One more plug for George at : He's written a wonderful artical (About 80 pages long) called Lister Longevity. He suggests that folks buy it before they get into one of these engines, and I'd have to agree. Some manufactures do a better job than others, I think mine falls somewhere inbetween. (George knows which ones are good, which are bad.. and which are a good gamble!) "Lister Longevity" goes into a lot more depth than his pages at , and it not only tells the reader what they may be getting into, but it also details lots of assembly/disassembly proceedures - lots of tips on improving them.... the document in my opinion makes the engine a much more valuable thing.
Something as simple as a small lawnmower engine belted to a car alternator can do a wonderful job of charging batteries very efficiently. Most lawnmower engines have crummy mufflers...this is real important, noise pollution is intolerable. It is best to use an oversized engine...run it slow and gear up the alternator. It will run quieter, and last longer. 5-10 horsepower is a good match for a 30-50 amp alternator. Home Power Magazine has had some excellent articles about building one of these. There's another excellent article on how to build one at .