How to Build a Stationary Bike Generator

The Pedal-A-Watt stationary bike generator system
The Pedal-A-Watt stationary bike generator system (Image:

If the energy we expend while exercising could be harnessed, it could be used to power lights, charge batteries, run televisions, and even power appliances or help recharge electric cars. A stationary bike generator can be used to convert the energy produced from the movement of the pedals into usable electricity. Many devices can be plugged directly into the 12v DC output. An inverter can be used to convert the power to 120v AC as well. Alternatively, the power from the bike can be used to recharge a deep cycle battery (or bank of batteries) for use at a later time, such as to power lights after the sun has set.

Things You'll Need

  • Stationary bike
  • Training stand
  • 12v generator or permanent magnet DC motor
  • Deep cycle battery
  • Volt meter
  • DC-to-AC inverter

Select the bicycle to be used. It should have multiple gears to keep you in the most efficient power zone, but does not have to be in completely perfect mechanical condition, so long as pedaling powers the rear tire. A bicycle that is fine for making power, but otherwise not roadworthy due to faulty brakes or a twisted frame can be picked up at a garage sale fairly cheaply.

Choose a training stand to hold the bicycle in the upright position without allowing it to fall over. The appropriate training stand should not get in the way of pedaling, and should elevate the rear tire off of the ground or floor. These stands usually slide into place by the rear wheel bolt, allowing the bicycle to still be easily removed for road use if desired.

Test fit your 12v DC generator or permanent magnet motor (which will produce electricity when spun) behind the rear wheel. The tire should fit into place by the output shaft where a belt would normally connect, or it should rest directly on the shaft itself. Once you have an idea for where the motor will go, use plywood to construct a mount to hold the motor in place against the tire. Different sized motors will require different motor stands and mounts.

Attach a voltmeter to the motor to measure how much power it is producing, and then hook it up directly to your electrical devices. A car cigarette lighter adapter can be connected to the power leads for an easy, universal adapter. Now, simply power your devices directly from the bike, or charge batteries for use at a later time.

Disassemble the front end of the stationary bike, and remove the mechanism that normally provides resistance. On an air bike, this is a series of blades that act like a fan to slow pedaling due to aerodynamic drag. You should be left with a directly driven rotating gear, and when pedaling the bike, you should no longer encounter any resistance.

Connect the shaft of the generator or motor to the stationary bike's gear system. You should be able to mount the generator into place in the void area where the resistance mechanism was formerly located. The generator will need to be securely fastened into place to keep from moving under the rotational force that will be placed upon it during use. L-shaped metal brackets can often be used to secure the motor to the frame of the stationary bike.

Run the wiring from the generator motor to the power outlet, or to the battery bank. Make sure that no wiring gets in the way of the physical movements of the bike during use. Replace the stationary bike's speedometer with a amp/volt meter to measure power output instead of speed. This lets you see how much useful work you have performed during your workout, and how much total power is being produced.

Tips & Warnings

  • If you don't want to do the work of building a system from scratch, several pre-made commercial models exist. The faster you pedal, the more power you produce.
  • Make sure that all wiring is secured from moving parts or the metal frame, otherwise you could face electrical shock.

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