2019 Micro Minnie 1706 battery charging system question

[dakman70]

Hello all you very smart people.....

I'm looking at upgrading my house batteries to lithium but don't know if the standard house battery charger will work with a lithium setup.

So before I actually start with the new installation, I thought it wise to access the collective wisdom of the Minnie brain trust... ;>)

Stephen

[tinglett]

My 2019 2108DS came with a WFCO 8955 installed alongside the breaker/fuse panel under the refrigerator. You are correct that this charger will be unsatisfactory for charging lithium batteries. It will work, but with the charge profile for lead acid batteries it'll be slow as heck and make you unhappy. I'll wager a guess that this is the same charger you have.

I did the "simple thing" and replaced the WFCO 8955 with a Progressives Dynamics 4655LIV which I purchased from Battleborn (where I got my batteries -- but you don't need their batteries of course). I documented the process here: https://www.winnieowners.com/forums/...iv-359008.html . There is more to the story beyond that single thread, where a learned a lot of stuff, but it'll give you an idea what you are up against.

To cut to the chase, the new charger works well, but I do have a couple comments. One is that you won't ever see much more than 30A going into your batteries because they are such a long distance away over 6 AWG wire. A 1706 will have a shorter cable run, which may make a difference, but I bet not by much. A 30A charge isn't bad, but it takes a while to go from flat to full (I have 200 Ah of battery). The PD4655LIV really can produce 55 amps with heavy wire. The other comment is that I went through the effort to replace the fuse panel, but I don't feel like I got much out of it. My recollection is the new charger had some extra status LEDs on that panel, and I've found them rather useless. I believe the original panel would have worked just fine.

There is no "programming" for the PD4655LIV. It is absolutely hard wired for lithium batteries, so keep that in mind. You'll need the new batteries before you do the charger upgrade.

There are possible alternatives that, in my opinion, would be trickier to do. I've been learning a lot along the way and probably would make a more aggressive change if I were to start now, but I think this drop-in charger was the way to go to get started.

[creativepart]

WFCO does make a 8955 model for LFP batteries. The WF-8955-AD has auto detect, hence the AD in the model name. And, it can auto detect the type of battery, including LFP.

This is being installed in new Winnebago TTs - but I don't know when they started installing this model.

The previous model the, 8955SPEC did not handle LFP battery charging properly and they also briefly made a 8955-LI that added LFP charging profiles but was not auto detecting.

I found an interesting thread on this 8955SPEC topic on a Solar Power forum. You might gain some insight by checking this out:

https://diysolarforum.com/threads/wf...charger.53791/

Here's a video of someone that changed out the charging section of the converter. He also changed out the 12 fuse board but I see no benefit in doing that part.

Hope this helps:

https://www.youtube.com/watch?v=oEutPVI-2R8

[MDJDCarter]

I have looked into a conversion, but we have not pulled the trigger just yet. What I have learned is the following:

You will need a new charging system that is set up for lithium. Some newer RV's may have a charger system with a switch to go from Lead-Acid (LA) to lithium, but most of us don't have that. The LA charging system will charge the lithium batteries, but it will be slower and never more than about 80% charged. You spend a lot for the batteries so you really want something that will give you a full charge to make it worthwhile.

Next, when you are driving, the alternator is topping off the charge on the house batteries as well as the chasis battery. The lithium batteries need to get hit with about 14.5 volts or a little more whereas the LA battery needs 13.4 volts which the alternator puts out. It is also difficult for the alternator to "see" the lithium batteries to charge them. I suppose you could take the lithium batteries off of the alternator altogether, but then they would charge only when connected to shore power or some other alternative.

Your lithium batteries maintain a steady 12 volt output, more or less, until about the last 5% of charge. Only then do you see a voltage drop. LA batteries have a voltage drop that follows directly the percentage of charge -- that is how your battery monitor knows how much charge is left, 12.6 volts=90%, 12.3 volts=70% (not real figures, but that is the idea). You have to know how much current you are drawing and how long to be able to calculate the remaining charge in lithium batteries.

Lithium batteries are expensive and have some temperature issues, they particularly do not like to be real cold. You may want to consider moving them to a more secure area and/or inside your RV. They are lighter and can be stacked on their side or even upside down, unlike LA batteries. Lithium battery chemistry has evolved over the years. Lithium-Ion batteries are the ones most prone to catch fire. They develop little sharp fingers of lithium metal as they go through the charge/discharge cycle. These fingers can eventually short out, generate a lot of heat and catch fire. The LiFePO4, lithium-iron-phosphate, batteries would be my choice, safer, reasonable energy density, and should go for about 1,000 charge/discharge cycles (LA batteries usually are good for about 200 cycles).

