tickets say "no wet-cell batteries".

Yes, but a sealed lead acid isn't a wet cell battery, it's a gelcell. The rules are, as far as I know, designed to stop anything that could spill corrosives on the aircraft, which then fizzes and falls apart. Same reason mercury thermometers aren't allowed (mercury on aluminum in the presence of moisture dissolves it remarkably fast).

I'm sure I've come across something about gelcells being permitted, although to be completely safe it might be a good idea to check with the airline.

Patrick