I refer to the main charge wire from the alternator to the positive battery terminal. Is 6mm wire ok or do I need to go bigger?

6mm will take about 30A, so willbe fine
dean

what is the engine? most car engine alternators should be putting out quite a bit more than 30amps.

6mm diameter should be 4 gauge which can handle alot more than 30 amps so should be fine.

It's a V6 Duratec but I have changed the enormous standard alternator with a smaller Nippon Denso jobbie (allegedly with the same output.
Rescued attachment Alternator1.jpg

When you say 6mm I assume you mean 6 square millimeters? According to vehicle woring products' website this will carry between 42A and 50A depending on the type of wire. (Standard PVC wire will take the lower figure and their thinwall wire will handle the higher figure.)

So, assuming the alternator is 55 or 65 Amp then I would recommend you go up a size if possible. Rather than use heavier wire I would use two 4 sq mm wires (8 sq mm total) as these are easier to work with. This will give you a total capacity of 70 - 78 Amps which is much better.

I hope this helps,
Craig.

I was going to use 6mm sq thinwall (I've used thinwall for the rest of my loom) but I didn't think of using two smaller wires - good idea

[Edited on 21-3-06 by RazMan]

No probs!


By the way, you don't have to take the alternator feed back to the battery. You could take it to the large positive cable on your starter solenoid if it is closer. It will sometimes be easier and neater to connect to than the battery. My Rover V8 engine wiring loom connects from alternator to solenoid in this way rather than run another cable half way round the engine.

HTH,
Craig.

[Edited on 21/3/2006 by craig1410]

Excellent idea - that will be a lot tidier

That looks much more like at least an 80 amp alternator to me, if it is equivalent in output to the original V6 Duratec unit it could be even more as 100 amp units are common on modern engines over 2 litres.

I'm not sure about the output as I can't find a part number on the casing. The same alternator is used on late Micra's and small Rovers so I doubt that it will be as high as 100A. Anyway the output will only be as high as the demand placed on it, and I won't be running any high current accessories - a CD head unit is about all in fact. Also my main fuse is only rated at 40A.

[Edited on 21-3-06 by RazMan]

You'd be wise to try and find out exactly what the maximum output of the alternator is. I agree that it is unlikely that you would be able to draw more than 50-60 Amps from it on a Locost type vehicle but it is possible if the battery was run down quite low and you had a number of other loads on it. The battery alone could probably take 30+ Amps initially as it recharges immediately after starting. Add to that 5-8 Amps for ignition, 10A for wipers, 10A for heater blower, 10-20A for radiator fan and it soon adds up.

As I said, it is unlikely to happen in practice but the cable should never be the weakest link and you don't really want to put a fuse between alternator and battery as it is a sure way to blow up your alternator if the fuse blows while the alternator is running.

A pair of 6mm thinwall wires should happily carry 100A if you are in any doubt as to the alternator output.

Cheers,
Craig.

The base model 1.1 and 1.4 litre petrol Rover 25 and Rover 45 alternator is rated at 75 amps the 1.8 engined version have an 85 amps alternator


The alternator in 1.8 engine in the 75 is rated at a whacking 105 amps

Ah, so I had better go on the safe side and use 10mm sq - sorted