electric bike conversion

[acedovick]

I recently purchased 2 280 W, 36 Volt, 10.2 Amp generators.  I want to hook these up to a small 10lb flywheel which is powered by the pedals on my bike.   the motor I will be using is 2

P250 - Bionx 250 watt & NiMH battery

Motor     250 watts, 7.7 lbs

Battery     NiMH - 24V 8A, 9 lbs

these are motors housed right on the wheels of the bike

http://www.greenspeed.us/graphics/bionx/bionx_electric_kit-6.jpg

I dont know much about electronics and I was wondering since the 2 generators produce more power than is needed to run the motor.  how would I arrange the circuit to charge the batteries whenever the generators are producing more watts than the motor requires?

also these generators used to be hooked up to a treadmill which was geared so that a slow jog could max the speed of the generator.  so I know I will be able to max them out while biking.

any advice would help.

Moved to a more appropriate section.

[willib]

It sounds like a fun project

i honestly dont understand what you are tring to do though.

you have two motors , that you want to use as generators?

Do you want to generate electricy , or power your bike with the motors?

sorry but you werent to clear on that point.

[stephent]

Hmmm---2 of the 250 watt genny's? On one bike or treadmill?

You must be quite an athelete cuz most folks can maintain only short bursts of maybe 200 watts (doubtful) and 150 for short spurts and mostly 100 watts for longer periods.

Try using one instead.

[s4w2099]

I wish this guy were in my backyard pedaling for power.

"Lance Armstrong and his coaches, Chris Carmichael and Johan Bruyneel, popularized the importance of leg power (wattage output) in cycling performance. Two of the key strength factors are peak power output (PPO), which is the highest power in watts you can generate within a six to 30-second time period. Lance's PPO was well over 1000-watts, but what's really amazing was his ability to sustain high wattage out, referred to as mean power output (MPO), of over 400 watts at 83% of his VO2max. In relative terms, Lance's strength to weight ratio improved significantly over the course of his seven Tour championships. This translated into an 18% improvement in efficiency and power output."

[acedovick]

the 2 280W DC generators are brushless ones that use Neodymium magnets.  max is 2750RPM.  Its fairly easy to get them up that high.  these are great gennys.  I want to buy 2 of the motors (250W) that are connected to the bike wheels, have them connected to the output of the gennys.  the motors I am using come from a electric bike conversion kit.

something like this one

http://www.greenspeed.us/bionx_motor_bike_kit.htm

the flywheel is going to be powered by the bike pedals. the rear gear that normally powers the rear wheel will be moved to the center of the bike (where most battery packs are stationed).  this will enable me to stop pedaling for short periods of time and not have the bike stop on me.  

The Generators have been tested and it is quite easy to get them up to the required 2750RPM.  I am going to start off with one genny and one motor.  I dont have enough money right now to buy both the motors.  

Is there any way to set up a circuit so that when the output to the motor reaches 250W the rest of the current is diverted to charging the batteries?

[Bruce S]

acedovick;

   I had to re-read your questions and information a couple times today to try and get an idea of what you're trying to do:--)

Must be a lack of coffee or that it's Friday, something:--).

Here's what I think you're trying to do and what the possible solutions could be.

The hub motors are very nice to add to exisiting bikes, however unless you get a fraily large one they aren't very good starting from a dead stop, just not enough torque to really get going without really using down the batteries.

A couple questions:

The hub motors you're going to be using ? do you have the control circuitry for them?

Some of these have regenerative circuits in them that will go a long way to doing what you're wanting to do.

Are you also going to have some other energy storage device other than the flywheel? i.e. Supercaps or battery?

Circuits can be built to do what you're wanting to do, and the circuits for the hub motors and the Hieztmann<-sp? add-on motors and controllers thave this already built in, they don't kick the motor in until a certain speed is attained by the pedler.

Some of the things you might want to look at is weight. The flywheel and generator may exceed the safety of the bike ( not so much of a problem if this is a trike or quad).

Is it possible for you to post pictures of the generator and flywheel?

How good are you at mechanics? moving the gearing from the back wheel to the middle is not a trask to be undertaken by a novice. You'll need mig/tig welding abilities and certainly a drill press with highspeed high tinsil strength bits to be able to mount the stuff, plus the flywheel will need to be both statically and dynamically balanced to keep it from making the bike shake uncontrolably at the high rate of revs you'll need to keep the gens at power-producing levels.

Hope some of this helps and do upload pics if possible of all parts involved so we can help as much as possible.

Bruce S

[southpaw]

Sounds like propelling the bike with 2 hub motors and driving 2 generators with the pedals to charge the batteries and supply the hub motors with power, using no mechanical connection between the  pedals and wheels. Interesting, but probably not as efficient as just pedaling a normal bike. It would allow you to pedal at a constant rate and if you could keep from falling over could pedal at any speed even when stopped. Or perhaps I'm way out in left field.

[acedovick]

there is a regenerative circuit in the kits.

"GENERATION

Bionx offers four levels of power generation. Regenerative braking activates when the rear handbrake is used. It is possible to charge the Bionx battery pack by pedaling against motor resistance. Generation mode makes it harder to pedal so its often used when going downhill. Please note that the generative mode does not replace the existing brakes, but considerably increases braking quality, especially on extended downhill runs."

There will be batteries as well.  It is going to be a Trike.  I am taking welding at BCIT and the shop at the school has all the equipment I need.  I am basically dismantling a bike and using the parts on a frame that I will be building at the school.  

I am upgrading some other courses while I am taking welding so that I can get into the precision machining course later on.  I'm sure I will be able to get the flywheel balanced.  

I still have a bunch of money that I need to save up before I can buy the parts I need so it will be quite a while before anything is starting to be assembled.

the gennys I have say this on the labels.

Model :MY1016

Voltage 36VDC   Rated speed 2750RPM

Rated current 10.2A   Output 280W

http://Http://www.unitemotor.com

I hope that helps.

[acedovick]

yes that is sortof the idea.  I can be stopped at a light and pedaling at full revs still which would extend the battery life.  the project is intended to move from the 1 seater trike to a 2-3 seater quad that all the people in it can pedal to produce power while in there at whatever speed they wish.

[Lurker 417]

A good bicycle drivetrain is commonly said to run at about 97% efficiency. That's pretty hard to beat.

[ghurd]

But that's not with a Wally-World $99 Huffy.

"Good" bearings, sprockets, chain, etc are not cheap.

True story.  My wife and her brother were doing a charity ride.

Down hill, he had to pedal his Huffy to keep up,

while at the same time, my wife had the brakes on with her Cannondale.

G-