Last checked: July 2026 — sourced against TSA “What Can I Bring?” and FAA PackSafe. Rules change; re-verify before you fly.
The verdict, in one line
Depends entirely on the chemistry. Ordinary dry batteries — AA, AAA, C, D, 9-volt, button cells, alkaline or NiMH rechargeables — fly in both carry-on and checked bags. Spare lithium batteries (the loose lithium-ion and lithium-metal cells that power phones, cameras, and power banks) are carry-on only, never checked, must sit under watt-hour or lithium-content limits, and need their terminals protected from short circuits.
Dry batteries: the easy ones
Standard consumer dry cells are unrestricted. That means alkaline AA/AAA/C/D and 9-volt batteries, plus nickel-metal-hydride (NiMH) and nickel-cadmium (NiCd) rechargeables, and most button/coin cells that are not lithium. Pack as many as you reasonably need for personal use in either bag. It’s still smart to keep them in packaging or a case so loose contacts don’t touch metal, but there’s no federal limit or carry-on requirement on these.
The one trap: some coin cells (the flat CR-type in watches, key fobs, and car remotes) are lithium-metal. They’re tiny and fall well under the limit, but they are lithium — so if you’re carrying a stack of spares, treat them like the lithium rules below and keep them in the cabin.
Spare lithium batteries: carry-on only
This is the rule that matters. Spare (uninstalled) lithium-ion and lithium-metal batteries — including power banks, portable chargers, and loose camera/drone cells — are prohibited in checked baggage. They must travel in your carry-on and stay accessible. A battery installed inside a device (your laptop, camera, or phone) may be checked, but the device is better carried on too. It’s the loose spares that are the hard line.
Whether a lithium battery is allowed at all, and how many, depends on its size. Lithium-ion is measured in watt-hours (Wh); lithium-metal (non-rechargeable) is measured by grams of lithium content:
| Lithium-ion size | Lithium-metal equivalent | Carry-on | Checked |
|---|---|---|---|
| 0–100 Wh | ≤ 2 g lithium content | Yes — no airline approval, reasonable personal quantity | Spares: No. Installed in device: allowed but discouraged |
| 101–160 Wh | 2–8 g lithium content | Yes, with airline approval — max 2 spares | No |
| Over 160 Wh | Over 8 g | No — forbidden on passenger aircraft | No |
To find the watt-hours, check the battery label. If it lists volts (V) and amp-hours (Ah), multiply them: V × Ah = Wh. Milliamp-hours? Divide by 1,000 first. A typical phone power bank (say 3.7 V × 2.7 Ah) lands around 10 Wh — nowhere near the limit. A big laptop-class power bank can approach or cross the 100 Wh line, which is where airline approval starts.
Protect the terminals
Every loose lithium battery must be individually protected against short circuits. A short between exposed terminals is what starts a fire, so the FAA requires one of these: keep the battery in its original retail packaging; tape over the terminals; or put each battery in its own separate plastic bag or a battery case. Never let bare terminals rattle against keys, coins, or other batteries in your bag.
The airline & international layer
The Wh tiers above are the global floor, but 2025–2026 brought the biggest tightening in years — driven by a spike in in-flight battery fires (the FAA logged dozens of US incidents in the first half of 2025 alone). New ICAO rules that took effect 27 March 2026 apply worldwide and hit power banks in particular:
- Power banks and spare batteries can’t be used or recharged during the flight on many carriers.
- They must be kept where crew can see and reach them — several airlines now bar them from overhead bins.
- Some carriers cap you at two power banks per passenger regardless of size.
Individual airlines can be stricter still on quantity and Wh. Before an international trip, check the dangerous-goods page for every carrier on your itinerary — the loose-lithium ban is universal, but the fine print is not, and an officer’s call at the gate is final.
Sources & verification
Every claim on this page was checked against the primary sources below and last verified July 2026.
- FAA — dry cells allowed in both bags; spare lithium-ion/lithium-metal batteries banned from checked baggage and must have terminals protected. faa.gov/hazmat/packsafe/airline-passengers-and-batteries
- TSA — lithium batteries 100 Wh or less need no airline approval in reasonable personal quantities. tsa.gov/…/lithium-batteries-100-watt-hours-or-less-device
- TSA — lithium batteries over 100 Wh (101–160 Wh) need airline approval and are capped at two spares in carry-on. tsa.gov/…/lithium-batteries-more-100-watt-hours
Related rules: Lithium batteries & power banks · Power bank · Laptop · Drone
FAQ
Can I put AA or AAA batteries in checked luggage?
Yes. Ordinary dry cells — alkaline and NiMH/NiCd rechargeables — are allowed in both carry-on and checked bags with no federal limit. Keep them in packaging so terminals don’t touch metal.
Can spare lithium batteries go in a checked bag?
No. Loose lithium-ion and lithium-metal batteries and power banks are prohibited in checked baggage. They ride in your carry-on only.
How do I calculate watt-hours?
Multiply volts by amp-hours: V × Ah = Wh. If the label shows milliamp-hours, divide by 1,000 first. Under 100 Wh needs no approval.
Do I have to tape the terminals?
You must protect them somehow — original packaging, a case, a separate plastic bag, or tape over the contacts. The goal is preventing a short circuit.
Are lithium coin/button cells a problem?
A single small CR-type coin cell is fine, but it is lithium-metal. Carry spares in the cabin and keep them from touching each other or metal objects.