Monday, December 5, 2022


RVelectricity – No~Shock~Zone by Mike Sokol – Issue 35


Issue 35 • October 4, 2020

Brought to you as a public service by Support comes from our sponsors, advertisers and the contributions of readers, who believe that an educated RVer is a safe, happy RVer.

Subscribe to one of our many online newsletters (including this one) about RVing.

Read back issues of this newsletter and many other articles by Mike Sokol on Warning: There is a lot to learn here.

Welcome …

By Mike Sokol

Welcome to my latest RVelectricity newsletter. Lots of new things happening in my lab, as well as some of my latest videos about all things electrical as they relate to recreational vehicles.

First of all, I’ll be presenting Part 4 of my CarGenerator™ Boondocking series, this time covering the basics of just how many solar panels you might need to run a residential refrigerator compared to a 12-volt DC compressor fridge. (It’s a fairly reasonable number for the 12-volt Danfoss refrigerator, but perhaps too many for a residential refrigerator.) How many solar panels would be needed to run your rooftop air conditioner overnight (way too many). And what recharging alternatives you have for days when the “sun don’t shine.”

Speaking of 12-volt refrigerators, Dometic just sent me one of their 10-cubic-foot 12-volt DC refrigerators for review. Of course I fired it up to see how cold it would get – which was pretty impressive. And I’ll begin testing total battery wattage usage in another week or so as part of my solar boondocking experiments. Read about my first look at the DMC4101 below.

I don’t have a full report competed on my Hughes Autoformer experiments just yet, but I do have some preliminary data I can share with you – and it’s not what I expected! In addition, I’m including a basic primer on just what an autotransformer is compared to a standard transformer, and how they work to boost or cut voltage for industrial power. Read below for my first results, and a little background on what autotransformers actually do and why they’re currently banned in campgrounds by the NEC. I’m not sure what my complete study will show just yet, but whatever it is may make an impact on the RV industry and campground power.

Finally, read this month’s Road Signs about a memorable Halloween when I built a UFO with blinking lights and a loudspeaker, then flew it down the main street of Hagerstown, MD, after dark in the fog. I’m pretty sure the statute of limitations has run out on that prank. Or so I hope….

Let’s play safe out there… 

P.S. And just a quick note that this newsletter is made possible by the voluntary pledges of the readers of We could not bring this to you without their support. If you deem what we provide to you here and at to be of special value and would like to be a part of our effort, please consider pledging a voluntary subscription. More information is here. We will include you in special emails, articles and videos exclusively for our supporters.

If you haven’t yet, be sure to join
my new Facebook group, RVelectricity.
(More than 10,400 members and counting.)

Hughes Autoformer testing

My Hughes Autoformer testing has begun. Here are details on how much additional current an air conditioner draws as the voltage goes below 100 volts. Hint: Everything You Know Is Wrong!

Since this is a rather complicated answer to what appears to be a simple question about Hughes Autoformers (and autotransformers in general), the results of my study will be presented in pieces over the next several weeks as I gather more information that’s been peer reviewed.

Note that while Hughes has sent me a demo unit at my request, they neither offered nor have I asked for any compensation for this study. That way it can be 100% unbiased. Hughes has also agreed to accept the results of my study, which will be sent to the NEC board for review.

Here’s Part 1, where I show how much extra current an air conditioner draws as the voltage is reduced. Read more HERE.

Email me at mike (at) with your questions.

Industry Updates

Dometic 12-volt DC refrigerator testing

Back in 2020 BC (Before COVID) I made a few acquaintances in the Dometic refrigeration division, and they promised to send me a 10-cubic-foot 12-volt DC compressor refrigerator as part of my study on refrigerator power consumption. I had almost given up on a test unit, when I received a call from my local trucking company about delivery. True to their word, a DMC4101 refrigerator has arrived for review.

