Using a residential fridge correctly when not connected to shore power

[TigeDuner]

We recently purchased a 2017 Winnebago SunStar LX 35F with a new residential fridge installed just before our purchase. After some help from this website, I was able to connect the fridge to our 1K inverter, which can provide 110 volt power from our two size 24 coach batteries (wet) when needed while driving or when parked and not connected to shore power. We have no solar power and the fridge draws 1.2 amps AC when running. I have read that since these residential units are insulated so well that you can "leave them off" or turn the temp up during the night and the fridge will maintain it's temp until we begin driving in the morning or start the generator to bring the fridge back to the preferred operating temp. Is this the proper way to use a residential fridge while 110 power is off? I am not sure our two deep cycle batteries will be able to handle too many fridge cycles over the night.

Any thoughts on this issue or personal experiences would be helpful.
TD

[l1v3fr33ord1]

TigeDuner-

Try running the refrigerator on your battery bank first. You may find it's sufficient.

1.2 A x 120V = 144W on AC power
144W / 12V = 12A on DC power
Assume 80 percent inverter efficiency (probably higher) 12/0.8 = 15A DC
Assume refrigerator is on 1/3 of the time 15A x 0.33 hr = 5Ah
Assume battery bank runs 12 hrs between recharges 12 x 5Ah = 60Ah

My coach's residential refrigerator (0.5A at 120V, steady-state) ran on a Bluetti EB70 portable 120V power pack overnight, taking out about 30Ah, which is in line with the estimate of 60Ah for your reefer, as above.

The refrigerator is a large draw on the house battery bank, but not the only one. On my first coach I installed a battery shunt and usage meter. Together they act like a fuel gauge for the battery bank. If you find yourself short on data to manage 12V usage, you may want to install a shunt and meter. I'd hold off, though, until you saw how it went without one.

Residential refrigerators are not (in my opinion) designed to be turned on and off frequently, or have their temperatures adjusted up and down frequently. They are built so cheaply nowadays. You could wear out the controls quickly.

Finally, in the category of "Nice to have, but perhaps not worth the anxiety," are refrigerator temperature monitors. I've gone without them at home for all my life. I bought a set when I my coach's propane-electric absorption refrigerator started to struggle in high ambient air temps. When I replaced the absorption unit with a residential I used the temperature monitors to dial-in the refrigerator and freezer compartment settings. After that they just were along for the ride. I bought the Acurite 00986; apparently it's replacement is the 00515M (link here).

[creativepart]

Here’s the thing… 2-group 24 batteries likely mean you have ~140 amp hours total. Best battery practice would be to limit your power usage to preserve your battery’s lifecycle. Repeated, as in daily, draws below 40% state of charge are going to chew up those batteries in no time. So you have maybe, at best, 85 amp hours available.

Driving you should have no problem because the alternator will keep things charged. But dry camping without shore power for more than a day is just about out of the question with your equipment. Your 120v fridge being run off inverter/battery is going to have you scrambling for power non-stop.

When camping in cold temps you probably are fine turning off the fridge overnight. But that’s only a partial solution.

What you absolutely need is, well, everything. More battery storage, more recharging capability. Solar power, generator running, etc. Short of spending on those things you pretty much need to always have shore power available.

I have a residential fridge. And I have 300w of solar, a 2000w inverter and my RV came 400amp hours of AGM batteries. So, more than twice the battery capacity of your rig. And we were limited to at most a couple of days dry camping If we also ran the generator 5-6 hrs each day and had plenty of sun.

I replaced the AGM batteries with Lithium and this has eased that pressure caused by the need to power the fridge but still dry camping requires 1+ hrs of generator in the morning and 2+ hours more generator time at dinner time, depending on any furnace need during the night.

To get to that level of camping without shore power or generator will cost you a few thousand bucks in upgrades. Until then stick with camping with shore power.

[wahoonc]

The modern fridges do better when left running, due to the energy star requirements they take a while to cool down after being turned off. According to the manuals, stabilizing the internal temperature can take up to 24 hours. I do use Accurite temperature monitors. I have used them for years in the RV and use them at home to keep a running check on my fridges and freezer. I have had a fridge unit go bad, without the monitor I probably would not have noticed for at least another 24-36 hours that the fridge had quit working. Thankfully the freezer was still cold.

