Saturday, February 4, 2023


RVelectricity: SoftStartRV update – Yes, it really works, and here’s proof…

By Mike Sokol

Dear Readers,
Since I published my initial peak starting current data last month comparing SoftStartRV technology to stock starting capacitors, I’ve had hundreds of questions about how well it works. In fact, I just wrote about this in

So let’s get those pesky questions out of the way first. Yes, I did gather this data myself. Yes, SoftStartRV seems to work exactly as advertised. No, a $10 hard-start capacitor is not the same thing at all.

But I wasn’t particularly happy with only being able to create a rough peak current graph showing the differences since my Fluke and Southwire recording meters would only sample the data 5 times a second.

Now that’s plenty fast enough if you want to monitor how much power something uses over a period of minutes or hours. But I needed to see down into the millisecond range (1/1000 of a second) to know how this product really works. And I simply couldn’t afford the $100,000 piece of test gear that can capture thousands of pieces of data in a fraction of a second.

So I invented my own High Rate Data Logger (which I’ve named HRDL, pronounced “hurdle,” like “turtle” but much quicker!) out of spare parts I had laying around in my shop. Yup, I built a $100,000 data logger out of $200 in parts plus an old laptop computer. Really, I did.

With HRDL I can now capture up to 192,000 data points per second at an accuracy approaching 1 part per million. More on how I did this and my plans for future analysis of all sorts of RV electricity things in my Sunday RVelectricity Newsletter coming tomorrow. But today I’m going to show you the basics of exactly what’s going on inside of a SoftStartRV box that allow you to start a rooftop air conditioner with a 2,000 watt inverter generator. So hold onto your seats, ladies and gentlemen, this is going to be a wild ride.

Here’s my basic overlay graph comparing the starting amperage curve of a Penguin II 15KBTU air conditioner using its factory starting capacitor compared to the SoftStartRV unit.

Note these are the actual curves generated from my own test data last week, not some graph drawn up by an artist with a sharpie. As my earlier 5-sample/second data graph hinted at, the factory capacitor works by drawing a lot of current for a short period of time, while the SoftStartRV unit works by drawing less than half that current for twice as long. But in my new graph there are thousands of samples to draw the curve more accurately.

This technology does two things for you. First, since the peak startup current is much less with the SoftStartRV technology, you can use a much smaller generator to run it (my Honda 2200is works great on a 15k Penguin II). Second, there’s much less of a “hammer” when the compressor starts up. As you can see from the yellow graph line, the SoftStartRV spins up your compressor up to speed gently over 1/3 of a second, while the stock factory capacitor puts the hammer down for less than 1/6 of a second with a much steeper rise time in current at the beginning of the compressor starting cycle.

There’s also a third possibility that this more gentle starting current from the SoftStartRV may help increase the life of your air conditioner compressor. I can’t be sure of that without a few thousand hours of testing, but I certainly don’t see any way for the SoftStartRV to harm your compressor.

So what else can I see with my new HRDL meter? Well, in the next higher resolution graph the red line shows that the stock starting capacitor has a 20-amp rebound current with a little wiggle at 30 Hz. Yes, underneath the top line you can see the actual sine waves in the background which form the 60 Hz AC current. And I believe that rebound wiggle in the graph after startup is probably a pressure wave in the Freon gas as it’s being compressed 30 times a second by the 1,800 RPM motor. Sort of like ringing a bell, but in this case it’s Freon coolant in a gasified state as is collapses into a liquid.

Yup, HRDL is accurate enough to hear the echo from Freon bubbles collapsing inside of the compressor, plus a whole lot of other things too cool for school (as we used to say). Want to know more about how I accomplished this data grab and my future plans for HRDL? Read my Sunday RVelectricity newsletter tomorrow for details.

And find out more about where you can purchase a SoftStartRV unit HERE.

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.




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2 years ago

Is it possible to start the air conditioner on my generator and once it is running turn the generator off and keep it running on the hydro. I realize I would have to shut it off before it went through the next start up cycle.

Terrence Courtney
2 years ago

Mike Sokol…Question I have is “Comparison of the Micro-Air system and the Soft-start RV.” I understand the Micro-Air requires 5 start-up cycles to have the unit sink before the system can be put into normal operation. Did I get that correct? Soft-start not so?
Another question…I have a 1997 American Eagle Class A with 2 Coleman 7000 series 13.5Kw ducted roof air conditioners. Will the Soft-start RV units work on these older units?
I really respect your opinion Mike…Keep up the good work !!!

j harris
2 years ago

Curious as to the how of this tech, no intention of some jury rig, just would like to know.
Timers? Quadracs? Magic? all acceptable answers ;- )

Dick Hime
2 years ago

Awesome detail, Mike. I love the analysis. It explains why the Micro-Air 364 I just installed does the trick. I love it. 

Mike Sokol
2 years ago
Reply to  Dick Hime

This is exactly how their engineers explained its operation to me, but now I can look at the actual current plot on a granular level.

Captn John
2 years ago

I guess I’ll buy one soon. Not a fan of hauling my 2000 watt Champion to the storage lot but happy I’ll not need both. My 5er is connected now to the grid but only at 20 so no one can use the AC.

