Instead of a bigger Battery

[mike837go]

Originally Posted by RoyBraddy

We camp alot off the power grid with our OFF-ROAD POPUP trailer.
...snip...

Roy Ken

That's the route I did follow at first: A 120VAC genset to supply all of our AC needs and charge the battery.

Unfortunately, for SWMBO and myself, our 120VAC needs are VERY LIMITED when we camp: Coffee Grinder and occasionally warm something up in the microwave.

So, I wound up running the 2KW genset for a several of hours a day just to make sure the battery was fully charged.

We are on 6.5acres of private land surrounded by many other private lots. Bothering the neighbors is not an issue, but listening to a small engine drone on for several hours instead of the waterfall in the northeast corner of the property... THAT is an issue.

So, I built a setup that'll charge the battery in a few minutes per day. And allow us to run the occasional 120VAC appliance for short bursts.

It fits our needs. Now to get the whole kit working properly.

[mike837go]

Ok, so the pieces fell into place this weekend...


I'm "throwing in the towel" on the 12VDC genset idea.


The belt-driven car alternator makes staring the small engine harder than expected. Bringing the battery load onto the alternator usually causes then engine to stall.


Then there is the matter of insuring the battery is fully charged before shutting the engine off. I failed miserably on THAT one.


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Last weekend, a neighbor gave me a 1,000W genset they haven't used in years and had a stuck piston.


A few hours work (the piston was hydro-locked, not seized), the carburetor and spark plug needed cleaning... Did I mention it is a 2-stroke engine?


So, now I have a 1KW power plant (much closer to our needs than the 2.8kw) that stows in the trailer during transport.


It starts much easier and connects up using standard concepts. Uses the trailer's own converter & battery charger.


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Only 'issue' now is the noise. Some experiments with thin-wall pipe and additional mufflers is planned...

[djtho1]

I have been where you are, and good luck. We did all you are talking about and more to try and quiet a generator, but in the end it doesn't really work because the exhaust is only part of the equation. The engine itself has quite a bit of noise associated with it and must be quieted as well. When we did that, it got hot enough to boil the gasoline in the tank and vapor-locked the motor. Damn near blew ourselves up that day. I don't say this to discourage, only to tell of some of the dangers and what we ran into. We finally ended up buying a Honda EU 3000 in 2001 after a dealer let us take one to try out, and have not looked back. That was after we took our "modified" unit to a camping area at a NASCAR race and ran it. 400 plus people cheered when we shut it down at night.

That being said, when you start modifying the exhaust, make sure you use flexpipe between your unit and whatever you come up with. Things won't break as much that way. I would also run the exhaust up above your camper. That will put any exhaust noise up aways. For insulation, we used 2 inch foam insulation, and it worked, just a little too well because it kept the heat in also (and yes, we did have it vented). For your alternator setup, could you maybe use a clutch or a belt system like the old roto-tillers used so that the alternator does not engage until the engine is running well? Just a thought.

[mike837go]

Hi djtho1,


The belt and pulley arrangement has been abandoned. A clutch-like system was considered along with a variable resistor to limit field current in the alternator...


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The 'new' genset is what is going to experimented on to quiet it a bit. Where we boondock, it is 600'+ to the next dwelling. So 'not bothering the neighbors' is not part of the problem.


You are quite correct that tailpipe noise is just 1 of several issues:
- Intake pulses
- Exploding fuel inside the cylinder
- Clank and smack as the piston reverses direction
- Vibration of loose sheet metal and governor/throttle parts
- Vibration against the motor mounts
- Resonance of the cage around the unit
- The parts inside the gas cap that allow limited venting


If I can get rid of the harsh, shrill tailpipe scream of a 2-stroke running at 3,600 rpm, it'll be worth it. And yes, flex has to be included. I like welding things. Not re- re- re-welding things.

[mike837go]

Back from a trip to the workbench....


Rebuilt the mounting system for the alternator and belt tensioning. Engine starts easily when not electrically loaded.


Need to mount the voltmeter closer to the battery. Still have to work out a way of bringing up field current gradually.

[eldermike]

You might need up to 5hp for that alternator and enough head room to keep the engine spinning. It's just a guess based on some dynamometer experiments I did many years ago.

[mike837go]

Originally Posted by eldermike

You might need up to 5hp for that alternator and enough head room to keep the engine spinning. It's just a guess based on some dynamometer experiments I did many years ago.

I thought 3hp would be enough...

12V @ 60A = 720Watts = just under 1 hp.

Usually plan on 3x inefficiency conversion between electricity and internal combustion.

The engine does carry the alternator once it spins up under load. Just can't read the voltmeter I bolted to the alternator.

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What do you mean by "head room" in this application?