A year and a half ago, we had a huge ice storm here and we lost power for six days. We had to stay with friends who had a generator, and all my tropical fish died.
We considered buying a generator as many were doing that the time. Lowe's, Home Depot, Walmart and others were making a killing on generators and chainsaws. But I did some research as I often do and read about the benefits of DC generators. They don't have to run at full throttle all the time like AC generators do and they are compatible with all inverters because there is no concern for clean power. Best of all, with a few parts and some know how, you can build one yourself.
So that's what I decided to do. One of the reasons it took so long was because I wanted to make it as utilitarian as possible, a true emergency generator, constructed in an emergency. I also didn't want to spend a bunch of cash, so I told people and waited for parts to come in. I bought an alternator on Ebay, but it didn't work. I bought another one for 10 bucks or so and it was a lot more powerful and it tested good at Autozone.
The alternator I bought was a CS-144 120 amp unit. Running at proper speed, it should be able to produce over 1500 watts. A few calculations and you find that to produce such that many watts, you need about four horsepower. There's another thing to remember also. Standard small engine horsepower ratings are way off. Briggs and Stratton engines have a standard that allows up to a 15% fudge factor straight off the top. In addition, they are tested at high speeds never seen in actual service. So to achieve four horsepower, you will probably need an engine rated at least six or seven horsepower. So I asked around for an engine.
Mark at church told me he had an old rototiller that I could have. It turned out to be just perfect, a FREE five horsepower engine. A little tinkering and I got it running again.
I needed something to build the whole thing together, I got a piece of 3/16 inch steel plate from a neighbor and welded some legs onto it. Onto that, I bolted the engine, and a plate on which to mount the alternator. I welded some pieces of half inch flat bar onto the second plate which hold the alternator.
Here are some pictures of the project.
And that's the generator. You can see the difference in the system voltage between when the alternator is active and not.
The next plan is to replace the inefficient L head gas engine with an overhead valve diesel engine, an engine that should be two or three times more fuel efficient. There's a bit more work to get that going, so I am happy with at least having something that works for now. Next I need to get a little bigger pulley so the alternator runs at something closer to a proper speed.
If you have any questions, I am always happy to answer them.