Jay58,
Look at a Trik-l-Start. Ideal for chassis battery maintenance.
There are also relays that do not cut in until 13.5 volts is achieved.
I do have manual control of the charging solenoids for my house bank.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.