I've used these BatteryMinders continuously on all my batteries for years with no ill effects and they're always ready with a full charge. I keep one on the chassis battery of my MH so it stays fully charged and ready. When I head south for the winter, I leave the batteries in lawnmower and the cars I leave behind connect to them. They prevent the harmful effects of leaving batteries connected and never boil out the water or sulfate the plates.
Highly recommended!BatteryMINDer Plus Battery Charger/Trickle Charger/Desulfator — 12 Volt, 1 Amp, Model# 12117TC available at NorthernToolBatteryMinder WebsiteFrom the BatteryMinder website wrote: