I wanted to post my experience with my WE BD36 here as I came here about a little over a year ago and many helpful people answered my questions.
First off, I've now commuted just under 1300 miles on my bicycle. My bike is a hybrid in that it is a 1986 10-speed complete with rams-horn handle bars with a 27" wheel on the back and the 26" BD36 wheel on the front. I ended up replacing the front forks with MTB forks which allowed me to put MTB brakes on the bike. I had previously created an extension to allow the original caliper brakes on the 27" fork to reach the 26" rim.
Originally I wasn't satisifed with the speed of the bike. At 36 volts, it's top speed was 25 mph, and it allowed me to average 18 mph for my
6.5 mile commute. After getting the motor specs from WE and leaving some questions here, I decided to add another battery and try 48 volts. After proving that it would work, it ended up being a major upgrade.
The stock bag wouldn't hold 4 batteries and the stock rack was flexing with the three I already had, so I ended up replacing it with a heavy-duty rack. And of course I had to buy a 48 volt charger. The Full and Low charge indicators are now mostly useless. In order for Low to accurately reflect a Low condition for a 48V pack, I would have to characterize the Low voltage drop with a 36V pack and then add a resistor into the circuit. But I have enough juice for my commute to run full throttle all the way. In short, using 48V with a controller designed for 36V I always read Full.
I initially purchased a trunk bag with panniers which unzipped from the sides and put two batteries in each side. This didn't work too well because 40lbs of battery was too much for the bags internal structure and it gradualy began to collapse. In addition, the weight was still carried so high as to make the bike very unstable if I stopped at a light and leaned a bit too much. I ended up getting a dedicated pannier set that brought the batteries (loaded side by side vertically) almost down to the axle. Ideally I'd like it to be even lower, but this is okay. I used closed cell foam from a computer monitor to line the panniers to keep the battery corners from digging into the bag. The trunk bag sits on top to carry my stuff -- it's panniers I use for clothing when it's cold in the morning but warm at the end of the day.
The happy surprise is that I'm still using the WE stock controller with 48 volts. I decided to give it a go when I saw another 48 volt e-bike somewhere with a controller which appeared identical right down to the harness. Others here had recommended I replace the internal capacitors. But I can do that when the time comes.
Regardless, I now typically average 26 mph with a top speed of 32. Although I have had an instance where I was peddling very hard heading down hill with a tail wind and hit 36, I generally try to keep it around 30 figuring Lance Armstrong can pedal that fast without assistance and he's safe in just a bicycle helmet.
The only other change I made is related to the throttle. I was dissatisfied with the spring-loaded thumb throttle because it wouldn't slide along the curves of the 10-speed bars. I ended up making a bracket for it that put it next to the stem, but that required me to stay upright. I ended up putting a friction lock on it so it would stay where I set it. Using a multimeter I figured out the wiring and added a slider rheostat like what you'd see on an old graphic equalizer. This I located on the inside of the left drop so that my left thumb could work it. So now when I get going in the morning, I set the throttle on max and my thumb lever on min. The only thing missing and is currently in work is to add some sort of switch which opens the throttle circuit when I engage the brakes. I had a couple of instances where I needed to switch to brakes faster than I could work the throttle.
Lastly, I replaced the RCA-type connectors used for the charger with a heavier duty shielded connector readily available from an auto-parts store. I'd been having contact issues during charging and had replaced the female connector a couple of times. With my pannier arrangement I also had a couple of instances where the RCA charging connector bounced and momentarily hit a battery lug. It kinda arc-welded itself. Finally, the male connector on the charger somehow shorted out internally right before I plugged in the charger. The resulting brief fire melted a portion of my wiring harness. It was a pretty blue flame though. :-)
One final observation. Because of the magnetic pulse nature of the motor, my experience is that pedaling helps primarily with range more so than speed. I found that pedaling as hard as I could I just couldn't go significantly faster than the wheel wanted to turn itself. The magnetic pulses are synchronized and pedaling hard would seem to eventually try to move the wheel out of sync -- I felt resistance. In fact, the time I hit 36 mph, I was initially at full throttle and then I turned it off part way down the hill. Then I could pedal as hard as I wanted with the front wheel just free-wheeling. In short, if the theoretical maximum speed is what the wheel turns at full throttle when you are stationary and lift the wheel off the ground, your pedaling overcomes your own plus the bike's mass to reach that speed, but no faster. But the extent to which the wheel itself must draw on the battery to reach that speed (if you don't pedal as hard) obviously effects battery life (range). It would be interesting to see if the down-hill (or manual) braking effect could somehow be used for battery recharging.
Anyway, I hope this helps someone. Comments welcome.