I've had several problems with my car's wiring oxidizing at the exposed ends near and under post clamp and causing electrical connectivity problems. The braided wire is a pain to brush clean and I wanted to solder them to the post clamp to prevent this in the future, to prevent oxidation from coming between the wire and the clamp.

Are there any problems with soldering the wire to the post clamp? What should I consider before doing this, or when doing this?

For example, I've read that one should make sure to keep the solder close to the post so that it doesn't stiffen the cables, causing breakage due to vibrations. Are there other problems to watch out for?

I'm currently using this style clamp: enter image description here

  • Electrical wire doesn't "rust". Is the copper getting a green patina, or are you seeing corrosion due to acid leakage from the battery?
    – JPhi1618
    Mar 4 '16 at 14:14
  • @JPhi1618 I don't remember the color, but it wasn't acid corrosion/buildup. It looked like oxidation on the wire strands-- I used "rust" generically/lazily, I'll change it. Mar 4 '16 at 14:17
  • That's fine, I just wanted the problem to be clear as possible. Is the clamp the type that has a strap that clamps down on the wire? A picture might help since your soldering/repair options might have a lot to do with the terminal type.
    – JPhi1618
    Mar 4 '16 at 14:20
  • @JPhi1618 I totally agree, I've added a photo of the clamp style Mar 4 '16 at 14:25
  • if you're intent on soldering check out quickcable.com/products.php?pageId=74 but for that style it's just a clamp on deal.
    – Ben
    Mar 4 '16 at 20:21

The first, most important step is going to be to get the stranded wire as clean as possible. You won't be able to scrape or scrub it clean - you will need a chemical cleaner. There are several "how-to" pages online like this that describe a simple solution you can make at home. The linked page uses a vinegar-salt solution to act as an acid to clean the wires.

Once the wires are shiny and clean, thread a piece of quality heat shrink onto the cable to protect everything once you're done.

Clamp the wire to the terminal tightly and coat the area to be soldered with flux. Use a torch to heat the wire and the terminal, but focus the heat on the steel strap. Be very careful to not overheat the terminal. They are made from a soft metal with a low melting point, so only apply just enough heat to the wire and terminal to melt and flow the solder.

Also, do this well away from the battery. It would be best to remove the whole cable for safety, but protect any plastic parts and keep heat away from oil and fuel if you can't.

Only use enough solder to fill in the clamped area. Reducing the flexibility of the wire is a concern.

Once everything is cool, slide up the heat shrink and heat it up to tightly seal the end of the wire.

Now, after reading all that, and imagining yourself doing it, consider buying a replacement cable that comes with a pre-attached terminal:

enter image description here

It's going to be cleaner and more durable than what you can do at home, but there is some expense to it (varies from $10 to $90 depending on the car and whether or not its a Volkswagen... Friggin $80 cables....).

  • 1
    im afraid that if he goes with the torch on the wire he'll end wicking solder way up into the wire if he heats it too much (ruining even the sheath) or have a cold solder. Mar 4 '16 at 15:48
  • The more I think about it, I think protecting with oil/grease/sealer/whatever would be much easier. I'm not sure if soldering is necessary, but it's what the OP asked for... @ErikvanDoren, is there a way to heat better than a torch?
    – JPhi1618
    Mar 4 '16 at 15:50
  • there are many ways to heat and solder, not sure if the OP has the tools or ability. But my comment was meant to point out that soldering is not as trivial as smelting some tin with a torch, it needs to be done properly, if too cold you have a cold solder which is a bad connection if its too hot it will send solder way up the wire ruining it. He needs to know how to solder, that's all i meant. Usually people solder the ring terminal on the other side of cable, which is easier to manage because they take the torch to the copper terminal not to the wire, here he would melt the clamp instead Mar 4 '16 at 16:13
  • PS: if he solders just to the strap it will soften it so that it wont be able to press and conform the cable all against the clamp body so its connection to it will be weak and rely more to the area around the clamping bolts. There are copper only battery clamps that wont melt down but they are a PITA in my opinion as they don't last forever in certain conditions and need to be replaced at one point, which would be more work if soldered Mar 4 '16 at 16:28
  • Yea, I was imagining heating everything but doing it from the strap side, but maybe that's not the best plan. I think your main point is "soldering this won't be easy", and I agree with that completely, hence the recommendation for a pre-made cable. Thanks for the input!
    – JPhi1618
    Mar 4 '16 at 16:34

You don't need to solder them, clean the terminals really well and apply some dielctric grease or buy some battery terminal protector, this is a spray that you can spray on the terminals and this will keep the battery form corroding. I personally use heavy duty bearing grease to apply over and around the terminals, this helps really well keeping the terminals from corroding.

