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.