I've been thinking about buying a 1.5 amp battery maintainer to leave hooked up to my deep cycle 24/7. That a good idea? My only concern is that it'll do more harm than good. As you can tell, I'm brain dead on this.
I don't see how it can do any harm, I use one on my deep cycle when it isn't hooked to my camper, going on about 4yrs now, I also use one on my 48v golf cart, ( designed for it ) it supposedly cuts down on the sulfate buildup , and extends the life of batteries, can't vouch for that yet, but I haven't heard anything about them being a disadvantage ?
Unless the battery is just sitting there for months and months at a time, without being used, battery maintainer doesn't do any good. But a battery will eventually self-discharge, and sometimes there are things that put a small drain on a battery (like a clock or something).
For example, if you take your boat out every few weeks or less, a battery maintainer doesn't give any benefit at all. Except it makes your wallet lighter.
And I know of a battery that was destroyed by a Battery Tender Jr. That is the little one - the "wall wart" type. Apparently it didn't have any circuitry to detect that the battery was fully charged, and it trickled it to death.