Welcome to RV Electricity Issue 14

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By Mike Sokol           

Dear Readers,
Here’s a quick update on my residential refrigerator test and what it takes to boondock on solar power without a 3-way fridge. No, I haven’t forgotten you. It’s just that talking manufacturers out of gear to test and designing a valid experiment takes time. But I’m happy to report that I’m on track to begin gathering data in mid-January.

The Process

Now, while many of you couldn’t care less about what’s under the hood, there’s a small segment of readers here who are groupies/geeks and want to know how it all works. And I welcome them for peer review. You see, I don’t do anything in a vacuum. Every hypothesis I postulate, every experiment I devise, all empirical data I collect, and every conclusion I reach is subject to peer review by some of the most intelligent people I know. That is, I have a number of really smart colleagues around the planet that review my work and tell me if I’m doing valid science or not. And these guys are specialists in their own fields of nuclear power, marine power, utility power, pro-sound and lighting power, as well as others that are just plain smart about everything. And our own RVtravel.com staff includes a “persnickety” (her term) copy editor who makes sure everything I write is grammatically correct and makes sense. So you can be sure that before I release any data to the public it’s been vetted for content and clarity by a lot of different people.

That doesn’t mean we (or, more specifically, I) can’t make a mistake, so your job is to keep us (me) honest. If something doesn’t seem right or a conclusion doesn’t seem to fit the data, then by all means, speak out. That’s the same rule I have in my university classroom where I teach as an adjunct professor. If you see something, say something – politely, of course. And then we’ll dig in and find out what went wrong. Sometimes it’s as simple as the arithmetic, and other times it’s a silly premise that just happens to match the data set. But just know that I’m here for you, and doing everything I can to educate everyone from the RV manufacturers to the customers on how this electricity stuff works.

So let me show you what I’ve collected for the fridge experiment. It’s going to be really cool. (Get it…?)

The Gear

Here’s what I’m assembling for Phase I of the residential refrigerator boondocking test.

Welcome to RV Electricity Issue 14Vitrifrigo has sent me an 8 cu. ft. marine-grade refrigerator with a 12-volt Danfoss-style swing compressor. While this isn’t as large as many of your residential refrigerators, it’s a good beginning to get a baseline of energy requirements using the most efficient refrigerator technology available.

Welcome to RV Electricity Issue 14VMAX USA has sent me a VMAXTANKS 100-amp/hour AGM battery with built-in solar charger system. This will be another baseline for battery storage. I’m also promised a 100-amp/hour Lithium battery from another manufacturer I met at the RVillage Rally One earlier this year. That battery should arrive the middle of January.

Welcome to RV Electricity Issue 14Thornwave Labs has sent me their Bluetooth Smart DC Power Meter which will track the incoming and outgoing current charging voltages, etc. This will link to the next cool monitoring gadget to catalog the data every 5 minutes.

Welcome to RV Electricity Issue 14RV Whisper LLC has sent me their RV Whisper WiFi Monitor Station, which will gather the charging data supplied to it via a Bluetooth link, and send it to the cloud, which I’ll be able to view on my computer in my office, or even my smartphone no matter where I happen to be. And I can then export this data and turn it into a number of graphs to help visualize what’s happening.

Welcome to RV Electricity Issue 14Xantrex Technology has sent me their Freedom XC-2000 pure sine inverter/charger, which I’ll eventually use to power a standard 120-volt AC residential refrigerator (as soon as I can talk a manufacturer out of one). But for now this will be a 12-volt DC test.

The only things missing from this test are the solar panels, but they’re promised to arrive in a few weeks. In the meantime I can get the rest of the test setup configured and metered up. Once the solar panels are in place I’ll be able to directly compare 100-amp/hr. Lithium vs AGM batteries on a refrigerator with a Danfoss-type swing compressor. And once I swap in a full-size 120-volt AC residential refrigerator, that data will become available as well.

The Science

I want to know just how many solar panels and how many batteries (both AGM and Lithium) are needed to run a residential refrigerator on an extended boondocking trip, and if there’s enough power left over for the other basics such as water pumps and maybe a furnace blower. Yes, I know those furnace blowers can be real energy hogs, but just how much of an appetite do they really have? And are there other technologies available that will improve the efficiency of an RV furnace blower? (Think, brushless DC motors.) I’ll also consider LED lighting and anything else that will reduce the electric load in boondocking mode.

Yes, there are lots of moving pieces, but it’s all coming together. I should have an update for you by my next RVelectricity newsletter.

Let’s play safe out there… 
Welcome to RV Electricity Issue 14

 

Click here to return to RV Electricity Newsletter Issue 14.

Welcome to RV Electricity Issue 14

Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

 

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Don Homola

As if you don’t already have enough factors to consider, there’s always the amount of refrigerated product in the refrigerator/freezer which will affect cycle times, etc.

Stephen

Are you going to test the compressor conversion kits for refrigerators also?

Garry Hammond

Hi Mike – I can’t tell you how valuable this research you are doing is.
It will be a game-changer for both RVers, and hopefully for RV equipment manufacturers as well.
The current refrigeration technology is, well… ancient – in ALL RVs.

I assume you will do your baseline measurements at around 70 deg. F.
Hopefully, you will also have time to go from just above the freezing point up to over 100 deg. F.
So we will also have data on what effect temperature has on refrigeration efficiency.
Of course, humidity can also play an important role on refrigeration efficiency as well.

