Positive battery terminal contacted body, Jeep wont start

[KennethS]

Technically, if you're running a 160A alternator, you should at least be running 1/0 battery cables.

The cable from the alternator to the battery should be larger since the alternator current is flowing through that cable to charge the battery. The increased current is not flowing through the cable down to the starter, so whatever is large enough to carry the starter current is sufficient. The negative battery cable is that same size, so it seems to me (maybe I'm wrong) that the only larger cable needed is the one from the alternator to the battery.

 

[DeltaNu1142]

Agreed... the starter cabling should be sized for the starter. But that alternator current flows to (for the sake of argument) ground, too... so there's at least one other cable that needs to be sized for the alternator. Maybe it's the ground terminal to the engine block, or to the frame. I haven't looked at alternator to see where its ground connection is.

 

[KennethS]

The alternator is typically grounded through its mounting bolts and brackets to the engine block. The negative battery cable is also connected to the engine block, so it is already larger size than the alternator-to-battery charging cable. There should also be a ground cable from the engine block to the body/firewall. I haven't looked on the TJ - the one I am familiar with on one of my other cars is a thick braided strap from the back of the block to the firewall.

I was just thinking the feed to the fuse panel would likely need to be adequate to support any increased current. Dunno how easy it would be to modify that.

 

[jjvw]

The cable from the alternator to the battery should be larger since the alternator current is flowing through that cable to charge the battery. The increased current is not flowing through the cable down to the starter, so whatever is large enough to carry the starter current is sufficient. The negative battery cable is that same size, so it seems to me (maybe I'm wrong) that the only larger cable needed is the one from the alternator to the battery.

Dodge didn't do it that way.

 

[jjvw]

The alternator is typically grounded through its mounting bolts and brackets to the engine block. The negative battery cable is also connected to the engine block, so it is already larger size than the alternator-to-battery charging cable. There should also be a ground cable from the engine block to the body/firewall. I haven't looked on the TJ - the one I am familiar with on one of my other cars is a thick braided strap from the back of the block to the firewall.

I was just thinking the feed to the fuse panel would likely need to be adequate to support any increased current. Dunno how easy it would be to modify that.

You need to go look at your TJ.

 

[KennethS]

You need to go look at your TJ.

Fortunately I have not needed to do any electrical work, so I have not studied the wiring. So what am I missing?

 

[jjvw]

Fortunately I have not needed to do any electrical work, so I have not studied the wiring. So what am I missing?

What you are missing is that all the main power and grounds are all the same 6awg. All this fancy sizing for this and that didn't seem to enter the minds of the OEM engineers.

Having gone through this on mine about a year ago as part of the highline fender install and me being an electrician, my main takeaway was that the automotive industry (and Warn) does not follow the National Electrical Code for wire sizing. And there was no correlation that I could identify. And there was even less than no correlation found on the dozens of inconsistent charts I found on the internet.

Using Jeep and Dodge as my main examples, followed by Warn, I could never identify a valid reason to increase the wire size of the main power and grounds from the factory 6awg. I ended up bumping everything up to 4awg anyway and with no way to justify it.

 

[KennethS]

Thanks for the info. I looked up 6awg and it can support 60 Amps, so I reckon the auto engineers figured that it was adequate for the vehicle's needs (unless someone installed a monster stereo, but that ain't the manufacturer's concern).

 

[Lou]

Thanks for the info. I looked up 6awg and it can support 60 Amps, so I reckon the auto engineers figured that it was adequate for the vehicle's needs (unless someone installed a monster stereo, but that ain't the manufacturer's concern).

There are many factors that come into play. Stating 6 awg can support 60 amps is not enough. Cable type? Temperature? Length? Voltage? All go into play for current carrying capacity.

 

[DeltaNu1142]

I tend to overbuild the crap out of things, because it doesn't require a lot of thinking. I'm building a bench around a dining table at my house, and the legs are notched 4x4 posts spaced at 4' and blocked on all sides. When I'm done, I'll be able to park the Jeep on it. I probably could have done it a bit cheaper, but it would have required more thought.

