Charging Battery with Alternator - Warning

Have had to do it myself,but i dont make a habit of it.

Had a crew that would work with the truck radio playing,and run it dead constantly.
It was equipped with an isolator and a second battery for a winch.
So they would use it to boost.
Smoked alternator and burned up several isolators. Finally the cause came out in a discussion,put an end to misssd diagnosis and comebacks.