Battery Cable Upgrade - Grounds

About to embark on the alternator upgrade and i seem to have a general understandng of the process. I do have a couple questions as it relates to grounding. #1; I will be replacing the - fenderwell; - to block; - to firewall cylinder head bolt. Do I need to replace - to alternator and starter with the same guage (my case 4AWG)? #2, should I re-do the existing connections for the smaller guage grounds going to the block from the wire loom? #3, the two wires that connect to the alternator (I believe alternator and injectors) should they stay connected to the alternator or redirect to the PDC? #4, and my final question with replacing the alternator positive wire (black) with an ANL fused run from the battery to the alternator should I remove the 60 amp fuse in the PDC? Does that fuse support any other device. Thanks for all the write-ups very helpful.

Bosbury1 - 1994 Jeep Cherokee Country

My experience is general, but 4 AWG seems a little lite for a starter, if you are looking for increased capacity.

4 AWG has an AMP rating of 80 (70 engineer speak) solid core and the AMP rating diminishes to almost half for the finest type strands, in a stranded cable.

A starter can draw over 200 Amps for a few seconds when it initially spins up.

The number of strands in a wire (cable) is one instance where more isn't better, the fewer the strands the better. The down side is the fewer the strands the stiffer the cable gets.

There is a point of diminishing returns on wire size, the connection can turn into the choke point.

5-90 would be the guy to ask for this. My experience is general.

Most of the AMP to AWG wire size tables, are for a solid core wire. This table may help you out, http://www.engineeringtoolbox.com/wire-gauges-d_419.html . Though just looking at it quickly, the table seems to have factored in a 15% (+/-) buffer, which is pretty standard for basic electrical engineering.

As the wire gets smaller the resistance goes up, the higher the resistance the more heat that is generated. If a high amperage is introduced, that exceeds the wire/cables specifications, it may work for a short period of time (like initial starter amp draw) as the heat will dissipate and heat sink. But if the amp draw is constant (like automotive sub systems) the heat can grow exponentially. My point is the wire size depends on the anticipated AMP load plus 15% (typically) and for how long the wire is amp loaded, at or beyond the specification.

I'm not an engineer, my experience is on a more practical level.

The two wires connected to your alternator are sense and field. They route directly back to PCM. From the PCM a wire is directed to a fuse in PDC. This fuse runs to the switching side of your ASD relay. Another fuse in PDC supplies power to the ASD relay. One of these two fuses removed would result in a non start of your engine, as the fuel injectors wouldn't work.

That is an odd table and I'm not sure how you are interpreting it. If you believe cores is referring to strands I believe you are wrong. I believe when it refers to cores it is talking about current carrying wires inside a pvc covered cable, aka romex. A 12-3 romex has 3 current carrying conductors and one bare ground. I don't believe you will ever find single strand 250mcm, it would be like trying to bend a sold 3/4 bar. Also I have never used any solid wire above #6.

Amount of strands has nothing to do with current carrying capacity. Electricity doesn't flow through the copper, it flows on the surface of it. A 6awg wire with 1 strand has the same capacity as a 6awg wire with 1000 strands. The strands are for flexibility and vibration resistance. If you have a solid wire attached to the engine and the frame it will be constantly flexing and will eventually break in the one spot it flexes from fatigue. Sorta like bending a paperclip back and forth.

If you are looking for current carrying abilities of wire look for something by the NEC (national electrical code) or similar. I didn't find one labeled NEC in my brief search but this one is correct in its ratings, http://www.armstrongssupply.com/wire_chart.htm

Thanks for the update. With regard to #4 I will keep it on the alternator. What about #1 and #2.

blubullett said:

That is an odd table and I'm not sure how you are interpreting it. If you believe cores is referring to strands I believe you are wrong. I believe when it refers to cores it is talking about current carrying wires inside a pvc covered cable, aka romex. A 12-3 romex has 3 current carrying conductors and one bare ground. I don't believe you will ever find single strand 250mcm, it would be like trying to bend a sold 3/4 bar. Also I have never used any solid wire above #6.

