Thanks Tim, I appreciate the input. Duane

jeeperjohn, I use MS paint or one of those things that have been in my computer since Win '95.
Nothing to them really.
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I guess taz is blowing off again...
I have him on the ignore list so my life is easier than the rest of you have it ...
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Some FACTS,

If you have over a 100 amp alternator, and you think you will be draining your vehicle at full capacity, you may want to use a 2 Gauge wire from the alternator 'Batt' terminal to the solenoid...
A 2 gauge wire will transmit over 100 Continuous amps with out overheating.
(Keep in mind your alternator usually idles at under 10 amps for most of it's life, so this would be a HUGE waste of time and money...)
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If you are using any alternator on planet earth smaller than the one needed to launch the space shuttle,
(like a Delco SI series that most of us are running)
10 Ga. wire us usually enough.
10 Ga. will handle over 30 amps continuous, and will handle short term loads over 50 amps...

If you have one of the alternators that will power a small city, Like some of the 'Electric Everything' vehicles use, it's probably a CS series...
And if you are loading it until the amp gauge smokes and screams at you...
In that case I'd use an 8 or 6 gauge wire.

I weld and jump completely dead vehicles with 4 gauge wire, so that should tell you something right there...
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If you have an average vehicle load, as in the usual, lights, wipers, ignition, ect...
You alternator will only be supplying about 30 to 40 amps to the vehicle.
That's 8 gauge wire with no heating...

Since CJ's don't have electric defrosters, or 'Power Everything' (I'd settle for 'Power Anything!) your alternator is going to 'Idle' at about 10 amps.
That's usually what it takes to power the ignition, brake lights/turn signals, fuel injectors and keep the battery topped off with the A/C running.
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MORE FACTS!

The first fact is your battery supplies the current for you devices, not the alternator.
The alternator is a 'Pump' that fills the battery back up after usage, so the entire load (and in actuality, the battery is over charged when the vehicle is running), so virtually none of the vehicle load is coming from the alternator

Here is the Brown & Sharp used by everyone for low voltage DC wiring...

10 Ga./ 32.5 amps continuous with out heating from resistance.
8 Ga./ 46.1 amps continuous.
6 Ga./ 65.2 amps continuous.
4 Ga./ 92.3 amps continuous.
2 Ga./ 131 amps continuous.
0 Ga. (also expresses as 1/0) 185 amps continuous.
00 Ga. (also expressed as 2/0) 220 amps continuous.
000 Ga. (also expressed as 3/0) 262 amps continuous.
0000 Ga. (also expressed as 4/0) 312 amps continuous.

4 Ga. is usually plenty to get a stock engine started if the battery/starter run is kept short.
(and I've never seen a 'Long' run on a SWB Jeep even when the battery was in the extreme rear of the vehicle!)

Now, this information pertains to virgin copper wire, not alloyed wire used in most 'Battery Cables' and 'Automotive Wiring'...
Welding cable is virgin copper for no other reason than welders won't put up with nonsense.

Remember, this wire will transmit much more amperage, these are the ratings at which the wire will NOT heat up.
If you transmit more amperage through the wire, it will pass, but the wire will begin to heat.
For the short duration you are cranking the engine, the 4 Ga. wire is plenty...
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Now, for a bit of information...
Our electric air compressors need a 70 Amp relay to stay alive...
We feed that 70 amp relay with an 8 Ga. wire.
This seems like a contradiction in the scale, but it's not, and here is why...

First,
The compressor will require about 68 amps to get started when pulling against a pressurize line.
The compressor kicks on at 135 PSI, so the piston/motor has to overcome that 135 PSI from a dead stop.
That will spike amperage required to get things started MOMENTARILY to around 68 to 70 amps.
Within a half second the motor is turning quickly, and the amperage required drops to about 30 amps.

Same principal with your starter motor on your jeep engine...
A Hard 'grunt' to get things started moving, then amp requirement drops way off...
That's why you can start most vehicles with a lawn mower battery with no problem...

