I'm not sure what you find confusing - you
cannot put spare batteries into checked luggage...
https://www.flytap.com/en-ca/baggage...0-baaae4dd0cd7
Spare or loose batteries
Alkaline batteries, lithium batteries (up to two grams), and lithium-ion batteries (up to 100Wh).
- In checked luggage: not allowed
You have a lithium battery (
LiFePo4) that's 1200 Wh - a potential fire hazard. You cannot take it either in a carry-on or in a checked bag.