@Brad-Tittle Thanks for this, Brad ... saved me a bunch of time. I didn't get anything on my LCD until I cranked the contrast pot all the way to its limit I connected the backpack to 5v on the expansion dock (first attempt was with the breadboard dock, which doesn't have 5V). seems like bad design on the backpack the backpack should be 3v not 5v.
TL;DR: Serial LCD backpack is 5V.
-- pryankster