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There was some interest in another thread about eBikes in general and one we put together in particular. Others may have them or be interested so I thought I'd start a thread.
To start off, eBikes are a FANTASTIC way to get around Boston. Most will go 20mph without pedaling for 10-25 miles. You can use the bike lanes, wear what you want, park in bike racks, etc etc. They are in all ways legal a bicycle, period.
We bought the components for this bike, then paid a non-profit biking organization in Maine to assemble it. The hub is a very typical and relatively low-cost Crystalyte two speed hub motor. We bought the rear wheel assembled with the hub: all we had to do was mount the gear cassette and tire. We used Michelin Transworld City tires that are very rugged and allegedly puncture proof. We added a bicycle speedo, a meter that displays voltage and wattage, and a cruise control. The "throttle" is a thumb button on the right handlebar.
Many low-end bikes are 36 or even 24 volt, but 48V seemed to be the best tradeoff between cost and performance: there are systems running now at up to 72 volts. Our first battery pack was four 12Ah SLA batteries that together weighed 30 lbs. Those gave up the ghost after about 18 months and I purchased a LifePO4 48v pack that has about double the range (still haven't maxed out range yet, but it's well over 10 miles) and has a charge cycle life of over 1,000 charges. I've had it for two years and it shows no signs of degradation. Fully charged it's usually a bit over 50v. I believe it shuts itself down at 38v. The lowest output I've ever seen so far was 44v.
There are better choices for donor bikes now. It's pretty easy to find one with a front suspension and disk brakes, both advantages. Light weight doesn't really matter. By far the most popular rim is a 26" mountain bike, because ride, traction and durability trump light weight and low drag.
Hub motors have advanced as well. Most choose a direct-drive hub like the Crystalyte, some of which even offer regenerative braking. But direct drive motors have some drag if unpowered, so for pedal use or higher performance, there are a number of geared hubs available.
There have been big gains in batteries. You can now buy a 12Ah 48v LifePO4 battery for a little over $400, down from $1,000 a number of years ago. Li-Ion batteries are even lighter and less expensive but have a few issues and are now less popular. All the cheap kids toys have SLA batteries, usually 24 or 36V.
The two most helpful forums are at endless-sphere.com and the ebike forum at bikeforums.net.
This is not a technology demonstration bike like Audi made or a $10,000 toy for rich guys. It was put together as a workhorse when almost no on had even heard of them. Most of the people selling parts at the time were enthusiasts who did it as a sideline, and that's still somewhat true.
BTW there are do it yourself electric motorcycle plans available, some of which are almost but not quite fast enough for a highway commute. But they are heavier, more expensive, and require registration. To my mind the eBike is a much better choice give the current state of battery technology.
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