Control load torque on generator

In my project I am using a DC motor as a generator to charge a 12V battery.

I want to be able to control the load torque on the generator, as it is rotating, by controlling the charging current into the battery.

My understanding is that the charging current could be varied by switching a MOSFET using PWM from the Arduino.

I guess what would essentially be happening is that the switching varies the electrical load seen by the generator.

Am I right in assuming this can be done and the MOSFET and PWM is the right way to do it? If so, can I have a suggestion as to what the electrical circuit should look like: e.g. do I need more components, how would the MOSFET be wired etc.?

PWM is a digital way to convey an analog value of between zero and one hundred percent, no more and no less. The PWM signal is either full on (high) or full off (low) at any time. 20 percent time high is 20%. It is a digital not an analog signal.

It ONLY varies the TIME the load is connected, not the actual load.

You should be using a charger specifically designed for the type of battery you are using. Use one that allows you to vary the charging current.
Applying the output of a generator directly to a battery is not a good idea.

Yes I am aware that a charge controller should be used when charging a battery. Let’s assume I have that in place.

Now, can you answer my question?

Ok, yes true, I am aware of that. And how is that related to answering my question? Could you elaborate a bit?

What is the maximum current to be regulated?

Assuming you have a charge controller as you claim then all you need to do is change the charge controller charging current.
A lower current will reduce the load.

@barrydol
Permanent magnet? Brushed or brushless?

This is incompatible with using a charge controller on a battery, which prevents the battery from being destroyed by overcharging.

For useful advice, you will need to provide quite a bit more information about your entire setup. See additional questions above.

Does the motor, which you are using as a generator, have field coils or does it use permanent magnets? I suggest if field coils then you need to control the field current.

2 Likes

What is rotating the generator shaft?

2 amps

Permanent magnet. I think it is brushless, but I can’t find any datasheet.

Unless someone corrects me a brushless DC motor is really a 3 phase AC motor with a built in inverter to drive it. Not capable of being a generator.

Permanent magnets unfortunately.

I think of the defining characteristic is that it has a permanent magnet rotor. You might have to disconnect some of the control circuitry but it should work as a generator.

I don’t think that is relevant to my question and I’d prefer not to get into it as it will distract from the actual question I am asking.

It works as a generator. That much I know. My question is not related to that.

It will work as an alternator.