Charge controller for pedal power?

[jawnn]

We hooked up an exercise bike to a motor and found that it is very hard to push the last bits of electrons in the batteries, and the bigger the harder, so I am thinking that an adjustable charge controller will make it easier by pushing less into it.
Is that possible???

And where can I get such a controller?

The next machine will be a bicycle with different gears so I may not need it. But I will need a charge controller of some sort.

[Bruce S]

You could use a controller made for either solar or wind, but without more specifics it'll be just guessing :-).
The reason it gets harder is the battery's way of telling you its getting near full on charge.
Could you post specifics of your pedgen? and battery size(s).

[hiker]

put a bigger pulley on the motor so its not so hard to pedal...[you can make one out of plywood -just stack them togeather for the right width]
made a few of those in the past--used car alts- motor conversions-home built alts-
have fun.......................hiker.  i tend to ramble on so you can kill the vol. if you want !!!   ;}
    http://www.youtube.com/results?search_query=hiker71453

[OperaHouse]

Need a few more details.  Likely your battery is 12V and your generator
can produce a lot more than that at the desired speed, say 30V. For a
normal sustained pace you will produce about 50W and short periods about
100W.  At different charge levels the battery will have different loading,
but this is a red herring and should be ignored.  That said you need a step
down converter to match the generator to the battery.  I would measure the
voltage of the unloaded generator at the speed your rider prefers. Report that
along with the battery voltage. 

Normally these just regulate the output voltage.  You would also need to
regulate the input voltage.  Otherwise it would feel just as it does now.
Regulating the input voltage means that the converter does not even turn on
until a certain soeed is reached that represents say 28V.  Going over that
speed will be progressivly harder.  A rider could select any speed they prefered
and still have efficient transfer of energy.

Normally I would suggest going to ebay and finding a 100W step down converter
from China. I wrote a thread a while back that operated a solar panel at its power
point in exactly the same way. The 100W range falls in the converter hole of
offered products with open construction that can be easily modified.  There are
a couple in the 50W range that could be used in parallel.

Another option would be to use a 555 timer and a FET similar to motor speed controls
offered on ebay.  These would connect the battery to the generator for a percentage
of time.  These would control loading and not have speed knee.

[jawnn]

This is a good answer, even if I do not understand it.
What is a FET? And what is “speed knee”?

A schematic would help…sound like a pulse width modulator, something I need for a different project.

Yes 12 volts and we got the pedal generator up to about 40 volts without a load.

[Bruce S]

Might be different for some, but for me speed knee is that extra push you give during the down push of each knee.
The known open voltage is a good reference for deciding which controller to get so it can handle spikes , say if you disconnect the loads on purpose or by accident, but its more important to know the max voltage and current you'll be getting from the pedgen and using to recharge the batteries.
PLUS you'll want one that hold the max voltage to the type of batteries you are using.
Bruce S

[dave ames]

A brushed pm dc motor as a generator with an unloaded voltage of 40vdc?

Should be able to work in a PWM regulator between the generator and battery to vary the power taken off and control the pedal effort level needed to something that can be sustained.

Been using this one in this scheme for many years.
http://www.electronickits.com/kit/complete/motor/CKMX066.htm



We put it in an enclosure with some metering and mounted it on the handle bars:





Our wacky wiring diagram..we have since moved the meter to the battery side..Note the voltage jumper and current flow thru the module..(the battery pack is connected to the motor outputs)


Great fun!
Cheers, dave

Any pics?

Also note that the pair of irf1404's (the FETS) are only rated at max 40vdc..I have seen an open voltage of around 50vdc with a fast pedal and low duty cycle setting without smoking the unit.