Upgrading RV battery to Lithium Iron Phophrate (LifePO4)

[Minh Nguyen]

Hi all,

I have a 2020 Thor 22FE freedom Elite (Motorhome class C). Maybe in a year I have to replace the batter as lead acid battery normally lasts about 3 years.

Currently, I think my engine battery (under the hood) connects to my deep cycle RV battery (under the door steps of the RV home) somehow. There is a button, if my engine battery is dead, I can press and hold on that button so I can jump start my engine battery / motorhome from the deep cycle RV battery. My deep cycle RV battery is also recharged when I drive the RV.

Now here is my questions, can I just replace my lead acid deep cycle RV battery with a lithium iron battery (LifePO4) that I can buy from Amazon or the store? Or do I have to add some other devices into "the configuration"? I would like to keep the jump start feature that I current have, but I am not if still works when I drop the LifePO4 battery in place of the current lead acid one. It is really convenient, I don't need to keep the jump start cable, I don't need another car, I don't need to call Good SAM / AAA. But I am not sure that lifePO4 battery can jump start my engine battery? Will it damage the lifepo4 battery if I accidently press that button with the lifepo4 battery connected?

I am willing to spend a few hundred more to buy the LifePO4 because it has less weight, give me more power and it will last longer. Please advise.
Than you very much.

[Chateau_Nomad]

Many threads explain this on the forum... short answer is YES. You must change the device which controls current going from the alternator to the lithium batteries, AND you must change the converter to one compatible with lithium battery's charging profile.

So... it's not as simple as just plopping in lithium batteries to replace your lead-acid ones. In addition to the expense of the batteries, you have those extra components/labor... AND it adds $$$ fairly quickly.

Now... something to consider might be AGM batteries as a trade-off between the expense of lithium. No need for component change, and better performance than flooded lead acid batteries.

[dkoldman]

Originally Posted by Minh Nguyen

Hi all,

I am willing to spend a few hundred more to buy the LifePO4 because it has less weight, give me more power and it will last longer. Please advise.
Than you very much.

Do you really see battery weight as a factor? If you needed 6, or 8 batteries; the weight might have some relevance; but don't forget you have a truck, imagine how many batteries you could haul from wal mart in it and not notice a difference.

More power and last longer I see. Do yourself a favor, Buy AGM batteries with the highest AGM rating you can find. I bought 2 125 AH AGMs similar to what you are doing before my FLKA were even two years old. I just didn't like the maintenance on FLA and I wanted more power. I went from 65ah per battery to 125ah per battery

[Minh Nguyen]

I was looking at this battery and it has like about 130 lbs a piece. if I buy two it is going to be like 260 lbs? I am not too worry about the weights the RV truck can haul. I am afraid of the compartment under the steps where I have to house 260 lbs.
I also saw the 100Ah, it has half the weight but half the Ah as well.
Do you know any brand that has more ah and less weight?
Thanks

https://www.amazon.com/Renogy-Batter...ci_mcx_mi&th=1

[Judge]

You need to get the Schematics for your coach from the Thor Owners Site to determine your electrical configuration first.

First, your Chassis and House Batteries are likely only connected with a solenoid for the Emergency Start Switch capability. You would have a BIM160 (Battery Isolation Manager) if your House and Chassis Batteries are truly connected so the Converter / Charger can charge the Chassis Battery on Shore Power and so the alternator can charge the House Batteries when the engine is running.

I doubt you have a BIM in your coach baut if you do, you would need to replace it with a LI-BIM-225 (~$175).

You then need to determine if your Converter / Charger is capable of charging LiFePO4 batteries. Most Thor Class C's do not come with a Converter / Charger capable of properly and maintaining LiFePO4 batteries. You would need to replace the one in your coach with a WFCO or Precision Dynamics Converter / Charger approved for LiFePO4 charging ($200 - $300).

