I am in the process of doing a second as an accy batt. I dont plan to use for cranking, just air comp, lights etc. My second is a GRP27 deep cycle. I am not sure yet what I will be doing for charging system yet. Thinking of the KISS. A constant duty solenoid with ignition switch on off switch, and wired to vehicle charging system. Fused of course.Thoughts? I have heard where isolators lower voltage and don't like that idea.