Tuesday, November 28, 2023


RV Electricity – My shop is going solar

By Mike Sokol

Part of my test lab will soon be going solar as I begin experiments in June to see just how many solar panels are needed to indefinitely power a 12-volt DC Danfoss compressor refrigerator compared to a 120-volt AC standard residential refrigerator with a pure-sine inverter. The plan is to hook this all up with a RV Whisper® monitoring system so I can automatically gather information about battery in/out amperage, room temp, sunlight times, etc.

If all goes well I’ll be able to begin publishing this data in July. I’m also pitching a few CPAP manufacturers to see if they’ll send me one of their products to determine just how much battery and solar power is needed to keep them running through the night without shore power or a generator. If all goes well with that I should have real info to publish by August.

While I’m at it, I’ll also include some testing to compare inverter efficiencies and harmonic content. As many of you know, some electronics and motors are not very happy being powered by cheap inverters that produce modified sine waves with up to 35% harmonic content. A lot of that 35% harmonics turns into heat inside electronics and electric motors, which I suspect is what’s causing the damage.

Since I have a high-end FLIR infrared camera I should be able to narrow down why this happens and the kinds of devices to avoid plugging into a modified sine wave inverter. Maybe I’ll even get to burn up a few things in the shop. Yes, I have fire extinguishers close by. Of course, this is why I always recommend you install pure-sine inverters whenever possible.

Email me at mike (at) noshockzone.org with your questions.



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

Email me at mike (at) noshockzone.org with your questions.

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




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Wolfe (@guest_81598)
3 years ago

One flaw in asking manufacturers for CPAP equipment is that usage is extremely variable by the user, pressure settings, “bad night”, room temperature and humidity, whether heat/humidity is enabled on the unit, DC or AC cord…. etc!!! What I suggest is people with a P3 type AC or DC watt meter more and send you the week-averaged Watt-hours directly. Bigger real world sample and easier. Remember NOT to monitor battery drain through an inverter since that adds wildly disparate efficiencies of its own.

I look forward to your more technical experiment articles!

Dan (@guest_81275)
3 years ago

I currently have a 3.8cf Unique 12v fridge which I run on a 300 watt solar setup. I have 3 100ah AGM batteries for storage. No problem running the fridge with freezer on a continuous basis as long as the interior temp stays below 78 degrees approx. This is the setup In my cargo trailer RV conversion.Keeping the freezer compartment full seems to help reduce the run time also.
Looking forward to seeing your results.

Wayne (@guest_81260)
3 years ago

Maybe to give a small head start or ball park of power needs for a CPAP, I use a Resmed aircurve 10 cpap powered with optional 12 volt power cord, two 6 volt 225amp hr Deka golf cart batteries, and two 100 watt solar panels. The solar panels fully charge the batteries on sunny days. Starting the night at 100% charge the batteries are still about 70% in the morning and that includes powering the refrigerator and other parasitic loads. By my calculations the cpap uses less than 70 amp hour to last the night. I look forward to your experiment results

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