Onan’s New Inverter Based Generators - Mike Mas

[Idle-Up]

Hey Guys - I thought it would be an interesting topic to discuss Onan’s newer style “Inverter Based Generators” which use a processor controlled variable speed protocol to vary the generators rpm to match immediate load demands. In any case, inverter based Onan generators are quieter, more fuel efficient and will last 2-3 times longer than a standard Onan thanks to the fact they spend most of their time operating 50% slower than past Onan generators.

Fortunately my new Renegade Verona - Was equipped with a 8 kw “Inverter Based” gen-set. As soon as you start the generator, you'll note it's a departure from the older Onan generators which were required to operate at high rpm's even when there was no loads placed on the generator.

Presently all the newer 6 kw & 8 kw Onan diesel generators - Are "Inverter Based Generators". Onan just released their first gas / propane inverter versions called 2500i - 2800i for B & B+ Vans. Last time I checked, the 10 /12 kw Onan’s were still using the older constant speed protocol. The primary difference of the older Onan generators is they were required to run at a set speed around 1800 rpm. This was mandatory for the generator to maintain a true 60 cycle wave form. Any deviation in speed, would cause the sine wave frequency to change.



The term Inverter Based Generator - Can be a bit confusing to some RV owners. While this technology is new to Onan's RV units, inverter generators have been around for decades. In fact, my 15 year old Honda 1000 portable generator has this inverter technology. When you start a inverter generator it will run at a high idle speed for a few minutes to reach operating temperature. Once this is accomplished, the generator then slows back down to idle speed just as your main engine would waiting for a load.

These newer inverter generators - Operate differently as they now dump the alternators output into a built in inverter module which maintains the generators output at a constant 60 Hz, regardless of rpm. As soon as a load is applied, the inverters processor samples the required amperage, then quickly increases engine speed to a level to maintain that load. It’s this process of allowing the engine run slower which conserves up to 40-50% fuel compared to the older generators which were required to run at nearly 50% throttle constantly.



On a few Occasions - When I wanted to top off my Renegade’s lithium batteries set, I'll use the generator to power my Xantrex 3012 inverter to charge the batteries at 150 amps, or at 300 amps using my second onboard Xantrex Pro 3000 inverter charger. The beauty of this new generator is runs just a bit over idle speed to accommodate this charge cycle. In fact, you hardly know the generator is working. This same process with my older Onan generators was awful, since the generator would have to run at high speeds even though it had a very minimum load. This low speed charge cycle only consumes around .10 gal hr. verses half a gallon an hour on the older generator units. You'll also note that when running the roof AC unit, as the compressor cycles off, the generator lowers to idle again conserving fuel and reducing noise.

In my discussions with a number of RV owners - I was surprised to find out that many owners did not realize their RV’s were equipped with this new technology generator. If you’re not sure you have an inverter generator- Just start the generator with no loads applied. If the generator stays at idle with no load, then you have the new inverter set. If it runs at a constant fast speed with no load, you have the older ten-set.

While on the topic of Inverters - Most Renegade’s from 2020 now use an inverted based compressor motor for the refrigerator as well. This system requires half the power of past units. The refrigerator in my Renegade only draws 3 amps, where the same 18 cu ft refrigerator in my Newmar drew 6.5 amps to operate. The inverter controlled compressors have the ability to run at seven different speeds for efficiency drawing as little as only 1 amp to maintain temperature.

Since my coach runs entirely - On it's own 16,080 watt hour Lithium battery which runs the A/C, my generator is seldom used. My coach is a little over a year old now, and I’ve only run the generator 3.1 hours for testing and exercise. Regretfully some type B and B+ & C manufactures are now removing the generator when they install a lithium package, this is not a good practice. I would not own an RV without a generator.

I did want to mention in the article they also offer a a unique advantage for RV lithium battery charging, since you can charge your lithium batteries with the gen at idle, preventing the use the engine with all its DPF extended idling problems.

In conclusion - I could not be more pleased with its quiet running and economical fuel operation. Congrats to the folk's at Onan for this major improvement in RV generators.

