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Issues going lithium in motorhome

R8rBri

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May 16, 2021
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Hi All. I have a class C motorhome and have always wanted a better power solution to lead-acid. I made a relatively impulsive purchase at Costco last year when they had the Lion Energy lithium ion batteries on special (Safari UT 1300). I am finally getting to the point of installing it (replacing my two 12v 68Ah SLA batteries). The marketing made the battery sound like it was a simple plug and play replacement for a lead acid. Well, it appears that there are multiple issues I was certainly ignorant of.

1. My WFCO WF-8955AN converter would not fully charge the lithium battery. I would need a new converter that could handle the lithium charge profile. Doh! But, OK, I can swallow that.
2. Much more concerning to me: I could fry my alternator since the lithium battery will suck as much power as it can get as it recharges (causing my alternator to possibly burn up), and/or when it's done charging it could kill the alternator by immediately shutting off it's use of that power.

I don't fully understand how this all works and I'm sure I'm making errors in my explanations here, but I trust you all know what I'm trying to say.

My questions:
Am I over-reacting to these issues/possibilities?
Are there any other speed bumps I don't list here that I should know about in going from lead acid to lithium?
It seems that a new converter is necessary, but is there a relatively inexpensive way to remedy the alternator issue?

If I can't get this to work safely/reliably I may end up giving up my lithium dream for now and just return the battery to Costco

Thanks in advance for your help!
 
Keep a lead acid starting battery and get a battery to battery charger. When alternator is charging start battery the house batteries will charge from the starting battery through the battery to battery charger.
 
Both issues you've identified are true. There is a small amount of panic on both topics, but the concerns are valid.

A new converter will likely provide a better charge in terms of the charge profile and, if you choose to, a faster charge by moving up to a larger amp rated converter.

If when you fire up the motorhome, the LiFePO4 batteries are at a very low state of charge it could tax the alternator. If the alternator is a large one, it may not even notice that it's working hard.

I chose to replace my converter with one that has a LiFePO4 charge profile and a larger amp rating. I did this even though I rarely use the converter.

I don't use alternator charging with my 560 Ah LiFePO4 battery bank. But if I did, I would be using a DC-DC charger with a LiFePO4 charge profile that has an input rating that isn't going to stress my alternator.
 
yes those are "real" issues...
you have a lead acid battery 3-stage charger.. it will "work" and you will still have more available power than you had with SLA. You will also not be able to get the maximum out of your li batteries but maybe thats not that improtant. It looks like your battery charger has only one 14.4/13.6/13.2volt charging profile. you want to find the specs for your "new" batteries and make sure that will be safe and not upset the internal BMS. make sure your charger does not try anything like "desulphation mode"...

the alternator can be overloaded because your lithium battery is willing to take a LOT more current than your SLA.
Consider changing that alternator OR getting a seperate current limiting charger (then again, maybe, look at your battery specs and see if it will limit current on its own, some do).
 
WFCO was probably already chronically under charging the SLA batteries. Did you ever see 14+ volts into the low battery?

For this I recommend a Powermax PM3. Deck mount or MBA depending on the WFCO is fine. Go same amp rating unless you want to look at wire etc to verify if your system is built for more amps.
https://powermaxconverters.com/product-category/converters-ac-dc/

Renogy and others make a DC-DC charger that can be placed between the alternator and LFP battery to limit the amps and charge at the correct voltage. Again this would improve charging no matter the battery. You could check how the charging system works directly if you have the meters and know the alternator specs etc.
https://www.renogy.com/12v-dc-to-dc-on-board-battery-charger/
(20 amp is fine)

So the full upgrade will be a few $$ more than expected. We have all heard that before ;)
Sytem will be better in several ways not just the battery.
 
Thanks for all of the awesome advice, Everyone!

Honestly, I keep coming back to all the $$ and if I will utilize the awesomeness of this new system (if I go this way). But, that is all on me and I've flip-flopped about 4 times in the last few days :)

One question I have that may "get me by" until I do this the right way: What bad things could happen if I installed a switch to disconnect the house battery and alternator? I know that would stick me with charging the house battery via my generator so I'd lose the convenience of charging while driving, but I also wonder if it's a workable solution. This seems simple, but I feel like my ignorance is obscuring obvious issues with this possible workaround.

Again, thanks to all of you who have replied! I really, really appreciate knowledgeable advice after days of internet searches on my own.
 
WFCO was probably already chronically under charging the SLA batteries. Did you ever see 14+ volts into the low battery?

For this I recommend a Powermax PM3. Deck mount or MBA depending on the WFCO is fine. Go same amp rating unless you want to look at wire etc to verify if your system is built for more amps.
https://powermaxconverters.com/product-category/converters-ac-dc/

Renogy and others make a DC-DC charger that can be placed between the alternator and LFP battery to limit the amps and charge at the correct voltage. Again this would improve charging no matter the battery. You could check how the charging system works directly if you have the meters and know the alternator specs etc.
https://www.renogy.com/12v-dc-to-dc-on-board-battery-charger/
(20 amp is fine)

So the full upgrade will be a few $$ more than expected. We have all heard that before ;)
Sytem will be better in several ways not just the battery.
Thanks time2roll! I had been looking at other converter replacements and B2B chargers and the ones you point to are about 1/2 price of the other options I'd seen. Part of it is just not knowing what would work out of the, what seems like, bajillion products out there.

Super helpful and great appreciated. Thanks!
 
What bad things could happen if I installed a switch to disconnect the house battery and alternator?
A lot of us are just disconnecting the charging from the alternator if you don't need that function. Otherwise a DC-DC charger is in order.

Fun fact on the UT-1300 batteries - they will only charge to 13.9 volts before the internal BMS disconnects.

 
Removing the alternator charge connection will not hurt a thing. But I think you will want to figure out how to reconnect at some point.
 
How is the alternator wired to the battery? What gauge wire is it? It's entirely possible the current to the battery will be limited by the wire size.... or disconnect it as suggested by others and add a DC to DC charger when you get around to it.

If you existing charger has an AGM profile .... that will be "good enough" to charge your battery. You may decide to replace that later, but it isn't absolutely necessary for it to work and still have significantly more power than you had before.
 
I am in the same boat. Am am not certain if it is even a concern for you, but I need to make sure when I get around to installing the batteries and new converter that the wiring from the converter to the battery is of adequate sizing to run from the converter positioned above the trailer's axels' to the tongue where the battery box is. The charge rate of the original converter was constant 3A the new PD one is 45A... Or I may end up putting the batteries in a closet closer to the converter... NOT sure how I am going to move forward till I can ID what is there now VS what would be needed.... Just a thought for you. .....(and now I can add worries of if the direct power line to the trailers battery from the trailers lighting plug is cool. ugh....
 
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