Bob p
2 years ago

Great work Mike, developing and building a tester for $200 worth of parts that does the job of a $100K tester. Be careful the manufacturer of the $100K tester may put a contract on your head. Lol

Mike Sokol
2 years ago
Reply to  Bob p

Well, that’s a lab grade unit, while HRDL uses more modest components. Plus I don’t think there’s going to be a run on high speed data logging. It’s hard enough to convince most RV owners to but a $30 meter…😁

Karin S.
2 years ago

Once again Mike….THANKS!! This info is so great. To be able to see via HRDL what is actually happening is awesome. I did have my local RV shop install mine a few months ago, as I was already a believer, but now I have your actual testing to back me up when I tell friends about this. 52 amps start up vs 24 amps is pretty dang impressive.

ps. I value your opinion and knowledge so much, I have created a bookmark titled “Mike Sokol” and save any article or write up you do. I then go back and review them often to keep me up to date. 🙂

RV Staff
2 years ago
Reply to  Karin S.

Good idea, Karin — keep Mike’s info handy. Yep, he’s not only extremely knowledgeable, but he’s pretty darn cool, as well! 😀 —Diane at

2 years ago

Yes. They made a believer out of me. Retired HVAC&R mechanic so I was used to working with hard start kits. My 2k Honda in Eco mode would just barely start my 13.5 Coleman and my Progressive EMS would chatter the contactor badly. I picked up two EasyStarts and installed the first one on my boat. It will now start on my 1800 watt inverter which it wouldn’t do before. Installed the other on my trailer and the a/c starts smoothly now on the Honda in Eco mode with no EMS chattering. They were only $249 each after discount code. I had originally questioned them until I learned how they work. Now I highly recommend them for anyone running a/c off of a generator. Can keep it in Eco mode. Fuel savings and quieter! Nice graphing!!!

Mike Sokol
2 years ago
Reply to  Glenn

Thanks… I always make friends with design engineers so I can figure out how their designs work. And then I integrate that information into my own knowledge base which I can use to explain other phenomena. Lots of fun. 👍

Tom Smithbrother
2 years ago

So, by using an inexpensive hard start kit to A/C will run on a small portable generator or not ? Yes, it not as good but is it workable as I DO NOT wish to spend almost the the cost of a whole A/C system for that elaborate starting system. .

Mike Sokol
2 years ago

No, a hard start capacitor had an even higher peak starting current than a factory capacitor, which I can now demonstrate in a few weeks using HRDL. So it will trip the generator even more quickly. I know nobody wants to spend money they don’t have to, but in this case there’s no cheap solutions. An advanced soft start controller is the only way to do this.

2 years ago
Reply to  Mike Sokol

Awe, Mike, you tease! 🙂 I really wanted to see OEM start cap vs hardstart cap vs softstart uber gizmo. Awesome seeing real data though!

I have a strong suspicion this “new tech” isn’t as new as you think but only the RV marketing of it – industrial equipment often had issues with startup surge. If I get a few minutes to breathe and experiment this summer I will build a HRDL of my own and experiment a bit with my rig and mad scientist ideas… I *think* this may be solvable at 1/5 the cost, but I’ll have to tune based on recursive data…lol.

Bryan Douglas
2 years ago

Thanks for the article Mike. I have a 2006 Itasca Ellipse with the basement air, will this work on it?

Mike Sokol
2 years ago
Reply to  Bryan Douglas

Not sure. I’ll ask their engineering department.

2 years ago
Reply to  Bryan Douglas

Should work on any compressor driven a/c. Even works on home central systems.

Robb Niebeling
2 years ago

WOW! This is amazing info! We, in the RVing community are really fortunate to have your years of expertise and knowledge available to us. My question is- do some brands of air conditioners have this kind of technology built in, or are they all the same? We have a 2019 Grand Design 337RLS.
Thanks for the great info.

Mike Sokol
2 years ago
Reply to  Robb Niebeling

I don’t know of any factory air conditioner that uses this soft start technology, but if I find one I’ll let you all know.

Last edited 2 years ago by Mike Sokol
2 years ago
Reply to  Robb Niebeling

That’s a very good question. Call me Mr. Skeptical, but if it works that well wouldn’t all AC’s, or other appliances needing a starting capacitor use something like that? Or is simply new technology that isn’t widely used yet? My next question will involve replacing big green, belching, shaking, boat anchor Onan with a lovely red Honda inverter generator.

Mike Sokol
2 years ago
Reply to  Dan

The standard starting capacitor costs $10 and works just fine with an air conditioner connected to the power grid that’s not overloaded. But standard or hard start capacitors don’t play well with inverter generators or campground pedestals already loaded to the max. Since SoftStartRV costs $300 there’s no RV or Air Conditioner builder who will add it for free. And yes, this is a fairly new technology that’s now miniaturized enough to fit in a rooftop air conditioner. Capacitors have been around since the time of Ben Franklin’s kite experiment in a lightning storm.

2 years ago
Reply to  Dan

Mike is right on. No mfg is going to add this technology into an rv until the public demands it. There goal is to build the cheapest unit possible & sell it for the highest price possible. I bought my soft start type product two years ago from MicroAir Easy Start, which, I believe might be the original inventor of this technology. It has worked phenomenally well for the last 2 years & it’s easy to install (less than a half hour). Prior to installing my Easy Start, I had constant trouble starting my Dometic 13.5KBTU AC unit with two Honda eu2000’s hooked up in parallel, producing 4000 watts/33 amps. As Mike’s chart shows, the original hit is 40-60 amps, depending on the size of the AC unit. The draw on my Hondas would overpower them & regularly kick out my Dish receiver, causing a 10 minute reboot. Now my AC starts quietly & runs smoothly.

Al C
2 years ago
Reply to  Robb Niebeling

I remember reading that Micro Air’s units are factory installed on some AC units, but not units intended for RV use. Folks have theorized that use on home AC’s would improve the life of the compressor due to eliminating the hammer start, only time will tell.

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