I’m going to try doing that…what brand of batteries did you use?That's how a modern day vehicle tells you the battery(ies) need replacing.
Replacing the auxiliary battery is not fun: you have to remove the main battery, which weighs 50 lbs; then the fuse box with all the connections underneath. This is just to be able to reach the cover for the auxiliary battery. Then you have to remove that cover, disconnect the aux battery and pull it out. The you have to put everything back together. It took me 3 hours to complete. Reconnecting the fuse box took the longest. There is not much room to get my hand in there and push the connectors in place.
I am amazed how smoothly the Jeep starts now.
I replaced both batteries in on pass; I don't want to have to do the same thing six months later for one or the other battery.