Introduction: Homebuilt Generator (Riding Lawn Mower) 1Kw

Picture of Homebuilt Generator (Riding Lawn Mower) 1Kw

Well like most of us, I was looking to find a way to minimize expenses in creating an alternate energy power source.

The easiest way to perform this task was to re-use existing equipment installed in my home, & power toys to minimize costs.

My favourite expression to utilize cross functional synergies.

Well, I was able to put together the following items

At Home items

a) 2 Batteries (Used for my Motor Boat) 140AH

b) Lawnboy lawn tractor 10 HP (1980s vintage)

Sale Items

a) Xantrex 1000 power inverter ($89.00) Cdn Tire

Regular Priced Items

a) Fan Belt 4L44 Cdn Tire $ 11.00

b) 12V Car Led Lamp Cdn Tire $ 2.50

c) AC Power Monitor (UPM Em100) Cdn Tire $ 25.95

d) Battery clamps Cdn Tire $ 5.95

e) Booster Cables Cdn Tire $ 20.00

Optional: Siemens Generator Panel Box (and Circuit Breakers) $280.00

Note: Extensions cords will do in a pinch!

Scrap (Yard) Items

a) Cadillac Alternator (120amp) with Built in Regulator $ 35.00

b) 4 Position Switch (Scrap from old Battery Charger)

c) 6 Gauge Wire (Old Battery Booster Cables)

d) Panel Mount (For Switch and light)

e) Tie Wraps (Keep all loose wires tight and away from Belts)

Total Cost *Including Electrical Panel $ 469.40
Without Electrical Panel $ 189.40

Step 1: Alternators

Picture of Alternators

Of special note, when assembling this conglomeration of items special care needs to be taken to research the specific products selected.(I.E.)


The cheapest way to connect an automobile alternator is to select one that has a built in regulator. In many instances they are denoted as a single wire connect. If you have external sense lines coming from the alternator (As Below) , wiring can become a little more difficult as you may need a resistor value of approx 35 ohms leading from the Generator Light wire on the alternator to + DC voltage. You also have to have a Power Switch to disable the charging of the stator at initial power up time. I.E. The resistance of the alternator can generate enough force feedback to make it too difficult to start you engine.

Step 2: Power Inverters

Picture of Power Inverters

Low cost power inverters (Modified Sine Wave) actually have power being generated on both the Live and Neutral lines. Typical home wiring has the Neutral and Ground wires tied together. Hence if you try to connect a (Modified Sine Wave inverter) directly to home wiring it will not work and short out the inverter. The neutral has approximately 60V on it instead of the usual 0V.

Step 3: Generator Panel (Optional)

Ensure that when you plan your implementation to purchase a Generator Power panel that supports a bonded Neutral. (I.E. the neutral line is also switched) and that you do not tie the neutral to ground at the panel

Step 4: Nice to Haves

a) Voltmeter (Monitoring your battery voltage as power is being drawn. If the voltage drops continuously, your alternator is not providing sufficient power to meet demand)

b) DC Shunt (Measure DC current coming from alternator. Note: You may be able to play with the resistors on the stator to increase power). Crompton 100 Amp Dc Shunt

c) UPM EM 100 Energy Monitor or (Kill a Watt). (Measures the AC power voltage current, Peak Current, and Wattage. Constantly monitor inverter output versus maximums)

Note: Can also be used in advance to determine average and maximum loading levels by appliances in your home to enable you to size your generator properly.

Step 5: Formulas

Picture of Formulas

a) Fan belt sizing

Belt length = ((Alternator Pulley Diameter + Motor Pulley Diameter) *1.5708) + (2* Center to Center distance of Alternator and Motor Pulleys)

b) DC Power Shunt. Typically continuous running load on current shunts is in the order of 60-65%.

When purchasing, make sure you have a 50% factor above your expected maximum running load.

i.e. 150% of your maximum load factor.

