Electric Bike

Well enough arm twisting from Paul, so here is a long awaited update on my electric bicycle (in the making). Basically the project was started in late 2006 and, as with most endevours, has ended up taking considerably more time than originally anticipated.

The controller has been designed from the ground up and has been engineered with vehicles more substantial than an electric bicycle in mind. For this reason, every standard feature for a vehicle has been incorporated into the controller, though they are unlikely to be used for the given target bicycle. The overall idea is to evolve the controller once this first objective has been achieved. The following features have been incorporated into the design:

1. A (high efficiency) step-down DC/DC converter to regulate (40V to 95V) down to 12.5V 5A Output max.

2. Indicators, break light, headlight and tail-light outputs.

3. Backlit (4 line x 20 character) LCD display that displays speed, mileage, battery status etc.

4. Full microprocessor control of speed and motor torque for 2 independent Brushless DC motors.

5. Full protection against excessive battery discharge, motor overload and controller temperature etc.

Briefly, the following specification applies to the controller:

1. Nominal battery voltage = 72V DC

2. Rated continuous output current per motor = 20A

3. Burst current per motor = 40A (thermally modelled by the controller to protect the motor and associated wiring)

4. Rated power per motor = 1.2kW (1.6hp)

5. Fully protected against overload, reverse polarity, over temperature etc.

6. 3 Phase MOSFET drive (under microprocessor control) for each of the 2 DC brushless motors

The controller is being designed (note present tense...) to be fully protected in addition to ensuring driver safety while operating, even in the unlikely event of controller failure whilst driving at speed. This is an issue not really addressed by many other controllers of brushless DC motors which have the potential to lock the wheel up in the event of a catastrophic failure or battery disconnection.

Well, more is to be added later but in the mean time, see the video below of a test run when operating at 72V DC. Oh, and feel free to contact me with any comments or enquiries, I'm always interested to here peoples responses to this eco-friendly, inflated oil price beating project.