Amount of strands has nothing to do with current carrying capacity. Electricity doesn't flow through the copper, it flows on the surface of it. A 6awg wire with 1 strand has the same capacity as a 6awg wire with 1000 strands. The strands are for flexibility and vibration resistance. If you have a solid wire attached to the engine and the frame it will be constantly flexing and will eventually break in the one spot it flexes from fatigue. Sorta like bending a paperclip back and forth.

If you are looking for current carrying abilities of wire look for something by the NEC (national electrical code) or similar. I didn't find one labeled NEC in my brief search but this one is correct in its ratings, http://www.armstrongssupply.com/wire_chart.htm

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Like I said I'm not an engineer, but the basic I was taught is up the wire size (diameter) when using strands in place of solid core. The fewer strands the better. It all boils down to being able to bend and work the cable and other considerations like vibration.

Anywho AWG 4 sounds small for using as a ground, engine to firewall or as a plus cable to the starter. Check with 5-90 he has a much better grip on the automotive aspects. Most of my experience is on compressors and electric motors.

We work a slightly different system here, everything is a wire cross section measured in mm squared. Maybe that is the confusion. The diameter of the wire changes as strands are added. Maybe I was confusing diameter with gauge? I rarely work with AWG other than control circuits.

When I guestimate wire size I always err on the side of caution.

When replacing solid core (which is the standard used in most AMP to wire size tables), I multiple by 1.8 (quick calculation) when switching to stranded wire. I've likely wasted a lot of copper over the years, but I've rarely to never had any heat damage to my wire ends.

Here is what Kelly (5-90) did http://www.kelleyswip.com/electric.html

I've had poor results using very fine stranded cable. You have to compromise a bit. Thin enough strands to be flexible not so thin it gets fragile.

SAE J 1127 STG-(AWG), I typically use STG-1 or 2. I went out and read the markings on the cable in my 88 XJ. SAE 1127 STG is MIL Spec., Chrysler Spec and Ford Spec. The cable I used doesn't have the AWG size on it, best guess is AWG 2.


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The stuff I used for the rear head to firewall ground is starting to fray from vibration, so I'm not going to recommend that. I believe it is Abrams tank jumper cable (no kidding), AWG 3/0 or 4/0 with hair fine cable strands. I have some other stuff about the same size with slightly thicker braided strands (kind of a cheese cloth weave and not actually braided) I'm going to try.

8Mud said:

Here is what Kelly (5-90) did http://www.kelleyswip.com/electric.html

I've had poor results using very fine stranded cable. You have to compromise a bit. Thin enough strands to be flexible not so thin it gets fragile.

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Not sure where you are getting that fine stranded is bad, the fine stranded cable that's available (ie: welding cable) works great and is in a ton of XJs. 4 AWG is fine for the starter, it's a definite upgrade over the factory starter wire. I know there is cable available that uses finer strands than even welding cable but it's harder to find and is generally quite a bit more costly. I still doubt it would be an issue though.


All of 5-90s cables are welding cable, and he recommends 4AWG as a standard upgrade, with 1 AWG available if you think you need it. So yes, 4 AWG is sufficient.

To answer #1 - The starter and alternator don't have separate grounds to replace. #2 - don't worry about it.

donthelegend said:

Not sure where you are getting that fine stranded is bad, the fine stranded cable that's available (ie: welding cable) works great and is in a ton of XJs. 4 AWG is fine for the starter, it's a definite upgrade over the factory starter wire. I know there is cable available that uses finer strands than even welding cable but it's harder to find and is generally quite a bit more costly. I still doubt it would be an issue though.


All of 5-90s cables are welding cable, and he recommends 4AWG as a standard upgrade, with 1 AWG available if you think you need it. So yes, 4 AWG is sufficient.

To answer #1 - The starter and alternator don't have separate grounds to replace. #2 - don't worry about it.

