Wiring Advice Wanted for Bicycle Alternator

[onefunkeedrummer]

So after a few fits and starts, I've finally gotten a bicycle powered alternator built, using an old alternator from a car.  One wouldn't think that the wiring would be that difficult but, after every wiring configuration that I can logically concieve of, it still doesn't produce power.  Below are a few pictures of the design.

Now I know that the two smaller wiring tabs are the connections for the field current to the rotor coil, and the sampling current. The large post is the output that runs back to the battery for charging.  The way I was trying to wire it, there's a 14g wire from the + terminal on my marine/RV battery to the field current tab, and a 4g wire from the output post on the alternator back to the positive terminal on the battery.  

For starters, I've read elsewhere on the web that, when current is supplied to the rotor coil, the outside casing on the alternator should produce a magnetic field strong enough to stick small pieces of metal to, like screws or paperclips for instance.  None of the alternators I've been able to get for free have done this.  Does this rule of thumb hold true to your knowledge or is it some BS Wive's Tale??

I also wonder if supplying current to the "sampling current" tab is necessary for the alternator to produce power.  In vehicle alternators, the sample current tells the regulator how much voltage is in the battery so it knows when to increase or decrease current to the rotor coil to keep the battery between 12-14 volts.  I figured if there was no current supplied to that tab, the internal regulator would always read a sample current of zero and thus, be fooled into sending the maximum amount of voltage to the rotor coil (14V?).

Another question I had was whether or not some sort of ground is required to close the circuit.  One thing I tried was running a wire from one of the mounts to the neg. terminal on the battery.  Is this even necessary?  I haven't heard about any of these homebrewed alternators having a ground wire involved.  

I've tried everything I can think of to get these alternators to work and the only thing I can think of being the problem is that I have three dead alternators in my possession.  They all came from automechanics that didn't know if they worked or not.  Nevertheless, once I get ahold of an alternator that I KNOW actually works, it would help to have all of these questions already answered so I don't have to waste all of that time experimenting and risking getting zapped!

Thanks for any and all useful input you may have.

Getting a bit large on file size on those photos. I will leave it this time but please read the info on resizing photos for more friendly download. Lots of our users are on slow connections. Also resectioned to a more appropriate section.

[fungus]

As it is set up is there any connection to the negative terminal of the battery? I believe that for alternators the negative input/output is connected to the case since cars are negative ground systems that use the body for the negative/ground connection. This connection would definitely be needed. otherwise no current can flow.

Here is a site where an alternator is used for a pedal generator. http://www.c-realevents.demon.co.uk/altgen/altpedgen.htm

[jimjjnn]

Yep, Case is negative unless old style Ford which is ass backwards

[jimjjnn]

Also, I'd remove the regulator and install a potetiometer or rheostat so I could manually control the Field Current.

[alancorey]

How fast are you spinning it?  I've heard they need 1000 RPM or more.

  Alan

[Ungrounded Lightning Rod]

significantly more.

Engines tend to idle at over 1000 RPM and the pulley on the alternator is significantly smaller than the one on the vibration damper to get a RPM multiplication.

[hiker]

take the field wire and hook it to the batt. lug on alt...this will give full power to the alt. field...hook a ground wire to alt...then just hook the two wires to a batt,

alt batt. wire is + and alt ground -

looks like you have a external rectifier..discard that..

good luck......

[Flux]

Make sure you fit the warning light, these alternators use that as part of the build up.

Most will build up without it but may need 5000rpm.

Unless you remove the voltage regulator and use a switching regulator (buck converter) for the field you will pedal most of your energy into supplying the field unless you drive it at 2000 rpm.

The things are designed to produce high power from small size and low cost. For pedal power your main consideration is efficiency, that is not their strong point.

Flux

[ghurd]

I don't know about full power to the field.

Most fields take 5 to 7A?  Thats a lot of amps to make up for before making any power into the battery.  A lot of peddaling to break even.

Mostly sounds like a poor choice of alt to me. Wind related, but still worth reading...

http://www.otherpower.com/otherpower_wind_alternators.html

G-

[Nando]

There are three problems with car alternators.

