1st Phase - Project E - Bike

After reviewing my future plans and considered income level I have figured that it will be several years until I have the space and finances for a full scale EV - project. This is rather dejecting. The idea came to me however that I could probably begin doing other projects on the cheap. After reviewing Oregon's driver laws, I discovered that electric bikes require neither registration nor insurance - but are limited to 20mph and must be pedal powered in addition to any electric motor. This handicaps, while strict, shouldn't be to much of a burden for a project bike. So the adventure begins!

My plan is this: I have little funds, so I am going to try to keep the bike as low cost as possible. I plan to utilize Craigslist's "free" section and the Yahoo freecycle group as much as possible. I should be able to find a free bicycle or at least put one together by the end of the month.

Others have tried similar projects in the past, and are excellent references. It seems that a starter motor for a passenger vehicle (1 - 1.4 kw, 12v) paired with a 12V battery will do the trick. Some have tried upping the voltage to 24V, but this is generally not a good idea (damages motor, battery, potentially even wiring due to over amp-ing). Since electric bikes in Oregon are required to have pedal power anyway, the system might as well be used as an assist for the electric motor.

The nice thing about using a starter motor is that they are relatively cheap and extremely easy to find. My hope is to snag one for free but I would still be willing to pay a few dollars. I have a shopping advantage in that it doesn't really matter which motor I get.

Batteries are going to be the difficult part. Traditionally e-bikes have been equipped with lead - acid (car) batteries, but these are large and heavy, and often make the rider sit in funny positions. I would prefer to employ lithium ion, an expensive and powerful substitute. Currently A123 systems makes Li Polymer packs which run on ebay for 10$ each. I figured for my system I could use eight of these, packing them into two packs and running those packs in parallel, giving me 13.2 nominal volts and 4.6 Ah, with constant current draw of 140 amps! The whole deal would weight ~ 600g!

For throttle a simple switch is often used but I would like to construct my own variable current model. I imagine a couple of copper plates in a modded gripshift could accomplish the task - more on that later.

Locomotion will travel through a double freewheel hub, with a single speed on each end. This way you can coast off the pedals and throttle, plus you can combine the two energy types. Such hubs are available at 50$ online - and unlikely to be found free on craig'slist. Same goes for the single speed freewheels (25$ each).

So, budget for my-first-electric-bike:

Donor Bike - free
Starter Motor - free
Extra chain - free
Gripshift - free
A123 Systems batteries x8 - 90$
Double freewheel hub - 50$
Dual single speed freewheels - 50$

I don't know the cost of copper wire, leads, or other electronics I will certainly need, but I don't imagine they will be difficult to purchase. I also am not sure how I will mount everything, but that is for another post.