Originally Posted by
j2simpso
.... It is against FAA and IATA regulations to pack any device containing a battery in the cargo hold due to the risk of there being an unconfined fire. ....
That is factually incorrect per
FAA Fact Sheet – Lithium Batteries
The restrictions only applies to LiION and not other batteries. And the restriction only applies to removable LiION batteries. I beleive there is also a max watt-hour rating.
Devices containing lithium metal or lithium ion batteries, including – but not limited to – smartphones, tablets, and laptops, should be kept in carry-on baggage. If these devices are packed in checked baggage, they should be turned completely off, protected from accidental activation and packed so they are protected from damage.
Some governments (China) have stricter requirements. Some airlines have additional limitations -- UA has a limitation on carry-on smart bags without a removable battery.