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Open Roads Forum  >  Tech Issues

 > Is an RV generator worth it?

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4x4van

California

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Posted: 02/11/19 02:46pm Link  |  Quote  |  Print  |  Notify Moderator

CoeyCoey wrote:

HadEnough wrote:

CoeyCoey wrote:

2oldman wrote:

HadEnough wrote:

Yikes. 00 is where I'd be. At least.
Yeah. His post seems to indicate he's running 4 separate #10 to the inverter. Length of wire, connections and TIME are what make #10 for 30 amps risky. Running high-amp draws requires extra due diligence. Charts are one thing, operation is another. I speak from experience.


I'll go by what engineers have discovered rather than the anecdotal experiences of someone online, thanks. Also, been an aircraft mechanic for over 25 years, and never have I seen an issue from using the wire sizes stated in the charts.


Well, you didn't name the distance yet, now did you?

If we're having a pee niss contest here, things I've designed and built are still in space and make the news on occasion, as they send data back to Earth regarding plasma levels in the heliosphere.

But I do stand corrected in the sense this is an inverter connection you're talking about. I had thought this was your run from the monster alternator you'll need to install to the battery bank.

In any case, get the generator fixed. As an engineer you should already see that you absolutely cannot run your air conditioner off the setup you propose.

Your LRA is around 3500 watts. At 12v that's 291 amps between the inverter a d batteries not counting losses from the inversion process. So round to 300 amps on those wires.

You're at 1500 watts all day long running that air conditioning. That's 125 amps per hour battery draw all day long. Or... If running that engine you need to increase the idle and have about a 200amp rated alternator to keep up. With no other load. Except at idle, even high idle, a 200amp alternator puts out less than half its rated current. Or put another way, you can't do this. You can't get an alternator that will keep up with an RV air conditioner. You'd have to use a belt driven compressor.

By the time you Rube Goldberg all that together, you would have made a far better choice just fixing the Onan.



Listen genius. It doesn't matter the length, because even at 24 feet, the gauge for 30 amps is still 10 gauge. And if you had any reading comprehension skills, you would have realized I am not the one with the broken Onan, and that I mentioned the alternator would be 120vac for my setup, and that my batteries would be 24vdc. I will have 20kWh of battery power and run the AC for over 10 hours, and use the 120vac alternator to produce 3,000W at 1,200 rpm if I need it. Also, the intermittent LRA would only require a 12 gauge wire from the batteries to the inverter. If you are such a great engineer, how come you don't know that continuous current requires larger wires than intermittent current?

So, go take your know-it-all self and join the club of the other know-it-alls with poor reading comprehension skills I have already admonished for spewing ignorant **** on this forum in the week that I have been here.

OK then.[emoticon]

Coeycoey, it might interest you to reread Hadenough's post and realize that everything after "In any case" was referring to the OP, not you. Sit down, relax, and have a beer.


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camperdave

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Posted: 02/11/19 03:41pm Link  |  Quote  |  Print  |  Notify Moderator

FWIW, at least on my generator, disconnect the fuel line and some wiring, then pull 4 bolts and drop it with a floor jack. Not real tough to pull it out.

I'd for sure fix it, I love having the built in genny. AC as needed, and high powered battery charging.

Long term idling of the truck engine is not good for a number of reasons, I would not do that on any frequent basis.


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jharrell

Safety Harbor, FL

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Posted: 02/12/19 07:22am Link  |  Quote  |  Print  |  Notify Moderator

CoeyCoey wrote:

Listen genius. It doesn't matter the length, because even at 24 feet, the gauge for 30 amps is still 10 gauge. And if you had any reading comprehension skills, you would have realized I am not the one with the broken Onan, and that I mentioned the alternator would be 120vac for my setup, and that my batteries would be 24vdc. I will have 20kWh of battery power and run the AC for over 10 hours, and use the 120vac alternator to produce 3,000W at 1,200 rpm if I need it. Also, the intermittent LRA would only require a 12 gauge wire from the batteries to the inverter. If you are such a great engineer, how come you don't know that continuous current requires larger wires than intermittent current?


Interested in an automotive alternator that does single phase 120v steady 60Hz 3000w continuous at 1,200 rpm do you have more details?