Danny Braun

Thank you Mike for ALL the solar information. I designed a solar system for my cabin and will use it on my fifth wheel rig someday. I also designed a camping solar generator to supply electricity. Hope to hear from you soon!!!

Trent Mills

I would be interested in a “from zero” and a “loaded and cold” scenario. I think of loading the fridge while driving (on alternator) or while at a site with hookups. The solar and batteries would not be used for the initial cool down of the food loaded in the fridge.

Bill Lampkin

You might want to do a ‘Literature Review’ on RV refrig power use, and include that in your research. Many have done their own measurements, albeit maybe not with as ridgid controls as your experiment.
Check Technomadia, Gone With the Winns, many others. Useful info, if only to corroborate your findings.
Good luck!

Gary Sandahl

I’m interested in knowing how much the inverter and it’s internal fan will drain the batteries even with minimum load. I have 3 solar panels and 3 100 Ahr lithium batteries. If I leave the inverter on at night, the batteries are all but drained by morning even though I have all 120 volt items unplugged (and running my fridge on propane). I hear the inverter fan coming on and off all night. Not sure why, unless there’s a loop I don’t know about between inverter and converter that’s constantly trying to charge up the batteries using power taken from the batteries. My issues aside, for the refrigerator test it would be good to isolate, as part of the equation, how much the inverter is draining the batteries even without load. Or with very minimal load, such as a cell phone charger. My inverter is 3000 watts, pure sine wave. I’m also wondering if a 2,000 watt or 1,500 watt inverter would have less drain on those batteries, and if so, would it be useful to have two separate inverters – one dedicated and sized for the refrigerator circuit, and another for other 120 volt circuits.

Greg Illes

Mike,
It looks like you and I will be running similar experiments in similar timeframes, although I expect yours to be much more thorough.

I’m going to be installing a Novakool RFU9000 in my RV in January (after a LOT of research).

I don’t know if you covered this previously, but the Vitrifrigo / Novakool (Danfoss compressor) units are hardly what I’d call “residential” refrigerators. The 12V Danfoss compressor uses far less power than a standard house-type residential refrigerator, and has no conversion inefficiency. As far as I’m concerned, a normal 120V residential fridge, run off an inverter with its own overhead of 1.5-3.5A operating current, is simply a no-go for any realistic boondock application.

Looking forward to your results,
G.

John Maddox

I am interested in this test because it would give me an alternative to running on propane when driving if I switched to a 12 volt refrigerator. When I asked about running on 120 volt while driving there was talk about my truck not being able to result the battery fast enough or safe enough due to the wiring for the truck to the trailer not being the right gauge. This could be an alternative

Randy Shrimplin

1.The Solar part of this experiment is going to be difficult if not impossible to quantify. Sun angle, cloudy days, ect play a huge part in how much charge you get from them.
2. Inverter technology residencial fridge’s don’t mind modified sine wave inverters because the simply change the AC back to DC to run the motors. (not 12vdc but DC) A normal AC motor does not like mod sine wave and an older compressor will likely have an AC motor. You should also consider the efficiency of the inverter. Watts in will not equal watts out. With today’s electronics prices there is no good reason to use a mod sine wave inverter.

On another note: Why 12VDC? Just because it is “the standard” doesn’t make it the best. My theory, “The only worse than 12v is 6V.” My belief is that the only reason 12VDC exists is that when the auto industry figured out that 6v wasn’t working, a 12v battery was the biggest they could fit under the hood (Think 1930’s battery technology)
Why not set up a 24 or even better a 48 volt storage system and then invert that? More efficient, smaller wires and the list goes on. After all, this is the way it is done for home systems, and it is coming to RV industry (Already in high end coaches)

Mike Sokol

Sorry for the confusion. The survey is on the main page for RVelectricity Issue#13 at https://www.rvtravel.com/electricity13/

SteveK

What survey?

Don Barylski

Mike I don’t understand this statement, are we talking 120 volts of dc power.

“For 120-volt DC power I’ve been promised a VSG12-100 battery from VMAX, which includes an on-board charge controller so I can plug a solar panel right into it. But believe it or not, Trojan turned me down cold when I asked for ”

Dave Telenko

Hi Mike, HMMMM just wondering about Trojan batteries, it sounds like they don’t like it for someone to run an independent test on their batteries, On the 120 volt RV refrigerators, isn’t there an inverter built into them to drive the compressor at variable speeds. I think its to achieve the Energy Star rating on most if not all 120V refers. I was in a discussion on the Forest River forum & that subject came up & got an answer from one of the members! I bet there is a lot more information coming after you do your test.
Dave

Dave Marshall

Didn’t see the survey.
I’m a light weight long distance hiker. Many of my hiker items easly become preper gear. I keep my backpack in my fifth wheel.

Joe Dobry

Try Lifeline Battery for the AGMs/Li batteries.

mike

Hi Mike, You could try East Penn Manufacturing/ Deka Batteries to see if they could supply you with the battery you need. I know that in the past, they have donated for test purposes. I’m looking forward to your air conditioner tests. I’m the guy who asked you about putting a fan in front of the breakers. It works great and I will be installing a 12 volt fan permanently near the breakers.

BuzzElectric

Mike I’d love the prepper stuff as I’m a Chico, CA resident that was threatened by the Paradise fire. I have a Paradise family living in a trailer out in front of my house connected to my 30amp RV hookup.

Sue Norwood

Mike, I don’t see the survey.