I would also recommend you look at BigBattery. They offer the best dollar per Ah value for a high quality LiFePO4 battery plus they have a very good BMS and a built-in On/Off switch. Also a 10-year warranty, free shipping and no tax.

https://bigbattery.com/promotion/

I installed three 170Ah LIFePO4's from BigBattery last year and the start my generator with no problem. Depending on what you get, they should allow you to start your engine using the Emergency Start switch if the chassis battery is run down and cannot.

[DavidEM]

Judge is correct that installing a Li-BIM 225 is an easy way to maintain bidirectional charging and aux start capability. But the Li-BIM 225 may not charge the Li batteries effectively from the chassis battery. This is not so important if you don't rely on driving time to charge your batteries, ie you have significant solar or you run the generator to charge the house batteries through an upgraded Li converter/charger.

There are ways to overcome these problems with an Li battery system, but they are a bit of a kludge and no one AFAIK has come out with a complete solution.

David

[dkoldman]

Minh in response to your note I received in email

"I was looking at this battery and it has like about 130 lbs a piece. if I buy two it is going to be like 260 lbs? I am not too worry about the weights the RV truck can haul. I am afraid of the compartment under the steps where I have to house 260 lbs.
I also saw the 100Ah, it has half the weight but half the Ah as well.
Do you know any brand that has more ah and less weight?"


I wouldn't buy any 130 lb battery.... even if it were free and I had a Peterbilt Truck as a Chassis for my RV

My AGM batteries are 75lbs each. They are 125ah and rated to last 6 - 8 years. Brand I would suggest is VMax Tank 125 SLR. Google on Amazon get the price, call VMax tank and tell them you trying to decide between the VMax tanks and something you see at Sams because it is cheaper and see what they say.

For the record, I am not anti Lithium, for the RV I bought and the way I use, I don't gain by retrofitting for Lithium's to work. I am also price conscience. I suspect if I ever buy another RV 6- 8 years from now, it will come standard with Lithium's, maybe not even a generator. I can wait....

[Minh Nguyen]

Thank you very much. That's a lots of information.

[Minh Nguyen]

Thank you for your advise

[Minh Nguyen]

According to what I understand, my motor home battery is a deep cycle battery and deep cycle battery is not recommended to jump start the engine. So is there different type of deep cycle batteries? one that can jump start and one that cannot?
Thanks

[Beau388]

Originally Posted by Minh Nguyen

According to what I understand, my motor home battery is a deep cycle battery and deep cycle battery is not recommended to jump start the engine. So is there different type of deep cycle batteries? one that can jump start and one that cannot?
Thanks

There is nothing wrong in using the deep cycle house batteries to help out the chassis battery. The trick is to limit the current flow from house batteries to the chassis battery. In most cases Thor MC has done this by limiting the size of the cable carrying the current to chassis battery.
The proper procedure for using the emergency switch is hold the switch down for 3 to 5 minutes to partially charge the chassis battery. After that time, with the switch down, try to start the coach's engine.
The cable between the batteries is usually a number 8awg cable, so the current flow will be order the 30 to 40 amp range (assuming the chassis battery has about 6 volts) and safe for any 100 amp-h FLA deep cycle battery.

[16ACE27]

Originally Posted by Minh Nguyen

According to what I understand, my motor home battery is a deep cycle battery and deep cycle battery is not recommended to jump start the engine. So is there different type of deep cycle batteries? one that can jump start and one that cannot?
Thanks

The purpose of the Emergency Start switch is to tie the two battery banks together so the house battery bank can charge and ASSIST the chassis battery in starting the engine. You're not starting the engine solely off the house batteries. In fact you may need to hold the Emergency Start button in for several minutes if the chassis battery is very low in order for this start to work.

So to answer your direct question - YES there are pure deep cycle batteries and combination deep cycle batteries. The combination is normally what you see in a boat or RV and they actually say Marine/RV battery because they are made to start boat engines and run electronics/trolling motors. They don't give the best boondocking capability but they are cheaper than pure deep cycle batteries.

