I use maintainers, but had one go bad and boil a battery one time. I solved the problem by buying a cheap mechanical timer that I plug into the wall and then plug the maintainers into it. I find 30 minutes a day is all you need.I usually set them to turn on for 15 minutes 12 hours apart. The timers are less than 10 bucks. I go to Florida for the winter and have never had a problem.
$$6.98 at Home Depot :
https://www.homedepot.com/p/Defiant-...ode=6302&gQT=1