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maillemaker

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Posted: 02/12/19 09:04am Link  |  Quote  |  Print  |  Notify Moderator

It's right behind my flux capacitor! [emoticon]

Steve


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pnichols

The Other California

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Posted: 02/12/19 02:18pm Link  |  Quote  |  Print  |  Notify Moderator

jharrell wrote:

CoeyCoey wrote:

Listen genius. It doesn't matter the length, because even at 24 feet, the gauge for 30 amps is still 10 gauge. And if you had any reading comprehension skills, you would have realized I am not the one with the broken Onan, and that I mentioned the alternator would be 120vac for my setup, and that my batteries would be 24vdc. I will have 20kWh of battery power and run the AC for over 10 hours, and use the 120vac alternator to produce 3,000W at 1,200 rpm if I need it. Also, the intermittent LRA would only require a 12 gauge wire from the batteries to the inverter. If you are such a great engineer, how come you don't know that continuous current requires larger wires than intermittent current?


Interested in an automotive alternator that does single phase 120v steady 60Hz 3000w continuous at 1,200 rpm do you have more details?


Here ya go ... 120V AC belt driven "generators" for underhood installation on various vehicles: https://www.fabcopower.com/generat/bgen.htm


Phil, 2005 E450 Itasca Spirit 24V

jharrell

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Posted: 02/12/19 04:12pm Link  |  Quote  |  Print  |  Notify Moderator

pnichols wrote:


Here ya go ... 120V AC belt driven "generators" for underhood installation on various vehicles: https://www.fabcopower.com/generat/bgen.htm


Interesting I could not find any googling but thought someone must make them, although it doesn't do anything to regulate the frequency its a 3600 rpm alternator just like my Onan 4000 has so you have to get the pully right and then make sure to high idle the engine at the correct rpm to get 60hz. Their docs warn not to have anything plugged in when not at specific rpm. Any idea on price?

Think I would prefer high output 24 or 48v alternator with rectification charging batteries then running inverter for 120v so it would charge properly driving down the road too.

pnichols

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Posted: 02/12/19 05:11pm Link  |  Quote  |  Print  |  Notify Moderator

jharrell wrote:

pnichols wrote:


Here ya go ... 120V AC belt driven "generators" for underhood installation on various vehicles: https://www.fabcopower.com/generat/bgen.htm


Interesting I could not find any googling but thought someone must make them, although it doesn't do anything to regulate the frequency its a 3600 rpm alternator just like my Onan 4000 has so you have to get the pully right and then make sure to high idle the engine at the correct rpm to get 60hz. Their docs warn not to have anything plugged in when not at specific rpm. Any idea on price?

Think I would prefer high output 24 or 48v alternator with rectification charging batteries then running inverter for 120v so it would charge properly driving down the road too.


Hmmm ... they do say it's designed to "operate" at 1200-1500 engine RPM ... maybe that's to insure proper control of frequency (i.e. to keep frequency "around" 60 Hz in that RPM band).

But they do say it will not be damaged at up to 10K RPM spin speed. This is a bit misleading in that customers could possibly infer that the frequency of 60 Hz was somehow kept constant regardless of spin speed up to 10K RPM.

Note at the bottom of the page that they sell an optional solid state voltage regulator to insure constant voltage level regardless of spin speed.

All of the above begs a question: What good does it do to have constant voltage level at any spin speed but at the same time having frequency (Hz) not maintained regardless of spin speed?

I guess that's the solid engineering that Honda uses in their inverter generators to insure constant voltage and frequency at all engine speeds - with only the amount of available current being affected by engine RPM?

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Posted: 02/12/19 06:05pm Link  |  Quote  |  Print  |  Notify Moderator

pnichols wrote:


Hmmm ... they do say it's designed to "operate" at 1200-1500 engine RPM ... maybe that's to insure proper control of frequency (i.e. to keep frequency "around" 60 Hz in that RPM band).

But they do say it will not be damaged at up to 10K RPM spin speed. This is a bit misleading in that customers could possibly infer that the frequency of 60 Hz was somehow kept constant regardless of spin speed up to 10K RPM.

