Electric Bikes - Is it possible to turn motor into Generator

Hello. I have very little knowledge about E-bikes and E-kits. I am wondering if there is a kit out there with possibly wheel hub/motor of which you could charge the battery via pedaling.

I am wondering this because I am planning on touring and still trying to work out some kinks and explore options. This option would be nice to know because I could potentially charge the battery without having access to an outlet (camping majority of the time).

Well...here's the deal.

1 kilowatt hour = 1 horsepower for 1 hour. If you have an empty 36V/10A battery pack (360 watthours, about .4 kilowatts), you need about .8 kilowatts worth of power to "fill it up".

It's been said that an average guy can put out about 200 watts of power for an hour, pedaling, so you would need about 4 hours of pretty hard pedaling to charge your battery, and that's without any of that effort going towards moving you down the road, which probably requires another 200 watts to go 10 to 15 mph on the level.

Physics suck.

Regenerative braking (or pedaling) is not as easy as it seems. Particularly with modern battery packs which have narrow ranges of acceptable charge voltage and current. If you are determined to do this as a lay person, I'd suggest a Bionx system, they've already done the heavy lifting.

It's been said that an average guy can put out about 200 watts of power for an hour, pedaling, so you would need about 4 hours of pretty hard pedaling to charge your battery, and that's without any of that effort going towards moving you down the road, which probably requires another 200 watts to go 10 to 15 mph on the level.

Physics suck.

Thanks for the input. I understand how hard it is to pedal with that type of resistance especially with the load I would be carrying. My reasoning that I did not care to mention would be that, while camped, I would have the rear end of the bike lifted on a stand and pedal purely the generator on nights where I did not have an outlet to plug into. There would be no way I would want to charge the bike while riding unless I had some type of downhill grade to help me out.

This option is likely to not happen for me, although, an ebike would be fun to have for my 10 mile single way commute to school. This current technology just does not seem practical for any type of long distance travel.

Don't tell that to Justin Lemire-Elmore who took an e-bike across Canada last year.
http://endless-sphere.com/forums/viewtopic.php?f=2&t=5652&start=0&st=0&sk=t&sd=a

The Bionx system allows for regenerative braking and regenerative pedaling. It is very hard to charge a battery back up that way. I had some first hand experience with it last week. I discovered that my charger was blown at work when I was trying to recharge. Since the battery likes to be charged at 50% or above, I decided to use the regen mode on the way home. At regen level 2, was working up a sweat while going about 6 mph. :p It took me an hour and a half to go 10 miles. I only got about one bar of charge out of my pedaling. Ugh.

Fortunately, it's still under warranty, and they've already shipped a new one out to me. :)

"Physics suck" Da*n right, I hate physics, ruins everything, all the best ideas are ruined by physics. What we really need are hand held cold fusion generators! I'd work on it if it were not for physics and a complete lack of knowledge on where to start and how to proceed. One thing I can tell you though - solar doesn't really work well on a bike. That da*n physics, again.

The best regen result I've gotten on my BionX (PL350) was being able to maintain slightly over half the battery's capacity (beginning with a fully charged battery and overly enthusiastic Monday morning throttle action) over the course of a week's worth of commuting (170kms approx).
Using level 1 assistance (uphills/headwinds), no assist (flats/tailwinds) and riding the various regen levels (level 1, flats/tailwinds, level 2 flats, levels 3 & 4 downhill) and/or regenerative braking (everytime I used the rear brake).
That is with me essentially running the battery down to midway in the first couple of days then taking a more conservative approach to how I used the assistance over the next few days and then using human power, inertia and gravity to recharge the pack at every opportunity.

Hello All,

I have also been thinking about what is possible or practible in a bicycle generator while you ride.

Currently I am working on adding an Xtracycle Freeradical (www.xtracycle.com) to my Cruzbike Freerider (www.cruzbike.com), a similiar bike can be seen at:
http://www.ecovelo.info/2008/05/25/gallery-johns-xtracycle-cruzbike/

Rather than using a freewheel on the rear, the rear wheel would either be an electric rear wheel, or just a regular rear wheel with gears. Since the bike is front wheel drive the gears on the rear wheel could be used to run a bicycle generator. The magnet motor, power inverter, etc... would be monted on the rack directly above the rear wheel. There is a lot of do it yourself bicycle generator links online.

I don't know how much our friend Physics would get in the way. Maybe with the right type of batteries, e-wheel, controller, etc... you could generate enough power to keep a spare battery charged up.

Any ideas?

Jeff

I suggest a high power charger and good batteries that can take a 30 minute lunch.. and an extension cord !( A123, PSI, few others.. ) There are usually outlets all over the place, even if you have to travel 1km to find one it's not really a problem in most places ( Justin made it with 100km streches between charges)

Hello All,

I have also been thinking about what is possible or practible in a bicycle generator while you ride.

Currently I am working on adding an Xtracycle Freeradical (www.xtracycle.com) to my Cruzbike Freerider (www.cruzbike.com), a similiar bike can be seen at:
http://www.ecovelo.info/2008/05/25/gallery-johns-xtracycle-cruzbike/

Rather than using a freewheel on the rear, the rear wheel would either be an electric rear wheel, or just a regular rear wheel with gears. Since the bike is front wheel drive the gears on the rear wheel could be used to run a bicycle generator. The magnet motor, power inverter, etc... would be monted on the rack directly above the rear wheel. There is a lot of do it yourself bicycle generator links online.

I don't know how much our friend Physics would get in the way. Maybe with the right type of batteries, e-wheel, controller, etc... you could generate enough power to keep a spare battery charged up.

Any ideas?

Jeff

Jeff, If you have taken physics you will understand the law of conservation of energy. Because of this, you will encounter losses via ambient temp, line losses, friction from road and aerodynamic surface area, etc. So charging a battery with another battery (essentially what your thinking) will not be linear in the respect of biking.

People have already explained how bad it gets running on regen mode with the bionx system, 10 miles in 1.5 hr is pretty bad. The only real practical way would be if the generator were extremely small, but then you could be encountering issues as to how the battery takes the energy. Batteries are very sensitive and if they are not controlled properly (charge/discharge controller) they will stop working, or worse, blow up or catch fire.

Another idea that may work would be to take a look at Ultra Capacitors.

Speaking of ultracaps :
http://endless-sphere.com/forums/viewtopic.php?f=6&t=7511&start=0

Doable.. but not practicle for most situations.