gauge of wire for Alternator to battery? - Page 2

Mike Pearson · 05-18-2012, 08:15 AM

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.

Jim Wahl · 05-18-2012, 10:46 AM

Quote:

Originally Posted by Mike Pearson

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.

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

.

Ron Gusack · 05-18-2012, 01:12 PM

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.

Sean Marconette · 05-18-2012, 01:46 PM

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

novassdude · 05-18-2012, 01:48 PM

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.

t.tosto · 05-18-2012, 03:14 PM

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.

68camaroSS · 05-18-2012, 04:09 PM

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.

L78 Nova · 05-18-2012, 07:08 PM

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

Ron Gusack · 05-20-2012, 03:50 PM

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?

Run to Rund · 05-20-2012, 08:47 PM

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.

05-18-2012, 08:15 AM	#11
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,443 Likes: 613 Liked 1,915 Times in 574 Posts	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. __________________ Mike Pearson 2485 SS

05-18-2012, 01:12 PM	#13
Ron Gusack Member Join Date: Feb 2009 Posts: 244 Likes: 1 Liked 7 Times in 6 Posts	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.

05-18-2012, 01:46 PM	#14
Sean Marconette Senior Member Join Date: Mar 2006 Posts: 977 Likes: 792 Liked 275 Times in 76 Posts	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 __________________ Sean Marconette 84 Mustang 5060 SS/N

05-18-2012, 01:48 PM	#15
novassdude Senior Member Join Date: Mar 2002 Location: usa Posts: 752 Likes: 204 Liked 136 Times in 49 Posts	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.

05-18-2012, 03:14 PM	#16
t.tosto Member Join Date: Aug 2007 Posts: 154 Likes: 116 Liked 62 Times in 23 Posts	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.

05-18-2012, 04:09 PM	#17
68camaroSS Junior Member Join Date: Aug 2008 Location: columbia TN Posts: 88 Likes: 0 Liked 0 Times in 0 Posts	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.

05-18-2012, 07:08 PM	#18
L78 Nova Junior Member Join Date: Dec 2009 Location: Winnipeg, MB Posts: 92 Likes: 252 Liked 23 Times in 13 Posts	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.

05-20-2012, 03:50 PM	#19
Ron Gusack Member Join Date: Feb 2009 Posts: 244 Likes: 1 Liked 7 Times in 6 Posts	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?

05-20-2012, 08:47 PM	#20
Run to Rund Senior Member Join Date: Sep 2007 Location: Henderson, NV Posts: 583 Likes: 8 Liked 54 Times in 27 Posts	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.