Micro Hydro Help Needed PM Motor

[rtompkins]

Hi,

I am very new at all of this but here is what I've got.  I bought a 100Watt 24v Permanent Magnetic Motor, I welded a shaft and attached a turbine.  I hit the turbine with my water hose and it spins like crazy.  When I connect a 12v light bulb it lights up bright as can be.  I also connected it to a multimeter, I have no clue what setting to put it on but I tried the V... set at #20.  The display reads 15.4 when I run the turbine.

I have a 12v deep cycle battery that I would like to charge.  Could someone please tell me specifically what else I need?  I'm guessing something to drop it down to 12v?  Some sort of regulator?

Any help would be greatly appreciated.

Rich

[kurt]

"100Watt 24v Permanent Magnetic Motor"

would that happen to be a dc Permanent magnet motor?? it kinda matters on how to hook it up.

if it is a pm dc motor then you just need a blocking diode in series with the motor then just hook it direct to the battery and if you spin it fast enough you will start to charge the battery.

the battery will hold the voltage of the motor down to its level until it gets full at that point you will need a dump/diversion controller with dump load. a user here goes by the handle ghurd sells handy little dump controller kit and resisters for a dump load that would work pretty good for a 100w setup

[rtompkins]

Thanks for your response.  Yes, it is a 24V DV Motor.  Will the blocking diode reduce the Voltage to 12V?  The dump/diversion controller you mentioned, does this redirect the power once the battery is full?  I'm kind of worried about overcharging the battery.   Is there such a thing as a step down charge controller.  Something that will drop it down to 12V and take care of the overcharging problem?

Thanks again

[kurt]

http://www.fieldlines.com/story/2004/6/2/33325/13962

http://www.fieldlines.com/story/2003/11/4/124345/260

http://www.fieldlines.com/special/index_faq

read that.... then try Google searching the board for more info on the subject if you need it.

[Ungrounded Lightning Rod]

The blocking diode has nothing to do with holding the voltage down.  What it does is keep the battery from spinning the motor, discharging itself in the process.  Current can only go from the motor to the battery, not the other way around.

What limits the voltage is the battery:

 - The voltage produced by the motor is proportional to its speed.

 - The current out of the motor is proportional to the EXCESS of its voltage over that of the battery plus the diode voltage drop, divided by the wiring resistance (including the motor's coils).

 - The load on the shaft is proportional to a constant times the current out of the motor.

So once the motor spins up to where it's generating 13.5 to 14 volts or so, the current into the battery causes the motor to put enough load on the shaft that it stops speeding up.  Turn up the water pressure so the water is pushing on the shaft harder, the motor will speed up a little bit - enough to push a bunch more current into the battery - and that extra current will put a bunch more load on the shaft and keep it from speeding up more than the little bit.

The battery's voltage is nearly constant - rising only a tiny bit with increasing charge and with increasing charging current.

So the battery regulates the motor's generating voltage by regulating its mechanical load on the water turbine.  See?

[rtompkins]

Great! I now understand the role of the diode.  I'm going to go to radioshack and see what they have to offer.  However, I'm still a bit confused as to why a 24v motor/generator will not need to be stepped down to 12v to charge a 12v battery.  I think I unserdstand that putting a load on the motor will create resistance and slow down the RPM's, I realized this when I attached a 12v 50w lightbulb to the water turbine, the RPM's slowed down significantly but still lit the bulb.  

If the battery regulates the motor's generating voltage by regulating its mechanical load on the water turbine then I guess all I need is the diode and I'm good-to-go.  Hmmmm... but what about overcharging, isn't this where the charge controller comes into play?  

[ghurd]

Radio Shack.  About all they have for something like this is 276-1185, a 25A 50V bridge rectifier.

Put in on a heat sink.

Use both AC input terminals.  Change "PV" to motor.

http://www.otherpower.com/images/scimages/2050/BrgAsDiode.gif

Any open voltage higher than the battery voltage is sort of converted into charging amps.

Get it working before deciding on a charge controller.

G-

[rtompkins]

bridge rectifier?  Ok, this is something else I know nothing about, I'm a programmer with little if no experience with electricity.  Change "PV" to motor... What is PV?

[kurt]

PV is short for photo voltec panel or solar panel as they are called.... a bridge rectifier is basically just 4 diodes wired in a square potted in hard plastic usually used for converting AC electricity into DC electricity but you only need it as a blocking diode and it will work fine as that just wire it up according to the diagram. if your gonna run any current through it be sure to mount it to a heat sink like a big hunk of metal and use heat sink paste. (you can get that at radio shack) Google is your friend on this sort of stuff. there are hundreds of basic electronics tutorials out there on the net that explains what a bridge rectifier is and does with pictures and drawings and everything...  

you are not reading the links provided and doing your own research or you would understand that the battery pulls the motor/genny's voltage down to its level for charging. the battery decides the voltage and is perfectly happy doing that until it is full then you need to divert the excess current into a dump load to keep from overcharging the battery

[rtompkins]

Thank you all for your help with this little project.  I will post youtube videos if I can get it working.