Negative/Earth return cable

SlySimon said:

I have read somewhere that running a decent Earth return cable from alternator or engine bay is a very good idea. Apparently it can cut down on corrosion. Obviously as electricity will always take the path of least resistance a decent sized cable will be needed.
This is a 'mod' I intend to do. However I am unsure just how big to go with the cable, where best to attach it (obviously on the battery terminal clip at one end, engine block/alternator/subframe at the other) and whether running it under the car will be the best route.
Any thoughts?

Click to expand...

Can't see the benefits to be honest. Positive earth cars used to suffer from corrosion but never heard of it on negative earth.

You would be best using a cable the same size as the positive cable, but you cannot disconnect any of the chassis earths anyway, unless you are going full twin wire spec that fuel tankers ans specialist vehicles use.

The idea comes from the fact that boats have sacrificial anodes as when you put two dissimilar metals in salt water it causes an electrical current which increases corrosion. The addition of the sacrificial anodes means they corrode instead of your metal prop or engine.
Taking a cable from where most of the electricity is used back to the battery should reduce the current going through the rest of the car considerably.
Most cars won't really suffer from it, but when you have the battery a long way from the block the electricity has a long way to travel.
Probably also why earth returns on rear lights of so many old cars get so corroded and why a lot of cars corrode around the battery tray.

The positive earths cars probably suffered from it as they were old, and had poor rustproofing. My MK2 Fiesta rusted for Britain and it was, of course, negative earth.

Run a nice big strip of copper along the bottom of the chassis from the battery to the engine, remembering to attach it securely with self tapping screws every few inches to ensure short earth paths. Report back after the winter.