Here are the top three questions we get in the shop on electric bikes that recharge as they are ridden:
1." Do you have that electric bike that recharges itself?"
Regenerative braking is marketed as the holy grail of electric bikes these days as people dream of infinite battery life. But while it is true regenerative braking does extend your range by up to 10 percent, you have to ride 200 miles downhill just to charge the battery enough for a 20 mile ride.
2. "How long do you have to go down hill before the battery is fully charged?"
Theoretically, you can go down hill and recharge a bicycle without a charger or wall outlet. If you ride a bike with an electric motor kit like the BionX in regenerative self-charging mode 4 down a very steep hill, the electric bike completely recharges itself after about 200 miles. Of course, it is a little hard to find a 200 mile stretch of continuous, steep downhill!
3. "Do I have to pedal to recharge an electric bike?"
The answer is, sadly, yes (very much so). BionX correctly advertises their regenerative feature as exercise mode. If you set your BionX system to recharge mode 4 you will get a very good workout, but not an efficient way to recharge the batteries.
So there isn't a bike that will magically recharge itself, and you can't recharge your battery by pedaling for 10 minutes out of your commute. You can have a bicycle that recharges itself (with a little help from you) if you are into a very good workout. On the other hand most people use electric bikes for their intended purpose, making it super easy for the rider to get around!
If you have an average electric bike or a conversion kit, like the EZeebike or BionX motor kit, they are typically rated at a continues 350 watt output (around 700 watt peak or one horse power at takeoff). If you are in decent shape you can produce around 80 watts of energy by pedaling, so it would take about 5 to 10 times longer to recover the energy you are getting out than it was to spend it.
This might sound inefficient, but an electric bike is still the most economical, environmental, and most sustainable form of personal transport. There's just not an electric bike that recharges itself... yet... or anytime soon (unless they change the laws of physics)
The electric bike that comes closest to recharging itself - or charging up as you pedal - is the Sanyo eneloop electric bike. Sanyo has developed an "energy loop" system which senses excessive momentum (when the bike is trying to push beyond 16 mph on a downhill stretch, or when the brake handle is applied) and then converts this extra momentum into energy to charge the battery.
Because the Sanyo eneloop electric bike is very light, has a low wattage motor and a lightweight battery, it could be the best electric bike next to the impossible. The Sanyo eneloop electric bike is probably 2 to 4 percent more efficient than a BionX motor kit, although the BionX is more powerful and has longer range per charge.
We all want something for nothing, but before you call up asking any of these questions, consider the following tried and true wisdom:
1.There is no free lunch!
2.You gotta give a little to get a little.
3.What goes up, must come down.
4.Perpetual motion machine, yeah, wouldn't that be nice!
5.If it seems to be too good to be true, it probably is...