starting up of the alternator

Hello my USfriends. When I start the motor of my excella, the alternator doesn't produce more than 11.5V. I have to accelerate once to 3000tr/mn for get a voltage of 12.5V (on the batteries, and 13.5V on the diode bridge but my main battery was low ). After 3000 tr, when the engine get down to 1000tr, the voltage rest ok 12.5V.

So when I drive, if I never pass through 3000, my batteries will not reloaded !

Is it normal the alternator doesn't begin to produce down 3000tr ? And no more than 13.5V ?

Thank you ( ouf ! sorry for my fran-glish :sad: )