+2 to the Schumacher brand float-chargers. I've got a few and only had one go out over many years, and keep a couple of my AGMs plugged in ($30K Harley-Davidson and Optima Blue-Top AGM) as trickle chargers. Some of them have the higher-amp setting which would provide both a fast charger and a float-charger. As a jumper we use a WAGAN power-dome. After so many years of using the small Schumacher float-chargers without issue, it's obvious from some of the products other folks rely on that we've saved a tidy sum of $pending Green indeed. :)