How to turn a lawn mower into an electric generator

Any item that is no longer used for its original function can have a new life, even an old lawn mower. Perhaps you are used to recycling and reusing objects for decorative purposes, but this is completely different.

With the motor of a lawn mower (still working) you can build a portable 12V electric generator . That voltage is enough to charge devices in remote locations and even power small appliances like lamps, radios, and televisions. In addition, it can be used to power a car or boat battery. And in case you don’t take long trips or camping, it can still help to have an emergency power source at home.

The generator will run on gasoline, but you can make your own biodiesel , recycling oil; a much more ecological and economical option.


  • A vertical axis lawn mower motor
  • A GM Style automotive alternator with internal regulator and external control switch
  •  3 ft (91.44 cm) of red and black wires from a car battery
  • A “V” belt



1. The first step is to get a lawn mower that has a still running engine. The best are Craigslist or Free-Cycle; the recommended motor is a 3-5 horsepower Briggs and Stratton. The vertical shaft mounted motors are easy to get, to use, to maintain and to replace if necessary. 

2. Next, what you need to find is a car alternator with an internal regulator. It’s easy to get because all cars have it, but to make it cheaper get it rebuilt or from a junkyard.

3. Get red and black car battery cables from a hardware store. You need at least one meter. Make sure you have the battery cable terminals. 

4. Join the engine and alternator. For this, it is advisable to place both on the ground (away from anything, but not outdoors). Drills a hole in the shaft of the vertical axis motor.

5. Place the alternator next to the engine, and between them mount a “V” belt to help transfer the engine power to the alternator (this is available at a hardware store). The length of the strap should be kept to a minimum to reduce lash and associated wear and tear. Don’t buy them from an auto store because they are less sturdy.

6. Also buy a cast iron pulley. Choose it with a 3/4 hole (inside hole) and with a lock nut, and a diameter of 4 “to 5” (10.16 to 12.7 cm) overall. They are relatively inexpensive.

7. Attach the pulley to the mower shaft, at a distance that helps you secure the “V” belt to the alternator.

8. Slide the alternator off the engine onto the 2 “x 6” (5.08 x 15.23 cm) dash, until the pulley is snug and tight. Drive in some screws to secure the alternator in place. Next, remove the alternator and pulley and reinstall the alternator a few inches past the screw holes you used to hold it away from the engine. This will help add tension to the pulley.

9. Reassemble the alternator, using a pry bar to help get the pulley over the cast iron pulley (flywheel) on the mower engine and over the alternator flywheel.

10. Finally, connect the alternator wire terminals to an automotive or marine deep cycle battery.

11. Connect a DC to AV converter on the battery. Now you can turn on your accessories! 

To be more sure you can check the following video:

Important: The Bioguide seeks to provide information to people to help them in the search for their personal and autonomous development. The instructions provided require personal responsibility in order to guarantee maximum safety conditions. All procedures must be carried out with the necessary precaution and safe from children. The site is not responsible for possible consequences caused by the use of the information offered.

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