Charging System Question

[auto10x]

2006 6 L. I have monitored the system voltage and have noticed the following: Voltage before startup is 12.6. When I turn the key on and wait for the glow plugs to heat up the voltage is about 11.5. Engine starts right up and voltage is about 11.8 - 12. Approximately 1 minute after startup the voltage instantly pops up to 14.3.

The question is; why does the system wait about one minute after the engine starts for the charging system to pop up to charging voltage - 14.3? Why does it not begin max charge rate immediately upon startup?

Thanks,
auto10x
Bill