??Dumb generator question??

[sjptak]

I am be no means electically smart, only know enough to make myself dangerous. That's why I'm going to ask you eltrical types this stupid question. I've seen all the posts about the 12v generator by Onan that are in some of the older TT's. I guess its all about keeping the 12v batteries charged while boondocking.

Now I got this idea, it'll make a lot of noise, but if you are boondocking away from others, will it really matter? What's to stop a body from hooking up a weed whacker motor to a 12v delco alternator with some sort of isolating switch or regulator so that if at the end of 2 days, the batteries are low, during the daylight hours run the darn thing and get a charge?

Its nothing I would want to run in a campground, but if I were away from the crowd.....I don't know. You guys tell me if it would work or not. John HD, I'm looking to hear from you. You seem to got the electric sense. Not to mention all you other electricians.

Seems to me that this could be a lightweight thing, maybe add a better muffler, regulate it so it wouldn't overcharge.....To a not so smart guy, it almost seems like a good idea. Ley me know. I've got the parts to start building one. My wife'll kill me if I get another project going, so I really hope it won't work.

[74Argosy24MH]

Not enough hp from that small of an engine. But the alternative energy crowd is pretty big on this as backup power for a string of sunless/windless days. The most common ones I have seen are nothing more than an alternator belt driven off a 5 hp B&S horizontal shaft.

John

[mldenis]

I can't recall which issue it was, but the ARRL journal, QST, published a construction article for a 12 V generator using a lawn mower engine, and the mower deck to make a 12 V charging system. Your weed wacker motor isn't powerful enough, but a small Briggs would do the trick nicely.

You might try www.arrl.org and see if you can search their archives or online index. I think you can order back issues for a fair fee and get the details there.

Cheers,

M Denis

[Pick]

Agree with everyone above, you need at least 5 HP to run an alternator. The Amish in our area do this all the time. On one of the other RV sites, Escapees, I think had a thread on this. One gentleman was making the brackets for around $50 to do this.

[Sav'h Steve]

Pick,

I went to the ARRL site a minute ago and found that you had to be a member to access those articles. I might go to the Escapees search just for curiosity.

When the money tree starts growing again (stocks), I might bite for the Honda EU2000i that every one raves about.

My wife likes to stay in the RV parks, so there is less need for one. When power goes off at home, it usually is back in 6 hours.

Take care,
Steve

[PatCrusse]

Sounds like a neat idea, especially if you have the parts laying around. But it may be easier to just hook some jumper cables up to your tow rig, or make an exstended umbelical (sp) cord, and run your toe vehicle for a few hours? If the tow vehicle has a gas engine, it would probalby eaven be quieter.

[mldenis]

I went to the ARRL site and found the article. Published in June 1997 issue, page 45. I have also found websites dealing with alternate energy with like construction articles and bracket designs for lawnmower powered DC generators.

A good source for the alternators are Fleet Farm. I bought a 70 amp unit about 3 years ago for about $40. Be aware that you'll need a ballast resistor and a switch, but there are details on that in the article.

Good luck.

M Denis

[mldenis]

Pick,

Another route to a cheap generator is to haunt your local tool rental center. In 1999 I bought a used 1500 watt generator this way for about $250. The rental center rolled it's tool inventory periodically and had this one and another larger one (which I also bought) for very cheap. This particular unit weighs about 60 pounds and has a 12 VDC plug as well as 110 AC. It is very compact.

I don't own a Honda Euro type, but my snowbird neighbor does and it is sooo quiet. A real nice unit.

