speaking of Generators ...

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Has anyone else wondered if one brand is more efficient than another? Suppose you're facing a three day blackout, and want to power a 1000W average load. How many gallons of gas will you need? Materials: 1 generator (keep outdoors when operating) 1 kw-hr meter 1 space heater (on extension cord if you want heat somewhere) This will only test up to 1.5 kw loads since those cheap kw-hr meters are limited in the power they can handle. Warm up the generator and let it run out of gas. Add exactly one quart of gasoline. Plug in the meter, and plug the space heater into the meter. Start the generator, and wait. I tested one Made in China 1000W unit, and was disappointed that it only made about 1 kw-hr out of a quart of gasoline. That's barely 10% efficiency. A small engine should make at least 20% mechanical energy. Is the alternator really losing 50% to heat?
 
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Try a good honda or yamaha inverter model, I'm sure they will do better. I guess I could test my yamaha EF2800i for you, going by the specs it might do 2kwh per liter.
 

JTK

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 Originally Posted By: oilyriser
I tested one Made in China 1000W unit, and was disappointed that it only made about 1 kw-hr out of a quart of gasoline.
It ran for an hour on a quart of gasoline? That's pretty darn good. Your average 3500watt will burn 1gal/hour at near full load. Fuel efficiency about doubles at half load. A high dollar digital inverter style generator that can vary engine RPM will be the most efficient. A gasoline powered generator is one thing I would not recommend going over sized on. How are you going to feed it when times get tough? Joel
 

oilyriser

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I tried half load, and fuel efficiency was about 25% worse. Home Depot had a bunch of generators, with run times listed at half load. I did some calculations, and most of them also came out to 1 kw-hr per L, which is pathetic, though better than the Chinese brand. One of them, with a Yamaha motor, worked out to 1.4. It should be possible to build one that does 2.0. Storing gas at home is dangerous, and making generators more efficient reduces the amount you need to store. If you're a contractor who uses generators enough to wear them out, a more efficient one costing maybe $100 more will give a lower total ownership cost. I'm wondering where the waste is. I've looked up small engine data on the B&S website, and those things calculate out at well above 20% efficiency. Are they just cheaping out on copper windings?
 
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Yamaha EF3000 specs Produces 1.72 kwh/L at full load, and at 1/4 load this drops to 1.1 kwh/L but you get 20.5 hours of run time on a tank. A general rule is that motors are more efficient at full throttle at their peak torque rpm so it makes sense that only running a 1/4 load consumes more gas per kwh. If you have a fixed rpm generator(most if not all cheap ones) their efficiency isn't that far off the inverter models at full load but at quarter load they still have to spin 3600rpm and so they don't get much more run time. The reality is that most generators spend alot of time at partial loads so an inverter model makes sense to save gas, plus they are better made and quieter. I had mine running on my porch for a power outage and some bible pushers came to convert me and the first thing they asked was what is that blue thing humming away? They were shocked that it was a generator and we could talk normaly 10 feet away from it.
 

oilyriser

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That's not bad. Another thing generators often have to do is run a fridge. This appliance only takes about 150 watts when running, but needs about 1000 for the first second, to start the compressor. A generator has to have either a very quick throttle response, or a heavy rotating mass, so as not to goof up a load like this. If you could rig up a dummy load that switches in for a few seconds before the fridge tries to start, so as to get the throttle opened up wide, you could start a fridge even with a small genset. I wonder if the small efficient inverter types are up to this.
 

JTK

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My cheap Coleman Powermate 1500/1850max watt suitcase generator powered by a 3.5hp briggs will light off a big fridge without issue. Start-up loads do cause the RPM and frequency to bounce a bit, but it does stabilize. Joel
 
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I don't think a 1000W honda or yamaha inverter would have much trouble starting a fridge, unless you've got a 1960's one... I use my generator in load sensing mode and it starts a tablesaw or mitresaw with no trouble. It opens the throttle and the rpms rise abit while the saw is on then they drop again. Probably its not the best thing for your fridge but for a few dozen start cycles every couple years I don't think you'll have a problem.
 

oilyriser

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120V x 7.9A = 1000W? Half load would be 474 watts, assuming you actually get 120V rms. A 0.6 gal tank lasts four hours. That's 3.16 kw-hr per gallon, or 0.83 kw-hr per litre. The other thing cheap generators do is put out only about 107 volts at full load.
 
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That Listeroid looks great Cujet. Did you buy it like that or did you rig it yourself? Tell us more about it!!
 
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 Originally Posted By: bigdreama
That Listeroid looks great Cujet. Did you buy it like that or did you rig it yourself? Tell us more about it!!
I built the entire thing. I like to tinker. Below is a link to Bob's website. My lister is on this page. I am the one kneeling by the engine. Also, the engines are in my hanger, next to my boss' aircraft. http://www.f1-rocketboy.com/lister%20series%202%20page%201.html There is not much to tell. It's a real SHTF generator set. It will run on waste motor oil without even a hint of trouble. It powers my house with ease and is very quiet. I plan on installing it into a concrete generator shed someday. Chris
 
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I wonder why you felt you had to order a new engine from India to build a genset? That is only a 4K to 5KW genset - or that was one I saw at the end in a video. You can buy those here in the states for a LOT less than I'll bet you put in the engine along by the time it was shipped to USA, not counting the labor and parts... Still interesting.
 
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 Originally Posted By: benjamming
I wonder why you felt you had to order a new engine from India to build a genset? That is only a 4K to 5KW genset - or that was one I saw at the end in a video. You can buy those here in the states for a LOT less than I'll bet you put in the engine along by the time it was shipped to USA, not counting the labor and parts... Still interesting.
Nothing that you can buy here can match the longevity and the operating economy of a Lister. There are stories of some of the original Listers powering third world villages and running continuously for DECADES! Great job Cujet, thanks for sharing. \:\!
 
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