Home-Built DC Generator Ideal For Off-Grid Living

2007 - Volume #31, Issue #4, Page #20

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When Rob Davis priced commercial AC generators for his off-grid home, he felt they were too expensive and used too much fuel. Bringing in power lines would have been even more costly, at nearly $80,000.
A DC generator made the most sense to him, but commercial ones were too expensive so he built one, and then another, and another, each time increasing in power. Today he has two generators, a 6 hp direct drive system and a 9 hp with overdrive. All appliances are AC-powered with energy supplied by battery or directly from a generator through an inverter.
"They run the washing machines, central heating, welder, all the heavy loads," says Davis. "When we want to charge the batteries, I just set the generator on idle."
Davis uses Robertson Subaru gas engines, though he would like to switch to affordable diesel engines. As it is, he estimates his average monthly fuel bill for producing electricity at only $40 a month.
"If you have an AC generator charging the system, the most you can get out of it is about 35 amps, and it has to run at 3,600 rpm's all the time," says Davis. "Mine are at full output at 2,800 rpm's, and if I just want to maintain the system and keep it charged, I run it at 1,250 rpm's."
Davis says he can produce 45 amps for 2 hours and only burn a quart of gas with the 9 hp system. The secret, he says, is the overdrive. "It's just like a car you put in overdrive to save fuel," says Davis. "If I want more power, I just increase the throttle."
The difficult thing about building a generator system with overdrive was to find the right combination of pulleys. "I used trial and error and burned up quite a few belts before I got it right," he says.
Since Davis has gotten it right, he has built DC generators for friends and neighbors. Others hear about his generators by word of mouth. He sells the 6 hp system for $2,500; the 9 hp system for $2,850. Without their electric starters, they'd each sell for $150 less.
Contact: FARM SHOW Followup, Rob Davis, P.O. Box 1109, Tehachapi, Calif. 93581 (ph 661 972-5540).

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Home-Built DC Generator Ideal For Off-Grid Living ENERGY Miscellaneous 31-4-20 When Rob Davis priced commercial AC generators for his off-grid home, he felt they were too expensive and used too much fuel. Bringing in power lines would have been even more costly, at nearly $80,000. A DC generator made the most sense to him, but commercial ones were too expensive so he built one, and then another, and another, each time increasing in power. Today he has two generators, a 6 hp direct drive system and a 9 hp with overdrive. All appliances are AC-powered with energy supplied by battery or directly from a generator through an inverter. "They run the washing machines, central heating, welder, all the heavy loads," says Davis. "When we want to charge the batteries, I just set the generator on idle." Davis uses Robertson Subaru gas engines, though he would like to switch to affordable diesel engines. As it is, he estimates his average monthly fuel bill for producing electricity at only $40 a month. "If you have an AC generator charging the system, the most you can get out of it is about 35 amps, and it has to run at 3,600 rpm's all the time," says Davis. "Mine are at full output at 2,800 rpm's, and if I just want to maintain the system and keep it charged, I run it at 1,250 rpm's." Davis says he can produce 45 amps for 2 hours and only burn a quart of gas with the 9 hp system. The secret, he says, is the overdrive. "It's just like a car you put in overdrive to save fuel," says Davis. "If I want more power, I just increase the throttle." The difficult thing about building a generator system with overdrive was to find the right combination of pulleys. "I used trial and error and burned up quite a few belts before I got it right," he says. Since Davis has gotten it right, he has built DC generators for friends and neighbors. Others hear about his generators by word of mouth. He sells the 6 hp system for $2,500; the 9 hp system for $2,850. Without their electric starters, they'd each sell for $150 less. Contact: FARM SHOW Followup, Rob Davis, P.O. Box 1109, Tehachapi, Calif. 93581 (ph 661 972-5540).

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