Battery voltage driving me crazy

[WranglerMan]

If you have the genesis dual battery system you will want your charging system to stay above the 13.1V threshold so that the 2nd battery charges while running. Just an FYI I also have the genesis dual battery system with a fridge full time etc. I found that by simply disconnecting the IBS sensor on the battery ground cable my alternator voltage is constant 14V+. Might want to go that route if the 2nd battery is not charging sufficiently for you.

This is sort of correct, from my understanding chatting with Shane and Mike from Genesis yes you do need to see above 13.1 but this is sort of misleading.

On startup the Genesis system looks at voltage on the main crank battery and upon starting once it sees 13.1 for several minutes it closes the solenoid and connects the two batteries together and charges as one and from my understanding this reduces the load on the alternator so if your JL Sits say for several days and the voltage slowly drops to 12.7 +/- .1 the Cole Hersee solenoid opens and separates the two batteries to protect the main crank from getting lower if you are pulling off the aux but it does not keep if from getting lower due to parasitic draw from what comes off the PDC.

Once you start your JL the alternator first starts charging the main since the batteries are disconnected if the main is below the threshold and after several minutes of seeing it above 13.2 it closes the relay and connects the two batteries and they are treated as one big battery.

I have been testing the Genesis system for a few weeks and the batteries are connected as one over 99% of the time it’s only when your main falls below the 12.7 threshold that they separate and then it’s only for a few minutes.

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[WranglerMan]

I have a 2018 Sport. Purchased as certified pre owned in Nov last year with 7k miles.

My volt meter always ran at 14-14.2. On Saturday I had a EVIC message that my aux switches were unavailable as battery was charging. The dealership got me in. Turns out both batteries failed their testing. Both batteries replaced under warranty. After picking the Jeep up the volt meter was again at 14-14.2. Yesterday and today it’s at 12.7-12.9v

was curious as to why the difference from one day to the next. but being both batteries were replaced I assume this is the normal.

it takes a bit of time for the IBS to see the correct voltage so it then can tell the alternator how much charge to throw at the batteries, the days of seeing 14+ voltage all the time are long gone with these smart charging system but if your JL stays parked a lot you will see those 14’s but it should not stay there after a long drive