Picture of Lawnmower Power Generator With A Twist

This is a 500 watt power generator big enough to power tools, and home electronics.  If you try plugging in kitchen appliances, heaters, window AC units will shut down, you need a 2k-3k watt power converter for large power comsumption appliances..

 It's not difficult to build this project, if you know how to wrench things apart and have a basic understanding of how things work with engines and electrical components then you'll do just fine.  If you want to save money on the build, go to junkyards, recycling centers, and landfills which is where I got most of the parts.   You'll be surprised the stuff you can find for pennies or better yet FREE.   I spent $40 for all the parts needed for this project.  

There are a few optional parts not needed to run this little power jewel.   The lawnmower tires, enclosure, vehicle battery, handle, voltage meter, 120VAC outlet, light, and on/off switch for light.   I decided to go all out with this one by adding all those extra features, just took me longer to make, 3 months exactly.  A schematic diagram will show how to wire everything up.    The AC outlet you see on the panel is tapping from the power converter which already has AC outlets.  I just wanted to make an extension of it so I wouldn't reach around the back to plug in things....

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kill-a-watt4 years ago
Nice, I'm looking at building one of these. I want to add a circut to recharge or jump car batteries and maybe add field control to convert mine to a light-duty welder.

The 3.5 HP engine is limited to maybe 2500 watts total.

You are using a GM Delco 10si alternator, which can only put out about 900 watts at 14volts times 63 amps. I assume the unit is self-excited, so if you pulled one out of a junked car, you would probably have to install a "one wire" kit. Although the 10si is  ubiquitous, with that engine I guess you have headroom to use a larger alternator.

Technically, that cooling fan on the alternator is running the wrong way, but I'll bet it works fine because it's not located in a hot under hood area of a car. The alternator itself doesn't care which way it spins.

"Battery" is not in your parts list. I'd recommend a deep cycle type. If you use the less expensive wet-cell type, get a battery box for the battery and bolt it down. Acid burns.

Good job with the safety-nazi stickers. No one could fault you there!
cid2323 (author)  kill-a-watt4 years ago
I bought the alternator at a parts store with a 2 wire harness connector. I didn't mention the battery because it is not required to start the generator, it's just an optional feature.
confirmed with a search: 7127 is "self-exciting" or "one-wire". The "-12" means that alternator is "clocked" at the "12 o'clock" position.

Looking at the back of the alternator, think of the field winding contacts as the hour hand and the pivot bolt hole (the unthreaded mounting bolt hole) as "12" on a clock. By assembly, the alternator can be in four positions. 3, 6, 9, and 12 o'clock. If you know how to restrain the brushes, you can take apart the alternator and "re-clock" it for different applications in different cars.
MarcF25 months ago

Maybe I missed something, but I dont understand the reason for the variable resistor. Is it solely to keep the engine from stalling? Would a larger hp motor eliminate the need for the pot?

xained6 months ago

Hi, I tried your setup, but my engine shaft is turning to the left, and the alternator turns right (otherwise no power), had to turn it upsidedown. Nice project !

sidecar123 xained6 months ago

just ran across your post. you can turn the alternator in either direction, it will work

fine either way. hope u haven't given up on this project. good luck

xained sidecar1235 months ago
Damn, an old mechanic told me there was a 'direction' in which it has to turn ... so I had to make A LOT of adaptations .. Anyways, here's a pic of the ongoing project. (finished now, but no pic)
Not at all as perfect as yours, but got everything for free, so no complain about the 'look' from my part. ;-)
Thanks for the idea and the share of your project !
More of a question... I want to do the same thing... but, I have a bunch of alternators (4 or 5). Would this be overkill or make more power? good? bad?

running more than one alternator is the same concept of using multiple batteries. you can either up the voltage which is pointless as most inverters will only take up to 15 volts maybe a little more or you can up the amperage but again pointless because you are limiting the amps purposefully for the inverters use. I would imagine if you had an inverter that is rated for a much higher input, then try it out. I'm not an expert by any means so I would also be happy with more input on the subject.
cid2323 (author)  bigtreehouse2 years ago
You just need one, alternators vary in amps and voltage, 65 amps to 100+, and voltage 14.3 to 26.5 depending what you want to hook up on it. If you need more power related to voltage don't forget to match the converter if you need A/C voltage. Some alternators can get pretty expensive if you buy them from store, if you get one from junkyard look for a military vehicle, they all have alternators that run on 24vdc or other military equipment such as generators etc.
Catfish558 months ago

Might be a dumb question as im not very knowledgeable about electricals, but would you be able to build it with dual or even triple alternators to increase the power output? I cant think of any reason why the motor itself couldn't turn more, but I understand you would potentially have to get an converter capable of higher output as well.

