Adding Lithium Battery Bank to existing RV Lead Acid House Batteries

[Kh128]

Hey everyone I’ve been searching around but hoping someone can answer more direct here. Wondering if there is a simple way I’m able to keep my house batteries while adding solar + lithium bank,

I’m adding 3 x 320W Panels with 40A charge controller, 3k Inverter and 4 x Lithium iron phosphate 12v 100ah batteries to an RV.

What I’m having trouble understanding is how to tie it in with the existing House batteries (Lead Acid) .

The RV has shore and Gen that I will run with the Inverter through an auto transfer switch. Inverter being default.

Am I able to hook the 2 seperate battery banks to the DC fuse panel on a similar switch? Or what is a useful solution? It seems unnecessary to remove the existing house batteries to replace for solar if all can be combined somehow.

Another idea is just to supplement from the Lead Acid bank with a DC DC charger. However I am uncertain if the House batteries get charged from converter solely or alternator as well. Lots of words… thanks in advance for reading.

 

[jberger]

I wouldn't try to combine Lead and Lithium in the same bank. They have different charging profiles and discharge rates.
If you decide to split them, you have the added complexity of two chemistries, longer charge times on the Lead, etc. for no advantage other then not having to wrangle the lead out of the bays.
I pulled out all of my lead acid (actually AGM) from the house bank and swapped them for LFP. Much easier to charge (fast), and they work very well on the road.

Adding solar and charging with an all LFP bank would be as simple as just adding your solar and MPPT.

Finally, don't use a bunch of small batteries, buy the largest Ah batteries you can afford. Every time you add a battery, you have to manage it and make sure it stays in balance. Also look for something with bluetooth at a minimum, so much easier to check the batteries when you can see what the BMS sees.

 

[Net10]

Although it goes against conventional advice, Lithium and Lead batteries can be combined.
Investigate the Bank Manager @
https://www.emilyandclarksadventure.com/bbms.
It appears there are over 500 of these systems in operation.