Note: Some manufacturers build in a safety load factor of 1.2

i.e. Crompton 100 Amp Dc Shunt

c) Pulley Size Calculator. Yup thats right, you notice that when you purchase an alternator these days they may not come with a V Belt pulley, and the size of the existing pulley may not match that required for the Horse power rating / RPM for your engine.


Errol1951 (author)2016-02-03

What was wrong with the built in generator or was the output to low. The problem with most alternators is that when your battery reaches 85% they drop back to a trickle charge

kflack (author)Errol19512016-02-04

Responded earlier to the same Question...Here was the response

The charger for a ride on provides very low charge current for such a small motor/battery starter requirement.(Some as low as .5 amp) The use of a car alternator is to be able to use the entire output power capability of the ride on mower (100 amp or more) under full load conditions.

Keep in mind when under load the battery will supply (in this instance) up to 125 amps @ 12 volts of power to feed a 15 amp 120 volt circuit. The alternator will go into FULL charge mode as soon as the draw is large enough.The battery acts as a dynamic load balancer, as the motor can not respond instantaneously to varying loads.

It is really 2 independent operations taking place. Battery supplying instantaneous response to changing load conditions. Alternator providing a constant charge current source to replace the battery drainage.

anas.muawam (author)2016-01-21

ok thanks

mpandersen (author)2011-02-05

Great article !!! My step-daughter REFUSES to turn off the computer when she is done, SO I want to make a pedal powered generator to get back at her. (If this seems cruel, I REALLY do need to lose my Molson Muscle !!! LOL) My wifes' car quite working right after I replaced the alternator :-(, so now I have a nice new shiny Delco Remy CS 130 series alternator I can't return. Would anyone be so kind to email me a wiring diagram of the circuit ? I'd hate to wire it up incorrectly and destroy it ! I've also stripped all of the relevant wiring & battery out of the car. Many thanks in advance. My eMail is :

MEGACYCLES (author)mpandersen2015-11-22

maybe convert an old singer treadle model to generate power?! I enjoyed operating the old machine without sewing as a kid... loved it. Something about getting it to start with say the large hand wheel and almost effortlessly getting it to "sing" out some high rpms....

MEGACYCLES (author)2015-11-22

thanks. .. I will investigate more. Question: I have a 04 crown victory police car. I might be removing the high-output generator because of parasitic drain within it's diode array. Would anyone know if the take-out unit might be useful in a similar project at the cost of the core charge?

Gen-set (author)2009-03-17

I have a Craftsman lawn tractor with a 19.5 B&S; Twin-II I/C engine, that would work perfectly for the reasons that kflack stated. Driving a Delco CS-144 140A alternator should be NO problem!! Last year, I built a 1.5kW gen-set using a 6hp B&S; Lawnmower engine, another Delco CS144, a Xantrex Prosine 1800 Inverter and up to 300Ah of batteries, for up to 5 hours of silent runtime before I have to re-start the engine.

efoster6 (author)Gen-set2015-05-08

I see 2 problems with this first car alternated only use full change up to 80% and then drop back to a trickle, 2nd I would have thought that your ride-on would already have an alternator built so why not use that one

kflack (author)efoster62015-05-13

Question 1 -(kflack Homebuilt Generator) I don't fully understand the statement your are trying to make but will take a shot at it.

If you mean that car alternators start charging batteries at 80% and you are not getting the full use of Battery cycling then you are correct. The intention here is not to store and cycle the batteries but to use them as a constant current source for the loads that the inverter needs in real time. The alternator simply maintains the the battery charge status at as close to 100% as possible.As a mater of fact, using standard lead acid batteries, in this instance instead of deep cycle batteries is recommended. 

In Gen-Set case it looks like he is manually charging up a storage bank and turning off his generator while cycling.In his case a Deep Cycle Battery would be applicable.

