Considering LiFePO4 battery upgrade for 2015 T@B, would appreciate reality check

glesieutre · September 20

I've got a 2015 T@B S-Max, with inside kitchen. (I guess it would be called a 320 today.)

In 2016, I installed a Marinco 701 Battery Disconnect Switch. In 2018, I upgraded the stock Interstate HD24-DP (64 Ah, 20-hr; 41 lbs) to a Trojan T-1275 plus (150 Ah, 20-hr; 85 lbs). I constructed a frame for it (https://tab-rv.vanillacommunity.com/discussion/2387/fitting-a-group-27-battery/p1, thanks @ScottG) and it fits in the front tub. This was a great upgrade.

We also now have a lightweight Renogy 220W solar suitcase and a Renogy Voyageur solar charge controller (PWM, 20 A). This controller is located at the array, with a run of about 30 feet of 10-2 wire to the battery.

We rarely camp with hookups, and I am generally responsible for monitoring battery status. Our 3-way fridge still works well on propane (knock wood), and we are miserly with other power draws, so our actual energy needs are not that great. When camped in the shade for days, we have been forced to bump up the battery charge occasionally by connecting to our TV. (We don't want to carry a gas-powered generator in our TV.) On a recent trip, I had to leave camp for a couple of days, and my wife was stressed about dealing with the battery / solar system. (We've experienced low battery and the CO alarm a couple of times over the years...) Since I retired recently and we might be traveling more, I think it might be time for another upgrade with more capacity and less uncertainty.

It seems that lithium-iron phosphate batteries have come a long way in the last few years. I am particularly intrigued by a few 300Ah batteries that have dimensions on the order of 13.4 x 7.6 x 9.8 inches and weigh less than 60 lbs, because I think these would fit in the front tub. And the useful "energy" increase from about 75 Ah to something exceeding 250 Ah is very attractive for peace of mind.

I've read a lot of the posts here and think I understand how this might work and what some of the issues are. But I have questions. And would like to make sure I'm not missing something.

First, I think we need a real battery capacity monitor, not just a voltage reading from a 12-volt port. Maybe a Victron with shunt. Any suggestions? (I anticipate doing any installations mentioned here myself.)

Next, I wonder if a LiFePO4 battery needs to be installed in a vented battery box or if it can go right into the frame in the front tub. Some of these are rated to IP56, which suggests to me that I might be able to get away with weatherizing the terminals somehow, but not necessarily enclosing the entire battery. We don't do a lot of cold-weather camping -- at least not so far, but would that be a reason to try to find a place inside, under a bench? (I have not explored the available real estate for that purpose, yet.)

The factory converter is a WFCO WF-8735-P, which is not made for lithium batteries (13.6 VDC out). It handles 30 A, with 4 AC branch circuits (GFI, Alde, A/C, fridge) and 6 DC circuits (fan, fridge, light/radio/TV, pump/LP detector, Alde/outlet/AC fan, battery charger). I don't think this would fully charge a lithium battery, as that requires 14.6 V. Is that correct? If so, any recommendations for a slot-in (fingers crossed) replacement? I (and my wife for sure) would rather not be switching between this converter and a special-purpose lithium charger when on shore power. (Or maybe we stick with the factory converter and it only charges the lithium battery to 80% and that's still a pretty good upgrade? And on good days, the solar takes it higher?)

I understand that the alternator from our tow vehicle (Subaru Outback 3.6R, 6-cylinder, said to operate at >14.3V) also will not fully charge a lithium battery and, in fact, might permit it to discharge while towing. I've read that this can be addressed with a DC-DC boost converter, perhaps located near the T@B converter under the bench. Any recommendation about that?

While I'm at it, I might as well consider the solar charge converter. Is there something better I should be using, perhaps locating it close to the battery? How long can a 10-2 wire run be without significantly reducing solar input to the battery? We've been in shady sites where 30 feet has not been enough to get good sun.

Am I missing anything?

Thanks in advance for any feedback and advice.