1. RPM that need to be a bit higher than 1000 RPM for some power generation
   
2. The Regulator requires power to produce power, up to 12 % of produced power.
   
3. The alternator needs a power source feeding the field to start producing power, very few have good remnant magnetism and if so much higher RPM is needed.
   
   

Solutions try to have a small pulley for the alternator, ideally around 1.25 inches maximum that with the bike wheel if 26 inches in diameter produces 17.3 multiplication ratio that with a rotation of the wheel around 70 RPM the alternator produces around 1200+ RPM.

Remove that alternator Regulator and get a resistor in series with a 5 amps diode from the output to the field positive terminal, include a switch to cut the current fed by the battery, the negative of the field to the negative of the battery and alternator.

Resistor for the bias, human produces around 75 to 100 watts long term, so the resistor needs around 10% ( start a try) so around 10 ohms 20 watts resistor with capabilities to reduce is resistance value to obtain the desired working resistance and generated power.

To replace the resistor, ideally would be a small circuit that sets the initial output power and a current sampling resistor to reduce the current to a desired foot resistance workout.

An even better one, it is a controller with MPPT ( Maximum Power Point Tracking) that adjust the charging current depending on the workout desired level.

Nando

[Nando]

A better solution is to replace the alternator with a Bruhsless Permanent Magnet motor.

One that comes handy is the Ge ECM MOTOR, 1/2 HP that produces about 240 watts if rotated above 1200 RPM and does not need a field current.

This motor at 1325 RPM produces 130 volts Star connected and the windings can be re-wired to reduce the generated voltage as needed.

An alternative is to get TWO (2) Truck Radiator Fans and place them in a common 1 inch roller and the wiring of the motor in series for 24 volts production, up to 24 volts at 8 amps are possible.

Nando

[Norm]

If you were to substitute the right 30 volt Ametek for that alternator turning the bike

wheel just 60 rpm would probably give you enough charging voltage to charge a 12 volt battery.

It looks very nice ....you're just one step away from success. Wish I was that close in mine.

      ( :>) Norm.

         

[valterra]

What is gripping the chain on the bicycle wheel?

[hiker]

try a flat belt[auto]..woundnt have to worry about slippage..

toss the pully back on the alt...

heres a shot of a old pedgen i built a couple of years ago--blew up --lost all the mags on one rotor.............. :}

[gotwind2]

Exactly what I did - see my diary entry here - worked v.well

http://www.fieldlines.com/story/2007/3/17/181323/331

Ben

[onefunkeedrummer]

Yep, I've been doing it that way.

[onefunkeedrummer]

I've never heard of those two things in my life.  I really hope this doesn't have to be that complicated or I'm in trouble.

[onefunkeedrummer]

My estimations put the RPM's between 1500 and 2500 depending on the mechanical resistance.

[onefunkeedrummer]

Nope, the alternators I have are all internally regulated.  What looks like a regulator in the picture is actually a 2 pole toggle switch so I can cut off the field supply from the battery when the system is not in use.

[onefunkeedrummer]

I just have a few rubber rim strips with double sided tape between them and the rim and each other- spins the alternator great without any slippage when there's no power running to it.  The chain tension is adjustable with the turnbuckle on the outer support bracket (see picture) and I think that helps.  I chose a chain drive because it's low friction and reduces side loading of the alternator pulley.

[onefunkeedrummer]

The GE DCM Motor or Ametek sound promising but are they easy to wire up?  I don't know a whole hell of a lot about electronics so the KISS principle needs to be in full effect here.  I would also add that I'm very low budget!

[zeusmorg]

 I remember doing this about 10 years ago with some stuff i had sitting around. Used Bosch alt,and an old bike frame. My "gearing" was a bit simpler than yours though, i just pressed the pulley of the alt up against the tire. It did work! however it wasn't too practical once the regulator kicked in(got the thing up to a high enough speed to start charging) it was like CRANKING UP THE HIGHEST HILL KNOWN! My origonal idea was ok it's winter so i have to keep in shape, so I'll build this exerchargebike and juice up enough charge to power a 12 v light to do my nighttime reading by! I gave up when the exertion caused my front forks to pop out of the wooden rig I'd built to hold it.. that and the fact even as an ardent cyclist, i couldn't keep up the force required long enough to get much of a charge. If i do remember correctly it was a 12v 35a alternator.