The Improvised Electrical Device – A bicycle alternator

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The Improvised Electrical Device – A bicycle alternator

The Improvised Electronic Device was born out of a desire to be electrically self-sustaining in the remote places I plan to go.  It’s not that I’m trying to save the planet, I just don’t want my iPod to go flat.  While it’s not uncommon for bicycle tourists to have a few gadgets these days, I’ll be travelling with the following electricity-hungry devices:

  • Notebook computer
  • Digital Camera
  • Garmin GPS
  • iPod touch
  • Mini USB powered speakers
  • Zoom H2 field recorder
  • Front and rear bicycle lights
  • SPOT satellite GPS messenger

My plan was to have a battery pack that could be charged with a standard AC/DC adapter whenever mains power is available.  The battery pack could then be used to run or charge any device that needed power, and be gradually topped up by a Schmidt SON dynamo hub on the front wheel of the bicycle.  Sadly after much searching I, like others, have come to the conclusion that such a device doesn’t exist.

Charging a battery from a hub dynamo is no simple task.  Getting the (fairly small amount of) AC power from the dynamo hub to a battery efficiently is one problem.  Being able to also charge the battery using a DC adapter and preventing the battery from exploding due to overcharging is another.  Enter the Tunecharger – a circuit made in France which is designed to do… well, exactly that.

The Tunecharger uses MPPT – Maximum Power Point Tracking to feed power to the battery while constantly monitoring the voltage.  An End-Of-Charge voltage can be set to prevent overcharging the battery.  Thanks to Alex Lockhart and Garote and Chris Devenish (whose blog appears to have disappeared now) – the descriptions of their devices led me on the path to building my own.

The IED contains:

  • Tenergy 18650 66mAh battery pack (11.1V nominal)
  • Tunecharger circuit
  • Texas Instruments PTH08000W circuit
  • Texas Instruments PTN78000W circuit
  • Random voltage regulator circuit from ebay
  • 12V car socket
  • Lenovo socket for DC adapter
  • 2.1mm DC plugs for 9.3V and 9.0V
  • Four USB ports
  • LED battery voltage display
  • Various status lights
  • Lots of switches/button
  • The general appearance of having been built by a mad scientist

It remains to be seen whether the device will hold up to the harsh conditions of touring but so far it seems to work.

3 Responses to “The Improvised Electrical Device – A bicycle alternator”

  1. Roy says:

    Hi,

    Amazing!

    Question: You know, car battery is charged using its alternator when a car is driven. Battery normally does not need external charger as long as it is “alive”; alternator keeps the battery “alive”.

    My question is: Can your circuit/design be used in the same way for electric bicycle? If yes, how do you connect it to bicycle? How much it costs?

    Please reply. I am very much interested.

    Regards

    Roy

  2. Jordan says:

    The bicycle alternator works by stealing a (very small) amount of energy from the rotation of the front wheel and converting that to electricity. The maximum power drawn is approximately 8W at high speed (40-50km/hour) – and there are losses involved in converting the AC power of the hub dynamo in to DC power to charge the battery.

    The short the answer is “not really” – any power produced will be less than the power required to move the bicycle – see the Laws Of Thermodynamics.

    I would suggest you investigate developments in bicycle regenerative braking which might be more in line with what you want to achieve. Have fun!


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