There are a couple of places online for instructions, but for some reason, they dont say how to get the case open.  So here ya go.  Press along the seem with a flat head screw driver straight into the seam, CAREFULLY.  You dont want to go through, just crack the epoxy seal (you will hear it crack).  Then VERY CAREFULLY pry the case open a little bit at a time.  Remember that stuff in the batteries can severely burn you.  I found out by trying, LOL, so here is a pic of the cells inside.  Sorry for the blurry photo.  The cells are Panasonic.