[Swiftbow]

I did a simple measure of how much voltage drop the battery experiences with my cars fan:

No fan - 14.45V
First setting - 14.40V
Second setting - 14.35V
Third setting - 14.31V
Fourth setting - 14.27V

I have this data but don't know how to apply it for determining power drain. The car is an '09 Focus. I tried googling to find alternator specs but was unsuccessful. On older Focus's the alternator was 105amps. I would suspect mine is probably close to this but even if I use this value, isn't this only true at high rpms?

Would the equation Watts = Volts x Amps be applicable or is there a change of amps with rpm?

I also wonder if I can further use this to calculate horsepower drain by Hp = (Volts x Amps x Efficiency) / 746 But I don't know what to use for efficiency and I once again wonder if efficiency changes with rpms?

Anyway, if some of you could help me make some useful information from the voltage measurements ... I'd appreciate it!

Doug