I ended up leaving it on the post, but unclamping the two clamps that hold the two positive wires.
That wasn't easy either, but if you wedge a screwdriver in between the wire and the clamp, you will be able to pop out the clamp. When you do that, you can remove the plastic battery cage.
Hopefully you won't have as much of a problem as I did with the new battery. The replacement I bought was a little bit taller (Maybe a quarter of an inch) and it was extremely difficult to get the hold-down bar on.
Don't forget after you do this you gotta go to each window and manually lower/raise each window (at the door) otherwise only the drivers window will work at the master switch (And none will have auto up/down)
Had to replace the battery today. Saw this post and thought I'd post a pic of the clips. You need to insert a screwdriver in the slot(s) and it will pop off, repeat on other side. The only issue is it is very tight in there/awkward to get at. Took me a few minutes to figure out how to get even my short screwdriver down alongside the box.
I had to replace my battery today and understanding how this clamp worked helped but I could not get a short slotted screw driver to open it. I discovered taking a pair of needle nose pliers and pulling in the direction its supposed to open popped them right off in about 5 seconds. I wished I had done this first and not wasted 20 minutes trying to get that thing off. They popped right back into place when I put the battery case back on.