Can you take button cell batteries on a plane?

The rule for button cell batteries comes from the Civil Aviation Bureau's list of restricted items and is the same on domestic and international flights.

A button cell is judged by its chemistry: a lithium coin cell follows the lithium metal rows, and an alkaline one does not.

ANA lists button batteries next to dry cells

ANA's domestic FAQ has a single line for dry batteries and button-type batteries and accepts them in the cabin and at check-in. ANA's line does not separate lithium coin cells from the others. Japan's national list has no row called button battery: its battery section sorts by chemistry, with dry cells first and lithium metal batteries after.

South Korea's list names the CR series

South Korea's list is the one that describes coin cells in words. Its rows for lithium metal batteries of 2g or less say this generally means button-type lithium batteries of the CR series. A spare one is marked for the cabin and not for checked baggage. One fitted in electronic equipment is marked for both.

A cell inside a watch is not a spare

Japan's list accepts a device holding a lithium metal battery of 2g or less in the cabin and as checked baggage. Its spare row, which includes cells taken out of a device, is cabin only. The FAA's battery table gives watches and LED flashlights as examples of small consumer electronics that use non-rechargeable lithium metal batteries.

Loose cells: cover the terminals

Japan's list asks for short-circuit protection on spare lithium metal cells. Australia's CASA spells out how: original retail packaging, tape over exposed terminals, or each battery in a separate plastic bag or protective pouch. South Korea's list asks for the terminals of alkaline batteries to be insulated as well.

Non-lithium button cells at the TSA

The TSA's dry battery entry applies to typical non-lithium dry batteries and names the button cell among the most common sizes, next to AA, AAA, C, D and 9-volt. The entry is marked yes for carry-on and yes for checked bags, and says the batteries must be protected from damage and from creating sparks.

In the United States, the United Kingdom, South Korea, Taiwan and Hong Kong the authority's page lists button cell batteries as allowed in carry-on.

Each row comes from that authority's own page. Airlines can be stricter, and the screening officer has the final say.

What to do

Move button cell batteries to the bag you check in before you reach security, within the checked-baggage limits above. Narita Airport states that anything given up at the checkpoint is discarded and cannot be returned.