Oh right I never knew it extinguished, you still have a problem, you shoulden't have to rev it to start charging, agreed they are known for being a LITTLE lazy!

It's either lazy diodes or something is wrong with the field circuit (Check the thin blue wire WITH the ignition on, what power is present?)

Ideally the power at the battery should match that at the alternator, a common problem is the heavy duty cable running from it to the battery builds resistance over time and so you get a loss between the two (Akin to the fuel pump circuit) which, incidentally is another chronic weak point if you diden't know?

Martin