My general rule of thumb has been to take all batteries with me in carryon. I have a messenger bag that I use for my laptop and GoPro stuff, and in that I take several 18650 rechargables for my lights, several GoPro batteries, and now on my upcoming trip to Utila I will be adding a few LiPo batteries for my Phantom drone and batteries for a pair of Kodak SP360 4k's. I guess I have gotten lucky going thru Cancun, Cozumel, San Pedro Sula and even, lol, Utila and my US connecting cities, Atlanta and Miami (I fly from Newark, NJ). Batteries are always individually wrapped to protect the contacts (The airlines are most worried about contact being made / short and then fire from what I understand). Always thought I would be hassled and so far, so good. On my last trip to Cozumel I brought my 7 cam 3d printed gopro rig, and because I was fearful of it breaking (its rather fragile) I carried it on a selfie pole. Yes, lots of attention, like "whats that" or "you can't film in here" (wasn't filming anyway) but nobody gave me issues. I was more worried about someone smashing me on the head and running away with it to be honest!
I did read a TSA posting about limits on batteries, either a max number of watts / watt hours / amps, or something like that. Basically everything I have was well under the limit. Those kids hoverboards are a huge offender as their batteries are just too large. I wish I bookmarked the TSA page..