 2026