I just had that one lying around. But actually the high voltage ones tend to get up to charging voltage at reasonable rotational speeds. Rotating this onenwith a drill, I measured 12V open circuit at around 180rpm.
Using a 12V battery as a load, I measured 2A at around 1000rpm.
The wind turbine itself will probably never reach the 2A. Anything over 1A will probably only be reached at wind speed so high that there will be ample cooling.
I tested it with a drill and measured 2A into a 12V battery at high rotational speed
Did you have a diode between the motor and the battery? Did you reach the 14-ish volts that would be necessary to actually charge the battery?
At 2A you will have a significant loss of power inside the motor....
What is the resistance of the motor?
Well, no. Doesnât the battery clamp the voltage in the circuit to 12V, and only rises to 14V volts when charged? I mean, 2A were flowing so the battery was charging.
I donât know the resistance and canât measure it right now.
With no diode, the battery was actually "charging" the motor.
Yes, I had a schottky diode. I realize a slightly higher voltage is requird then for charging due to the voltage drop across the diode.
There was a diode
So, now that I have divulged the detailsâŚany tips or advice or suggestions or whatever on the torque control part?
I was thinking it might be similar to this:
Thoughts?
Is this a lead acid chemistry battery?
If yes, then they are charged initially at a constant current and a voltage of around 2.1 - 2.25 volts per cell for the first 70-ish% of charge. Then they are topped off at a constant voltage of about 2.3 volts per cell. A 12V battery has 6 cells.
The way your generator works under wind power makes me think that it would operate analogous to a solar panel so a MPPT charge circuit might be appropriate.
Any input from the forum?
I think the use of the term lead-acid battery is a bit misleading. MY AGM lead-acid batteries will not charge on a regular flooded cell battery charger. They need a bit higher voltage. So, which type does the OP have in mind?
Of course. I'm just attempting to get OP to engage in a dialog and give us all the information needed to help them with their project.
Yes, itâs a lead acid battery
You need an MPPT charger, which would be a custom design for that generator and expensive.
I'm also wrestling with the fact that getting 2A out of the generator at a voltage high enough to charge a battery at 1000 rpm seems to violate conservation of energy for the published motor specs.
Another problem would be the seeming incongruity of proper battery charging and being able to load the generator in such a way as to control its speed.
Does anyone have a thought about MPPT in this application?
I see @jremington is entertaining the MPPT approach as well.
Ok, maybe I do need an MPPT for charging a battery. But please bear with me; letâs say for the sake of argument, and learning, I just want to implement what I described here initially: set the charging current with dependency on rotational speed. How would I do that?
And by the way, I would also implement a charge controller which looks at the battery voltage to detect when it is charged and then diverts to a dump load. But Iâm not asking about that right now. I want to take one step at a time.
Well that happens automatically. More speed, more current. If you mean control the rotational speed by varying the load then I think that will require some sort of circuit that diverts some of the available current to an electrical load to apply reverse torque to the motor while using the rest to charge the battery. Bear in mind that the current usable to charge the battery will vary according to the state of charge of the battery.
Edit: I see OP has introduced the concept of dump load. That is what would be used to control motor speed.