LifePo4 Question

[SolarPoweredRV]

I have a 206AH SOK 12v battery. Planning to add one or two more batteries with a Victron Multiplus install this spring. Also, have solar with the new RV so likely going to add one more panel for now and potentially change things out after a year if I feel like improving on the system will be useful after boondocking more this summer. Now to the question...

I see there are more battery options these days that seem to have positive reviews (mainly Will Prowse), such as the Power Queen brand. Wondering how well it would work to add one or two 200AH 12v Power Queen batteries in parallel with my existing 206AH SOK? Reason being that the Power Queen is $650 and an SOK is $1030. So, for a bit more I could add two Power Queens vs one SOK and end up with 7.2kw total. It seems like matching the capacities as closely as possible would be a good thing, but not sure if other differences would be an issue?

At the time, I bought the SOK because it was half the price of Battle Born for the same watt hours.

If you are using Buss Bars to connect your batteries to your load, mixing batteries with internal BMSs is possible. However, whenever you mix electronics from different manufacturers you run the risk of introducing gremlins into your system (note: "Electronics" refers to the BMSs, and Voltage control circuitry inside the Converter, or Inverter/Charger and the Solar Charge Controller). Gremlins are hard to find and hard to fix, especially if you have something like an "Auto Sense" Converter.

If you did choose to mix your batteries, and like the OP, the voltages were slightly different you would run the risk of the BMS not stopping one of the lower voltage batteries from over charging while the system is charging the higher voltage batteries. If all your system charging components allowed you to set the max charge voltage (Victron for example) to match your lowest voltage battery(ies), then you could combine the batteries and eliminate that overcharging/BMS failure risk. You would however loose a small amount of energy storage capacity from those higher voltage batteries.

A better solution might be to purchase all newer batteries and sell your older battery(ies).

An even better solution, might be to buy new batteries and create a 24 volt system to power the Inverter and leave the old battery on the 12v side of the coach. You can attach all your charging to the 24v battery bank and use a DC to DC Converter to power the coach and keep the old battery charged up. Your Inverter would be pulling power from the 24v battery bank and your 12v battery will keep everything running on the 12v side (this also provides extra amps to operate the slides and hydraulic system (or electric leveling jacks) needed for motor startup.

[Riverbug]

If you are using Buss Bars to connect your batteries to your load, mixing batteries with internal BMSs is possible. However, whenever you mix electronics from different manufacturers you run the risk of introducing gremlins into your system (note: "Electronics" refers to the BMSs, and Voltage control circuitry inside the Converter, or Inverter/Charger and the Solar Charge Controller). Gremlins are hard to find and hard to fix, especially if you have something like an "Auto Sense" Converter.

If you did choose to mix your batteries, and like the OP, the voltages were slightly different you would run the risk of the BMS not stopping one of the lower voltage batteries from over charging while the system is charging the higher voltage batteries. If all your system charging components allowed you to set the max charge voltage (Victron for example) to match your lowest voltage battery(ies), then you could combine the batteries and eliminate that overcharging/BMS failure risk. You would however loose a small amount of energy storage capacity from those higher voltage batteries.

A better solution might be to purchase all newer batteries and sell your older battery(ies).

An even better solution, might be to buy new batteries and create a 24 volt system to power the Inverter and leave the old battery on the 12v side of the coach. You can attach all your charging to the 24v battery bank and use a DC to DC Converter to power the coach and keep the old battery charged up. Your Inverter would be pulling power from the 24v battery bank and your 12v battery will keep everything running on the 12v side (this also provides extra amps to operate the slides and hydraulic system (or electric leveling jacks) needed for motor startup.

Interesting idea about leaving the 12v battery separate. I do intend to install a Victron Multiplus. My new 23LDE has the Furrion solar package with 12v fridge, which I never had before. So if I left the two banks separate, then I would also have separate solar for each bank? That would also be ok because I assume I would swap out the Furrion charge controller at some point and add more panels anyway; maybe I would leave it as is then and just add new/separate solar for the inverter bank?

[SolarPoweredRV]

Interesting idea about leaving the 12v battery separate. I do intend to install a Victron Multiplus. My new 23LDE has the Furrion solar package with 12v fridge, which I never had before. So if I left the two banks separate, then I would also have separate solar for each bank? That would also be ok because I assume I would swap out the Furrion charge controller at some point and add more panels anyway; maybe I would leave it as is then and just add new/separate solar for the inverter bank?

You also have the added advantage of building the "new" system from scratch which can make your installation much simpler.

[A.Texas.Yankee]

Just to clarify, I didn't have an over voltage situation with the BMS, just with the Solar controller overcharging by .1V which caused no battery issues, but did cause a hiccup with my PD-9160ALV.

Ah, yes. When you have multiple charging sources it makes things more complicated.

Thanks @A.Texas.Yankee and @ajg617 - after your comments about the BMS etc., it prompted me to review more about this on the SOK website and came across a page that states you should "not mix different capacity or model batteries". So that tells me if I shouldn't mix within the SOK brand I definitely shouldn't mix different brands. Apologies for not seeing that sooner and taking up everybody's time. I really appreciate the responses!

No waste at all! We are ALL here to learn.

[Riverbug]

You also have the added advantage of building the "new" system from scratch which can make your installation much simpler.

If I go this route I might actually try my hand at building my own batteries then too. Guess I'll have to keep researching. Thanks for the ideas!

[Redapple63]

Awesome stuff! Please lots of pictures!

Bill