So, in summary, switching to LiFePO4 house batteries means a new charging system, a new charge monitoring system, modification of the alternator and other engine components, securing the batteries, and tighter temperature control. In return they should last at least 5 times longer than LA batteries, they can be completely discharged as opposed to only 50% for LA, and they have a higher energy capacity for the volume. That is 2 group 24 LA batteries of 100 amp hours will give 100 aH of power at 50% discharge; and 2 group 24 LiFePO4 batteries of 200 aH will give 400 aH of power. Power is everything.

[carpedatum]

Originally Posted by creativepart

WFCO does make a 8955 model for LFP batteries. The WF-8955-AD has auto detect, hence the AD in the model name. And, it can auto detect the type of battery, including LFP.

This is being installed in new Winnebago TTs - but I don't know when they started installing this model.

I have a 2022 Minnie 2327TB that came with that WFCO 8955-AD. The "AD" means auto detect. Expecting that to work, I swapped in a 200Ah Renogy liithium iron phosphate battery for the factory group 24 AGM battery, placing it in a new, larger battery box in the factory location on the trailer tongue, and quickly ran into a limitation. Simply put, WFCO's auto detect, at least in my case, was very unreliable. WFCO recommends that to make it reliable, you must place their converter no more than 10 feet from the battery (by wire length).

That would have been a huge tear-up for me. However, what I was observing at the time were disappointingly-low charge rates from the WFCO, which I never could get into Lithium mode, despite working with their tech support and following all instructions. Since my generator is built into my tow vehicle, the idea of having to run it all day just to recharge the TT battery was not OK with me.

In my opinion, WFCO's auto detect implementation is an engineering failure. They would be far better off with the same sort of manual battery chemistry switch or setting that other manufacturers have been using for years. They stand by it, though.

I replaced the WFCO 8955-AD with a Progressive Dynamics PD9160ALV, meant specifically for lithium batteries. This more or less tripled my charge rate, making it entirely satisfactory.

The swap was a PITA because of the converter's location, behind the load distribution panel, but the wiring was compatible and in the end I'm happy - I added a small inverter and a shore power switch on three AC circuits, and can now run all 12V loads and some small AC loads (the TV, a fan, mobile device chargers, etc.) overnight, and recharge in a reasonable amount of time during the day.

I did choose to review and upgrade all the breakers connected to the battery at the time. Not sure if that was entirely necessary but since I didn't want to upgrade the 6AWG wiring, I wanted to make sure it was well-protected.

Anyway, long story short, I would factor in replacing the converter with one meant for Lithium battery chemistries (or if you have the WFCO 8955-AD, somehow rewiring such that the battery cable to it is no longer than 10 feet).

[Marine359]

Hi Stephen,

Don’t know what model year or model your WBGO TT might be, but having made the transition from standard OEM lead/acid to LiFePo4 three years ago, a lot has changed since then. I don’t regret at all that we put some bucks in and did it with the objective of being able to boondock for several days without the need to run a generator. We got what we wanted, but installation was non-trivial as a DIY project. If you’re looking for a simple “drop-in” replacement solution, you’ll not be happy, and will wind up starting over from square one. We chose to toss out the WFCO charger. We Based the new system on a 2000w inverter/charger that could charge at 80 amps. Wiring it was challenging. Then adding the 2Kwh LFP battery, solar, and solar charge controllers was pretty easy. Using bus bars and a ST fuse block also made it easier. If you have an absorption fridge that works well, you’ll save a bunch of money because you won’t have the need to feed 600Wh/day to a 12 compressor fridge monster. We love our fridge, but it did require more money up front to build the electrical system it requires.

Ok, let’s say, I’m starting out all over today with a OEM lead-acid battery on the tongue and 30 amp charger/ inverter. Because prices are so much lower, I would definitely choose the path of using a mid-size or large powerstation as an all-in-one solution. A powerstation can pretty much replace most of the components you’d need for the setup I installed. You pretty much just pop the powerstation into the pass through, make a few connections, and you’re off and running. Guaranteed you could install everything in a few hours. All you need to do is decide how many Whrs per day you’ll need. My advice would be to start with 300w of solar on the roof and 100w of portable solar. If your trailer already has an MC4 gland on the roof, you can do the solar in less than an hour. Choose a powerstation that can accept two solar inputs, or one solar input and a high voltage dc input. You can wire your OEM charger output directly to one of the solar inputs or high voltage input, so no need for expensive charge controllers. The other solar input can accept 300w parallel from the roof. Route your 30amp shore power cable to the powerstation, and BAM, you’re pretty much done, and will have plenty of amp hours for boondocking. If you go small on the powerstation (like 2Kwh), you can add an expansion battery to double capacity, or get a small generator (15 amps) to charge the powerstation through its ac charging port. To go cheap, get a 2Kwh powerstation ($1,600) and carry along a 100 or 200ah LFP ($300-500), which you can charge with an inexpensive programmable smart charger. Either from generator, shore power, or from the powerstation if it’s topped off.

