JCG
100 W
- Joined
- Nov 10, 2008
- Messages
- 174
Hi all,
I'm pleased to have found this place. I'm in the stage of figuring out what is needed for an e-bike conversion project that I'll be working on with my students, and since e-bike conversion kit retailers provide very little in the way of electrical specifics, I'm turning to the experts... and those with valuable experience.
First off, this project is a precursor to a full electric vehicle conversion (of the old GM EV-1 which was donated to my University - from purely battery power to a series hybrid). To test the drivetrain ideas in a low-cost way, I decided that an e-bike might make a good platform for learning and experimenting. Here is the basic idea.
Main source of power/main energy storage: human muscle.
Secondary source of power/secondary energy storage: ultracapacitor modules.
That's right, no batteries are planned for use in propulsion. I live in Washington, DC and commute about 3 miles each way to work on my bike. There is a lot of stop-and-go, and a lot of close calls when you don't accelerate fast enough for the guy in the car behind you. With the Ultracap Bike, I plan on using the limited capacitor storage to provide quick starts from a rest (or very low speed) and will require an electric motor with good low-end torque. It won't be used at higher speeds, but I wouldn't say no to 20+ mph while the power lasts. I believe that a 500 W motor would suffice.
The ultracaps will be two 16 V, 330 F modules connected in series, for a total bank of 32 V and 165 F. I have already received them as a donation from Maxwell Technologies. I've tested them, and they are a lot of fun.
I foresee the following issues:
1) Regen braking is a must. Not just that, but STRONG regen. I need a controller that can send up to 30 A or so back to the ultracaps when I ask it to (gradually at first, of course! Charging a capacitor is like a short circuit).
2) I also hope to be able to use regen on the fly. That is, to be able engage it while cruising on a flat slope, and pedal against the generator resistance to charge the caps slowly if they need it. I envision using a front hub motor, separate from the normal rear wheel and cassette, to do this.
3) Ultracaps, like any caps, will drop in voltage as they discharge. I'm planning on draining them to no more than half of nominal potential at any time (16 V). This would be accomplished by using 75% of the available energy (63 kJ). If my motor is cranking out 500 W, that energy should last up to two minutes in a single burst, but as the voltage drops from 32 to 16 V, the current would jump from ~15 to ~30 A, for example.
I'll need a controller that can accept that input voltage range, and a motor that can take that voltage swing as well (without using a DC-DC booster, I hope). Would a range of 16-32 V input require a 36 V motor? Should I overvoltage a 24 V motor for part of the time? Will the controller care? I've heard that the Kelly controllers can be programmed...
Asking a motor and controller to deal with such a large voltage swing, and to send large currents back in regen, is not something I've seen discussed with relation to e-bikes yet. Thanks for taking the time to read, and thanks in advance for any help or suggestions as to what to buy!
J. Ganley
Howard University
I'm pleased to have found this place. I'm in the stage of figuring out what is needed for an e-bike conversion project that I'll be working on with my students, and since e-bike conversion kit retailers provide very little in the way of electrical specifics, I'm turning to the experts... and those with valuable experience.
First off, this project is a precursor to a full electric vehicle conversion (of the old GM EV-1 which was donated to my University - from purely battery power to a series hybrid). To test the drivetrain ideas in a low-cost way, I decided that an e-bike might make a good platform for learning and experimenting. Here is the basic idea.
Main source of power/main energy storage: human muscle.
Secondary source of power/secondary energy storage: ultracapacitor modules.
That's right, no batteries are planned for use in propulsion. I live in Washington, DC and commute about 3 miles each way to work on my bike. There is a lot of stop-and-go, and a lot of close calls when you don't accelerate fast enough for the guy in the car behind you. With the Ultracap Bike, I plan on using the limited capacitor storage to provide quick starts from a rest (or very low speed) and will require an electric motor with good low-end torque. It won't be used at higher speeds, but I wouldn't say no to 20+ mph while the power lasts. I believe that a 500 W motor would suffice.
The ultracaps will be two 16 V, 330 F modules connected in series, for a total bank of 32 V and 165 F. I have already received them as a donation from Maxwell Technologies. I've tested them, and they are a lot of fun.
I foresee the following issues:
1) Regen braking is a must. Not just that, but STRONG regen. I need a controller that can send up to 30 A or so back to the ultracaps when I ask it to (gradually at first, of course! Charging a capacitor is like a short circuit).
2) I also hope to be able to use regen on the fly. That is, to be able engage it while cruising on a flat slope, and pedal against the generator resistance to charge the caps slowly if they need it. I envision using a front hub motor, separate from the normal rear wheel and cassette, to do this.
3) Ultracaps, like any caps, will drop in voltage as they discharge. I'm planning on draining them to no more than half of nominal potential at any time (16 V). This would be accomplished by using 75% of the available energy (63 kJ). If my motor is cranking out 500 W, that energy should last up to two minutes in a single burst, but as the voltage drops from 32 to 16 V, the current would jump from ~15 to ~30 A, for example.
I'll need a controller that can accept that input voltage range, and a motor that can take that voltage swing as well (without using a DC-DC booster, I hope). Would a range of 16-32 V input require a 36 V motor? Should I overvoltage a 24 V motor for part of the time? Will the controller care? I've heard that the Kelly controllers can be programmed...
Asking a motor and controller to deal with such a large voltage swing, and to send large currents back in regen, is not something I've seen discussed with relation to e-bikes yet. Thanks for taking the time to read, and thanks in advance for any help or suggestions as to what to buy!
J. Ganley
Howard University