Exactly, but I'm not a big fan of either. A slight oversimplification is that trickle chargers that turn themselves off are maintainers. I don't own anything other than a boat that has any use for this type of battery maintenance. Having watched all my boating friends use trickle chargers and cook batteries in the early days, I don't care to try the maintainers. I'm sure they work. So does leaving fully charge batteries in the boat in fall, and recharging them in spring. I get a year or more out of mine than most anyone else, even today. Maintainers included. I used to pull them each fall, but in Maryland a fully charged (good condition) October battery will make March without freezing. Watched my brother do this for 5 years before I bought in. Disconnect one terminal. It works. Recharge and go.
Keep in mind these are deep cycle or dual purpose batteries. Deep cycle are all around superior even to the dual purpose. If it's heavy it has good guts. The deep cycles start all smaller gas engines fine. Starters aren't needed unless you get over say 300 HP or do cold weather starts. The dual purpose are 4 year boat batteries and the deep cycle are 5 to 6 year and seldom 7 year batteries (since 1982 same boat). Starter batteries are 3 year batteries on my boat. Doesn't matter on any of these if you pull them or not. Same lifespans.
Motorcycle and car batteries (pure starters) are much more temperamental. One real hard discharge and a year or two old starting battery could easily be history. So a maintainer makes sense with them unless the are in a heated environment for the winter. Still need to pull one terminal though if your heated. /forums/images/graemlins/grin.gif
