The Big 3 just turned into The Big 7

[Shepherd214]

I was just testing the output of my alternator and at idle its putting out around 30A to the fuse box but from the fuse box to the battery its only 10-12A. Is this normal? Everything is tight and the resistance in the cable is good. It doesn't make sense.

 

[19963.4lsr5]

I was just testing the output of my alternator and at idle its putting out around 30A to the fuse box but from the fuse box to the battery its only 10-12A. Is this normal? Everything is tight and the resistance in the cable is good. It doesn't make sense.

Your battery only draws what it needs. When it’s fully charged you will only see 2-3a going to the battery.


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[octanejunkie]

In any closed DC circuit, amperage is the same no matter where you measure. So, every single amp produced via the alternator travels on both the positive and negative equally. At this point, one wire cannot simply “always be bigger” in comparison to the other. I think that rule of thumb is misleading to folks without education.

Unless you’re assuming the positives are going different locations and they all share a single larger ground, then yeah that’s fine.

The statement “you can always run a smaller power wire” or whatever was said was what I was hung up on.

If you don’t believe me, try it. Build a simple circuit with a battery and a light bulb. Use an amp clamp and you’ll see the positive and negative carry the same current, as long as the system is closed. Therefore, the wires should be sized the same in my opinion, or it becomes a potential choke point.

Good topic, so here's my question (and I think I know the answer)

If I run a larger gauge wire from a high amp alternator to my battery, let's say 2AWG (0.256" conductor), I'm planning on running 2 smaller negative battery feeds, 8AWG (0.1285" conductor) one to the block, and one to the frame.

Does the sum of the 2 smaller conductors equal the same return path as the single larger conductor feed path?

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[brillo_76]

Good topic, so here's my question (and I think I know the answer)

If I run a larger gauge wire from a high amp alternator to my battery, let's say 2AWG (0.256" conductor), I'm planning on running 2 smaller negative battery feeds, 8AWG (0.1285" conductor) one to the block, and one to the frame.

Does the sum of the 2 smaller conductors equal the same return path as the single larger conductor feed path?

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No. Use the American wire gauge for Amp capacity of copper wire.

2 awg does not equal 2 of 8 awg. So that's not going be even exactly.

However, if you use 1 of one gauge and 2 or 3 of a smaller gauge that equals the sum of the 1 gauge. Then yes current will be matched.

So to answer your question yes but just not your example is all...

I try to think of current like flowing river. It's going to take the path of least resistance as it travels along the valence electrons of the copper wire.

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[octanejunkie]

No. Use the American wire gauge for Amp capacity of copper wire.

2 awg does not equal 2 of 8 awg. So that's not going be even exactly.

However, if you use 1 of one gauge and 2 or 3 of a smaller gauge that equals the sum of the 1 gauge. Then yes current will be matched.

So to answer your question yes but just not your example is all...

I try to think of current like flowing river. It's going to take the path of least resistance as it travels along the valence electrons of the copper wire.

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Okay, makes sense.

Looking at ampacity, two 4 awg wires carrying 75-85 amps each should equal the flow of a single 0 awg carrying 150 amps

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[octanejunkie]

Okay, looking at the CS144 alternator to saturate larger gauge wiring, what about that 120 amp fuse/fusesble link in the fuse box?

What about upgrading that to 140 amp?

Bussmann FLM-140 Male Terminal Fusible Link (Automotive - 140 A (Violet)), 1 Pack https://a.co/d/0mKXssD

 

[AbuHaroon]

How to fuse your circuits

Okay, looking at the CS144 alternator to saturate larger gauge wiring, what about that 120 amp fuse/fusesble link in the fuse box?

What about upgrading that to 140 amp?

Bussmann FLM-140 Male Terminal Fusible Link (Automotive - 140 A (Violet)), 1 Pack https://a.co/d/0mKXssD

First post -

I am not sure what is the Alternator output for the CS144 Alternator. However I can give you some guidance on the fuse you should use.

Fusing is to save the circuit from shorting out. Where you have the fuse burn up before the wires of the circuit itself gets overheated and short out.

Lets say the Alternator (device load) max output is 150 Amps.

The fuse size should be = 1.25 x Device Load so if its an 150A Load

Fuse should be = 150x1.25 = 187.5Amp fuse. Which you may not find. So I would upgrade to a 200Amp fuse to be safe. Thats a 1.33 factor but you should be safe having the fuse blow before the circuit overheats.