We added a powerstation to our existing setup, and now have all the power we could ever want. But starting out with a powerstation could save you big bucks, lots of time, and gives you a nice gadget to have around the house when the grid goes down. BTW, if you add an easy start to your roof A/C, a powerstation with access to about 4Kwh will run the A/C on hot/humid nights.

Just my 2 cents.

[tinglett]

I got started with Lithium as the result of horrible FLA battery experience trying to run a CPAP machine. I don't regret going down the long road as I really do love to tinker with gadgets and the RV upgrades became yet another hobby. Which is fine. I can probably name a few others here that probably are doing the same, though maybe some are in denial.

However, if I wasn't into the RV upgrade DIY thing and the main thing I wanted to solve was a CPAP machine, Jim's advice of a portable power station is exactly the right path. I recently bought a little Jackery 300 Wh station and will report on the story soon as I get some experience with it. I think it would have solved the problem just fine.

For the "run the whole rig on a power station idea," I think my only question would be what to do about the FLA battery that already sits on the rig. Do you really want the lithium power station charging that thing? Is there some alternative? Dunno. I just started thinking about that now.

If I were to start over I probably would use a Xantrex like Jim has, but I would have placed that and the batteries in middle of my passthrough (my 2019 has a different layout). I'd use the existing 6 AWG wire as the 12v supply back to the fuses and leave those as-is under the 'fridge. I would need to figure out how to route the 125v AC wire to the Xantrex. Since I haven't done it, I haven't yet learned what gremlins are in that idea. But it's interesting to think about. But in the very short run I would have bought that little Jackery!

Oh, and my wife already quickly "stole" the Jackery. She runs a nifty little Bernina 475 sewing machine with it. It's looking like she can run that sewing machine for 24 hours before it needs a recharge.

[Marine359]

Yeah Todd, a small 300Wh powerstation will run my cpap for 3 days on level one. Charges up with portable solar, and we alway throw it in the back seat of our tv to charge while driving. As backup, I installed a 12v/usb outlet near foot of bed serviced by the house lfp’s fuse block. The idea of using a bigger powerstation for all power needs intrigues me because there’s no installation. And, so what if your FLA is still in place.I’d like to hear from somebody who has actually done it. My logic says, the RV is just tricked into thinking the powerstation is a FHU pedestal. Everything would work the same way as if you were at a campground on a pedestal. Certainly there would be some efficiency loss from using the powerrstation to feed the old converter/charger. But hey, once the FLA is charged up, who’ll know the difference. At that point, you’d just be trading a little efficiency loss for the convenience of a simple plug in solution, allowing the 12v FLA to power all the 12v loads like it normally would when it’s on SP. Every watt used by the FLA would be immediately be replaced by a watt from the charger, just like a pedestal. I haven’t worked out any equations, but seems to me as long as the FLA is in good condition, everything should work peachy. Guessing maybe a 15-20% loss going from dc internally in the powerstation to ac through its inverter, then back to dc again through the charger. When we hook our EcoFlow to SP, we don’t notice any appreciable power loss as the Ecoflow powers the inverter/charger to send dc charge current to our house LFP. When we do this, I can also just turn off dc charging altogether, and the dc circuits works just fine servicing dc loads from the house LFP. When house LFP SOC reaches 50%, I give it a 20 amp charge from the Ecoflow. When the EcoFlow needs some juice, on sunny day, I just plug it into the Xantrex gfci. A bit of loss there too, but doesn’t matter when it’s a good solar day. I think there are some Youtoobs out there now of folks keeping their old FLA/charger setup and adding a powerstation. I would however recommend the Bluetti instead of the Ecoflow D2M, because the Bluetti has a 30TT outlet. With the EcoFlow, we’re limited to 20amps outlet, but it still seems to work fine. Haven’t had to start generator except for needing A/C one time.