Stay Safe Guys - Mike

[pianotuna]

The first generator to be equipped with an inverter circuit was Honda's EX300, released in 1987. In order to stabilize frequency and improve generation efficiency, the EX300 employed a “3-phase multi-pole high-speed generation system,” which spun a rotor at high speeds to generate a 3-phase alternating current.

[Bruce_Brown]

Mike - YOU are the one who was delivering WRONG information.

Time to Man Up and admit YOUR mistake.

[Groover]

My 2013 QD 6000 looks just like the one in the picture. The manual for it covers the series up to the QD 7500. And it does speed up and slow down with load just as the "new one" does.

I wish that my coach had offered the 7500 had as an option, I really could use the extra power at times. The catch on the 7500 is that it has the same motor as the 6000 and being naturally aspirated it may not produce rated load at higher elevations. The saving grace is that you rarely need all of the air conditioners running at those elevations.

Incidentally, the engine came with a Kubota oil filter on it. That is fine with me, Kubota makes some great engines.

[wborst]

Mike,
Why don’t you give Onan a call and ask when they came out with there diesel inverter generator. I’m sure you will learn that the diesel QD 7500 is in fact a inverter generator. Since you won’t believe those of us who own this generator, maybe Onan would be willing to enlighten you.

[Reisender]

Idle-Up wrote:

Reisender wrote:

Idle-Up wrote:
Thanks for all the replies Regretfully, Bruce it looks like it's impossible to get a few members to believe they don't own an inverter generator. All they need to do is start their generator up and listen to it race without a load, nothing like the new 6-8 kw diesel Kubota engines at idle most all the time.

Stay Safe - Mike

Mike. Our 2003 7.5 Onan quiet diesel was an inverter generator. Starts quiet. If you turn on a load it speeds up. Turn on another load it speeds up more etc. I think you may be confusing older Onan gas generators with diesel generators.

Cheers.

Thanks for the reply - Your 2003 is not an inverter diesel generator.

The changes your hearing is not that of an inverter generator, what you’re hearing and mistaking for a faster speeds is actually the engine speeding up momentary from a drop in rpm from as load was applied. In addition, it only sounds like it’s running faster but it's just additional “mechanical” noise from the Kubota diesel engine working harder with the load. Once the load is gone, the engine gets quieter (appears to be turning slower) but only because it’s no longer working and relaxed with less diesel mechanical noise.

The newer inverter diesel generators idle down so low you can barely hear them running. There is a no comparison to the older generators. believe me I've been doing this since 1978 and owned over 20 diesel Onan's since then. The first Inverter generator I owned was in my 2020 Renegade. As soon as I heard this difference in operation, I called Cummins / Onan and they confirmed it was a Inverter generator.

I also mentioned this same Inverter generator in more detail in my In Depth article which I authored you can find it at:

Renegade In-Depth Review



Regards - Mike

Sorry Mike. You are wrong on this one buddy. Walk on to any lot with a diesel pusher 2001 and newer and check out the genny. If it’s a 7500 QD it’s an inverter generator.

Cheers and safe travels.

[Shot-N-Az]

So Mike…the fact that my QD7500 had an inverter doesn’t mean it was an inverter generator?????

[Idle-Up]

Reisender wrote:

Idle-Up wrote:
Thanks for all the replies Regretfully, Bruce it looks like it's impossible to get a few members to believe they don't own an inverter generator. All they need to do is start their generator up and listen to it race without a load, nothing like the new 6-8 kw diesel Kubota engines at idle most all the time.

Stay Safe - Mike

Mike. Our 2003 7.5 Onan quiet diesel was an inverter generator. Starts quiet. If you turn on a load it speeds up. Turn on another load it speeds up more etc. I think you may be confusing older Onan gas generators with diesel generators.

Cheers.

Thanks for the reply - Your 2003 is not an inverter diesel generator.

The changes your hearing is not that of an inverter generator, what you’re hearing and mistaking for a faster speeds is actually the engine speeding up momentary from a drop in rpm from as load was applied. In addition, it only sounds like it’s running faster but it's just additional “mechanical” noise from the Kubota diesel engine working harder with the load. Once the load is gone, the engine gets quieter (appears to be turning slower) but only because it’s no longer working and relaxed with less diesel mechanical noise.

