2022 Solis House Battery Replacement / Lithium

[johnpitts01]

We have 2022 Solis on 2021 Chassis.
The coach batteries need replacing.
Would like to do bolt in Lithium batteries like Renogy mounted under the coach where the factory batteries are located. Dont want the batteries inside the coach.
Do I need a DC-DC charger installed also?
I've done a search and read a numberr of posts. Can't find a definitive answer. I've seen some posts where folks indicated they just swapped the batteries recognizing they will only charge to 80% on shore power and will top off from solar.
What about charging the batteries from the chassis???
Is that a problem or no?
If a DC-DC charger is needed / recommended where in the electrical system is it installed?*
any and all comments and help are appreciated.

[creativepart]

Let's start at the beginning.

The Solis comes with Lead Acid (LA) Batteries. So, all the equipment is setup for that specific type of battery. The Converter on your Solis is also the battery charger. And, so is your engine's alternator. So, is your solar charge controller.

The term "drop in" doesn't really apply to anything other than the battery size. They are sized to drop in place of your LA batteries.

LFP (Lifthium Iron Phosphate) batteries require different charging profiles than the OEM setups for your LA batteries.

So, in general, you need to set up all the House battery charging to reflect the LFP battery's charging needs.

That CAN mean (but doesn't always) that you need to change or adjust the settings on your Converter, change the settings on your solar charge controller and finally, delete or modify the charging from your alternator.

You have a brand new Solis. It's likely that the Converter is either adjustable or even auto sensing for battery type. But... you have to be sure. Look for the model number on your converter and research that model. Find out what it can do for charging LFP batteries. If it can't handle them natively, then you need to see if they offer a modification for LFP. If not, you MAY need to replace the converter.

Your Solar Charge Controller will have a built in setting for LFP batteries. So, all you need do is change the setting.

Lastly, the alternator can be the most difficult to deal with. Some folks ignore the issue and just hope their LFP batteries don't damage their alternator. Sone install a new LI-BIM in place of the latching solenoid that came with the RV. These are simple ON/OFF devices. They connect and then disconnect the alternator every few minutes to protect it from over heating.

Others, take the safest route. They disconnect the alternator from charging the LFP batteries entirely and install a DC-DC charger. The great thing about this is it both protests the alternator from overheating but it also applies the exact LFP charging profile your batteries are looking for.

It's not a cut and dried decision. You get to read up on all these things and decide for yourself what you think is best.

One last thing. You can simply drop in the new LFP batteries and do nothing else. They will not blow up. They will work and charge. But they will not charge and work to the full potential that you are paying for when upgrading to LFP batteries.

I don't have a Solis. I replaced 400aH of LA batteries with 400aH of LFP batteries. My onboard charger doesn't have a LFP charge setting but is completely adjustable so, I've set it up for my batteries. I simply changed the settings in my Solar controller to LFP. Finally, I disconnected the alternator from the House batteries and installed a DC-DC charger.

You may decide to go a different route and that's perfectly fine. Just understand what the choices are and do what you think is best.

[Ray,IN]

creativepart; That is perhaps the best most complete write-up I've ever seen/read on any of the RVing forums.

[johnpitts01]

Thanks for the detailed explanation. I will research my converter. My Xantrex solar charger has Lithium setting. Where would a DC-DC charger be installed in the coach/chassis wiring diagram?

[creativepart]

Originally Posted by johnpitts01

Where would a DC-DC charger be installed in the coach/chassis wiring diagram?

I bought the Victron Orion 30-amp charger. I connected it to my Chassis (starting) battery and my House battery bank. BOOM, that's all.

The Victron is unique in that it is self-sensing. It senses the alternator charging the Chassis battery when the motor is running and this turns on the charger. When you turn off the motor it senses that as well and turns off the charger.

This makes installation a breeze. Other DC2DC chargers require that you run a separate ignition trigger line that tells the charger when to turn on and off.

Installing the Victron was really a simple process because of this feature.

[john1715]

Awesome thread guys and such detailed responses! Hey John, did you figure out the converter? I called winnebago and they said they didn’t install an “inverter”…? I have a 2024 solis 59px.

Also, my current setup is (2) 120ah agm batteries. Can i swap those both out for (2) 400ah lithium batteries? Or am i going to run into problems because of the new higher amp hours?

Thanks!

[creativepart]

Originally Posted by john1715

Hey John, did you figure out the converter? I called winnebago and they said they didn’t install an “inverter”…?

Hopefully you can see the problem here. You just said "Converter" and said Winnebago says they didn't install an "inverter."

