Battery cable bolts loose - but it is more complicated than that

New battery - 6 weeks old. Went to start last night - nothing. Popped hood and negative cable was loose. Bolt just spins and spins can’t tighten. Threads on the bolt are fine. The metal on these bolts (which I have replaced before) are hard and don’t corrode or strip easily. The problem is with the side-post / “internal” lead or soft metal inside the side of the battery to which they screw-in. This same thing happened a few years ago and after trying to different new packages of replacement bolts - they didn’t make any difference - I just gave up and got a new battery but that battery was old and it wasn’t a big deal. This is a new battery. It would be no problem is the battery was protruding stick-post or top-side post, but my battery type is 75 which has the recessed side things and that is why it is such a problem. Is there a simple cheap fix to this problem? All of the bolts seem to be the same, standard size.

not sure if Heli-Coil would be of any help?

Call the place where you purchased battery and see what they say.

Who installed that battery 6 weeks ago?

If the battery seller/installer won’t take care of it, you could try a strip of copper shim material in the too-big threads. You can buy assorted thicknesses of it at hardware stores or on line. Be sure to use copper, for its electrical and mechanical qualities.

That may be what the seller/installer does, but make sure they don’t cheap out and use a strip of Pepsi can!

If you must attempt to repair this yourself I would suggest installing a piece of threaded rod larger than the original bolt.

A good battery shop can repair the battery with lead but these days only industrial battery suppliers likely have the equipment even though it is quite simple.

Are you sure the bolt going into the battery isn’t damaged causing the internal threads in the battery to be wrecked? I used to replace those bolts about every year just as a maintenance item. I don’t know what to suggest to repair the threads in the battery and you do need to use the bolt designed for a side mount.

You could try installing a thread cutting bolt slightly larger than the existing bolt.

Bring the existing bolt with you to the hardware store so they can supply you with the proper diameter/length bolt.

A thread cutting bolt will have no problem cutting new threads in lead.


The battery bolts are steel and the terminals in the battery are lead. The lead will give way before the steel will. Generally, these problems are caused by cross-threaded or over-tightened bolts. Whatever you do be careful not to overtighten the new connections.

I believe the originally equipped bolt is size SAE 3/8-16 if that’s of any help. If the internal threads are stripped (and not the bolt) it does seem like you could just use a slightly larger bolt. Find a chart of bolt sizes, both SAE and metric, and figure out which the next largest diameter is. You might could use a dremmel tool and cutting wheel to cut little notches in the end of the next sized bolt as shown in Tester’s photo above and make it self tap that way. That does seem like it is a very frustrating problem indeed. I would have guessed there would already be a solution for this in the auto parts stores, have you tried asking/looking there?

Thanks for the suggestions. Right now I have a half-ass fix with a piece of electrical tap stretched across the battery. This is just the latest in a long list of results I get any time I EVER take my car to a shop for any work - no matter where, no matter for what, no matter how minor. I leave with loads of cosmetic damage - scratches, dents, chipped paint, black marks that take years to wear off, - but even worse are new mechanical issues - sometimes worse than the reason I bring it to these places to begin with. I had this battery - brand new - put in 6 weeks ago, and nobody has touched it except FIRESTONE (where I will NEVER go again) - and of course the problem is that no matter what kind of work any place does - the first thing they will do is to disconnect that negative battery cable. So my assumption is that when they re-attach it, they just keep going too hard and strip the post inside. So tired of crap like this.

A poor connection at the battery can and eventually will result in various expensive failures from the alternator to one of the electronic modules. It would be much cheaper to immediately replace the battery and save a damaged $100 battery from becoming a $thousand dollar multi system failure.

And you can add your name to the already overflowing list of people who have been poorly served by Firestone. That company’s reputation is at the top of the list of my places to avoid for car repair and service.

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I forgot to ask…What would be the symptoms while driving of such a very loose negative battery connection. Now that I have had time to think about it - ever since I left that Firestone, I have had some really weird behavior while I am driving, but of course didn’t know about the connection issue until a couple of days ago. Obviously, you’d experience it when starting (or failing to start), but what about once you are driving down the road going over bumps and that thing is intermittently touching and not-touching every second or two the whole time? What would you experience as a result of that?

Loose battery connections can affect the engine computer and its ability to read the engine control sensors accurately. What the effect of that would be depends on which sensor reading gets affected. But it could definitely cause drivability problems. Poor idling, stalling, hesitation, overheating, etc. Longer term it could damage the starter motor and alternator. Folks here post occasionally with drivability problems that are solved by improving the connections to the battery.