Alternator Output & Cable Size

[Jamiep]

Evening everybody, I am in the process of rewiring the Hood and need to order some terminals and other bits and bobs for the alternator. I think I have a standard Sierra unit which I believe outputs 55 amps.

My question is, what size cables should I use for the 2 main outputs? Is it 55 amps split over the two outputs because the current damaged set up only looks about 3mm^2 each to me.

 

[Longboarder]

You need 4.5 mm² solid copper to carry 35amps, 7mm² for 50 amps. If you are happy your alternator output is only 55amps then you can use 2 x 4.5. Remember that is the copper area, not the diameter but sellers specify in mm² and amperage often. I would be tempted to over-specify and use 2 x 7mm.

 

Nigel

[Jez Morton]

Depends how you wire them on some one wire goes to bat and one to loom. You would need to assume full load through one terminal as a min I would use 4mm but 6mm would not cost much more and would be more sympathetic to a diy job.

 

Jez

 

[Jamiep]

Thanks for the reply guys, The reason I doubted myself was because the Haynes manual shows a parallel feed to a junction which then splits to battery and relays. My limited electrical knowledge would suggest to me the current will always take the path of least resistance so unless Ford got these cables exactly the same length one would always carry the load so they would need to be 6 or 7mm^2 each but mine don't look any bigger then the 3mm^2 33amp thin wall cable I have. So thought it may be 27.5amps each output.

 

BTW I'm not 100% positive that the alternator is 55 amps, I can't remember where I got that info from.