Note at the bottom of the page that they sell an optional solid state voltage regulator to insure constant voltage level regardless of spin speed.

All of the above begs a question: What good does it do to have constant voltage level at any spin speed but at the same time having frequency (Hz) not maintained regardless of spin speed?

I guess that's the solid engineering that Honda uses in their inverter generators to insure constant voltage and frequency at all engine speeds - with only the amount of available current being affected by engine RPM?


Their manual can be found here:https://www.fabcopower.com/manuals/Power%20Mite%20Manual.pdf

This is what they say:

Quote:

If you have a specific use for 60 cycle frequency, the shaft of
the AC generator must turn at 3600 RPM, at this speed the
AC generator will produce exactly 60 cycles.
Note: The engine speed would be approximately 1200 to 1600 rpm to
obtain 60 cycles at full load. If the engine is equipped with a tachometer it would not give a true indication of the AC generators output frequency because of different pulley sizes. The shaft speed of the PowerMite™ must be turning at exactly 3600 rpm. The speed can be measured by using a stroboscopic thahometer or by plugging an AC frequency meter into the power outlet.


And

Quote:

If the Power-Mite® is running over l0,000 rpm will it damage
hand tools or lights?
ANS: No, tools and lights are AC/DC and they run more efficient at
higher cycles up to 75 HZ.The Power Mite can withstand
intermittent speeds up to 10,000 RPM with out damage, if
properly installed.


Not sure how 60Hz at 3600 means 75 at 10,000 but still don't want 75 Hz either.

Inverter generators like the Honda are very different, going from 3 phase AC rectified to DC then inverted back to AC at the exact frequency needed so they are RPM independent. My Onan 4000 just has an RPM governor and tries to stay at 3600 rpm but it not perfect goes from 58 to 63Hz depending on load.

pnichols

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Posted: 02/13/19 10:44am Link  |  Quote  |  Print  |  Notify Moderator

I guess I see a potential product brewing here: An box that can be mounted under the hood close to the engine with a pulley sticking out the front/side so as to be conveniently belt driven off the engine. The output of the box would be just like that coming out of inverter portable generators - 120V 60Hz single phase AC - with the amount of current available depending upon how fast you wanted to spin the engine ... with all engine speeds being allowed ... including idle engine speeds.

FWIW, I prefer to idle our RV's V10 gasser for an hour here and there for quiet non-solar 14V DC battery charging. Having to run it at 1200-1500 to do the same - or to supply 120V 60Hz would be a non-starter for me. Given this, the ultimate version of the product I suggest above would be various current/wattage versions of it so one could purchase any capacity they want but still have it powered via pulleys from an idling (500-600 RPM) engine, instead of a rev'd up engine.

However, I guess the market would be so small that the pricing would have to be sky-high.

jharrell

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Posted: 02/13/19 11:12am Link  |  Quote  |  Print  |  Notify Moderator

pnichols wrote:

I guess I see a potential product brewing here: An box that can be mounted under the hood close to the engine with a pulley sticking out the front/side so as to be conveniently belt driven off the engine. The output of the box would be just like that coming out of inverter portable generators - 120V 60Hz single phase AC - with the amount of current available depending upon how fast you wanted to spin the engine ... with all engine speeds being allowed ... including idle engine speeds.


Again if you just get a good high output alternator rated for continuous duty and feed batteries then have a big inverter off the batteries you basically have a inverter generator, but even better unlike the Honda it has a battery based buffer/regulator and even functions with the engine off for a time and can be easily augmented with solar [emoticon]

My stock 175amp 12v alternator->ACR->Battery->Magnum 3000 inverter works pretty well. The alternator seems to be able to do 80-90 amps continuous or about 1000w. I don't like to push it like that if I was serious I would upgrade the alternator or perhaps add a second just for house. A few times I have accidentally run my roof A/C going down the road with my generator off, the Magnum was running it from batteries and the alternators and solar where doing what they could but the batteries where slowing going down.

Winnebago and others are doing a Volta system now on their class B that uses a secondary 48v alternator->Lithium Battery->Inverter setup instead of generator:

https://voltapowersystems.com/energy-storage/

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