Two Batteries?

[*BN*]

Duramx Trucks come with Two batteries and TWO alternators?
One battery starts the engine and runs normal functions, what is the 2nd battery and alternator for?

[Beer-30]

Diesels have two batteries 90+% of the time. Glow plugs take alot of current, and extra help for the starter with outrageous engine compression. (17:1 or so). Some passenger car diesels have only one batt, but every pickup I have seen has duals.
The second alt is optional. Usually for work trucks/service trucks that may want an arc welder run off of the engine. Also, some types of service requires it. Ambulances to name one.

[ChumpChange]

Duramx Trucks come with Two batteries
It's to help jump-start fords. :D