Originally Posted by
moondog
With the exception of e-cigarettes/vapes, the FAA doesn't prohibit electronics devices containing Li-Ion batteries in checked luggage.
Wow, I never realized this and could have sworn it applied to all Li-ion batteries. It looks like spare batteries & portable chargers are also prevented from being checked, but that exact same spare battery is fine if it is attached to the (powered-off) device that is using it.
https://www.faa.gov/newsroom/lithium-batteries-baggage