IATA has developed new regulations for transporting lithium batteries, which came into effect on 1 April, 2016.

[ARTICLE UPDATED 29 JULY 2016]

The following restrictions apply:

1. Small lithium batteries with ratings of less than 100 Watt hours or less than 2 grams of lithium content may be included in carry-on baggage. They may be installed in equipment or carried separately and there is no limit to the number of such separate batteries you can include in carry-on. Batteries in this category are typically used in mobile phones, MP3 players, cameras and most portable computers up to laptop size.
NOTE: Spare batteries may not be placed in checked baggage.

2. Lithium batteries with ratings between 100 Watt hours and 160 Watt hours can also be carried in carry-on baggage. They can also be included in checked-in baggage, provided they are installed in equipment.  Up to two spare batteries may be included in carry-on baggage but they can’t be packed in checked-in baggage.

3. Larger lithium batteries with ratings over 160 Watt hours, which are typically used in vehicles like mobility chairs, scooters and electric bicycles, must be presented as cargo and shipped in accordance with IATA Dangerous Goods regulations. They cannot be transported on passenger planes.

To calculate the Watt hour ratings for a battery, multiply Amperage hours by voltage using the following equation: mAh x V/1000 = Wh. Two examples are provided: a) the battery for a Panasonic GF8 camera is a 680mAh, 7.2V unit with a rating of 4.9Wh. b) the battery for a Canon EOS 5DS camera is a 1800mAh, 7.2V unit with a rating of 13Wh.

A one-page summary of the new regulations can be downloaded here:
http://www.iata.org/whatwedo/cargo/dgr/Documents/passenger-lithium-battery.pdf.