Recommendations on Power assist bikes?

Question

I was wondering if there is anything out there (power assist) that will help a bike go up hills that is powered simply by peddling the rest of the time? I was hoping to find something that doesn't have to be charged up all the time, run on expensive batteries, or run on gas. Is there such a thing? Something basically that is self renewing in power is what I'm hoping to find. It seems like power generated by peddling could be stored and used for something besides lighting?

If not what is the most energy efficient / cost effective way to go?

Answer 1

There are a few electric bikes that have a regenerative braking feature that can be used to charge the battery as you peddle. (It is like riding with a brake dragging)

The hassle is that there are a lots of losses involved in charging a battery this way. Drive train (about 5%) motor/generator efficiency(about 10-15%) motor controller (about 2%) battery chemical efficiency (10-25% depending on type battery. ) If your doing well only around 75% of the energy that you put in, will typically get stored in the battery.

The standard bicycle is generally regarded as the most energy efficient form of transport known to man. Around 95% of the energy put into a bicycle is turned into propulsion.

It is also more cost effective to leave the power assist off. Maybe investing in some lower gears is a better option.

A moderately trained cyclist can maintain an average speed close to the maximum legal limits allowed for power assisted bicycles (20 mph/32km/h). Putting a power assist on may help with hill climbing but will use more energy all round.

Still a power assisted bicycle is a lot more energy efficient than a car. Charging it from the mains will still be much cheaper and enerrgy efficient than driving a car.

Answer 2

Presently the Bionx system is the closest technically to what you are asking for.

http://www.birdrv.com/electricbike.php

http://www.bionx.ca/

they start at about $1,000 US.

But charging an assist e-bike from a wall outlet will cost about 4 cents a day.

check out this discussion groups notes:

http://endless-sphere.com/forums/index.p...

Answer 3

You're talking about a regenerative system, like a car, that uses pedaling in addition to braking to recharge the batteries. But you can't have a perpetual motion machine. Your pedaling power is most efficiently spent moving the bike, not charging the batteries.

That said, there are some remarkably good, efficient systems that will extend your range dramatically, or boost your top speed.  In addition, you can carry a lightweight solar charger to charge it while at work, etc. to be completely green.

BionX, Currie and Tidalforce make good systems. IMHO BionX is the best, Tidalforce is the most powerful (and has the best website) and Currie is the cheapest.