Alternator charging kinda?

[mikedevore]

The charging system quit on my race car at the last race.
The volt meter only showed 11.8 volts.
I removed the alt. & took it to get it tested. All they had to show if it worked or not was a red or green light. It failed.
Bought a replacement, tested it & installed, still not charging.
Went & got a voltage regulator, still not charging. My Napa gel battery had run down & I put my Yellow top Optima winch battery in the car & charged it between rounds.
Won the race.
I bought a new Red top & installed it in the car.
Now, when I start the car, the volt meter stays @ 12.8 volts, after the car idles for 5-10 seconds, the voltage slowley climbs to 14.5 volts.
So I changed it out with another Alt. that I had in the shop, same thing.
Changed out the v/reg with a spare I had at the shop, same thing.
When the key is turned on, I have the 12.8 volts on the gauge, it also shows the same with a meter at the battery, after it starts & idles for 5-10 seconds it will slowley climb to 14.5 volts.
My question is, why does it not charge immediatly?

 

[RedFish]

Low alternator rpm maybe ?
Just a guess

 

[67Dart273]

Are you absolutely sure the belt is not slipping?

Have you one pulley that you changed between them? If so, any chance the pulley is too thin and not actually tight on the shaft?

Describe your wiring? Trunk mount? What sort of circuit, IE does the alternator go through a solenoid / relay to the battery?

Can you check at moderate RPM check first battery voltage and then right at the alternator stud, and compare the two voltages?

Repeat with a load on the system, IE fans, pumps, lights, etc.

A difference of more than 1-2 volts with the battery a little low means you have a bad connection/ voltage drop between the alternator and battery

 

[mikedevore]

67Dart383, you have given some other areas to check.
The belt is a used one & it is riding low in the pulley.