gauge of wire for Alternator to battery?
 

What gauge wire would you guys use for a 1 wire 140 amp alternator lead to the battery positive side mounted at the rear of the car?
Is #10 gauge alright?

Re: gauge of wire for Alternator to battery?
 

I believe that #10 wire will only carry 30 amps, can't imagine 140 going thru that small of a wire - maybe a #6 is enough? I would think that should be a lot closer.

Re: gauge of wire for Alternator to battery?
 

Six or eight gauge, minimum.

Re: gauge of wire for Alternator to battery?
 

I've got a #6 but my battery is in the front

Re: gauge of wire for Alternator to battery?
 

20' long wire for 140 amps would be 0 gauge. See the table in this thread on yellowbullet:
http://www.yellowbullet.com/forum/sh...ad.php?t=47266

Re: gauge of wire for Alternator to battery?
 

Okay, so 6 or 8 gauge it is. I was lead to believe that 10 gauge was enough for the field stud from the alternator to the battery. Yes, the battery is in the trunk.

What type of wire is good? crosslink? solid strand?

Re: gauge of wire for Alternator to battery?
 

Use copper stranded that is designed for automotive use. It's more flexible then equipment wire.

Re: gauge of wire for Alternator to battery?
 

Be sure to use a fusible link or a maxi fuse on each end when using heavy gauge wire for the alternator. , you dont want to burn the car down if the wire gets pinched !

Re: gauge of wire for Alternator to battery?
 

I did a little research on this last year and ended up using 6 AWG fine stranded tinned marine battery cable boat wire on my 90 amp alternater, bought on ebay for 1.25 a foot.

Re: gauge of wire for Alternator to battery?
 

Funny thing is that I have been using #10 gauge on this connection for some time now with no problems, but I guess I got lucky with that one.
Could the car have not been getting full amperage to the electric fuel pump and electric cooling fan under full load?
I'm going for #4 or #6 to make sure it's right.

Re: gauge of wire for Alternator to battery?
 

If you put an ammeter on the wire you could tell what the alternator is actually putting out to the battery. I would say its no where near 140 amps. Size the wire on the actual load. Thats probably why the small wire has been working for you. Just remember the lower the voltage the higher the amperage is. Thats why the starter has such a large cable going to it.

Re: gauge of wire for Alternator to battery?
 

Ahhhhhh......... I never thought of that Mike. Makes perfect sense. Thanks. Jim


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Re: gauge of wire for Alternator to battery?
 

I embarrassed to say this, but I've run 12 ga for years with no problems. I do intend to beef it up though. I run a fan, fuel pump, water pump, tail lights, Racepak, digital 6A and headlights.

Re: gauge of wire for Alternator to battery?
 

The battery capacity has a lot to do with the load induced on the alternator. Think of it as the battery being a bucket, the bigger the bucket the more capacity it has, and does not ask the alternator for any more amperage than is being used to maintain the battery charge. The voltage from the alternator is also higher than the load from the battery. The higher the voltage the smaller the wire needed. Look at the overhead power lines coming from your local power plant they are extremely small diameter due to the voltage they are carrying.

Sean

Re: gauge of wire for Alternator to battery?
 

I do harnessing for a construction equipment manufaturer. We run 6GA for all our alternator charge wires. And they are a much shorter run that to the back of a race car. And as some one already mentioned run an inline high amp fuse for protection.

Re: gauge of wire for Alternator to battery?
 

If battery is fully charged(12.65 volts) then alt. will only put out amps to run all the race cars accy. requirements. Ign. system 10A, water pump 5A, fan 15A, lights 15A etc. These are approx. figures. An alt. is not intended to be a battery charger, just a device to maintain the elect. system during load. Therefore #10 Guage should be fine, most all autos from the 60's thru 80's had #10 off the alt stud. Just my thoughts on the subject,Tony.

Re: gauge of wire for Alternator to battery?
 

You have to consider the lenght of the wire you are running when the battery (and kill switch) is in the trunk. Ask the guys at powermaster or East Coast.

Re: gauge of wire for Alternator to battery?
 

Also keep in mind one wire alternators charge at full capacity (based on RPM) with no load sensing.

Re: gauge of wire for Alternator to battery?
 

I'm confused. If a 100 amp one wire charges at full capacity based on rpm, does that mean it's putting 100 amps through the charging wire @ 7,000?

Re: gauge of wire for Alternator to battery?
 

The 100 amp alternators in some stock Mopars about 30 years ago used 6 gauge wire and it wasn't real long--between 3' and 6' I guess. If you will only be using 30 amps, why have a 140 amp alternator? The point of using heavy enough wire is that the alternator can run up to its capacity when needed.

Re: gauge of wire for Alternator to battery?
 

#4 or 6 welding cable works very well

Re: gauge of wire for Alternator to battery?
 

Unless I missed it you do not have to run the alternator charge wire to the rear where the battery is....you already have a battery cable large enough to operate the starter in the car so all you need is a cable of enough capacity to go from the alternator to the junction point of this cable (starter solenoid)...that is why you don't need a real large wire from the alternator to this point (short run)......also the charge signal from the alternator can be very a "dirty" signal (not real clean) and this can cause all kinds of RF in the car if not handled well......

D L Rambo.....