Just wanted to chime in as well. Mine does the exact same thing. Definitely not battery related. I would say engine temperature related. If it sits overnight and I start it in the morning cold, it will dip, it always only dips once and then steady and smooth from there. The colder it is the heavier it dips. One time only it stalled out completely and had to restart. It didn't bother me too much at first but I would love to get it solved.
EDIT: Here is my cold start