I’ll begin a full review of its operation and power consumption in a few weeks, but for grins I simply loaded up the freezer with a 50% mix of frozen and room temperature meats and veggies, put a few 6-packs of warm beer in the fridge, set it to 5 Snowflakes of cold (yes, that’s the max cooling setting), and connected it to a 12 volt battery. Yes, it got very cold very quickly. Continue reading.

Survey Question

Feel free to leave a comment below. (And it may take a moment for the poll to load.)

Last month’s survey results:

While some 58% of you answering the poll weren’t interested in running your RV air conditioner from batteries, there’s a solid 32% (1/3) of you who are interested in how to make this work. Yes, it’s expensive and complicated right now. But as the price of Lithium (and who knows what other chemistry) batteries continues to come down due to manufacturing scale, and air conditioners become less power-hungry, there will be a point where it’s commonplace in an RV. So I’ll continue my experiments with solar, battery and hybrid inverter operation of rooftop air conditioners. If any other manufacturers want to confer with me on this, please let me know.

Tools and Other Devices

Trailer connector testers

I have a number of questions this week from readers about how to test their 7-way trailer plug. While it’s certainly possible (and sometimes absolutely necessary) to use a digital voltmeter, one of these indicator plugs is a handy way to begin testing. This one also labels each LED for the intended function.

Oh, by the way. I once found out the hard way that the original Sprinter vans had the backup light wired to the trailer brake connection. So when you put it in reverse, the trailer brakes locked while you were trying to back up. This gadget would help you figure that out in a hurry.

Learn more about this product or order at Amazon.

Last Month’s Posts

These articles are rated Moderate to understand for most RVers.

12-volt battery dangers (Warning: graphic content).
First-hand report on Hurricane Laura recovery operations.
RVelectricity Facebook group hits 10,000 members … and more great news!
Can I run my air conditioner from batteries?

Last Month’s JAM (Just Ask Mike) Session posts:

These articles are rated Easy to understand for beginners.

Driving over wires is a bad idea.
Be prepared for hurricanes.
Be prepared for a converter/charger failure.
How low of a voltage is too low?

Q&A’s from my Facebook group:

I’m getting a lot of interesting questions on my RVelectricity Facebook Group. Here’s a really scary one.

Q: I was called to troubleshoot because the RV wasn’t working properly. Ummm… Yea… Just so many things wrong in one little spot. Where do I begin? —Miguel Salinas

A: It’s hard to tell, but it looks like the outlet was fed #6 wires then smaller wires tapped off and went out to feed another circuit?!? Definitely a safety issue. The drywall screw reinforces the fact that this is a hack job by someone that just doesn’t give a sxxt about code. —Tim Beaulieu

A: This is a total disaster that needs new wiring run, not just taped up splices. I’m sure there was no inspector looking at this or they would have had a major conniption fit. Just one more reason I want to begin teaching campground maintenance crew classes about pedestal maintenance and safety. —Mike Sokol 

Email me at mike (at) with your questions.

The best book on RV electricity, hands down!
RV Travel contributor Mike Sokol is America’s leading expert on RV electricity. Mike has taken his 50+ years of experience to write this book about RV electricity that nearly anyone can understand. Covers the basics of Voltage, Amperage, Wattage and Grounding, with additional chapters on RV Hot-Skin testing, GFCI operation, portable generator hookups and troubleshooting RV electrical systems. This should be essential reading for all RVers. Learn more or order.

Boondocking Power Requirements – Part 4 of 4

Integrating solar panels into your boondocking plan

While you could just move to a cabin in the woods and live totally without electric power like humanity did 100 years ago, few of us want to give up our current lifestyles. So if you want to camp without shore power from a campground pedestal or run a generator all day, there are some special technologies needed if we want to maintain our electrically charged lifestyle while off the grid. Enter the solar panel – which is the topic of Part 4 of this series. Included is an interesting write-up from Jonathan Schloo, from CarGenerator. Read more HERE.