Inverter... Converter - these are two totally different things. You have a Converter in your RV, and apparently, not an Inverter.

To figure out what Converter you have and if it will work with LFP batteries you simply need to look for the make and model of your installed Converter (look for a label in the Power Center where all your fuses and circuit breakers are) and then look that info up on the internet.

[creativepart]

Originally Posted by john1715

Also, my current setup is (2) 120ah agm batteries. Can i swap those both out for (2) 400ah lithium batteries? Or am i going to run into problems because of the new higher amp hours?

The number of amp hours don't matter -- but I seriously doubt you have enough room for one 400ah battery let alone two.

[john1715]

Yeah thank you, I tried to edit my response afterward I figured that out haha. I’m used to a converter being called a tru. Anyways ok, awesome! I found the converter and it does have the auto sensing for LFP.

Thank you very much! The next step is figuring out the dc to dc charger. I don’t plan on changing my chassis battery but rather just the house batteries. So I would just need to find the line coming to the house batteries from the alternator to the charger, then connect that alternator line to the dc2dc charger then have the output from that going to the converter/charger?

[john1715]

Ok… disregard what I said, I have a lot of research/understanding to do with the dc/dc charger lol

[Hein]

Found this post while making an update to a Solis for a customer We made a tray insert that allowed us to place 2 group 27 batteries in each tray for a total of 420Ah. We installed a Victron DC to DC charger and retained the starter boost function by disconnecting the wire from the terminal 4 of the boost switch. This disables the solenoid for combining batteries when engine is running but still allows it to be used to boost the starter battery with the house battery.

We also installed a 12V IndelB Plein AC behind the pop top.

I'll do a video going over some of the details but happy to answer questions.

All the best
Hein
DIYvan

New to this forum but hope to be helpful.

[bobr]

Hello Hein, I saw your post regarding installing a solis pocket dc-dc charger. Would you mind sharing exactly where you installed it? I'm working on same project right now.

Also, your comment;
"and retained the starter boost function by disconnecting the wire from the terminal 4 of the boost switch". Sounds like power does flow back through the dc dc charger when the engine is not running, i thought it was only one-way.

Much thanks!

[heinvs]

Hello Bob,


We installed the DC-to-DC charger in the RH lower rear compartment. That location made is fairly easy to route cables to the combiner relay and chassis ground point located under the vehicle. We drilled through the floor in the cabinet under the sink.


All the best,
Hein
DIYvan


https://youtu.be/O4h1dcdZ-VU

[electric]

Exposing LFP batteries to elements under the van is not the best idea. It gets too hot or too cold, depending on climate zones, exposed to road debris, etc.
They do it with lead acid because it's cheap and easily replaceable, but LFP is a capital investment worth better protection.
You could at least build an insulated box with 1/2 inch plywood to house the battery, better yet, find a place inside the van for it.

[heinvs]

Appreciate your comments and concerns regarding under vehicle LiFePO4 batteries. We have been mounting Lithium batteries under vans for many years and have not experienced any failures or damage.

This customer will not be using their van in extreme temperature conditions so did not want the insulated heating system we normally use for under-vehicle batteries. The Xantrex batteries we used on this application have internal over-temp and under-temp protection and the temperature and state of charge can also be monitored via blue tooth.


All the best,
Hein
DIYvan

[bobr]

Originally Posted by heinvs

Hello Bob,


We installed the DC-to-DC charger in the RH lower rear compartment. That location made is fairly easy to route cables to the combiner relay and chassis ground point located under the vehicle. We drilled through the floor in the cabinet under the sink.


All the best,
Hein
DIYvan


https://youtu.be/O4h1dcdZ-VU

Thx Hein,
Sorry one last question. Did you eliminate the isolator/ selonoid downstream of dc dc charger or just wire to, as it.
I have read conflicting points of view about having both d2d charger and isolator, as they do similar jobs.
My concern is messing with the where the solar and shore power and alternator power all come together.

Again thx for your time!

[heinvs]

We connected the positive output from the DC to DC charger to the battery side of the combiner solenoid. Since we have more batteries; we established a new ground point where the negative cables from the batteries came together and connected the negative output from the charger and the existing house ground there. We disabled the engine run signal which energizes the combiner solenoid by disconnecting pin 4 from the boost switch.


All the best,
Hein
DIYvan

[bigb]

Welcome to the forum Hein, I know you from Sprintersource. Have used your switches but was not aware till tonight about all your other products and services.

I'm sure your knowledge and experience will be appreciated here!