True, and United changed their policy sometime between my May 2017 Cozumel trip and my April 2018 one. Last year I had to check my batteries in Cozumel and move them to my carry on in the Houston airport. This year I had to have them in carry on the whole way.It seems to change daily in Cozumel about the batteries. Going to Cozumel I was asked by United if I had any batteries in my checked bag--nope only in my carry-on. Good to go. In Cozumel I was told by security as I was waiting in line that all batteries had to be in my checked bag--so I had to move them out of my carry-on and into my checked bag. Then in Houston I had to switch them from my checked bag to my carry-on for my on going flight. United agents in Cozumel never asked me about batteries but I know others recently have had a totally different experience and were told by United in Cozumel that batteries needed to be in their carry-on--go figure. There's a new thread just posted about the "battery experience" in Cozumel--check it out.