Sponsored by CarGenerator™

Mike’s Video Quick Tips

Quick Hot-Skin Test – 1:10
Simple way to test a 30-amp outlet – 3:28
How to test a pedestal with a digital voltmeter – 3:36

Camco Store at
There isn’t much you need for your RV that Camco doesn’t have. If you think we’re kidding, then click through to the Camco store on Amazon where you’ll find some of their best-selling products — all for your RV or for you to make your RVing better. Click here and you’ll feel like a kid in a candy store.

Road Signs

Is it a UFO or an MFO (Mike’s Flying Object)?

As we are preparing for Halloween this year, I’m reminded of that one special Halloween in my early 20s when I went trick-or-treating for drinks at my friends’ houses. Don’t worry, I was walking … not driving. I had dressed up in a chrome jumpsuit from my glam-band days, put on a multi-colored wig, and built a set of frames for my eyeglasses out of LEDs that alternated between red and green spinning lights.

Yes, this was 1976 so these types of electronics had to be designed and built from scratch. But I wasn’t done yet, as I had also bought a weather balloon, a tank of helium, and lots more LED lights. Yes, I built my own UFO for late-night pranking. Read more.

Thanks for reading. Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.


Editor: Mike Sokol. publisher: Chuck Woodbury. Managing editor: Diane McGovern.

Everything in this newsletter is true to the best of our knowledge. But we may occasionally get something wrong.  So always double check with your own technician, electrician or other professional first before undertaking projects that could involve danger if not done properly. Tips and/or comments in this newsletter are those of the authors and may not reflect the views of

Mail us at 9792 Edmonds Way, #265, Edmonds, WA 98020.

This website utilizes some advertising services. Sometimes we are paid if you click one of those links and purchase a product or service. Regardless of this potential revenue, unless stated otherwise, we only recommend products or services we believe provide value to our readers. Amazon and the Amazon logo are trademarks of, Inc. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to includes links to other websites. We cannot control the content and/or privacy policies of those sites. Please be aware when you leave this newsletter or any other section of to read the privacy statements of any of those websites that collect personally identifiable information. Our own privacy policy applies only to and its affiliated blogs and websites.

This newsletter is copyright 2020 by


Did you enjoy this article?

Click on a star to rate it!

Average rating 0 / 5. Vote count: 0

No votes so far! Be the first to rate this post.


Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Dick and Sandy near Buffalo, NY
2 years ago

Many years ago we were at a campground just outside the Bad Lands. Of course it was very hot out, almost 100 degrees. The campground had 50 AMP sites and everyone was running all their air conditioners. The campground power grid was having a very hard time keeping up with the demand.

When the voltage to our coach went down near 110 Volts AC we pulled the plug and headed to Deadwood in the mountains that was at least 20 degrees cooler and that campground had full power. Was not going to wait for any damage from low campground power.

Stay well, Stay safe.

2 years ago

The picture above looks as if the ground wire isn’t there- only the wire strands around the screw. I couldn’t zoom close enough to see otherwise.

2 years ago

The trailer connector tester is a great tool unless you have a newer Chevy or GMC pickup. The plug in the bumper is mounted upside down. Using the one you show would mean you have to stand on your head to use it.
Would have been nice if they had the led’s rotate 180 degrees.
I actually made my own using a trailer connector, a small plastic work box and some 12 volt led’s.

2 years ago

Recently I camped at a state campground, my site was the one closest to the lake. Upon returning from an outing I noticed that I had an “Open Ground” error code on my EMS. Electricity was back on so this puzzled me. No damage to the TT. The next day we were in the TT and the electricity failed. The EMS had an “Open Ground” error code. I called the park maintenance crew and asked them to check the pedestal. Their reaction was this park was built in the 70’s and they are sure that some of the electrical connections will have issues and they don’t even know if the park is grounded.

Mike Sokol
2 years ago
Reply to  travelingjw

That should not be an excuse for providing dangerous power.

2 years ago
Reply to  travelingjw

Ask for a refund!

Subscribe to our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.