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The Rezistor - World's Quietest Vespa
Submitted by jstept on Mon, 04/07/2008 - 13:24
This weekend I rode the Rezistor to Spring Scoot, a scooter rally held annually each year here in Portland. It basically served as the initial test run and range tests. I started with a 6.6 mile ride on Friday night and rode progressively longer distances Saturday and Sunday. I finished with a 14.5 mile ride Sunday evening, much of it at full throttle. There seemed to be juice left when I got home, although my headlight (and presumably the rest of my accessories) seems to have given out a few blocks earlier. The controller, motor, and power cables were only a little warm.
I've been recharging right after every ride back up to full capacity. There's a little LED on each charger that changes from red to green when each pack is fully charged. After an 11 mile ride on Sunday it took roughly 4 hours to fully recharge the two 36V 20Ah LiFEPO4 battery packs from YESA.
The motor and controller are working well. I noticed sometimes that when I twist the throttle from a dead stop, a brief rattling noise comes from the motor and acceleration is delayed momentarily. If I give the bike a tiny push forward with my feet, then ease on the accelerator very slowly, this seems not to happen. I'm theorizing that the controller gets "confused" when the motor is at a dead stop, not knowing exactly what the rotor position is, and the rattling sound is caused by the rotor flipping back and forth. When I give it a little push, the controller seems to realize that the motor is spinning forward and it engages smoothly.
I also noticed some differences in acceleration, probably due from the presence or absence of the 10-second temporary current boost to 250 amps from the controller. Without the boost, acceleration is pretty slow, even slightly less than I would expect from a 50cc ICE scooter, but it's pretty decent if I get the boost. I find that, when stopped at a signal, I can get the boost pretty reliably if I put the forward/reverse switch into neutral while I wait, switching to forward when the light turns green (and then pushing the bike forward - I almost never get the boost if I hear the rattling noise). I don't know how often the controller allows the 10-second current boost to happen, whether it's a function of the fwd/rev switch, some amount of time between boosts, or something else.
I can feel the motor drag when I coast; I presume this is the regen activating. I'm learning to use the brake levers as little as possible to maximize my efficiency. I'm also riding hunched over a lot when at speed, since the Vespa's aerodynamics are bad enough without the addition of my torso as a sail.
Sunday I clocked 35 mph with my GPS, which seems to be about my maximum on flat road. I'm assuming I'm getting 100 amps at full throttle. At some point I may send the controller back to Team Delta to increase the continuous voltage, maybe to 150 or 175 amps. The motor is rated for 100 amps continuously, but it's getting plenty of ventilation, and with the way I'm riding it's not really a continuous demand.
Saturday morning at Spring Scoot 14. Breakfast was at Mickey Finn's in southeast Portland. Behind all the scooters on the street, you can just make out the Rezistor parked way in the back on the sidewalk, next to a door through which I ran my extension cord inside.
Charging up at breakfast on Sunday.
Twist'n'Play Scooter Club awarded me the rally trophy for Best Rat Bike. It's sitting on the floorboard and yes, it has a big rubber rat on top. The other rallygoers had many questions, many of which I really couldn't answer completely because I wasn't done testing it yet. It was especially fun to demonstrate reverse gear.
In general, I consider this weekend to be a success. I built the thing mainly as a commuter vehicle, and Sunday I rode almost three times the distance of my round-trip commute on a single charge. I have yet to find out what my ultimate range is, but I suspect it's not much further than 16 miles.