ok so this just happened to me coming back from japan and im still annoyed about it. i had four lipo batteries in my carry on, all under 100wh which i thought was the limit, checked this like three times before i left. the security guy at narita pulls them out and says i can only take two on board and the other two have to go in checked luggage which i know is literally not allowed for lipos. ended up having to just leave two of them behind. anyone else had this happen? is there an actual consistent rule or does it just depend on the airline and airport on the day

yeah this is a known thing in japan, some airlines there cap it at two spare batteries regardless of wh rating, it's not just a random decision it's actually their civil aviation policy i think. JAL and ANA both have it written in their baggage rules but it's buried and easy to miss. sorry that happened though, losing batteries abroad is the worst

honestly every country seems to have their own interpretation on top of the IATA guidelines and it drives me insane. ive started emailing the airline directly before every trip and screenshotting whatever they say so i have something to show at the gate if it comes up. doesnt always work but at least you have backup. also some people ship batteries ahead with a freight service which sounds overkill but after losing a set i get why people do it