Your RV's 12-volt system is the heartbeat of life in the coach — powering everything from lights and fans to slide-outs, water pumps, control boards for the furnace, water heater, refrigerator (in gas mode), and even some entertainment systems. In motorized RVs like Class A, Class B, and Class C motorhomes, this DC system is especially critical because it supports both driving functions (like chassis battery integration) and living-area comforts when you're parked. Whether you're boondocking off-grid or plugged into shore power, weak or neglected batteries can turn a relaxing getaway into frustration: dim lights, non-working slides, a furnace that