Tom, I have my StaynCharge supplying power from tow vehicle to the cranking battery which powers the AllCharge mounted over my batteries. At all times, on the road or on the water, the cranking battery gets all it wants, from truck alternator, or outboard alternator. The AllCharge services the other batteries with two 18+/- ga charge wires, in my case alternately charging two batteries besides the cranking battery. Each of the two batteries charged by the AllCharge get 5 minutes of top-off charge at a time, switching back & forth automatically. On long runs in the boat I've stopped to find the AllCharge red lights off, batteries full. They are just as hot as when formerly charging with an AC charger. There has not been the slightest loss of battery life. I have one of those batteries for trolling, the other for electronics. I used to have to use two batteries for trolling, but now that the AllCharge keeps them up I only need one. I can now run my dual night lamps on the bow plus the basic boat power bus off the cranking battery since it always gets charged if any get charged by the AllCharge. The power to the sonar/gps is clean and free of interference, always charged up.
Jim