Here is the exact bolt I'm talking about


The one that holds the battery down. Well the little threaded plate broke due to rust. I tried securing it but it is virutally impossible to clamp.
I need advice for removing it. I don't think I have a proper saw for removing it, I don't think I have a dremel bit that could handle a bolt that thick. I sprayed it with WD40 but still its too far gone. It might as well be welded.
I appreciate any help you offer!

That'* a tough spot to work in. Not sure how I would tackle that one. I am thinking small vice grips on the bottom and hope the bolt head snaps off? I just don't know. Maybe there is a member nearby with some different tools that could be useful.

Try the method Echo mentions.

Then I'd consider cutting the bolt head off with the dremel cutting wheel. It will probably take a couple wheels and a little time..but you will get it.

I know that if that were mine and I was sure that the bolt would not come loose, I would try to get vice grips or something on one end and then use my 4-1/2" angle grinder with cutoff blade to cut it off.

I'm assuming you don't have an angle grinder, torch, etc., so is there room to get a hacksaw in there with one person holding one side of bolt and you holding the other and a hacksaw? Even if so, not an easy task.

You could always drill the head off with the biggest bit you can find, use plenty of oil while drilling so the bit doesn't overheat and cuts nicely. Once the head is off, you can take that dremel cutting wheel to cut the stud off. Redrill the mount, and tap it. Will take some time to do but I think this is the most straight-forward way to do it.

An angle grinder would be perfect for the job. Too bad I don't own one or know someone who does. :(

I think the dremel suggestion will be the easiest given how small the space is. Before I pull out the big guns I'm gonna try "Liquid Wrench" and vice clamps.

Thanks for the help. With an 11 year old car in Minnesota I expect some rust. :?

Edit: Dremel did it. Cut the head off and slipped the bolt and nut through the bottom.

I second the advice to drill it off. Just put a half-inch metal-cutting drill bit in your drill and have at it, making sure to use plenty of lube oil while drilling out the head of the bolt. I had to do this on the brake rotors on a 1974 Corvette, to drill the heads off of five giant rivets that the factory puts on to hold the rotor to the hub. Just drill it out.