Believe them.... but it doesn't mean it is true
Here is a link to using nodal.
http://www.swarthmore.edu/NatSci/ech.../mna/MNA1.html
Series resistance to DC power sources are not negated.
With this said, the internal voltage loss is a function of current.
Both of these are internet sources, but I will believe the one immediately above.
Better yet.... Forget what I said, I should just let believe as they may. That is what I do