Jeff Morris wrote:

I'm curious - what are the heavy loads on these vehicles, and how much
do they draw? Not doubting, just curious.

A typical city transit bus can easily have a 200 amp load.

Summertime air conditioning, wintertime heating, not to mention all the
other parasitic loads such as marker lights, fans, etc.

Do refrigerator trucks run
off the alternator, or do they have engine driven compressors?

Every reefer I have ever seen has it's own stand alone system.

Lew