mkm,
Thanks for sharing this !
"This is because of an incident that occurred in the US some years ago. A passenger wearing a portable air purifier around his neck had accidentally put a non-rechargable battery in a battery recharger, which he then used in the air purifier. "
At least I can avoid or all of us can avoid this scenarios. So different airline has different rules. Yeah I wont put it in my carry on luggage and might as well not use it on board..