Question 2 -The charger for a ride on provides very low charge current for such a small motor/battery starter requirement.(Some as low as  .5 amp) The use of a car alternator is to be able to use the entire output power capability of the ride on mower (100 amp or more) under full load conditions.

jfontRI (author)2015-04-03

So I am a backyard tinkerer and have been playing around with making a wind turbine using an ac delco alternator. I know its not a great source of power, just playing around with it. The alternator model I am using has the pin connector with SLFP. I have a jumper wire connecting the S to the hot wire going to the battery. And the ground from the alternator bracket to the neg. terminal. But I am not getting any power generation. Is there another wire I should be connecting or something else?

kflack (author)jfontRI2015-04-06

Car Alternators need about 3000 + rpm to generate power.

Wind Gennie about 300 rpms is max....

Look to upgrading to a permanent Magnet Core in your alternator and then maybe you will see something.

cemb (author)2010-06-05

cemb: asks; at what rpm does an alternator need to spin in order to produce its max output

Josehf Murchison (author)cemb2011-07-12

Maximum power is usually controlled by the regulator; it is more rpms and efficiency, usually 2 to 2.5 idle speed of the vehicle the alternator is for.
An example a Mack truck’s idle speed is 400 to 500 rpm and max rpm is 1800 you might want to run the alternator at 1000 to 1200.
A Chevy Sprint’s idle speed is 1100 and max rpm is 10000 rpm its alternator you might want to run at 3000 rpm.

NightLord (author)2010-10-18

So, is there any good solution how to connect inverter directly to home power?

This is the kiind of inverter you are looking for

Josehf Murchison (author)2011-07-05

In reality house wiring has 220 across two live lines that go to ground at the neutral making 110 per side. Another little known fact is home hydro can fluctuate from 90v to 135v depending on where you are on the line and how modern the service is. If you are getting voltage from the neutral it is probably feed back in the lines finding a shorter rout to ground, I was shocked by a house circuit with the circuit breaker off that way.
To connect to house wiring you need a 220 110-volt power inverter with a pure sine wave signal synchronised to the service. The output is kind of like a centre tap transformer. Service transformers have the windings hooked up in ether delta or Y configurations they’re essentially a centre tap transformer. This is a simplified explanation.
I hope this helps.

kflack (author)Josehf Murchison2011-07-06

Absolutely Correct Josehf !

My reference to using a (Non Bonded Neutral) for the switch panel is a non standard approach to temporarily use (During a power failure) for key switched circuits. By using a non bonded Neutral it is possible to use a less expensive inverter (Square Wave) versus True Sine wave as you mentioned above.They in reality do not use the same methodology for power generation (Center Tap transformer) and hence the need to have the Neutral (NOT Bonded) to the ground line. It is not an accepted standard for household wiring to have the neutral unbonded from the ground line, but is the only way possible to use a square wave inverter on household wiring via a switched panel.

Your assessment above is absolutely correct and is a superior configuration (True Sine Wave Inverter) that meets existing legal wiring codes. In your instance above, with a True Sine wave inverter, the Neutral Line would remain bonded to the Household ground

FurtherThanTesla (author)2010-06-24

Oh, Hey! I made one of these last week!!! Min is made from a vintage 1980 Lawn Chief ride-on mower. The engine died, so i tore the whole thing apart and put in a 5hp honda engine. the new engine connects to the transmission, and also a 55-amp alternator. (I couldnt afford a more powerful one) it generatoe loads o power that run it's seven 55W halogen lights. i havent hooked an inverter to it yet, but i was planning on doing the exact same thing as you. I have it on youtube:

Rahdzhillaxxx (author)2010-02-28

I was half thinking of rigging  an alternator on a treadmill type of devise and just chaining the  yard tractor up on it.  this makes much more sense 

cchubb (author)2010-02-25

 One other little comment I would make would be to put one or two 12V biscuit fans on the brackets and aim them at the alternator. Those 100+ amp alternators run hot and heat is the major killers of the diodes inside. On a car they are usually cooled by the airflow over the engine, but on your genset here they won't get the same cooling airflow. 

