Cordless Drill Turned Into Bicycle-Powered Generator

The bicycle is a great invention. It is an extremely efficient method of transportation, even more so than walking. So why not harness that efficiency for other things? [Tony] had that same thought so he ordered a bike generator but after waiting too long for the company to send it, he decided to make his own.

[Tony] is an bicycle enthusiast so he had an old bike and an old training stand he could use for the project. Generating electricity from pedaling the bike requires some sort of generator. Lucky for him, [Tony] happened to have a cordless drill that stopped going in reverse. Since he had since upgraded, this was the perfect candidate for the generator. The drill was mounted to the training stand so that a pulley inserted in the chuck pressed against the rear wheel. Wires were added to connect the drill’s battery connectors to a 12vdc to 120vac inverter. As the bike is pedaled, the rear wheel spins the drill, which spins the drill motor creating DC voltage. That DC voltage is then converted to AC by the inverter. With a multimeter connected to the output from the drill, it is easy to adjust the pedaling speed to keep the output in the 11-14v range which is required by the inverter.

In the photo above, you can see a light bulb being powered by the bike. However, the bike powered generator could not power the larger load of a computer. The remedy for this was to purchase a solar charge controller and a 12 volt battery. The bike charges the battery and the battery can power the computer through the inverter.

25 thoughts on “Cordless Drill Turned Into Bicycle-Powered Generator

      1. Not that it should be, but if someone follows instructions and does really nothing to improve it’s efficacy.. it seems a little silly to report it.. Congrats to the hacker, I love people that do things, not really a news story though..

  1. I think a charge controller is a bit overkill for something like this. I’d just wire the generator straight to a SLA (through a diode of course). Just pedal as fast as you care to– it’d be pretty hard to overcharge the battery with something this small, especially if there’s a significant load on it.

    1. Over-charging is one thing, over-volting is another thing altogether. I’d be surprised if the charge controller, in this case, is little more than for just keeping the input voltage to the battery within a safe range.

  2. Has the speed control been bypassed? It needs to be out of the generator to load path. The reverse went out because something in the plastic switch broke, get rid of it and the speed trigger as well.
    Regular “AC” drills and power tools are in fact AC-DC! They go both ways.
    I have an AMF fitness bike that came with a car alternator and panel for putting a load into a big power resistor.
    Of course it plugs into the wall outlet to waste power! It waits for me to make it into a Soylent Green bike.

  3. As ehrichweiss noted, this hack is fairly old; here’s a Mother Earth News article from Jan/Feb 1981 showing how to hook up a car alternator to a bicycle for home power usage:

    http://www.motherearthnews.com/diy/bicycle-power-zmaz81jfzraw.aspx

    There’s a second article available for the following month’s issue; I know I have seen these kinds of hacks in alternative energy magazines and books dating to the 1970s. The idea is likely older than that.

    I do know that it’s unlikely that the geartrain and bearings of that drill will last long under that kind of torture; the design of a drill is mainly optimized for thrust loads, and not radial loads. It’s better to actually use an alternator or some other generator designed to be used as such.

    Finally – an average human being can’t really put out enough wattage over a long enough period of time to make it worthwhile; it seems like a good idea in theory, but in reality it doesn’t really add much as an alternative energy source. It is, however, a good way to get some exercise, so I can’t fault that.

    1. That’s why you need a charge controller or your battery looks like a short. If you think about how a battery works its only the internal resistance that prevents full power from being available instantaneously and pretty much being a super capacitor. There are simple plans around the net I think there has even been one or two on HaD. But the article used a prebuilt solar charger. Likely a cheap analog unit, they work well enough. If you want the most efficient conversion an MPPT charge controller is what you want but they are expensive generally.

      http://en.wikipedia.org/wiki/Maximum_power_point_tracking

      1. Yes but for say 5-20 seconds a few times per day. Putting it into continuous use to say recharge cellphone batteries would result in hours of use each day and likely wear the brushes in a few months or less.

  4. A Flywheel would help him out tremendously here. And I know the whole point here is to power a computer, but electric generation with a bike is usually not terribly efficient.

  5. Following the comments about on the (un)suitability of a drill for this task – sell the drill, buy a used car alternator – they are designed for the mechanical load and include high-current 13-14v regulator so you can pedal as hard as you like without worrying about over-under charging – you might say they’re made for the job…

    1. But then you have to spin the car alternator fast enough to first generate the field current (usually faster than you want to pedal). A better bet would be to build an proper alternator out of neo mags and wound coils designed for exactly the RPM you feel comforatable pedaling at.

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