That relay and 8 gauge wire, and compressor are bringing a 5 gallon tank up to 150 PSI in about 4 minutes.
After the initial amperage spike, the requirement drops off to about 30 amps, and the 8 Ga. wire is more than capable of doing 30 amps all day!

In fact, I know people that have used our air compressor relays, sockets and harnesses as starter relays in a pinch, and I know of one guy that has two in parallel starting his vehicle for over a year now!
That's a 140 amp capacity starting a vehicle in Indiana cold with what are basically driving light relays...

So, if you find yourselves buying into 'taz crap', just throw us a line and we'll be glad to help you with correct information...

Just to add a little - the batteries we use for automotive really can't take much more than 30 amps to charge it back up - whether it's totally dead or just down slightly. It will overheat and destroy itself quickly if you try to give it more than that.
Fortunately to get it to accept much more than 30 amps it takes at least 17 volts to "push" it in.

The alternator ground - the alternator case itself is bolted to the engine. That alone "should be" sufficient. But bolts tend to corrode, get loose etc., especially in the environments we subject our Jeeps to, so "should be" isn't always true. A ground strap from the alternator case to the battery negative is insurance that it's always getting a good ground.
And -- don't forget a GOOD ground - or 2 (insurance) from Engine to battery negative.
AND ground(s) from body to battery negative.

And as suggested, grounding one part of the body does not insure the entire body is grounded.

Poor grounds can cause lots of crazy symptoms that can drive you nuts!

JYG, never came across "glue fill heat shrink tubing" could you tell me where to get some? I live by shrink tubing and glob some liquid electrical tape (same as silicone, but colored so I can figure out what is what where on the ends if they don't look sealed.

Thanks for the wisdom, I now can get all those negative electrons where they need to be in short order. I can't wait to see and hear my CJ perform better beacuse of this. Great graphics Aaron.

Only time to hit the high points. My son and granddaughter came over to swim today. I cooked dinner on the grill and I still need to clean up after. Miles to go before I sleep.

How is it easier when you have to log-in/log-out or remove and re-add me to your ignore list to read what I posted? It’s obvious you read it.


It’s winter, it’s still dark, it’s cold and it’s snowing. I just started the Jeep and jumped my neighbors car for him before I left the house so the battery is low. I’ve got dual electric radiator fans, I’ve got the heated seats turned on, the wipers are on high, the headlights are on, the defroster blower is on high, I’ve got my emergency flashers on in hopes that it will help others see me on the highway and I just pressed the cigarette lighter in. I don’t have a rear window defroster but if I did, it would be on too. How much current is the alternator putting out at say 45mph?


Wrong, electrons don’t have road maps and will go the route of lowest resistance. The alternator voltage is a little higher than what the battery will supply also. Even if you were right and the battery was supplying current to the devices, the alternator would be replacing the battery charge as quickly as it was drained.


Actually, it’s Brown & Sharpe (with an “E”) and they standardized the gauge size for copper wire, it's the same as AWG. They may have set current ratings but NEC (National Electric Code) is normally recognized as the source for current rating although they round down for fuse size and they start at 14 ga. High or low voltage makes no difference in wire size. Everybody I know uses NEC so not “everyone” uses Brown & Sharpe. The ratings are NOT so that the wire will not heat up, the ratings are to keep heating to an allowable limit. Your 10ga is good for 30 amps unless you can find a 33.2 amp fuse link for the one shown in your drawing.

If you point was to impeach the source I used in the link, fine, show me the error. I’d have preferred to use the NEC table but all I found were part of large pdf links and not dial-up friendly for some of our members.


For your relay, the constant current is often not the most important consideration. As you say, inrush is another concern even for purely resistive loads such as lighting where the resistance increases as the filaments heat up. For inductive loads, the break current is often the most important. This is what causes arcing and burns contacts.

"""""electrons don’t have road maps """""

Gee - really? What do you think TAZ, they use GPS's in this modern day and age?



If the alternator's (+) output safely uses a 10 gauge, why would the alternator's ground system carry more current and need to be larger? Especially since it's in parallel with the brackets and engine block - far less resistive than your #2 or 0!

