I noticed an insulating tape on a cable coming from the battery on my used car I bought recently and opened it up to find this:
Is there a hazard to the cable or components if I keep the cable like this and tape over it again?
If I should repair the cable, would it be ok to cut out the damaged part and reconnect the ends with a soldering connector tube? I fear replacing the whole cable is not an option, so if this is not a good idea, I'm open for better ones. Here to learn.
You need to replace the cable as there is corrosion inside of the cable. There is no way to get rid of the corrosion, so replacement is your only option. The corrosion increases resistance going through the cable, which means it won't be as efficient as it should be. Heat can generate, which if it gets bad enough, might cause a fire. Butt welding (if that's what you want to call it) isn't a good option, either. This also creates a lot of resistance within the cable at the joint, which creates heat.
After disconnecting the negative battery terminal, if you cut out the corroded section of wire and then make a proper solder joint -- which begins with a secure physical connection between the wires to be joined -- the resistance of the soldered cable will for all practical purposes be indistinguishable from the original wire. Yes, solder has a higher resistance than copper, but current in a properly soldered joint passes through solder for only a small fraction of a millimeter because the two wires to be joined are already physically touching. Any added resistance from solder is completely trivial.
However, soldered connections in stranded wire that are subjected to vibration and physical bending can lead to fracture of the wire through metal fatigue. If you're planning to keep the car for just a couple of years, solder should be fine in the short term. But if this car is a keeper and if this wire is subject to movement because of engine movement, a better choice would be to cut out the corroded section, then use a split bolt connector. These are especially useful for high-current applications. I've used them on heavy battery cables to connect high current loads, and they have lasted the life of the vehicle. Insulate with many layers of high quality electric tape and you'll never have a problem with it.
If you attempt to cut this wire for repair, disconnect battery negative first to prevent blowing a fuse or becoming an arc welder. That looks like 10 gauge wire and if there's enough slack, cutting out the corroded part, stripping back insulation and either meshing the clean ends together or use a plain butt connector crimped onto both ends of wires, solder can repair this damage. Once cut, slip a piece of heat shrink tubing over one wire far back to prevent heat from soldering hastening the tubing to shrink. Once soldered together with electrical/electronic solder and flux to keep copper from oxidizing as its soldered, let the wires cool off before slipping the heat shrink tubing over the soldered connection. Heat shrink tubing should cover insulation and soldered wires. A match, lighter or soldering iron played under tubing should start shrinking it until it forms a tight insulated cover over the repair. Soldering requires clean copper wires free of corrosion to allow flux and solder to flow like water onto copper wires, looking shiny wet when soldering. Not disturbing the connection while soldering then removing heat should turn wet shiny solder into a dull grey color as it cools and hardens. If you've never soldered, practice on wires first before making this repair. A good solder joint will carry the amperage without overheating from a poor repair. Google videos of soldering for help. Soldering wires butted together isn't recommended for 10/8/6 gauge wires. Mesh clean ends together, 3/4 to 1 inch then solder. Technique counts to ensure all wires are meshed and packed tightly before soldering. The alternative? The correct copper ferrule or thin walled tubing that fits tightly over each end then crimping each end for a mechanical bond. Try pulling this apart. If wires pull out, crimping failed. Every small gauge connector using machine crimped terminals cannot be pulled apart. The same repair to a 10/8/6 gauge must be crimped to resist pulling apart. Soldering bonds wires and ferrule into one intact unit that cannot be pulled apart.
