On the 2012 Ford Escape the negative battery cable clamp is very different from the positive cable clamp. The negative has an upright bolt and nut that compresses a set of split bars when you tighten the nut. I have removed the nut but cannot remove the bolt as it has to be removed downward and the battery is in the way. The clamp is still blocked by the split bars and will not allow the clamp to be lifted and removed. So i ask, how do you remove the negative clamp from the post?
If this is what your battery clamp looks like:
Take the nut off from (in the image) right side. Then take the small piece under the nut off. The bar which goes through there should now be loose. Take a screwdriver an place between the two sides of the clamp just outside of the battery post, then twist the screwdriver to loosen the clamp up. You should now be able to remove the clamp by moving it back and forth and pulling it up. You don't have to remove the small bolt to get the clamp to release.
I just went thru that exercise. It turned out that the clamp had worn a groove in the battery terminal. You couldn't easily remove the clamp even though it was obviously loose. I finally inserted a tool underneath and pryed the clamp up and off. It took a surprising large amount of force for a little groove barely a 1/2 mm deep.