Basic electricity TAZ - read up on it!

I just bought a 6 AWG 18" long cable with eye ends last week - at AutoChina - from the local store, not from the internet. I'm using it to connect 2 batteries for 24 volts for my Ready Welder.

I don’t think he’s safely using a 10 gauge on the plus. I think he’s still in the build stage so he’s not running yet.

He’s also wanting to use an electric fan, but I wouldn’t expect you to remember that since you cant remember what wire gauge I said to use in this post.
I said 6 or he might get by with 8 for an 85 amp alternator.
I never said 2 and the 1/0 was for battery cables.
That fan he’s using is a high draw that wasn’t part of the original Jeep. While the 10AWG from the factory may have been sufficient for the original Jeep, it’s not with the addition of nearly constant draw, high current additions.

Using your same argument, if the Jeep safely operated without a dedicated ground from the alternator ground, why add one? The quote I remember from my father the best was, “If a job is worth doing, it’s worth doing right.” So, if you are going to the trouble to add a dedicated ground, why not spend the little extra so you don’t have to do it over?

“There’s a sucker born every minute.”

"""""4 AWG is the smallest I found on the AutoZONE website."""""

Then if they don't sell it - then how did I buy it there?
Now you are an authority on AutoChina's inventory too? We are impressed!

Obviously you have no clue as to WHY I wanted the smaller gauge. I have plenty of welding cable I could have used, but I WANTED smaller. Sorry, you are not an authority on my projects. Normally I don't buy anything but chemicals from AutoChina - but they were the only ones open at that hour. I prefer to buy quality products - they don't sell them. Even with that cable, I had to re-end it because one of the terminals fell off when I pulled on it!


Where did he say he's using an electric fan? You can't go back and edit what HE said, or didn't say!

Depending on the electric fan, most don't draw much except when starting up. TRY ONE!

In all your wire gauge "knowledge" and charts, and your statements about "it will only carry xxx" comments etc. you missed an important factor. Nowhere did you say anything about lengths. Resistance is what limits the current carrying capability. Length determines resistance. You never mentioned resistance at all.

Obviously a 6" piece of 10 will carry more than a mile of #1.

I said it was the smallest I found here or on their website. I have no idea what they sell to people in Kalifornia.


Nope, with the way your brain functions, I have no way of knowing WHY YOU WOULD DO ANY OF THE THINGS YOU DO. 18” is way to long for it to be a fuse link so that was out. So, give us the benefit of your “reasoning” such as it is and tell us why you would intentionally use undersize wire.


I gave you the link. CLICK ON IT!!!!!!


If you figure out how to click the link I gave, you’ll see he has a Taurus fan. Read the rest of the thread, it’s a known power hog. As far as your “TRY ONE!”, I’ll pass. I TRIED TWO, the same duals that came out of the donor Firebird that my TPI engine came out from. If I were to “TRY ONE!”, as you suggest, I’d have the same problem he does with clearance between the pulleys and the radiator.


WRONG!!!!!!!!!!!!!!!!!!!!!!!!! Length has ABSOLUTELY NOTHING to do with the current carrying capacity.

The longer the wire, the more VOLTAGE DROP it produces. This is a function of the current being carried and the resistance of the wire. You don’t understand basic electricity, READ UP ON IT!!!!!!!! You have confused the fact that you use a bigger extension cord to reduce voltage drop for high current power tools if the cord is long, say over 25’. It has nothing to do with the current carrying capacity of the wire gauge. Furthermore, I didn’t think there was a need to discuss the voltage drop BECAUSE I DIDN’T EXPECT HIM TO USE ANYWHERE NEAR 25’ OF WIRE.


Remembering something Thor asked you, if I provide the aluminum ladder, will you measure the gauge size of a high voltage overhead line that runs for MILES (plural).


From your comments, I think your electrical knowledge is limited to changing your own flashlight batteries. You’re in way over your head. Go play in the kiddie pool until you can swim with the adults.