[DavidEM]

All of the above is true, but how do you find a true deep cycle coach battery, one with thick plates, extra room for sulfate on the bottom, etc? Other than some very expensive brands most 12V "deep cycle" batteries are compromises: not the best long term performance for deep cycle use, but will help start a chassis engine in a pinch.

David

[lwmcguir]

My favorite is Trojan T105 AGM for the money and hopefully longevity

I have used them in the past but only have 4 currently that are starting on their 4th year in the Tuscany

Performance is close to new so hopefully a couple more years or longer

Its really about the amount of lead and battery construction

[dkoldman]

Originally Posted by DavidEM

All of the above is true, but how do you find a true deep cycle coach battery, one with thick plates, extra room for sulfate on the bottom, etc? Other than some very expensive brands most 12V "deep cycle" batteries are compromises: not the best long term performance for deep cycle use, but will help start a chassis engine in a pinch.

David

If the Judge will allow...

In this case OP was looking for Lithium batteries. If so; the premise "very expensive brands most 12V "deep cycle" batteries are compromises" does NOT exist for this thread.

Lost of options on true deep cycle AGM batteries, and it would be very hard to name any Mfg of the same that actually produces a true deep cycle AGM that will not deliver what a true deep cycle is promised to do.

For every person that might say they had one that did not last 6 - 8 years, I bet if you could look under the hood it was not treated properly. i.e. allow to be discharged less than 50% without worry, having a converter that is not designed for AGM batteries or with intelligent programming, or some other heavy duty use.

I have one AGM in XT5 that is 4 years old and looks brand new, no rust, no fuss. I have 2 AGM House batteries 15 months old and they have never been below 12.6 volts. I use all the time in tandem with my genny. But more importantly they STOPPED the corrosion inside my battery compartment

[Judge]

Originally Posted by dkoldman

If the Judge will allow...

In this case OP was looking for Lithium batteries. If so; the premise "very expensive brands most 12V "deep cycle" batteries are compromises" does NOT exist for this thread.

Lost of options on true deep cycle AGM batteries, and it would be very hard to name any Mfg of the same that actually produces a true deep cycle AGM that will not deliver what a true deep cycle is promised to do.

For every person that might say they had one that did not last 6 - 8 years, I bet if you could look under the hood it was not treated properly. i.e. allow to be discharged less than 50% without worry, having a converter that is not designed for AGM batteries or with intelligent programming, or some other heavy duty use.

I have one AGM in XT5 that is 4 years old and looks brand new, no rust, no fuss. I have 2 AGM House batteries 15 months old and they have never been below 12.6 volts. I use all the time in tandem with my genny. But more importantly they STOPPED the corrosion inside my battery compartment

I agree!

First.... LiFePO4 can be overkill for many and a really good AGM battery can meet the needs of many. But as you properly state.... getting the best performance and longevity for them... or any battery.... is treating them properly.

I'm going to replace the two 12V chassis batteries with AGM's at some point in my Magnitude because the flooded batteries are starting to corrode the battery hold downs in the engine compartment.

To the OP..... Many 12V batteries "labeled" Deep Cycle are typically marine grade batteries that are meant as both a starting and power delivering battery. You see a lot of these in boat and RV applications.

In reality, "true" Deep Cycle batteries are usually the 6V batteries and they are meant to be more of a power delivering battery that can handle a lot of discharge cycles. This is why you find them in golf carts, forklifts and other applications where devices need to run on battery power and only be charged up at the end of the day.

Deep Cycle batteries can be used to boost a chassis battery for starting purposes or even be the primary power source to start a generator.... as was the case with my original stock 6V house batteries in my Magnitude.

The BigBattery brand LiFePO4 batteries I used to replace the 6V batteries fire up my generator with no problems. As a matter of fact the starter spins up faster than it did with the cheap 6V batteries Thor installed.

