I've been riding around with it for a few weeks now, time for a review.
I had wanted a motor on my bike for a while, and had been looking at the 902 but it was out of stock when I was ready to order so I got a Smart Pie Vector. I wasn't looking for a really powerful motor, I just wanted something to level out the hills and negate the headwinds. 40km/hr with gusts to 60 is regular here.
I ordered the rear wheel kit for a 700c wheel. I got a 36v throttle and a thumb throttle. The bike is a cheapo $200 Nakamura. I had a really nice mountain bike but was hit by a car on it a couple of years ago, I have taken just about everything useful that would fit off of it and put it on the Nakamura, handlebars, shifters, derailleurs, pedals...
The first couple of rides I did with what I had, 6 6v12Ah SLAs. It ran but seemed to have issues under heavy load. I then bought 3 12v10Ah SLAs. Much much much better. They can deliver 30A, much more then the 18 the SP needs. At 36v the SP did exactly what I expected it to, it rode at a respectable 25km/hr on it's own and did fine on hills and against the wind with me pedaling. Acceleration was a bit slow, and going up a hill from a dead stop was a no go without human power, but it was a good ride.
But like everyone does at some point I imagine, I got curious. I wired up 2 of the 6v SLAs to get 48v. Oh my, what a difference. Two days later I replaced them with another 12v 10Ah. Acceleration is still a bit slow, but much better then at 36v. Going up a hill without pedaling can be done if it isn't steep. I still have the controller set to factory defaults so if I open it up on level ground it will do 40km/hr. If you are wondering if the Smart Pie is powerful enough for you, it probably is.
The motor is completely silent, you'd never know it was there and unless I point it out to people, they don't even see it.
A few words about running on SLAs. Everywhere you look people say don't do it, they are too heavy. I pedaled from Toronto to Newfoundland with far more weight on my bike then it has now with only my legs for power. It isn't unmanageable, you just have to use your head. Avoid big bumps like rolling off curbs, going up them isn't so bad if you are going slow. Make sure the battery is well mounted. I have an ordinary bike rack only rated for 40lbs. I replaced the flimsy steel steel strips that connect the rack to the frame under the seat with pieces of aluminum tubing and I attached what used to be the handle of a luggage cart to the back of the rack and the fender mounting holes down by the wheel hub. The rack is rock solid now. The battery sits on a foam pad and is held down with bungees and nylon straps as backup. It vibrates but I don't feel it because the rack doesn't. Same for minor bumps, it has just enough give to absorb the shock. The only time the weight is noticeable is when walking the bike or going up and down the steps at my front door, but I can lift it, unlike when I had my panniers on my trip. I do plan to switch to lithium power at some point, but being a diy type of guy I'll be making my own.
I charge them at work and at home, they are always in use, charging or full. At work I charge them in parallel at 12v 2A, so .5C. I work long days, they are done before my day is half over. At home I also charge in parallel but at usually higher rates. I usually leave the charger on auto and it charges between 1 and 2C. At the discharge rates and amounts I'm using with the charge rates and habits I am using these batteries should last their maximum cycles, much longer then I will need them for.
On the diy note, I made my own lights. The front light is made from a 1200 lumen flashlight. It flickers at a high rate using a simple circuit I threw together using the reverse breakdown voltage of a transistor as the trigger. There's a small box stuck up under the frame holding the circuit and a voltage regulator which steps down the power to the taillight which has a 555 timer based flash circuit built into it. I'm partial to bells over horns on bikes because they are instantly identifiable so I set about making a bicycle bell electric. In the end I went with an old school door/fire bell design made from a bike bell and an actuator I took out of an old photocopier. I save everything for making stuff out of, that's where the bits for the rack came from, my junk pile. The bell rings simply by breaking the circuit each time the magnet pulls it over. Took some experimenting with springs so it doesn't ding with every bump but it's good now. I mounted a digital voltmeter to the handlebars as a"fuel" gauge. Works perfectly.
I haven't reprogrammed the controller for a maximum 32km/hr because around here there are at least a dozen gas powered bicycles zipping around town. The police aren't bothering them, they probably won't even notice that my bike is powered anyway so I don't expect to be hassled. I rarely go the 40km/hr anyway, but I like having the option. There is a hill on my morning commute that I speed up before I hit.
Overall I'm very pleased with my decision to buy a motor. I think an SP would be more effective with a smaller wheel due to the increased torque, but it's more than good enough for my purposes. I don't pedal at all on my morning commute except half a stroke when moving from a dead stop, I'm too tired in the mornings lol. Going home I pedal along for most of the ride just for the exercise, I don't need to, the motor moves my 180lbs and the battery just fine.
