Older Onan genset question

SunriseMtl · 10-16-2021, 11:27 AM

I would like to know if anyone has modified an older Onan genset to be full sine-wave? I am not retired...yet. For the type of work I do and intend to do on the road, it would be good when not in a full service spot to be able to safely charge my camera batteries, run my laptops and such. I have watched a few videos where people have removed old generators and replaced them with either Champions or Hondas or one from Harbor Freight. But the thought of lifting the rv and removing the Onan and running new fuel and exhaust... a bit much . So I was wondering, why can't I use what is there and improve it.
Thanks!

**creativepart** · 10-16-2021, 11:38 AM

Just how old an Onan are we talking about? What RV are we talking about? More info would be helpful.

I don't think Onan's are "inverter" type generators... are they?

Looking online I see they are only not "pure sine wave" because they vary output with power demand and this can make the frequency a little variable.

Maybe the older ones are something different, but this doesn't register as a problem in Google.

SunriseMtl · 10-16-2021, 11:54 AM

First thanks for moving my question to a thread of its own. My Onan is original to my 1993 Winnebago Sunrise. It is not an inverter generator, so I was told by the previous owner. Sounds like I might just have to haul it out and put in an inverter generator like the Champion 3000 watt.

**creativepart** · 10-16-2021, 12:09 PM

I do not think you're going to have any issues with a 1993 Onan generator in your RV powering anything you want. There are tons of folks on the road with gensets this old and older powering laptops, fridges, TVs, etc without issue.

No need to pull any generator out to replace it with something else unless you plan to power sensitive medical equipment that requires special power requirements -- like MRI or Catscan eqiupment.

In fact, even folks with modified sine wave inverters in their RVs report no problems running the kinds of things you're talking about.

SunriseMtl · 10-16-2021, 12:12 PM

Thanks again, I will take your advice for sure! We are going up to prep the RV for winter storage tomorrow and I will run the Onan and see how one my older laptops reacts when I plug in the power supply. I do work with somewhat "sensitive" gear, my cameras/ lithium ion batteries/chargers and portable edit system.
Definitely will try out the old MacBook Pro first.

DavidM · 10-16-2021, 12:34 PM

OK, some education:

Onan RV generators (except for Onan's new "inverter generators" that I will discuss below) run at a fixed speed usually 3,600 rpm so the rotating generator element can generate steady 60 Hz power. It is pretty close to a pure sine wave and will work fine with any electrical appliance.

A short digression: INVERTERS take 12V DC and "invert" it to AC either MSW or PSW wave forms. Modified sine wave INVERTERS, not generators produce a stepped wave that approximates a sine wave. But some few electrical devices don't work well with this power. Pure sine wave INVERTERS produce close to well a pure sine wave shape and work with all electronic devices.

So again, all rotating generators that have a fixed rpm produce a pure sine wave that works with all electronic devices.

Now back to the digression about inverter/generators. Onan has a new RV inverter generator, now 2,800 watts but higher powered models are promised. It's engine operates at a variable speed and produces power at varying frequencies that directly is not suitable for any AC appliance. It has internal electronics that uses the principles of INVERTERS to convert the variable frequency to a stable pure sine wave 60 Hz, 120V AC. Its advantage like portable inverter/generators like the Honda is that the engine can run slower and quieter when full power isn't requires but the internal electronics speeds it up when necessary.

The bottom line of all this. Your existing Onan RV generator will work fine with all of your electronic devices.

Oh and don't even think about removing your Onan RV generator and putting in a Honda or similar inverter/generator. The cooling air and exhaust flow will be all wrong and the generator will over heat.

David

David

So back to

SunriseMtl · 10-16-2021, 01:00 PM

Wow! Thanks David, that kinda says it all. Can't say how much I appreciate the care and expertise of the members of this group. So very glad I joined!
Now can one of you postpone winter so Heike and I can start using our Winnie now?
Cheers,
Brian

CharlesMoore · 10-21-2021, 05:44 PM

Quote:

Originally Posted by SunriseMtl

I would like to know if anyone has modified an older Onan genset to be full sine-wave? I am not retired...yet. For the type of work I do and intend to do on the road, it would be good when not in a full service spot to be able to safely charge my camera batteries, run my laptops and such. I have watched a few videos where people have removed old generators and replaced them with either Champions or Hondas or one from Harbor Freight. But the thought of lifting the rv and removing the Onan and running new fuel and exhaust... a bit much . So I was wondering, why can't I use what is there and improve it.
Thanks!

I have a Class A 2002 Winnebago Journey with an Onan 7500. I have been charging lead acid batteries, running onboard appliances AND running from the generator my Dell 9020 Desktop computer with SSD, bluetooth and wifi, my Visio Smart TV, D-Link routers, switches and AP plus several hotspots continuously, charging laptops off AC, charging other transient sensitive devices and many other day to day AC powered items with zero failures. ZERO.

If you are really worried then tap into the batteries 12VDC directly.

NeilV · 10-22-2021, 06:06 AM

Quote:

Originally Posted by SunriseMtl

I would like to know if anyone has modified an older Onan genset to be full sine-wave? I am not retired...yet. For the type of work I do and intend to do on the road, it would be good when not in a full service spot to be able to safely charge my camera batteries, run my laptops and such. I have watched a few videos where people have removed old generators and replaced them with either Champions or Hondas or one from Harbor Freight. But the thought of lifting the rv and removing the Onan and running new fuel and exhaust... a bit much . So I was wondering, why can't I use what is there and improve it.
Thanks!

The Fixed Speed generators are pretty close in basic concept to what the power companies have been using to produce AC and generate their 60 cycles based on speed regulation so as long as the speed control in the generator is working your getting an excellent wave form pretty close to what you get at home from the power company.

The real benefit from a pure sign-wave inverter generator will be, simply put, a little bit better fuel economy since they can throttle down when lightly loaded and allow the inverter to maintain the 60 cycles and wave form.

Ray,IN · 10-24-2021, 07:13 PM

Try downloading the manuals for your model Onan genset here: https://www.cummins.com/rv-generator-manuals

I used to have the website for old Cummins/.Onan gensets, but a computer crash lost my old bookmarks.