Removing a rusty bolt from a battery clamp?

[Brian Elfert]

I have a standby generator with a small car battery to start it. I added a trickle charger to keep the battery charged. The battery finally gave out after 10 years.

The trickle charger was overcharging the battery which caused the bolt on the battery clamp to corrode. I assume the battery clamp is lead. I cannot for the life of me get the corroded bolt out. Any suggestions to get the corroded bolt loose? I am replacing the battery charger with a better one that should only charge the battery as needed so it won't overcharge.

[Gordon Eyre]

Use a wire brush and common household soda and brush well. Dry off the bolt and then soak overnight in a light grade of oil. If that does ont work, cut it off with a hack saw and replace with a new one.

[Stephen Tashiro]

The trickle charger was overcharging the battery which caused the bolt on the battery clamp to corrode.

Can we visualize this as a terminal bolt on a car battery? Or is it completely different?

On a car battery, if hand tools don't work, I'd apply penetrating oil to the bolt. Then, after letting it soak, I'd grab the square end of the bolt with a wrench or pliers and I try to remove the nut with a 6 point socket on a cordless impact driver (the kind of tool that carpenters use to drive screws - you can get a square bit for it that will hold a socket). If this removes the nut or snaps the bolt in two, then you're done. If it rounds the bolt off, then I'd get the kind of socket that's designed to grip rounded bolts and use an electric impact wrench (as opposed to an impact "driver").

Of course, that procedure depends on having enough clearance to use the tools. (On car batteries, I have to use a thin wall socket and an extension.)

[Dave Ogren]

The penetrating fluid that works great for me is "Thrust" made by Castle. Hard to find might have to call the factory and see who is the distributor in your area. Thrust has never let me down in all of the years that I have been using it, about 20. Then again a new terminal is fairly inexpensive. Good Luck.

[Brian Elfert]

This is exactly the same as a terminal bolt on a car battery. I managed to get the nut off no problem. I just can't get the bolt out. I'll have to try soaking it.

Replacing the clamp would be difficult. The clamp is made of lead or some other relatively soft metal. It isn't a stamped steel clamp like some cars. I have no idea how I would crimp on a new one. I looked at pulling the whole cable out, but the other end runs around the back of the generator where I would have to take the whole generator enclosure apart.

[Jim O'Dell]

You can get new battery clamps that cinches down on the wire. It's not the best to keep out future corrosion, but if you seal it good you should be ok. If you have a torch, you could soak the end with solder, that would help with the corrosion. For that matter if you have the torch, there are cable ends you fill with solder and the end of the stripped cable into to make a better/sealed connection. An ample glob of axle grease works pretty good to seal out corrosion too, but it attracts dirt. Go to an auto parts store like Auto Zone or Pep Boys or the like and you'll find the cable ends I'm talking about. Jim.

[Scott T Smith]

Brian, the head of the bolt is usually square and locks into the battery clamp. Also, when you tighten up the bolt the clevis part of the clamp deforms, usually putting the bolt into a bind. The first thing to do is to totally remove the nuts, leaving just the bolt. Next, place a flat head screwdriver in-between the ends of the clevis on the clamp and gently force them apart, removing the bolt from being in a bind. Then, add some penetrating oil to the rest of the bolt and use either a 1/2" open end wrench of vice grips on the head of the bolt, gently moving it back and forth about 1/8 turn until it frees up and can be removed.

[Fred Perreault]

Brian, like Scott said, assuming it's a top post, you have to take a tool and twist/spread the battery clamp apart to get the old bolt out. When you do this, it's likely that you will loosen the clamp enough to have it probably pop up off of the post. Battery clamps are usually lead or antimony, but some are harder of a brass type alloy. If the clamp hasn't decayed as badly as the bolt, then just cleaning it up will work fine. The large flat head screwdriver trick usually works well. There are battery terminal greases that work well when smeared on the reassembled clamp and post.

Good luck, Fred

[Jeff Monson]

There are battery terminal greases that work well when smeared on the reassembled clamp and post.

Good luck, Fred

Yes, and spray paint works very well also.

BTW, solder on battery terminals are available also, if yours is destroyed or corroded beyond use. The bolt on ends are not a great thing, maybe short term at best.

[ray hampton]

can you use a puller to remove the cable clamp, the bolt should be easier to remove with the cable free to move

[Brian Elfert]

The clamp has been removed from the battery and the junk battery is already out of the generator. I just can't get the rusty bolt out of the clamp. I'm going to try to work on this on Saturday when there is more daylight.

There is no requirement to remove the rusty bolt. I could just put it back together with the rusty bolt if I can't get it out. The clamp itself is not rusty or corroded. I would just feel better if the bolt was replaced. The nut was not completely seized this time. but the next time I might not be so lucky.

[ray hampton]

The clamp has been removed from the battery and the junk battery is already out of the generator. I just can't get the rusty bolt out of the clamp. I'm going to try to work on this on Saturday when there is more daylight.

There is no requirement to remove the rusty bolt. I could just put it back together with the rusty bolt if I can't get it out. The clamp itself is not rusty or corroded. I would just feel better if the bolt was replaced. The nut was not completely seized this time. but the next time I might not be so lucky.

If the bolt came with a square head, then it will not turn, it is possible that the clamp got tabs that are holding the bolt head, if you got a section of pipe with a inside dia. bigger that the bolt head, first thing , get a helper to hold the pipe, placed the nut on bolt , hold the bolt head in the pipe end and hit the nut-bolt with a hammer, tell your fingers to stay out of the hammer way, GOOD LUCK

[Keith Westfall]

Every once in a while, you hear about the amazing (?) properties of Coke. Soak the end in a bit of Coke for a bit and see what happens! I hear it will dissolve nails...