Kinda yes and Mostly No (most likely) on this one. an alternator turns mechanical work into electrical energy.So an extra alternator is more load for the lawnmower engine

But think of it this way. You can most likely pull one wagon with 100lbs of rocks in it, But if we were to add one more to that wagon to give you double wagons of 100lbs to pull weather you could or could not you would feel the extra 'Load'. And it would be very much the same with the mower engine. It 'might' be able to handle it but at first glance I don't think this could handle more then one underload.

fjr_scoot8 months ago

Very well done; a great project. Thanks!

After reading the posts on here. I see that my air run engine might be perfect for that. No gas fumes or any fuel other than the compressed air stored in the tank. And the engine recycles the air back to the tank for continuous running. Its a 10 hp tecumseh engine.
rairwin3 years ago
This would be a good aplacation for the geet fuel system and run the thing off of 85% water
cid2323 (author)  rairwin3 years ago
How would it run on water?
cid2323 (author)  cid23232 years ago
Did a little research on H2O engines, that's a cool idea. Have heard about it before but never bothered to read more about it until now. Might be a future project.
tedervlad4 years ago
cid2323 (author)  tedervlad2 years ago
karossii4 years ago
I'm curious... have you any idea on the efficiency of this unit? gallons of gas per KWH, for example...?
cid2323 (author)  karossii4 years ago
I don't know the specs for the engine, it's something I picked out from landfill....I do know with a small load and the tiny gas tank it will last up to two hrs none stop, which can be upgraded with a larger fuel tank.....I recommend stopping the engine every hr to check up on oil levels, especially with small engines..
ac-dc cid23233 years ago
It's essentially one of their 300 series, here:{0CBA2950-9AF3-4E9E-880A-68D471813041}#specifications

... but they're not going to provide a load vs RPM vs fuel consumption graph for it, nor is it likely you'd find a load versus output power graph for the alternator, the there's the small efficiency loss of the pulleys 'n belt and the conversion to AC and/or battery charging... you'd have to measure efficiency as a whole *machine* yourself.

While I'm thinking about it, the first thing to go on those engines is usually a carb diaphragm right above the fuel tank, if it starts sputtering out after some use try replacing that first (about $2 and 10 minute job). youtube videos of the repair:
cid2323 (author)  ac-dc2 years ago
You're absolutely right, to keep cost low just kept it simple for builders, some folks won't dare mess with carbs do to cleaning out or fine tuning them.
cid2323 (author)  karossii4 years ago
Almost forgot, with the battery as a backup will last 24hrs with the same load...
Very nice and clean
cid2323 (author)  MACKattacksnipe2 years ago
Thanks. Been away for awhile, working on some new stuff to post.
cid2323 (author)  MACKattacksnipe2 years ago
Thanks. Working on a smaller compact gen. Once I'm done with it will post on here to pass on for future builders.
cid2323 (author)  MACKattacksnipe4 years ago
Thanks. Happy Holidays.....
dsandds20034 years ago
This is a great idea. HOWEVER i did not see anything about NOT using this indoors. If you use it in a garage MAKE SURE you leave the door open. You WILL need lots of ventalation.
I love the portability of this, would be a GREAT item to use with my electric branch trimmer. GREAT job on the pics and diagrams.
cid2323 (author)  dsandds20032 years ago
I'm working on a smaller gen using a weed eater which makes way easier to carry as far as weight issues. I've been out of the loop on instructables for a while.
Aprositus3 years ago
Great project.
I'm not surprised that it stalls out when you try to draw too much power. Most inverters would have a breaker or some kind of overload circuit, but the engine can't provide the peak power needed to overload the inverter. It probably could though, if you put a bigger flywheel on it.

The flywheel helps keep the engine spinning when its working hard, by providing extra momentum to keep the whole thing turning. Today's lawnmowers are built with a minimalist philosophy to make things cheaper, though, so they're using the lawnmower blade to help the flywheel do its job. So, when you take the blade off, the engine can't keep running when it starts working hard.

I'm surprised it actually runs without the blades, actually. A lot of them won't.
paleotool4 years ago
Excellent work! It looks like a well thought out and explained instructable. I have been intending to make one from a junk lawn mower I have and this looks like a nice, neat design.
tedervlad4 years ago
Looked at it.
Translated it.
Whatzit for?
cid2323 (author)  Dr.Bill4 years ago
It's a power generator, DC to AC 120VAC. you can use it for electronics, some power tools, lights, etc. makes perfect for camping or light up a small cabin. Happy Holidays.........................
Dr.Bill4 years ago
This would be good for ham radio field days.
Shore do wish I had more room to work on stuff.
I give you a 5.0
cid2323 (author)  Dr.Bill4 years ago
would make perfect for ham or camping.
Nice build, just a word of caution!!!! DO NOT RUN THIS INSIDE A CLOSED BUILDING!!!! I notice in one pic you show this inside your house running a TV. This is an internal combustion engine and produces carbon dioxide which can kill you.
Carbon Monoxide is killer when running IC engines indoors or using BBQ grills for space heating purposes. DO NOT USE INDOORS, including a garage.
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