@Brett Hatch beat me to the reply. So….what he said.Just to clarify, when you refer to "your rechargeable batteries" that means spare or "loose" batteries, right? I have never had a problem traveling anywhere, including Mexico, with lights containing batteries, rechargeable or otherwise. Some lights have batteries that can't be removed.
As far as the Coz comment, it’s been noted in the Coz forum that some folks have had LI batteries taken from them when in carry ons, being told that they should be in checked bags. Don’t know full details.