My current setup is a 150 amp continuous duty solenoid. Three way switch. Position one joins both batteries with the ignition on. Middle position kills the solenoid so the batteries can’t be joined. The other position joins the batteries, but the power for the solenoid comes from the aux battery. I’ve typically only used that to self jump the main cranking batter from the aux battery.
The way I have it set up I will typically leave the switch in the first position as it will automatically join the batteries when I turn the key on and separate them when I shut the key off. It’s been that way for a long time and it’s stone cold simple and reliable. Just leave the switch and go. Even if you plan on extended storage let’s say as long as the key is off the batteries are still separated.
The only reason I plan on switching to an acr is for solar. If there is enough power coming in from solar that would be tied directly to the aux battery, the acr would join the batteries to allow the main battery to take charge from the solar. Once the solar input dips below the acr set voltage point the batteries would be separated again.
