I have the Minn Kota MK2 system in my boat. It dumps 10 AMPS per bank into the trolling batteries as long as the main engine is running. If I'm not on the trolling motor much, I have those batteries mostly charged by the time I get back to the dock. It's only $150 (ish), and I see no downside to having it. I actually want absolutely nothing on my cranking battery. I want it to be completely left alone. I'd rather run a 24V trolling motor, 1 house battery for electronics, and 1 cranking battery. All of this is moot because in 5 years, we'll all be using lithium systems. A single 24V lithium bat weighs 30LBs and covers the trolling motor. Then just a pair of 12Vs for cranking and house.