The dielectric grease can be used with any electrical wires, connectors. This does not hurt anything.

Here is a video that you can watch. https://www.youtube.com/watch?v=WAPsliigtFg

  • 2
    +1. Don't solder to a car battery. Ever. Use a cable with a ring and bolt the ring to the clamp. No soldering required and no breaking of connections involved.
    – Mast
    Mar 4 '16 at 19:07

What I would do is clean the terminals with some flux and a brush, or even a really fine grit sandpaper, and then if you need you can tin the clamps. What I've done is place copper foil between the post and the clamp, just to provide a bit of a buffer and give a bit more pressure on the post.

If it is really that corroded, check that your battery isn't leaking. In general it's going to be hard to make a good solder joint between oxidized parts, I wouldn't rely on it.

Edit: Ok, if it's a problem between the wire and the clamp, I'd get new clamps, or do what I said with the flux and brush on the clamps where the wire connects. If the copper of the wire is corroded, what I would do is trim the wire and strip a bit of the insulation so that the oxidized part is cut off and an unoxidized bit is exposed, and then crimp/screw that back into the clamp.

  • 2
    I think the OP's problem is the wire-to-clamp connection, not the clamp-to-battery-post connection.
    – JPhi1618
    Mar 4 '16 at 14:36
  • Ok, thanks @JPhi1618 I edited my answer to hopefully be more helpful. Mar 4 '16 at 14:44

Provided that the bad connection because of oxidation isn't because the wire wasn't clamped properly, as the mating surfaces would be somehow protected if clamped tight.

You might not want to solder to the clamp itself, depending on the clamp material or your ability to solder. If you do do it properly without having solder spreading down the wire (and there are methods for that) might be ok. I wouldn't solder onto the clamp body in the pic, however. If I really had to do it I'd solder the wire to a small plate of copper, with holes for the bolts, that will end being sandwiched between the body and the strap. You would end with the wire both soldered and clamped and the area around the bolts will be covered by the strap protecting it from oxidation. Some people will say that car connections are all crimped for a reason but, from what i hear, in some areas they do solder connections that are exposed to elements because of presence of salt etc.

However soldering seems a bit drastic to me, before going that way you might want to consider other usual manners of protection for the wire where it joins the clamps, a layer of white lithium grease or silicon grease (after having cleaned, clamped the wire and connected to the battery) will protect from oxidation without any other work necessary. A cap would keep most of the dirt out of the way. Other manner of protection like a shrink tube big enough to catch the connection to the wire or stuff like liquid tape might work to protect it but you cant see if there is oxidation on the wire without breaking all apart. Grease instead can be wiped off and reapplied without problem. Some don't like grease saying that it could make its way within the connection and use anti-corrosion products created for that, they are often a paste like product of various compositions, some with metallic particles in it to not give the insulating effect the grease would have if it goes between the connection, and are made to protect terminals and clamps from corrosion. I have heard debates between people about conductive grease vs non conductive with supporting arguments on both sides.

Point is: there are products made to protect the wire from oxidation on the market, and that might be simpler than soldering

  • Interesting idea about silicon, what about silicon caulk? Mar 4 '16 at 15:24
  • im talking about silicon grease. Caulk could work, i dont know, the idea is to keep the air away. But as i was saying about liquid tape etc if the wire start oxidating underneath you cant see it and to maintain it you have to break it up, reapply it etc. Grease or products made on purpose are always there as you use just a bit and they usually dont have an expiration date, you get them and they last for years, and are easy to use, clean off and reapply. Mar 4 '16 at 15:33
  • While a silicon caulk might do the job, you will have one heck of a time cleaning it off and reapplying it when it eventually weathers and needs to be replaced. I would use the products that are designed for this that have already been mentioned.
    – cdunn
    Mar 4 '16 at 15:37
  • yep something that can be visually inspected in a few seconds rather than half hour is worth a few bucks for the proper product Mar 4 '16 at 15:42
  • A variation I might suggest would be to get some copper tubing the same diameter as your cable (or a strip of copper you can bend into a tube). Solder your cable into that, then bolt the tube into the clamp. This would maximize your contact area, which could give you decreased resistance to current flow.
    – TMN
    Mar 4 '16 at 15:47

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