Ebike 2.0 Li
July 8, 2007
My second Ebike is based on a 2006 Giant Sedona ($200) with a few minor alterations. The motor is a Wilderness Energy brushed 36V (BD-36) ($325). The original battery was an 8 Ahr NiMH. Top speed on the flat was about 23-24 mph at first and faded down as the battery drained. After only about 200 miles, it was already losing some range. My commute is 14 miles one way and I don’t like dragging a big pack of nickel uphill.
I purchased 5 DeWalt 36V lithium battery packs (~$100 each) which have 10 A123 M cells and a charge controller inside. I tried using one battery pack to see what the range and power would be like. It died immediately. With a bit browsing, I found out that there is a 15A internal fuse. The control module was dead, but the cells were ok. With the four remaining packs, the bike would only go 18-20 mph on the flat because the DeWalt packs are really only 33V (10*3.3V) and this motor really wants 36V or a bit more.
So, I broke the fifth pack into five pairs of cells and with some soldering and an in-line 10 A fuse for safety, I made four “piggy-back” packs that are ~40V.
I stuffed four of these into the rear bag on the rack.
OK, OK it’s not very pretty, but it was my first test. I will try to clean up the wiring.
Even so, it worked well. Top speed on the flat is 25-26 mph and the range is 17 miles with light but steady pedaling. Now the real trick will be to see how many cycles/miles I can get out of them.
8 AHr NiMH 13 lbs batteries only (.61 Ahr/lb)
11AHr Li 13.5 lbs with a lot of extra case plastic and 4 charge controllers
11Ahr Li 9.8 lbs batteries only (1.12 Ahr/lb) (almost 2x NiMH)