Aaron

[TigeDuner]

Thanks for the math on how to figure the load of my fridge as well as the temperature monitor from Acurite. I ordered the monitor and it will be here in a few days. My batteries are 65 AH and are 18 months old. So, when I get new batteries, I will invest in better batteries for a start.
When we dry camp, it is usually in the desert where we go offroading for a weekend, for 2 nights at the most. I take a 2K portable generator with us to power up the TV, Sat receiver, and maybe the coach heater depending on the temps. I can leave the portable generator on while we are gone to charge the batteries, which would be for 3 to 4 hours or it can run while we are at camp since it is pretty quiet. For these reasons, I am not ready to invest in roof top solar panels with the equipment to complete the system.
Our RV is stored under a roof at our home and is plugged in to maintain the batteries. I have left the fridge on and at a lower setting for the reasons mentioned in the previous posts. Having a residential fridge is new to us - our 5 previous RV's all had elec/propane models, but this information should help us cope with the change.
Worst case, we could pack our cold stuff in coolers for 2 days and turn the fridge off for the trip. I am going to do a dry run at home and see how the batteries do overnight with the inverter. That will give me an idea of what to expect on our next trip.
Thanks for the comments guys.
TD

[creativepart]

TD, my fridge may use more power than yours, I don’t know, but with 400ah of lead acid batteries we could count on about 12 hours of operation on inverter with nothing else running. That’s limiting battery drain to 60% (40% state of charge).

Hope that gives you some idea of the load you are dealing with.

[TigeDuner]

Thanks for the calcs. It appears that I may need to get new batteries sooner than later if we have any "camping" plans in our future. To test my current batteries I am going to need a device that can show me the discharge rate and other information related to the condition of my batteries. Any ideas for this device?
Based on our usage, I think I will upgrade to AGM batteries and get two that will be 100ah each. This is all I have room for under the entry steps and should be a fair amount more than what I have. Looks like my generator will be part of the charging plan as well while we away from shore power.

[creativepart]

Originally Posted by TigeDuner

To test my current batteries I am going to need a device that can show me the discharge rate and other information related to the condition of my batteries. Any ideas for this device?.

The Victron SmartShunt is perfect for this. Since your battery compartment is open to the weather, they make a water resistant version.

It’s easy to self install and gives you all the info you need via an App on your smartphone. It counts all power into and out of your batteries and gives you not only a real world state of charge in percentage reading but also an estimate of the remaining time until you run out of power at your current usage rate.

Under $130 online.

https://www.amazon.com/Victron-Energ.../dp/B0BF636VBX

https://www.youtube.com/watch?v=oAbdmHo51uM

[cruizerEd]

Here is data from a 2013 fridge.

I used a kilowatt meter and I have a blue seas battery monitor for logging the batter AH.

I had 600AH of AGM (no 800 LiFEPo4) and that fridge would drain those batteries in no time without solar.

It is relentless and it isn't the only load.

I've attached my actual measure power usage.

[TigeDuner]

After a lot of research and help from this forum, I have decided to change to Lithium batteries, change out my converter/charger to a Lithium charging unit (Progressive Dynamics PD9160ALV) , and change the BIM to a lithium unit (LI-BIM 225) as well. I will be using one 200ah +/- battery.

But, I cannot locate the converter or the BIM in my RV. I could not find it on the wiring diagrams either, however I am not the best at reading them. Any help on finding these guys will be appreciated.

[creativepart]

Here's the wiring diagram book for the 2017 Sunstar 35F:

https://winnebago.com/Files/Files/Wi..._e35f_wire.htm

You should be able to find the converter and the BIM.

Do you know where your 12v Fuses and 110v Circuit Breakers are? Your converter is behind those fuses/breakers.

Do you know where the "push to reset" 12v breakers are in the basement compartment usually next to the door if you have a mid-entry. There is a sticker on there that says something like, battery disconnects and solenoids behind this panel. That's where the BIM is. It sits between the House and Chassis disconnect solenoid.

But double check with those electrical diagrams in that link above.

Here's a diagram from your wiring book and a photo of those push to reset breakers in the basement compartment with the sticker that tells you the BIM is behind there:

[TigeDuner]

Well, as I said before, I am not the best at reading wiring diagrams. But, that was mainly because I was looking at the wrong diagrams. I found the converter on the "body 12 volt wiring diagram" and it is located under the bottom of the cabinet under the sink. I have no idea how to access the converter unless I remove the cabinet bottom, which will destroy the bottom material since it is stapled in place. I also found the BIM on the "Chassis electrical box assembly" diagram and it is located in an exterior compartment behind the driver. This should be fairly easy to swap out. I suppose if you spend enough time with these schematics, you know where to look when on a search for a component or circuit.