Oh, another trick is to put an exhaust pipe extension on the genset and put the whole thing in a box (non-flammable ) to quiet things. Of course, holes for air to get in and the exhaust pipe outside the box, taking care for teh exhaust not to touch anything flammable. I've done this for quieting generators and it is effective to a degree. Of course, it adds more stuff to pack

M Denis

[sjptak]

I think that maybe I'll have to give all the above some thought and come up with something. I can fabricate and probably have the material out in the back yard. I'm sure a trip to the dump(recycle center) will produce a motor. People always throw away perfectly good lawn mowers cause they don't start. If only they knew........ I've got an alternator that I'm not using. I still think I've got an old ballast resistor that I used to carry in my 70's dodge pickup. This may be a real cheap project!

[uwe]

Here is a link to a Briggs and Stratton Small engine:

http://www.harborfreight.com/cpi/cta...emnumber=41103

[Raptorrider2001]

You might consider looking on ebay for one of the small Honda 350 generators. A great size for running a battery charger. Small in size, cheap to run and easy to store.
Just looked on ebay and found this little 650.
http://cgi.ebay.com/ws/eBayISAPI.dll...category=11771

[john hd]

stan,

sounds like a cool project!

a good rule of thumb to follow is 750 watts per horsepower.

so, if you have a 70 amp 12volt alternator you would need about 1.1 horsepower to run it. maybe a little more for losses if you choose a belt drive system.

my generator is home built, 4800 watt pinco 120/240 with a 5 horse briggs on it. put it on a presure washer cart and added a toyota car muffler.

all you can hear is the fan on the generator when it runs.

let us know how the project works out.

solar would be quieter, but not as fun!!

john

[john hd]

if ya really go nuts with this you could make it a really cool little stick welder too.

sparks and arcs!

john

[sjptak]

I do, however, like to make things. build things, modify stuff, you know I'm talking about. Any one can go out and buy a honda 2000 somethin' or another, but I just enjoy tinkering. I agree solar is quiet, and when I get my airstream, solar and an inverter will be a major portion of the expenseive mods, but what happens when you have weather like we've been having here in the northeast? Sun? Its been a long time. My wife and I did a bunch of landscaping, and I'm afraid its all for naught. Everything is rotting. The generator project just may help if I boondock in Oregon or Washington. I've never been there, but I imagine it to be comparable to our current weather.

[74Argosy24MH]

but what happens when you have weather like we've been having here in the northeast?

It it is not only the weather that hurts solar. Boondocking to me usually is back in the woods and all the shade really hurts solar, it is not a really an efficient means of electrical production for an a RV. The panels are fixed and no consideration is given to solar when sites are established.

A generator is necessary for extended stays. I would look for one of the 1800 rpm engines, noise is cut in half by reducing the rpm's and the life is longer. On the downside these are usually Kohler or Onan and they are heavy compared to B&S. The alternator does neeed to turn faster than this but that can be done with pulley ratios.

Supertrapp makes some awesome mufflers. They have a website but it is cars and bikes. They actually make mufflers for everything from small gas engines to large stationary diesels. I can stand next to my 4 kw onan and speak at a normal level.

John

[john hd]

one other thing to consider is a spark arrestor when camping on federal lands or any where else for that matter.

wouldn't want to be responsible for a fire like they have in arizona now

john

[mldenis]

in a previous post:

"a good rule of thumb to follow is 750 watts per horsepower. "

Actually, this is not the case.

Yes, it is true that there are about 745 watts per 1 horse power. However, alternators aren't 100% efficient, so, the generator industry uses a 500 watts per horse power rule of thumb.

So, a 3 h.p. Briggs would be rated as adequate for a 1500 watt generator.

[john hd]

marc

good point on the losses, the rule of thumb i was reffering to was for transformers.

most of them are around 86% efficent anyway. the other 15% is copper/core losses and heat.

your formula would be better because it would take into account reactive losses.

it takes power to push reactive load as well as resistive load.

at the power company we spend millions to eliminate reactive (var) loads with capacitor banks.

the 500 watt rule would give one enough headroom in a genset to prevent wearing/burning it out.

john

[Pick]

Here's a site that may help in the generator project:

Home made generator parts

How to Generator Page

[john hd]

pick

cool links!

john