Well, it depends on how many mechanical connections are between the battery post and the spot where you checked inside the AS....and how tight and clean those connections are.
Every connection has a voltage (drop) penalty, so what you see could be normal, or not. Try cleaning each connection and re tightening each. Star washers are never a bad idea, as they really "bite" and make good mechanical connections.
"If the women don't find you handsome, they should at least find you handy." - Red Green