First of all, I'm so glad I found this site instead of just buying some crappy kit on eBay! I've been reading the FAQ links, doing searches, and reading lots of threads. It really has me excited about converting my bike. I have some general direction, but I could use some more guidance.
I have a stock 2007 Trek 820 that I like a lot for general riding. Nothing fancy, but it fits me well and I'm comfortable with it. From reading on here, it sounds like it's actually a good candidate for conversion since it's a steel frame and all. One drawback is that the shifters and brakes are all one unit, so it would not be simple to swap to e-brakes. I don't know if this is a big deal or not.
I'd like to use this bike for commuting to work. My route is 17 miles one way, so it's a bit lengthy, but I can charge at work no problem. I live in Denver, and most of my route follows the S. Platte River, so I have nice wide, flat bike paths for 90% of it. There is only one steep hill at one end by my office, but I can truck up it at low speed with minimal power assist. It's only about 200' long. From the river trail to my house I have to ride up a long, steady incline of less than 5% for about 3 miles.
I'd like to be able to go 20-25 mph continuously so that I can make the trip in under 1 hour. I'd also like to pedal along with the motor for exercise. I'd like to keep the weight of the bike down because I will sometimes take it on the light rail, and I don't want to have to lift a 100 lb bike onto the train. I want to save on gas $$/light rail fare and get some exercise.
My build ideas:
I really like the idea of the MAC motors from Cell_man rather than a DD motor due to the weight savings. I'm not sure if the 6T or 8T would be better for my application.
LiPo batteries sound like they need more babysitting than I want to provide, so I'm thinking Ping batteries or similar. I don't want to spend too much, but I don't want to be disappointed and have to buy a bigger battery later. Should I go 36V or 48V? Would 15ah be enough to go 17 miles on relatively flat terrain while pedaling? The 820 has a nice triangle to put the battery in to offset the weight of the motor in back. I don't want to overdo the battery and make it heavier than needed because I'll probably lug the bike on the train sometimes too.
I'm 35, 6' tall, 210 pounds, in okay shape. Right now I use the light rail to get to work most of the time. It's about 4 miles from my house to the station, then a 30 minute train ride, then a 1-3 mile ride to work (depending on which station I get off at). I usually drive from home to the station and then ride a bike from the other end to the office. I've had a membership in the Bcycle bike sharing program for the last two years, and that works great but the bikes are heavy and slow.
For one summer I tried riding my Trek from home and locking it up at the light rail station. This was a piece of cake in the morning since the ride was all downhill, and it only took like 5 minutes longer than driving. Getting home was another story. It was much hotter by then and I had to slog uphill the whole way. It took me about 30 minutes to do the ride, or longer if I had a headwind too, ugh. I would get home at least 20 minutes later than if I drove. Not a big difference, but that's 20 minutes less each night that I have to see my kids before they go to bed.
Last year I decided that an e-bike might be just the thing to speed up my commute. Before I spent a lot of money to convert my bike, I decided to get my feet wet with a starter bike. I found a nearly new Currie eZip Trailz bike on craigslist for a little over $200. I did a test ride from my house to the station and back, and I made it downhill in 17 minutes and uphill in 19 minutes - much better than 30+ minutes on my Trek and I didn't break a sweat! The other day I decided to cut out the Bcycle and try taking the eZip with me on the train and then riding it the rest of the way to work. Screw that! This thing weighs like 100 lbs with the SLA on it, and it was a beast to maneuver up the steps onto the train. At the end of the day I decided to ride the whole way home instead of dragging the bike on the train again. I really liked the ride along the river, but that bike is s-l-o-w. It took me an hour and a half to get home, and the battery was on its last legs. I was getting passed by lycras the whole time. With a faster bike, that would be a really enjoyable ride and I could make the trip door-to-door in about the same time as my car-train-bike combo right now.
Thanks for any input and for reading that whole thing if you made it this far!