-George

Tabaz · September 20

I just replaced my two 6V golf cart batteries with two 12V lithiums. WFCO makes a direct replacement converter that will recognize the new lithium batteries. It is the exact same dimensions and configuration as your existing converter. Amazon for $199:
https://www.amazon.com/WF-8735-P-Black-Auto-Detect-30-Amp/dp/B0CYPMK9HH/ref=sr_1_15?crid=1AU60IPDIM754&dib=eyJ2IjoiMSJ9.jLzZI2nkL6Q8mcnnsETFI9Fz80WtIca5OLTAG5JFmlnycI56Ht20zEvJrhz-PfvzJP75AD7MfHGQ9A4DYEsgBrLJpKoAW1Rg6sGWIYPkb129a5CRhg8478gPk70fzbawDP-JLhfCpx5rEvS-WiQqcwTjALSsgHSLXSJ4WT_8SO4mAUuF8A4eht4oNGgcqPzsNMdgjWRGeQ02OT8f1aXZcKqtzG1vq3WTGIQGD-ghaKL4STLxdIFu7VqzZWVOevAzk3AuCoIEZS2WRUehx-ajXAfze1ugtRY7MvS6RtrDOaE.IwS2zhoPLYHrLpZ9xw7hHRW7u8AlW_LL_tI-umdIdr8&dib_tag=se&keywords=wfco+converter+for+lithium+battery&qid=1758399057&sprefix=wfco+converter+for+li,aps,300&sr=8-15

Replacing the converter is a time-consuming task. LOTS of wires going into that unit.

My old Victron wall mounted BVM 700 battery monitor will not show a 100% charge on the new lithiums. I may replace it with a Victron model that does, or go with one that uses a cell phone. The thought of running new wires from the battery tub, up through the floor and in the wall does not excite me.

ReenieG · September 20

I replaced my WFCO 8735P with the WF-8735AD but then needed a jumper sent from WFCO since everything I was told to do by the techs to teach it to auto detect failed.

FWIW, my new setup is 2 Eco-Worthy 100ah lithium batteries with bluetooth, put into THIS battery box which is removable. There's a strap to hold it in place, but I made mostly everything removable so that when I'm not using it, it can go into my garage.

I've also updated all of my solar adding a Vevor MPPT 30amp controller w/BT and a second solar panel on the roof.

I can monitor (like a smart shunt) the batteries via bt. I added a Vevor 2000watt pure sine wave inverter installed in my new Sea Biscuit center tub, which I have not wired into the WFCO directly, however I separated out the breaker for the converter so as not to cause a back loop if/when plugging in my converter into the outside shore power to use 120v plugs. I simply plug the inverter into the shore power plug with an adapter and extension cord.

This setup was borrowed from another person. HERE's my discussion and the YT video I used to adapt this.

I will see if I can find all of the discussions about how and what I did and create one discussion so if someone else wants to copy what I did they can. For now, here are some pics.

BTW, the products I use are alot less than some of the common name brands but IMO and research and experience, they are just as good if not better. YMMV

pthomas745 · September 20

If you are hardly ever on shore power, all you really need is a proper solar controller that will charge the lithium battery "completely". Many owners have changed to lithium batteries and have not touched the converter. There are many simple easy to deal with ways to charge a lithium battery "with shore power" if you ever need or want to, without having to do anything except plug the lithium charger into a wall socket.

Even if you don't do anything about a separate charger, the WFCO in your trailer "will" charge a lithium battery up to about 85 percent.

A shunt for lithium battery monitoring is a great upgrade for your setup.

Currently, your 150 amp hour AGM battery can deliver "up to" 75 amp hours before it drops below the "50 percent state of charge" level that would provide the greatest number of battery cycles. (On paper, of course). You are contemplating a 300 amp hour lithium battery. A lithium battery can continue to produce power all the way down to around 10 percent state of charge, or about 270 amp hours from that 300 amp hour battery. Sounds like you have a good handle on your power usage...but do you really think you need more than 3 times the battery capacity than you have now?

A lithium battery will usually have "low temperature charging protection" circuits. When the battery (the actual interior cells of the battery, not the air temperature) reaches "freezing" the battery will be permanently damaged if you try to charge it. It can continue to provide power, however. A lithium does not need any venting.

ckjs · September 21

@glesieutre: I second pthomas745's recommendations. Switching to a pair of 100Ah LFP batteries have been great for us - and we have the 12v fridge and a inverter for an electric kettle. I've never felt the slightest urge to get a DC-DC charger, or swap the WFCO for one with lithium support - our ~250w rooftop solar is enough.
Regarding shady site concerns: remember that you don't need to charge the battery back up to 100% each day. If you consume 25% of the stored power each day, and gain back let's say only 10% of that capacity, you'll draw down 15% per day. That still gives you over 6 days of power.

glesieutre · September 24

Thanks for the very helpful responses.

@Tabaz, thanks for the heads-up regarding the WFCO converter and the challenge of installation, as well as the Victron monitor info.

