Batteries and Electronics
Baggage equipped with lithium batteries must be carried as carry-on baggage unless the batteries are removed from the baggage. Removed batteries must be carried in accordance with the provision for spare batteries.
This restriction in checked baggage does not apply to baggage containing lithium metal batteries with a lithium content not exceeding 0.3 grams, or lithium ion batteries with a Watt-hour rating not exceeding 2.7 Wh.
See the regulation: 49 CFR 175.10(a)(26)