What to do?

[Mayday]

We sold our house in Colorado this summer and moved into a 2013 Mercedes Forest River Solera Class C rv. I put in new deep cycle marine batteries which are charged while driving or by a built in generator that runs on propane. The monitoring system for the batteries is just a set of red lights that measures the charge.
I've read your book and am starting to understand the basics of solar. My question is once I install lithium batteries and install a solar system, what do I do with the other system? Can it be integrated into the solar system as backup? Can I still charge the lithium batteries while driving? And will the generator be obsolete?
I am such a beginner so is there some resources I can study on this topic. Or is it really quite simple?
Thanks so much for your time.

 

[SCClockDr]

I'm on a similar quest. 400 watts Renogy Panels, 4 GC-135 6VDC LA batteries (Born in Apr 2011), Trimetric 2020 monitor, PD9270 Converter, Morningstar 300 watt solid state inverter, & OOYCYOO MPPT 12/24 volt 60 amp Solar Charge Controller. All this was done before I discovered Will.

I'm thinking of setting up an 8 cell 18650 test bank and then adding the ancillary system equipment BMS, 6 amp active balancer, Victron Battery protect, etc. to setup a test system & prove the concept.

Once it is up & running I can then commit to getting 8 LIfepo4 200ah cells and get them properly conditioned. then I can remove the current batteries and get it all installed in our 5th wheel & bump the solar array up to 1.2 Kw 24v.

I intend to split my 120 VAC distribution & supplying the trailer with the inverter but leaving the 15K AC & HWH as shore power/generator supplied. The absorption fridge may go either way once I get firm numbers on my consumption.

 

[svetz]

I put in new deep cycle marine batteries... My question is once I install lithium batteries and install a solar system, what do I do with the other system?

If the old batteries are working for you (that is you don't need more capacity); I'd say keep them until they need replacing; after all you might swap to a new vehicle by then. Just get an MPPT that works with Lead Acid or Lithium and you'll be ready to replace those guys in the future.

 

[SCClockDr]

If the old batteries are working for you (that is you don't need more capacity); I'd say keep them until they need replacing; after all you might swap to a new vehicle by then. Just get an MPPT that works with Lead Acid or Lithium and you'll be ready to replace those guys in the future.

I'm on your page, re the old batteries. I find they are consuming more water this year so the early signs of sag are evident. I expect an additional year before I see real issues.
When they give up is too late to get things ready especially when camping. So spring or fall 2020 is my time window to make the swap if all goes to plan.

 

[Mayday]

There was a recent thread on a recently-released item that goes between your engine 12v system and your house system, when your house system has Lithium batteries. You would use the same product, but put it between your house lead-acid batteries and your new lithium ones.

If I was to switch to lithium today, I would ditch my FLA house batteries. You shouldn't be mixing your chemistries on your house batteries. It's possible to interface the two but not worth it. And after you sell your FLA's, you'll still need that DC/DC adapter device.

Edit: If one of your house batteries will fit in your starter battery tray, I might suggest keeping one of the lead-acid house batteries, with a DC/DC one-way, to maintain it off your engine, or house system - in which case use a more expensive DC/DC charge/converter.

It's available on standby in case your starter battery dies. You CAN normally bridge your FLA starter battery with your house batteries, if the house batteries are also FLA or at least lead-acid, to give yourself a jump, OR to send charge back from the engine to the house. I'm pretty-sure if you go with the DC/DC converter from engine FLA to house Lithium, you can't jump yourself anymore. And eventually your engine battery will die, whereas if you keep your standby battery maintained, it should be a simple issue of swapping in the standby battery.

Some motor homes have a rack for the house battery up front under the hood, in which case you would tether your backup starter battery off your main starter battery. It also makes it easier to jump or swap them.

Thanks so much for your input. I don't quite understand it all. I'm all for getting rid of the lead acid batteries. I think I need to get a little more savy with this stuff before posting.

 

[Mayday]

In my Class C RV the house lead acid batteries can be charged three ways. The can be charged by the generator, while I am driving, or when I am plugged into shore power. Would I need to change anything if I just replaced those batteries with lithium batteries ( like a special controller or something like that)? I'll tackle the solar part after I understand how my present setup will accomodate lithium batteries.

 

[SCClockDr]

You might want to consider isolating your house lithium bank from the alternator charging system & use the solar while driving. That is my current setup with a WLA bank. The lithium bank will absorb all the alternator can produce without providing additional technology to limit the charging current & voltage.

 

[Mayday]

Thanks so much for all you guys' input. I appreciate it so much. We're on the road right now so we go in and out of cell service. Sometimes without for days. So, sorry for the delayed responses.