> although I don't think there's a limit on how many you can carry-on.
Correct. So long as it's for personal use.
> [1] Quantity limits: None for most batteries — but batteries must be for use by the passenger. Batteries carried for further sale or distribution (vendor samples, etc.) are prohibited. There is a limit of two spare batteries per person for the larger lithium ion batteries described above (101–160 watt hours per battery).
Correct. So long as it's for personal use.
> [1] Quantity limits: None for most batteries — but batteries must be for use by the passenger. Batteries carried for further sale or distribution (vendor samples, etc.) are prohibited. There is a limit of two spare batteries per person for the larger lithium ion batteries described above (101–160 watt hours per battery).
[1]: https://www.faa.gov/hazmat/packsafe/lithium-batteries