Sandisk1duo (author)2009-01-06

A little bit inneficient, AC motors would work better

darkride (author)Sandisk1duo2009-01-07

An AC MOTOR?? I assume you mean an AC alternator? The car alternator is an AC alternator that rectifies the AC to DC. You could remove the regulator I suppose to get straight AC but then the frequency of the AC would vary all over the place as the speed of the motor changes not to mention it would never be 60HZ or that you couldn't regulate the output voltage.
I'm sure the cost of a purpose built alternator designed to 120V would well exceed the intent of an instructible. You'd be better off buying a cheap generator!

willtoolman (author)darkride2009-01-29

Remember most electric motors are generators when driven. And generators become motors when plugged in. Or so I have been lead to believe, that is the premise of using a 3 phase idler motor to turn single phase into 3 phase on the cheap (generating the 3rd leg).

kflack (author)darkride2009-01-07

Hi In reality its a standard Cadillac Alternator with built in DC voltage regulator. The output is connected to a gang (2) of batteries for charging. To the batteries I have connected a Xantrex DC to AC Converter (Modified Sine Wave Generator). Simple ,functional, and the Lawn mower gets used every week (Summer) so the gas never goes stale. Tank also lasts almost 12 hours of use so I can sleep through the night, even during power failures (winter) as it keep our oil furnace going.

kflack (author)Sandisk1duo2009-01-07

Hi Alex You are correct, as this is typically what is used for standard generator(s) and they run at a constant speed to maintain frequency. Also as darkride mentioned, the speed control would not be available to ensure constant speed control or current control for that matter. The key here was to use as much available resources and get the "cheapest" possible way to charge the batery bank. It would be difficult to beat a $35 (cdn)alternator, both for price or endurance. The inverter is also so portable that it could, in a pinch be hooked up to your car battery and be used as a generator.

bleachworthy (author)2009-01-23

This is a great idea! It would combine with another project I found years ago that uses an alternator for arc welding (driven by an electric motor). this makes it more portable!

falconsabre (author)2009-01-15

great idea, easy and effective, i like it

Hands Without Shadows (author)2009-01-06

Nice N' easy. I like it. Whats the added resistance like at startup without load? Is it worth adding an electromagnetic clutch like the one on the deck or not so much?

Interestingly enough even without a load attached the armature inside the alternator is generating its initial electric field and it takes quite the kick to get it started. That's the reason for the "Generator Light" resistor. These creatures are actually built to get their initial charge from the initial current from the generator create this field. I highly recommend a bypass (Off Switch) disabling the light (Sense Line) until the motor has been started and is at a reasonable rpm before engaging. Still possible to start without it, but in cold winters where battery starting power is at a minimum I wouldn't want to take the risk when you have no alternative sources of power to start up you homemade genny.

killerjackalope (author)kflack2009-01-06

In desperation a hill an nerves of steel can help for startups... Nice project - at best you'd be able to run a 5KW generator from that engine, though that's guessing it's still got 10HP then you'd be able to have a reasonable amount of electricity if it was for any length of time... I like the idea of the lawnmower having a generator though, I wonder what else it might benefit from? A stove on the back?

You could build a water heater that connected to the exhaust. The heat exchanger would act as a muffler too.

kflack (author)Scubabubba2009-01-08

Now your talking green energy.... Actually I do need a new muffler on the beast, thats a great idea,except I'll have to refill it, and it would need to be stainless steel (no rust)....getting complicated....

Scubabubba (author)kflack2009-01-09

Saturn s-series cars ('92 thru '02) and maybe some others had stainless exhaust systems if you want to make a trip to the junkyard. If you treat it like a solar water heater you could have the heat exchanger in a small tank near ground level, then have a bigger tank (like an old water heater) elevated as a storage tank. Thermal expansion would drive the circulation through regular plumbing connections & you could get a hot gravity-fed shower or two in the morning when you have to run it all night. Put a toilet tank valve on a small side tank like a 5 gallon bucket (to keep it out of the heat) to automatically refill it from your regular plumbing system. How's THAT for complicated! LOL Great project you've got there -- there's a whole (very small) community of people who use the batteries in their '70s-era electric lawn tractors as power backup. Golf carts could work too. Anyways, nice ible, and it looks like it was fun.