Additionally its important to note that the "Wire size+length" of the circuit should be able to handle more Amps than the required load of circuit. If not its not the fuse that would burn up by the circuit wires itself. However for the most part the wire size+length is bigger than the load on the circuit. So you should be good choosing the correct fuse on the circuit.


Fuse size calculator - Here's a link for reference.

 

[octanejunkie]

First post -



I am not sure what is the Alternator output for the CS144 Alternator. However I can give you some guidance on the fuse you should use.



Fusing is to save the circuit from shorting out. Where you have the fuse burn up before the wires of the circuit itself gets overheated and short out.



Lets say the Alternator (device load) max output is 150 Amps.



The fuse size should be = 1.25 x Device Load so if its an 150A Load



Fuse should be = 150x1.25 = 187.5Amp fuse. Which you may not find. So I would upgrade to a 200Amp fuse to be safe. Thats a 1.33 factor but you should be safe having the fuse blow before the circuit overheats.



Additionally its important to note that the "Wire size+length" of the circuit should be able to handle more Amps than the required load of circuit. If not its not the fuse that would burn up by the circuit wires itself. However for the most part the wire size+length is bigger than the load on the circuit. So you should be good choosing the correct fuse on the circuit.





Fuse size calculator - Here's a link for reference.

Appreciate the cogent reply!

What I failed to mention is that I plan to put a 200A fuse in between the CS144 alternator and the battery.

The question above specifically is should I consider upgrading the 120A alternator fuse in the fuse box, too?

FWIW, I have not found a 200A fuse the same size as the factory fuse, the largest I found was 140A

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[Bad Luck]

Appreciate the cogent reply!

What I failed to mention is that I plan to put a 200A fuse in between the CS144 alternator and the battery.

The question above specifically is should I consider upgrading the 120A alternator fuse in the fuse box, too?

FWIW, I have not found a 200A fuse the same size as the factory fuse, the largest I found was 140A

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I wouldn’t worry about upgrading the fuse block main fuse unless you are repinning the fuse block and adding additional circuits/current draw to it.

 

[octanejunkie]

Additionally its important to note that the "Wire size+length" of the circuit should be able to handle more Amps than the required load of circuit. If not its not the fuse that would burn up by the circuit wires itself. However for the most part the wire size+length is bigger than the load on the circuit. So you should be good choosing the correct fuse on the circuit.





Fuse size calculator - Here's a link for reference.

Circling back to this

The CS144 is rated to put out 140A

I was planning on 200A fuses for all charge loads off the alt on 0 AWG, even though they are shorter runs, but also bc I'm going to to a second battery in the rear cargo area with a Redarc separator in between.

The current plan looks like this

The link you shared shows smaller gauges depending on ambient temp and voltage drop, for example

Which suggests O AWG is overkill...

 

[brillo_76]

Welding Wire in a 3rd gen... 0 AWG 150 amp 00 175amp...:lookout:

One thing is for certain...I don't think you are going to melt the wires from drawing too much current...

 

[3bears]

bringing back an old topic. About to do an upgrade...not so big...to the denso 105 amp alternator mod. While im at it gonna do the big 3. Here is the thing...everything I have read does not mention the size of the lugs...matter of fact the most common looked at thread/sticky says nothing to this other than using 3/8 lugs that are sloppy and fit bad making me think about the electrical current connetion thingy... without grinding the outside to make if fit inside. the alternator fitting. so if your gonna do the big 3 you need a lug to go to 1/4 inch for the alternator .
i did the big 3 on my first 3rd gen. ..dont remember this ...but im older now..and back then I had a full shop so could have done some changes,,,dont remember. but i got my new alternator...big wires and lugs sitting here in front of me....making sure I can do a one shot quick and easy swap and obviously i need to get some lugs for 1/4...well 1/4 at the alternator connection,,, well 7mm if we are goanna get picky,
and yes there was or still is a guy who sold the correct lengths and lugs on ebay for the 3rd gen...at nearly 100....when you can do your self for less than half

oh and btw,,,im not pulling big power or a wench...so im just jumping up to 4 awg

 

[TwoToneT4R]

Upgrading to a 200amp ALT

Hi all! Sorry to revive on old thread but...

My factory alternator just took its life and i've just ordered and received a 200amp factory alternator that's been beefed up. Im looking at buying the "Big 7" upgrade from jeepcables and I have a question.

Will 2gauge be good enough to support the bigger alternator or should I go with 1/0gauge? I'm running 2 12" subs with an amplifier and some aftermarket headlights and probably plan on adding more goddies in the future (fridge, winch).