Unequal discharge from two house batteries

[WilliamB]

Originally Posted by Elkman

After installing two Lithionics batteries in our 2021 Navion, I have been able to monitor them individually and I found that the SOC on one would be lower by up to 40% than the other one. I thought initially that the problem was with one of the batteries. Further investigation showed that the problem is with the wiring of the Navion that is resulting in DC appliances and loads to be hitting one of the batteries instead of both equally.

Prior to test with oven on
Battery #1 139AH
Battery #2 218AH

After running oven on
Battery #1 148AH
Battery #2 228AH

Inverter is drawing equally from both batteries so it is the other DC loads that are pulling more from Battery #2 which shows that it has provided 80AH more than Battery #1 or half again as much DV volts demand.

The gap became greater when I ran the Norcold 10 DC only fridge for several days. So at least I know to ignore the inverter draw from the batteries and focus on everything else.

With the factory lead acid batteries I would have been clueless about this unequal draw so upgrading to the Lithionics batteries was worthwhile in providing information on the state of both house batteries.

Has anyone else encountered this with their two battery installation?Has anyone else encountered this with their two battery installation?

If batteries are truly in a paralle configureation, then it has to be the battery. I have a question re installation on Navion. When it was done, did installer modify alternator charging system at all?
Thanks, Bill

[misteracng]

There is no modification to the alternator. Mercedes recommends max 40amps output from the alternator for charging so for my 2021 there is a charge point 40 under the passenger seat that limits to 40amps. I think this has replaced the solenoid previously used. The lithium install does add another combiner relay on top of that that accounts for the different voltage cut offs for lithium.