The newer inverter diesel generators idle down so low you can barely hear them running. There is a no comparison to the older generators. believe me I've been doing this since 1978 and owned over 20 diesel Onan's since then. The first Inverter generator I owned was in my 2020 Renegade. As soon as I heard this difference in operation, I called Cummins / Onan and they confirmed it was a Inverter generator.

I also mentioned this same Inverter generator in more detail in my In Depth article which I authored you can find it at:

Renegade In-Depth Review


Regards - Mike

[Reisender]

Idle-Up wrote:
Thanks for all the replies Regretfully, Bruce it looks like it's impossible to get a few members to believe they don't own an inverter generator. All they need to do is start their generator up and listen to it race without a load, nothing like the new 6-8 kw diesel Kubota engines at idle most all the time.

Stay Safe - Mike

Mike. Our 2003 7.5 Onan quiet diesel was an inverter generator. Starts quiet. If you turn on a load it speeds up. Turn on another load it speeds up more etc. I think you may be confusing older Onan gas generators with diesel generators.

Cheers.

[Reisender]

Our 2003 Revolution had an inverter based variable speed generator. The OP is confusing older gas generators with older diesel generators. The quiet diesel have been inverter based for at least twenty years. The gassers just started this year.

[Shot-N-Az]

Either everyone is talking past each other, or something else is going on here. I’ve read numerous posts from Mike and they are nearly always spot on.

However, my old QD7500 in my previous 2005 Newmar had an inverter. I had to replace it along with the rotor and stator. That was not a cheap repair. The engine speed was dictated by the load being called for. Upon startup, the engine would run about 1/2 speed before falling off to idle after a couple of minutes unless there was something calling for amps.

[willald]

Hmmm, interesting discussion.

Not going to get into the debate of just how long Onan has had inverter style diesel generators. I'll just say this:

When Onan comes out with a fuel injected, inverter version of their 5500 watt gas generator used in many gas class A motorhomes.....THAT, would be a huge, very welcome improvement. I could be tempted to do a genny upgrade for something like that, one day.

[DrewE]

Idle-Up wrote:
Thanks for all the replies Regretfully, Bruce it looks like it's impossible to get a few members to believe they don't own an inverter generator. All they need to do is start their generator up and listen to it race without a load, nothing like the new 6-8 kw diesel Kubota engines at idle most all the time.

I don't think anybody is disagreeing that the previous generation of GAS generators were not inverter generators.

However, some of the models of DIESEL generators have been inverter models--with variable engine speed, depending on load (and not constant engine speed operation)--for decades. It's really, really hard to convince owners of these inverter generators that they really do not have inverter generators, when their ears and owner's manuals tell them otherwise, and when perhaps a few of them may have had to replace the inverter module when it failed at some point.

(It is also worth noting that the new 2.8 kW gas generators have electronic fuel injection rather than a carburetor, itself a worthwhile upgrade and one I would be very happy to see on the 4.0 kW models used in most 30A gas motorhomes.)

[Idle-Up]

Thanks for all the replies Regretfully, Bruce it looks like it's impossible to get a few members to believe they don't own an inverter generator. All they need to do is start their generator up and listen to it race without a load, nothing like the new 6-8 kw diesel Kubota engines at idle most all the time.

Stay Safe - Mike

[Bruce_Brown]

Correct - the previous gas generators were continuous speed screamers. While quieter than many other gas generators they still weren't invertor style quiet.

[Rick_Jay]

So, based upon the link Bruce Brown posted, it looks like this is a new line of small capacity inverter generators. I'm guessing they didn't have the inverter technology in generators of this capacity before this, or maybe these are just newer inverter technology. I'm not really an expert on the Onan line.

But nothing in the Cummins release says this is their FIRST series of inverter generators, and the link posted by ScottG clearly states that the QD7500's use inverter technology, and I believe that line has been out for a long time for diesel rigs.

Mike, with all due respect, I believe you're misinterpreting the information published by Cummins.

~Rick