Well then you've been lucky. Depends on airlines, depends on countries, and depends on the agent you're talking to, even if you have rules printed. I got in **** from an Italian customs agent a few years ago for having SWIT Li-on batteries in checked luggage (under 100Wh), and had to take them out and put them in carry on. And again later on that same show going to the US. Since then we just started to carry them on and has been practically no fuss (other than once setting off the bomb warning at Heathrow... That was fun [emoji14] )
For instance, FAA says no to spares in checked:
Pack Safe – Lithium ion and lithium metal batteries, spare (uninstalled)
And CATSA says you can only if it's installed on/in an item, but all spares must be approved by airline for checked baggage:
Guidelines for Batteries | CATSA | ACSTA
Point of the matter is, sure you can try and check them if you like, but you run the risk of being stopped, or your luggage being refused to be loaded, or starting a fire on a plane.
It was just my advice to not check them and instead carry them on, as in my experience, that's the smoothest option for travel.
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