Looking for a way to save gasoline last year, I found some electric bicycle conversion kits on eBay. I chose one that seemed to be in the middle range of power, and fairly cheap at about $369 dollars.
http://cgi.ebay.com/...
The following describes what I bought, how well it worked, and what I recommend to others in that area.
Prices and kits vary, but this is the one I bought and installed on a cheap Murray mountain bike, which I inherited from my brother via a local yard sale. 600 Watt motor, some control stuff and wires, plus three heavy lead-acid batteries that sit atop an included rear rack. Took a few hours to assemble, a day to charge, and now it's ready to go.
The motor operates at 36 Volts, which means the battery pack charges at 36 Volts. Battery pack is 3 x 12-Volt lead acid batteries, wired in series. The kit comes with a charger that plugs into a 110 Volt AC outlet, rectifies the juice to 36 Volts DC. Ideally, such a kit (including bicycle) should be available at Target (they do have some decent candidate bikes for $100 to $200), but today it appears to be hobbyist turf.
We all know that bicycles are extremely efficient machines, much more so than any car. Using slightly more than half a kilowatt of power, this motor can send my bike zipping along at about 15mph for almost 15 miles, with very little pedaling. With active pedaling and high-pressure slick tires, range goes up quite a bit. In comparison, an electric car takes in the range of 20 Kilowatts or more to operate in traffic.
Theoretically, this bike should allow me to visit the local grocery store several times and bring back a bag of groceries, all without ever firing up my 2-ton automobile. In practical terms, after each ride the lead acid battery must be topped off to avoid losing capacity. If an outlet isn’t nearby, you’ll need to disconnect and carry it to the recharger. Lithium batteries are nowhere near this finicky. They can sit in a partially discharged state with little or no degradation.
A major consideration is climate. For instance, as I’m writing this, it is early spring in Minnesota. Riding any bicycle in sub-freezing temperatures is somewhere between freaking nutty and downright stupid. Spring is a little better (30’s to 50’s F), if you wear gloves and a helmet. Always wear a helmet, especially with a powered bike. They go unnaturally fast, and unexpected inertia can be a real bitch, especially as you round a corner and roll through a pile of sand...
About the time I was going to finish this, a fellow on eBay wrote me a message asking my recommendations for his own electric bicycle. After answering his query, I realized it was approximately what I intended to write here. Here’s the letter.
Letter to eBay Guy
A fellow traveler on eBay asked me what I would recommend in an electric bicycle for himself, taking into account his artificial knees. This should answer questions for people with any similar mobility problems.
- Electric bicycles really work. It’s not a bogus technology.
I got one of the cheapest kits available for about $369 dollars. For that I got a 600 Watt motor for the front hub (the only way to go), a lead-acid battery pack, a converter, and a thumb controller. After some frustrating delays the kit arrived a month late. I took my time and had it together in one day. A little trouble with a fluky connection, but not too bad. Then winter hit, so the bike stayed in the basement for a few months. In the recent warmer weather I finally got to test it. Works quite well. Today I froze my face off riding around the lake. Bring gloves, sun glasses and a helmet, because the electric bike's top speed is a bit faster than you might expect.
- If you plan to use it extensively, get one with LiFePO4 lithium batteries.
My el-cheapo kit came with lead-acid batteries, which will start to lose capacity after about 200 cycles. That's fine for occasional use, but not acceptable for a commuter. For that, pay the extra money and get the lithium batteries, which are much more rugged, hold at least three times more energy per pound, and will store a full charge for more than 2000 cycles. The three motorcycle gel-pack batteries in my kit weigh about 25 pounds and sit like a boat anchor on the rear rack. An energy-equivalent lithium pack would weigh about 15 pounds. Less bulky, too. Plus, every pound you subtract increases performance and range.
- If you weigh more than 200 pounds, get stronger motor, like 1000 Watts.
A 600-Watt motor gets my 250 pound body up a medium hill, but just barely. Acceleration from a dead stop is sluggish, so it's best to help by pedaling. Top speed is about 16mph. A full 1000 Watts (1 Kilowatt) would get me up a steep hill (pedaling optional) and probably would get me up to 25mph on flat road. They can go faster, but they're governed. Sub-1000 Watt motors are probably fine for smaller humans.
- Convert a used women's mountain bike.
A beach cruiser would be good too, or any bike with front and rear shocks. At least get one with a cushy seat. The step through design is handier. Put a wire basket ($20) on the front for groceries. The mountain bike I got was given to me by my brother, who got it at a garage sale. Kind of a nasty old Murray, but it works okay. Cheap bikes with tubular steel construction actually work best, because their frames and thick, sloppy welds can take the pounding from extra weight. Try to get a bike without knobby tires, because they drag too much. Electric motors love low-drag tires. I bought low-drag 100 psi slicks for $35 per. Big improvement in performance.
