The following is a summary of the current regulations:
- Li-Ion batteries are carry-on only. All Li-Ion batteries are prohibited from checked baggage.
- Batteries not installed in a device must have their contacts protected against short circuits. You can do this by placing the battery in its own bag, taping over the contacts, or other methods that will prevent some small metal object from touching any of the contacts.
- Batteries must be protected against damage. They should be in a padded case or other protective package to prevent damage.
- There is no quantity limit for standard size laptop batteries (under 100wh). This covers every battery that is currently ships with or fits into a laptop.
- Special external batteries with capacities of 100-300Wh have a limit of 2 spares. This size battery is not commonly used and is not shipped as the standard battery for any laptop.
Note that rules and regulations may change over time or in response to some incident. The US Government has a special website to provide the latest information concerning traveling with laptop batteries. This site can be found at: http://safetravel.dot.gov
