# Calculate Dynamo Max Power Output

1. Jan 15, 2010

### El_Guapo

Hi,
I have a small DC dynamo (with no spec sheet) which i digitally sample to find it's voltage at any given time. I want to display theoretical max power output, how can I calculate this?

Can I use P=V^2/R where V is measured. How do I calculate R? I read a wikipedia article which says to calculate the ac resistance of the dynamo and take the load as equal to internal resistance of the generator (max power theorem.) Will this work...I'm not too sure what I'm doing on this one. Thanks.

2. Jan 15, 2010

### GRDixon

I would use P=IV, and graph IV vs. various loads (external resistors). But be aware that very low (or no) resistance could result in very high current outputs, and might "fry" your dynamo.

3. Jan 16, 2010

### El_Guapo

But I know the maximum power will occur when the load resistance is equal to the internal resistance so I guess I could just measure the current flowing in this circuit. I'm just after a single number to act as a conversion factor to kw/h.