- For artificial knees this could be a great help.
I think in your situation I would get the full 1 Kilowatt motor and a good lithium battery pack. This would give you a good safety factor if your knees were really hurting and you had to get up a hill. The thumb controller lets you adjust the motor to help you as much as you need, from full pedaling to not pedaling at all. Of course, 25mph is far too fast for a bike trail, but the extra power on steep hills might come in handy.
- Pedaling is optional, but do it anyway.
The hub motors make very little noise (a faint whine), and they aren't visibly obvious, but I rather doubt if it fools people when somebody cruises up a hill at 15mph without pedaling, so you probably will find yourself at least "faking it" most of the time. Thus, you will get some exercise. But no more than your sore knees can stand!
The Skinny
If you really want to ride around on a functional electric bicycle where pedaling is truly optional (even on fairly steep hills), then get a 1000 Watt kit, a LiFePO4 battery (rated for 1000 Watts), and mount it on a sturdy mountain bike, preferably one with shocks and a cushy seat. If you have problems with arthritis or joints or just plain stiffness, then screw the gender stuff and convert a women’s bike. Get the front wheel conversion kit, because it’s a lot easier to put on, it doesn’t interfere with your original gears, and it divides the weight more evenly. Then put a nice little $20-buck wire basket on the front, because the whole point is to park your 4,000 pound car, right?
An example of a robust men’s conversion kit from eBay...
The delivered price for the complete kit (minus bicycle) should be around $850 dollars. If you can find better deals, do tell!
1000 Watt conversion kit (no battery)
I searched eBay for "electric bicycle kit 1000W"
http://shop.ebay.com/...
48V 20Ah battery
Important: Ensure the advertised battery is rated for 1000 Watt output. Many of them are rated for 500 Watts or less, which could fry your electronics.
http://cgi.ebay.com/...
Now, if everything goes well with shipping and stuff (check the reviews before buying!), then with a bit of patience and tinkering you should have a working electric bicycle within a month or so. Once assembled, this kit should get you around town for quite awhile, at least 1000 recharges, by which time better batteries may be available.
Meanwhile, always wear a helmet, sunglasses and gloves, don’t round corners too fast, watch out for piles of sand, beware of cars, etc, etc. And don’t think electric bikes are sexy. They are practical. If practical ever becomes sexy, somebody let me know.
Future Outlook
Where is my flying car, anyway? More realistically, the main factor is batteries. The short-term future will see better Lithium cells, but they’re at least a couple years away. During the interim, LiFePO4 batteries are far better than lead-acid or NiMH or the older NiCad crap. Lithium costs a leg (over $500 for a good pack), but it’s worth it. Lead-acid battery packs are cheaper, but they’re very heavy, finicky and start to lose capacity after only a couple hundred charge cycles.
Another area of improvement will be in the bicycles themselves. Although a cheap mountain bike is great for a kit, it is hardly the end-all of electric bicycle design. Schwinn sells some very nice triangle frame hybrids with batteries incorporated into their tubular frames, if you’re willing to fork over $1,200 or more. However, a well-designed recumbent hybrid electric would certainly be much more efficient, especially one that incorporated a wind-cheating faring, regenerative braking and gears. A 1000-Watt rolling lounge chair could easily keep up with neighborhood traffic (up to 30mph), along with a briefcase and a bag of groceries. Kits for such bikes are available today, but factory-built hybrid ‘bents have yet to appear. I betcha they’re on somebody’s drawing board, though... ;-)
One More Safety Note
A 1000-Watt electric motor will propel a 250lb. human to at least 20 mph on level ground, and it will reach that speed quicker than you realize. 20 mph may not seem impressive, but on a bicycle such speed carries serious consequences. Most people cruise on a bicycle between 10 and 15mph. Faster than that is considered obnoxious to others, but even more important, because Kinetic Energy = Mass x Speed SQUARED, the kinetic penalty for hitting a tree rises exponentially as your speed goes up. A wise man (The Tick) once observed, "Gravity is a harsh mistress." Verily so, but Gravity’s bitchy sister is Inertia, and she will mess you up far in excess the proportion that you tempt her surly nature. Heed you this warning, who seeks thrust from electrons as might cliff jumpers dressed to mock the flying squirrel.
Tip: If your electric must climb steep hills, remember that the same powered kit with smaller wheels will have greater torque (stronger pull) but less speed. Thus, a kit with a 1000 Watt motor will climb a steep hill more easily if its wheels are 20 inches in diameter rather than 26 inches. The effect is exactly the same as running the machine in a lower gear.
Question: Why do all LiFePO4 batteries come from China? Can't America make batteries?