Now for the isolator/combiner. I was thinking of using a Hellraoring system, but I'm not sure how it will interact with the Batteryminder. If i put the Batteryminer on the main battery, will it charge the aux battery becuase it will see the charger? Or, will it stay isolated? If it will stay isolated, is it acceptable to leave the combine switch on while the Batteryminder is plugged in? Or should i just go a different route?
Yes, it'll charge the aux battery if you put the Batteryminer on the main battery. As long as it can maintain above 13.4V when charging both battery.