Garrett (garote) wrote,

Bike Electrical System Project

Four months ago I bought a GPS tracker to attach to my bike. The unit is a Garmin Forerunner 305. I chose the 305 because it's small, multi-purpose (can be used for running and hiking as well as biking), USB-driven, can be clipped easily to a bike, and can be paired with a cadence sensor and a heart-rate monitor.

I'm primarily a Mac user, so I log my activity using Ascent. It's a pretty nice program. It can send trip data directly to Google Earth, so when I take (or plan) a ride up into the hills, I can get a detailed 3-D view of my route, showing the landmarks and streets. In the latest version of Google Earth, I can crank the time setting forward and it'll shade the hillsides according to the angle of the sun, so I can see whether I'll be riding in sunlight or shade or darkness.

With all this extra riding, I needed some additional gear. I bought a LED-based bicycle headlamp (A NiteRider Minewt X2) and a battery-powered flashing taillight. La bought me a pair of panniers. (Before this year, I had no idea what that word meant. It basically means a luggage rack for your bike, with detachable bags.) I loaded up an iPod Shuffle with riding music, NPR podcasts, and audiobooks. I wore that on my shirtsleeve, with the Sony MDR-G57 headphones I already owned.

This setup has served me well, but I want more. Much more. The things I want, in no particular order (some are more feasible than others):
  • A better pair of sunglasses.
  • A greater variety of bike shorts and/or pants.
  • A portable bike pump.
  • Some front-mounted panniers.
  • A light pair of gloves to keep my knuckles from freezing on late-night rides.
  • A better set of handlebars, raised up a few inches.
  • A helmet-mounted lamp, so I can get light where I'm looking as well as straight ahead, and have hands-free light during repairs.
  • A bike-mounted phone, and a wind-insulated headset, so I can talk to The La and others while I ride.
  • A bike-mounted iPod, so I can ride with a greater selection of audiobooks and podcasts, and control it easier.
  • A helmet-mounted digital camera, so I can grab crappy snapshots of stuff without stopping and fumbling around. (Note: this is amusing, but overkill. Heh heh.)
  • A map display that shows routes and can grab map data from cell towers when available.
  • A headlight and taillight that can be run off bike power, so I don't have to recharge them all the time.
  • An electrical source built into the bike, in the form of a hub-dynamo, integrated with a battery system, so I can charge gadgets as I go.
  • A battery system with enough drive to partially recharge a laptop, preferably a powered-down Macbook Air holed up in rear pannier.
All these things can be built and/or bought without much trouble, with the exception of the electrical system.

If you just want something basic and inefficient, you can convert your bike energy into light with a couple of off-the-shelf parts and some zipties. If you want to charge USB-based devices, that too is a solved problem. There is even a product from Germany called the Dynamode USB Charger that combines batteries, USB, and a hub connection in the same product ... but it's not rugged, powerful, or flexible enough to suit my tastes.

After an exhaustive internet search, I arrived at a cycling journal page written by a fellow named Alex Lockhart. As of this writing, he is still on his cycling tour, having re-entered the United States after a multi-month trip through Mexico. The journal is a fascinating travelogue, and also a boon for fellow touring cyclists researching electrical systems. When I first read the description of Alex's battery system, I decided that I wanted to construct something exactly like it.

The heart of Alex's system is a small circuit board called the TuneCharger, created and patented by a French company with the same name. The TuneCharger is, (quoting Alex here): "designed to use power from various fluctuating sources such as solar panels and wind generators to charge batteries. It uses Maximum Power Point Tracking to find the 'sweet spot' of the source, by varying the load and measuring the resulting power output, thus staying 'in tune' to the capabilities of the source. It uses pulse charging to charge the batteries, which gives a very short high-voltage pulse to the battery and then measures the voltage between pulses. This allows it to very efficiently charge batteries of any type."

Furthermore, the TuneCharger can accept the AC power and fluctuating voltage directly from a bicycle dynamo. The manual included with the circuit board even has instructions for the best way to wire it up. This is exactly the component I need to build a real battery system into a bicycle.
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