Optimizing Dual Battery Setup in 2018 Ford Transit With Marine Switch

[cliffrodriguez]

I did this to myself over 4 years of owning my 2018 Ford Transit 250. I installed two batteries (under drivers seat) and also installed a 4 Pos Marine Switch for the batteries who's output goes to the CCP bus. The 4 Position switch has: 1,2,1+2,off. I have an inverter on my CCP 1 as well as other stuff.

The alternator positive only goes to battery #1. The only time battery #1 and battery #2 are "connected" is when the 4 Pos switch is selected for 1+2.

OK, here is the problem (s):

1. with only one battery connected to the alternator, what is the best way to keep the second battery charged? Normally I leave the switch in 1+2 so then the two positives are connected and are charging (I hope).

2. Is there a problem with batteries periodically tied together at different charge levels (when the alternator is running)?

3. Lastly, should I have the alternator positive split to each battery. Would that work?

I made this pretty complicated. Now that I'm changing the batteries due to the inverter smoking and drawing them down to nothing, I'm reviewing this setup.

 

[booster]

If they are the same size, brand, and model batteries I would just keep them parallel all the time. That will run an inverter better do to less voltage drop and also keep the batteries at a similar point in their life so no mismatch when both are connected. I think essentially all 2X12v batteries are run parallel in RVs.

 

[otr]

just adding a side bar regarding how multiple batteries with play together... matching batteries, we have an off grid set-up with 2 pairs of 6 volt golf card batteries. I have know for some time that all of the batteries must match, same age, size, brand, etc. or else the weaker (smaller, older, etc) will draw more of the juice and essentially reduce the life and capacity of the newer stronger, bigger batteries.
We replaced them this past summer and only used one pair as our electricity needs are less. The dealer said we could add another pair, but within one year of replacing the first pair.