Battery Cables

[DoctorDee]

As part of the general tidy,(I like things to look right),I am changing out the battery cables on "Gladys". I hate electrics cos I don't understand them. However, I acknowledge that I am going to have to achieve a reasonable level of competency if I am going be happy with the old lady. So, simple starting point.... How do I decide what amperage the battery cables should be rated to, in order to function safely.

[IanS]

Is your engine and starter standard? if so use the same as ford used, measure the diameter of the copper to get the size.

For most engines 25mmsq (about 170A) is adequate.

The starter is very intermittant in operation and overloading for the short time you use it should not cause problems.

[DoctorDee]

If I understand you correctly, then the amperage the cable needs to be able to carry safely is dictated by the amount of current drawn by the starter motor. Although the engine is a std zetec with suitable starter motor the battery cables are currently fitted are agricultural to say the least....

[Guest snowy2]

it also depends how far away the battery is from the starter.....

but as a rule of thumb.....bigger is always better where battery cables are concerned.

[DoctorDee]

Thanks for the help on this...... I had to fit a different battery with a higher CCA....The posts are reversed, as a consequence the cables as fitted by the builder are a disaster zone..I needed to understand the logic behind the type of replacements I should obtain. Thanks for the reference to VWP. Used to use them in my Triking days, your reminder was timely.Once again,thanks. Off to my local John Deere dealership.

[Guest lotusPaul]

I'm my lotus I have an ER40 battery 1100cca it's a beast. I use 35mm2 (I think) red and black coated for power and earth. If I remember it's about 470 amp capacity cable. It had 16mm2 black welding cable as an earth and that was always warm to touch.

Now I'm no sparky magician but I took advice and thought bigger is better, it is ok to the point where you consider length and resistance over that length and thus the voltage drop.

So in the end I choose the cable bassed based on the fact it only just smaller than the original size as measured on micrometer and it would fit without drilling.8mm. It was also more flexible too.

My sparky mate done some calcs based on current draw and size over length etc. He said it was fine,bit of an over kill in size.

The earth was the important part to me because it was never gonna be great on a 47 year old car.

 

Conclusion, it works and wasn't massively expensive either,

[Guest lotusPaul]

Just to add to that above. Yes I was a little out. It was 50mm2 cable I used.

 

My appologies

[DoctorDee]

Thanks everyone. Thanks Lotus paul, please don't apologise.