Hello Oso,

You are saying that:

> Most alternators are rated at 6000 rpm, so it should produce the full
> 70 amps. You do need to subtract the excitation current from that, so
> I would not count on anything above 65 amps.
>
> Spinning it at that speed, the brushes are not going to last very
> long, 6-8 weeks would be my guess. If you cut the speed to about 3000
> rpm, the alternator should still produce 50-55 amps and the brushes
> will last a little longer, say 12-16 weeks.

I am wondering about this 12-16 weeks brushes life time. Some of us have 
cars which we mostly ride in the city, 90% of their life time, on which the 
normal motor speed is something from 1000-3000 rpm's. Usually there is 
something like 1.5 ratio between the alternator and motor shaft. Other 
people are mostly using their cars to run on highways, which means 2000-5000 
rpm motor speed. In both cases the life time of a alternator (including 
brushes) is at least 5 years, even more. It is that kind of equipment that 
you only change once during a normal car lifetime.

Am I wrong ? Am I right ?


Radu 





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