[DC7432]

I’m in the same position, thinking of replacing my 2-Interstate 31TMXU @130AH with AGM batteries. Question, why is it important to not let AGM’s go below 50%? Also will my stock convert charge AGM’s? MH is a 2014 Thor 31E thanks!

[Judge]

Originally Posted by DC7432

I’m in the same position, thinking of replacing my 2-Interstate 31TMXU @130AH with AGM batteries. Question, why is it important to not let AGM’s go below 50%? Also will my stock convert charge AGM’s? MH is a 2014 Thor 31E thanks!

It's not just an AGM but anything below 50% discharge will begin to damage any lead acid battery if you keep discharging past that level. This chart may help more than me explaining it.

This chart will also show why LiFePO4 batteries are attractive as they can be discharged down to 20% or even a little more so you have much closer to the full battery capacity to use.

[dkoldman]

Originally Posted by DC7432

I’m in the same position, thinking of replacing my 2-Interstate 31TMXU @130AH with AGM batteries. Question, why is it important to not let AGM’s go below 50%? Also will my stock convert charge AGM’s? MH is a 2014 Thor 31E thanks!

Follow the chart and you can't go wrong, but be advised that some charts are slightly different. i.e. Per my Onan Generator Manual EC-30, it says 50% SOC for AGM is at 12.4vdc. My AGS is set at 12.5 vdc Also you can talk with your future battery Mfg if they have direct support. I bought vMax tanks and they took the model of my converter and confirmed I was good. They will tell you to try to set AGS at highest level possible. In my case it is 12.5vdc. I never have had an issue with it starting too soon.

Wish I could have found 130ahs I bought two 125ahs as that was the highest AGM I could find. VMax 125 SLR

Some people will go down to 12vdc because intuitively; it sounds right, but you are slowly damaging your batteries.

Even if I had Lithium's and could go down to 20%, it is of no value to me because by the time I get down to 12.5 vdc my genset is going to be running anyway for some reason i.e. AC or just because I like to run my genny every day when traveling no matter what.

[Beau388]

Originally Posted by DC7432

I’m in the same position, thinking of replacing my 2-Interstate 31TMXU @130AH with AGM batteries. Question, why is it important to not let AGM’s go below 50%? Also will my stock convert charge AGM’s? MH is a 2014 Thor 31E thanks!

Lead acid battery chemistry doesn't depend on the shape size or type of container. This applies to flooded lead acid, no maintenance flooded lead acid, valve regulated lead acid, sealed lead acid, gel lead acid or adsorbed glass mat lead acid. That said, some of the best charging practices can change in order to get maximum life and full charge. Plate alloy, grid paste composition, plate separator composition can require alterations to the charging voltage profile. Unless the battery's manufacture specified different, generally all lead acid batteries do best with a three stage charger: bulk from 50% to 80% of charge capacity, absorptive from 80% to 100% of charge and float which maintains 100% charge over time. There is a fourth stage on some chargers, equalization. This stage overcharges the flooded battery causing bubbles to form between the plates stirring up the stratified acid.
As the Judge said, drawing any current out of a lead acid battery will shorten its life. The longer the battery is left in a discharged state will shorten the cycle life. The more current than is drawn out of the battery will shorten its cycle life. Here are some trade-offs: four draw-down to 5% remaining power will reduce it ability to be charged to 50% of original capacity. Leaving a battery 50% discharged for a month will reduce is capacity 25%. Drawing a battery down to 50% 400 times and immediately recharging will reduce the capacity to 75% of its original capacity. Drawing the battery down to 80% capacity 800 tines will reduces it rated capacity by 25%. Note: these are MY interpretations.

In other words lead acid deep cycle batteries do not generally fail all-at-once., but begin to deteriorate slowly. For flooded batteries, the amount of water the require increases greatly as they deteriorate. For AGMs the ability to supply power decreases.