@ReenieG, thanks for the description of your setup and the photos. I wasn't really thinking about an inverter but, if the battery capacity were high enough, it might be interesting to be able to run the A/C before trying to sleep in the heat. I'd be interested if you get around to posting a summary discussion of what you did.

@pthomas745, thanks for info that could keep my mods simple -- very helpful. I don't think I "need" 3X my current battery capacity, but I do think that anything I could fit in the front tub (not sure about 300 Ah at this point) would provide extra margin in the event of shade and bad weather. Peace of mind for my wife (and me) is worth a lot.

@ckjs, thanks for the confirmation of the keep-it-simple approach.

ReenieG · September 24

@ckjs just be sure to every so often charge those batteries to 100% or you will greatly shorten their life. This was input a friend learned from a professional solar installer company with his battleborn batteries.

FWIW you can achieve this with shore power plug in, or a battery charger without switching out the WFCO.

pthomas745 · September 24

Lithium batteries will outlast all of our trailers.

AnOldUR · September 24

@pthomas745
The batteries may outlast our trailer, but the obsession for bigger and better may not.

ckjs · September 24

ReenieG said:

@ckjs just be sure to every so often charge those batteries to 100% or you will greatly shorten their life....

Agreed. If anything, I have the opposing concern: with rooftop solar I need to make sure that the batteries are not fully charged in between trips. That's bad for their service life too. I try to keep it between 50% and 80%.

rcarey · September 25

Hi George,

I just recently moved from a 2018 Tag XL to a 2025 Tab 320 Black Canyon. My setup in the Tag had to take into account the nonlithium convertor. I am 99.99% off grid so battery management is important to me, especially since I often have a second fridge and a Starlink. At times I can be out in the boonies for a month. Now I am a buy once, cry once type of guy so hold on to your wallet!

In my Tag, the first thing I did was add a 206 Ah SOK battery. If I was to do it again, I would get a 300 Ah battery as battery price size and cost have decreased dramatically in the last 5 years. If I was installing it in the tub, I would get something with internal heating as I do occasionally camp at elevation where temps are below freezing. If you never camp where you need to charge at below freezing temps, the heating is not such an issue. Lithium iron phosphate batteries can be installed inside the trailer as they do not vent, if you install the battery inside the trailer, once again internal battery heating is less of an issue.

I love the Victron components, as they are quality and you get an all-in one ecosystem experience in the app.

I would not worry about changing out the convertor. Instead charge your battery using a Victron IP 22 charger mounted in the tub. The Victron will charge at about 29 amps/hour and top you off to 100%. Other options for charging below.

A Victron Smart shunt is mandatory for battery management. The 300 amp one is fine. It is hard to manage your power if you do not know your ins and outs.

For solar, I used a Victron 100/50 smart solar charge controller. In reality the 100/30 would be fine as you can over panel a bit as long as you keep voltages below 100. I generally use 2x 160 watt Ecoflow panels.

For the times when the sun does not shine or I am under the trees, I use a Ecoflow delta 2 max which has a 1024 Watt hour capacity. (If I had to do it over again, I would probably get the Max with a 2000 Watt hour capacity. At this point, I will probably will be buying an extra battery). To charge this, in general, I use the Ecoflow 800 watt car alternator charger which I installed in my Jeep. The Jeep can fully charge the Ecoflow generator in 1.3 hours as it charges at 800 watts/hour (even at idle) I also have the option to juice it up before I leave home and charge it with the solar panels. The Ecoflow Delta can be used to charge the trailer battery via the Victron IP 22 at around 29 Amps/hour. Unfortunately there will be some AC to DC conversion losses. I can also plug the solar generator directly into the trailer and power it as if it is on shore power eliminating the need for an invertor. It charges the battery slowly through the nonlithium convertor in the trailer so I usually just turn off the breaker for the convertor. The Ecoflow will even run the air conditioner for a couple of hours. The Eco flow is also nice as I can use it when I tent camp.

I have basically moved this setup over to my Tab 320, but I did not need the Victron IP 22 as the trailer convertor will charge the battery at about 25 amps/hour. Fortunately, the new Tab also came with a solar charge controller for the roof panels (100/30), I did add a second Victron 100/30 for portable panels. I put the 100 Ah Battleborn in the Tag when I sold it, and moved the SOK 208 Ah to the new Tab 320. The Tab also came with a Victron Smart shunt.

Well that is how I roll with power. My setup allows me to be off grid, without a generator indefinitely. And a sad goodbye to my Tag, we had some great times together!

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Considering LiFePO4 battery upgrade for 2015 T@B, would appreciate reality check

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