Thank You, And Everyone for Your Patience,

The fuse advice is welcome.

Today I connect everything like the above and drive for 30 minutes and it stayed at 15.3 v input the whole time, this is the alternator in 90% duty mode. My batteries are Odyssey Extremes. One (the secondary) is 9mos older than the starter,primary.

I shut down and check voltage while they are isolated, primary is 12.95v the secondary is 13.5v, a 055v spread. Is this OK or normal? Does it need more time to equalize? Will it ever?
I wonder how the RVC sensor sees things and is reacting? Does GM ship dual battery trucks with RVC?

Thanks

 

Update, Maybe I spoke too soon? I took another drive on errands and shes reading 14.4V input voltage now and was creeping down the more I drove and its at night this time with lights on. So I guess with everything disconnected for a few days she had to run in?
I have been reading how some choose to bypass the RVC system but if this is not going to over charge my batteries I'm good..

 

RVC is probably one of the better updates for newer vehicles, so your alternator doesn't have to charge full power all the time when the batteries don't need it.

You don't need to worry about the batteries ever being equal, because they won't be (while isolated). They have an age difference and different loads applied to them. Your starting battery will always have the very small load from the computers on the truck when off, so it will drain down very slowly over time.

Your 2nd battery with no load essentially will recharge very quickly with a drive so you shouldn't have to check on it for years unless you start drawing it down with something extra.

All of the Duramax trucks have dual batteries I think, and they are setup in Parallel configuration, so both batteries are connected to each other full time with no isolator. As far as I know there is still some sort of alternator/smart charging system on all of the newer vehicles but they may have done away with that physical sensor.

 

Thanks! All great news. Now that I know what to expect I can relax. I wasn't fond of the idea for RVC delete.