I've had an onboard charger in my boat since 1998 and it still works great. It's hooked up to wires leading to the motor and charges 3 batteries when the motor is running. You can also plug it in to charge at home. Wouldn't be without one. I use to camp at Kerr lake and would fish lights at night and troll during the day. Never had a battery fail me because the trolling kept them charged for the next night of fishing. 3 Interstate batteries has been used for over 5 years,and still work great.