A small trickle/minder/maintenance/tender charger is perfect for a motorcycle, third car, tractor, ATV, etc. where the battery is placed into storage fully charged to begin with. You want a 3-stage dual-bank AC charger with decent current capacity if you are seriously depleting a stereo deep cycle battery. A charger with 6+6 (10 or 12 total) amps is good for a couple of group 24s. If you have a larger stereo battery its a good idea to go with the 20 amp total charger. We are talking about smart multi-stage chargers rather than low/high/boost emergency garage chargers (which you should avoid and never turn your back on) so no more current will be applied to the battery than required.