kflack (author)Scubabubba2009-01-09

LOL Whoa ! Your not going to believe this but a) I own a Saturn SL2 (2000) b) I have 2 old (Non insulated) 30 gal ? Water tanks c) Just getting ready to replace my current hot water tank with a on Demand Electric. Was thinking of using the old tank as an exchanger for a Roof mounted solar Hot water heater panel. Man are we in sync or what...."Twilight Zone Music"

Scubabubba (author)kflack2009-01-10

Ha! It gets freakier! My '95 SL went to 317,000 miles. Replaced it last year w/ a used '97 SL, my wife drives an '02 SL. And I have 2 water tanks in my back yard waiting for some type of solar project -- that's probably why I thought of it. I'd do on-demand but my electrical system won't handle it -- I've only got 200 amps (sadness).

kflack (author)Scubabubba2009-01-11

I also have a 200 amp circuit, but expect to be able to get the temp up about 30 deg + with a solar water heater. I also was thinking us using the old tanks (Uninsulated) as an internal heat exchanger to raise the water temp to room temperature.As I have a air based heat pump it would be a poor mans water pre-heater by using the ambient air temp to pre heat the uninsulated tank with air that was heated with the heat exchanger...Just trying to figure out what to do with the sweating tank.Apparently the 'Sweated water" is from the air and is relatively clean if it can be filtered and bottled.

Scubabubba (author)kflack2009-01-12

So you've got ambient pre-heat, solar post-pre-heat, then the on-demand to top it off. I'll have to think if that'll work for me. There are comment threads on other projects where people talk about condensation water at painful length. Personally I'd water houseplants with it, but not drink it. If there's airflow over the tanks you'll get a bit of an air-cleaner effect, and the mostly pure, high-oxygen content water will slowly oxidize & dissolve the plating on the tank too. Eww!

kflack (author)Scubabubba2009-01-12

Element FourI guess a "Plastic Water" tank would be preferable to the "annodized?" aluminum (Yup, temporarily forgot how corrosive pure water is). There is a company that is working at bottling this stuff (From the Air Though)
Element Four

supremedragonx (author)2009-01-11

mabye i could install my old bolen gs 16

jongscx (author)2009-01-08

How many Amps does this output/would it be possible to scratch-build a decent welder with that size engine? Would be nice as it's self-propelled and self-contrained

kflack (author)jongscx2009-01-08

See Bradly CommentFound a link where someone actually did use it for a welder...

kflack (author)jongscx2009-01-08

Good Question....Keep in mind the current actually comes from the battery bank and the alternator is for charging the batteries. I have it running under my 100 amp rating (Fuse) and I figure its about 1000 watts charging, maybe 70 amps (DC @ 14+ volts)being pumped into the batteries under about 1/2 motor load or less.

dsandds2003 (author)2009-01-07

Is a good idea. Am wondering how this idea would work with a home made wind generator motor. Or a brushless DC motor??? I just might have to try something like this with a lawnmower engine, a wind turbine motor and run the small engine on home made fuel. I see LOTS of ideas generating from here!!!! Dave

funinthefalls (author)2009-01-07

Nice idea, however not that cost effective. I was able to buy a gas powered 1200w generator brand new at Canadian Tire for $119.00. But I guess if you have time to kill and money to burn this wouldn't be that bad.

kflack (author)funinthefalls2009-01-07

I probably wouldn't have built this 3 years ago if the cdn tire had existed at the time. I had already purchased the 1000watt (2000 surge)xantrex in the past and used it for quick power outages using the boat batteries (on trickle charge)I had. The generator (alternator) was only $35 (Scrap yard) so was the cheapest option to extend battery backup life... I bet your cdn tire generator will not run for 12hrs before refilling, and definately will not handle the same surge current that this baby can handle. Also, when you build one of these home gennies it becomes the talk of the neighbourhood....

funinthefalls (author)kflack2009-01-07

You are right, I am sure mine would crap out long before 12 hrs. Your idea makes sense now that I know u already had the inverter, I thought u bought that to make this project. I applaud your ingenuity

natebug (author)2009-01-07

this is a very great idea!!!!!

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