I realized a little while ago that the main role of a lot of engineers is to figure out how inexpensively a design can be executed. But if you don't mind spending a little extra... the safety margins get big. You just don't know how big, because you haven't given it enough thought.

 

[jjvw]

I tend to overbuild the crap out of things, because it doesn't require a lot of thinking. I'm building a bench around a dining table at my house, and the legs are notched 4x4 posts spaced at 4' and blocked on all sides. When I'm done, I'll be able to park the Jeep on it. I probably could have done it a bit cheaper, but it would have required more thought.

I realized a little while ago that the main role of a lot of engineers is to figure out how inexpensively a design can be executed. But if you don't mind spending a little extra... the safety margins get big. You just don't know how big, because you haven't given it enough thought.

If that is what we are doing, then dream big!

 

[DeltaNu1142]

If that is what we are doing, then dream big!

Story time! I'll try to keep it short...

I was working on a new power plant install in Europe, in an area that wasn't entirely free of corruption. I was responsible for assembling the generator with the help of craft labor. Generator in place, first job was to get all of the parts together. Neutral busbars tie the 3 neutral bushings together... they're about 14" wide, 1/2" thick, and 12' long, pure copper, and there were four of them.

I went to the materials guy to locate these things in the laydown yard. I told him what I was looking for, and he asked me to describe them. I gave him the info above. He laughed and said: "You're never going to find those."

 

[jjvw]

Story time! I'll try to keep it short...

I was working on a new power plant install in Europe, in an area that wasn't entirely free of corruption. I was responsible for assembling the generator with the help of craft labor. Generator in place, first job was to get all of the parts together. Neutral busbars tie the 3 neutral bushings together... they're about 14" wide, 1/2" thick, and 12' long, pure copper, and there were four of them.

I went to the materials guy to locate these things in the laydown yard. I told him what I was looking for, and he asked me to describe them. I gave him the info above. He laughed and said: "You're never going to find those."

That could easily be a few thousand bucks a stick at the scrap yard today!

 

[JMT]

That could easily be a few thousand bucks a stick at the scrap yard today!

Yep, that was my first thought. Copper that size would have legs.

My son is an electrician apprentice now. Last week they wired a few houses and one night someone came in, cut the wires and stole the box. They can’t re-use that wire because it’s been stapled, and so it’s considered used. He took that wire and turned it in as scrap for $190.

Lots of money in those copper busses ^.

 

[KennethS]

There are many factors that come into play. Stating 6 awg can support 60 amps is not enough. Cable type? Temperature? Length? Voltage? All go into play for current carrying capacity.

Yep. We know the cable is multi stranded copper. We know the temperature is around 200F, give or take depending upon geographic location. We know the length is under 4 feet. We know the voltage is 12-14 Volts. It’s not like those are unknowns.

 

[jjvw]

Yep. We know the cable is multi stranded copper. We know the temperature is around 200F, give or take depending upon geographic location. We know the length is under 4 feet. We know the voltage is 12-14 Volts. It’s not like those are unknowns.

And if you look at the 90°C column in the NEC you learn that the automotive industry and Warn is doing something different than that.

 

[KennethS]

I experienced similar with car designed and built in Sweden with an intercooler that was woefully under-designed for the Phoenix summer temperatures. I’m sure it worked fine in Sweden with their 70F summer temperatures, though.

 

[lBasket]

I experienced similar with car designed and built in Sweden with an intercooler that was woefully under-designed for the Phoenix summer temperatures. I’m sure it worked fine in Sweden with their 70F summer temperatures, though.

SAAB?

 

[KennethS]

And if you look at the 90°C column in the NEC you learn that the automotive industry and Warn is doing something different than that.

I looked it up and the NEC rating shows 75 Amps.

 

[macleanflood]

We have a whole cottage industry here outside Eugene/Springfield...and I've seen signs of in in Vancouver, California and Washington.

Folks grab free RVs or steal them, strip them for copper and metal...scatter the parts all over the woods...and rinse and repeat.

-Mac