So how do I get access to the converter?

[cruizerEd]

It all really depends upon your use pattern.
If at all possible try to build it out so you can add another battery later.

It's kind of funny, and I love our residential fridge, but if you want to use one off grid it cost a lot of money to upgrade what the manufactures supply.

[creativepart]

Originally Posted by TigeDuner

So how do I get access to the converter?

Your Power Center (fuses and AC circuit breakers) is not behind or under a panel, correct? Well, your converter should be behind your Power Center. If it’s there, and it should be, you would unscrew the four corners of the fuse/breaker panel and pull that away from the wall it is mounted to.

[creativepart]

TigeDuner
Your 2017 SunStar is available with either a Converter or an Inverter/Charger. Depending on how your coach has been optioned. Do you have a Magnum 3-button control panel in your monitor panel area?

If you do, you don’t have a Converter or a Power Center like the one in the photo above. And you would not need to change the inverter to work with Lithium batteries. You would only need to change the Inverter controller.

So, let us know if you have an Inverter Charger or not. Your inverter charger control would look like this photo.

[TigeDuner]

I do not have an inverter/charger or the Magnum panel. My RV has a 1K Xantrex inverter located in one of the passenger compartments. I will look into removing the power center to find the converter, but on our Adventurer 35U, the converter was under one of the bottom Kitchen drawers, which made changing it easy.
I do have room for extra battery storage in the compartment next to the entry steps, which is where our current batteries are located (under the steps).
I can only assume that as more and more RV's are equipped with residential fridges, the RV builders are learning what it takes to keep one going in each type of camping - shore, generator, solar, or battery.

[creativepart]

I did some looking in the 3d Parts catalog.

First off there are two versions of the 2017 Sunstar LX 35F. You can tell which you have by looking at your Serial Number (not VIN). Here are the things to look for:

IFE35F (Serial Number begins with 70E75W1)
IFE35F (Serial Number begins with 70E75W2)

Next - Looking at the electrical details of that second one, I guess you have the first one. Because it looks like the second version is the 2000w inverter model.

Next, I find the load center in the 3D Parts diagram but it doesn't show the converter in the drawing. In fact, I can't find it in the parts list anywhere. But I will say that 90% of the time it's behind the Power Center. Especially if Your Power Center looks like the photo I posted a couple of posts above. You'll see in that photo that even your Operator's Manual calls that the "Power Center (Converter)"

Looking in the 3D Parts resource I don't see anything under your sink cabinet base... BUT if the Converter is part of that Power Center it would be under your sink just not separate of the Power Center and you would access it via the Power Center.

Many times the Power Center and Converter are one self-contained unit. Other times the actually "charger" is separate but it is usually behind the Power Center, too.

Nothing is ALWAYS in RVs... it's just USUALLY.

But looking around in the 3D Parts Catalog I did find your BIM.

It is behind the Push to RESET fuses as I said earlier and you'll find that in the last basement compartment on the passenger side.

Here's a screen shot of the location. The BIM is YELLOW, you'll see it is in the center between the House and Chassis battery cutoff solenoids.

[creativepart]

Here's a link to that first Parts Catalog:
IFE35F (Serial Number begins with 70E75W1)
https://catalog3d.winnebagoind.com/2016/16ife35f.htm

And here's a link to the other version in the Parts Catalog:
IFE35F (Serial Number begins with 70E75W2)
https://catalog3d.winnebagoind.com/2017/17ife35f.htm

[TigeDuner]

Originally Posted by creativepart

Here's a link to that first Parts Catalog:
IFE35F (Serial Number begins with 70E75W1)
https://catalog3d.winnebagoind.com/2016/16ife35f.htm

And here's a link to the other version in the Parts Catalog:
IFE35F (Serial Number begins with 70E75W2)
https://catalog3d.winnebagoind.com/2017/17ife35f.htm

I guess you missed post #12 where I said I found the location of the converter and the BIM. The wiring schematics are pretty clear, as long as you look at the right diagram.

Thanks for all your help and the 3D diagrams. I was not aware of those.
TD

[TigeDuner]

And I do have the early 2017 model.