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I'm not saying it is bad, I'm just saying there may be better alternatives. Like I said or was trying to say, in very fine cable threads (strands) can be vibration sensitive and when/if they do heat up the outer strands have a tendency to melt. Hundreds of different kinds of cable out there, much of it has a standard thread diameter (one size for small cable, slightly smaller for medium and slightly smaller for thick, my guess is for flexibility. I've done a lot of cable repair, I see what tends to fail.

Also what I was trying to say is don't hold the AMP tables as gospel, the AMP rating (same AWG) of a cable changes as strands are added and it is also dependant how the strands are packed in the cable (a stack of circles has air gaps).

AWG isn't the only standard and not an absolute. I was just making some suggestions to ponder when choosing cable.

My first consideration is always whats available and also what I already have on the shelf. When in doubt up the AWG (lower number).

Kellys stuff is tried and proven, in the end, results are the applicable standard.

8Mud said:

I'm not saying it is bad, I'm just saying there may be better alternatives. Like I said or was trying to say, in very fine cable threads (strands) can be vibration sensitive and when/if they do heat up the outer strands have a tendency to melt. Hundreds of different kinds of cable out there, much of it has a standard thread diameter (one size for small cable, slightly smaller for medium and slightly smaller for thick, my guess is for flexibility. I've done a lot of cable repair, I see what tends to fail.

Also what I was trying to say is don't hold the AMP tables as gospel, the AMP rating (same AWG) of a cable changes as strands are added and it is also dependant how the strands are packed in the cable (a stack of circles has air gaps).

AWG isn't the only standard and not an absolute. I was just making some suggestions to ponder when choosing cable.

My first consideration is always whats available and also what I already have on the shelf. When in doubt up the AWG (lower number).

Kellys stuff is tried and proven, in the end, results are the applicable standard.

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The amp rating doesn't change with strand differences. That is what I was trying to tell you the other day. You are reading the table you posted wrong. Cores on that table is complete seperate covered wires inside another coating, not strands. That table is talking about home wiring, also called romex. And finer strands are better for vibration. I have been an electrician for 15 years so I'm not the brightest guy but I know a little about electricity. And Kellys stuff is really fine strand so you endorsing it and at the same time saying fine strand is bad is really confusing. I have Kellys battery cables and they are awesome.

blubullett said:

The amp rating doesn't change with strand differences. That is what I was trying to tell you the other day. You are reading the table you posted wrong. Cores on that table is complete seperate covered wires inside another coating, not strands. That table is talking about home wiring, also called romex. And finer strands are better for vibration. I have been an electrician for 15 years so I'm not the brightest guy but I know a little about electricity. And Kellys stuff is really fine strand so you endorsing it and at the same time saying fine strand is bad is really confusing. I have Kellys battery cables and they are awesome.

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The amp rating they give for AWG size is almost invariably for a solid core wire. I haven't looked at every table available. Maybe I used the wrong table?

Kellys cables seem oversize so any AMP rating lost in strand size (or not) is irrelevant.

The original poster seemed to want to make his own. What I offered was opinion, along with about 50 years experience in machinery and wiring machinery.

Kelly uses heat shrink on his cable ends, I believe, this is the point where very fine cable strands tend to fray. Kellys cables are over sized so heat is unlikely to be an issue. Corrosion over decades might be an issue.

Most drums of cable are labeled, AWG size, a wire type code, a strand configuration code, a DIN code, ASE code, mm squared size and if you are lucky an AMP rating, sheath temperature range (usually another code). And even the AMP rating isn't standard, maybe ten years ago they lowered it, almost across the board, by nearly thirty percent.

blubullett said:

The amp rating doesn't change with strand differences.

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If what you are saying is accurate, why all different kinds of cable?

All I was trying to do was make a point that rating cable Amperage by AWG size charts isn't always accurate and buying cable just by AWG size isn't necessarily good for a particular application. If I used faulty information trying to make my point I apologize.

The topic wasn't sharp shooting me or Kellys cables (like I said they work and they last) (it is what it is, rarely what somebody says it is and almost never what somebody says it should be). The topic sat there with zero replies for days. I was trying to be helpful, You never gave any advice except that my advice was wrong. I can't see how that was helping the poster at all.

OK I'm wrong, so what, what advice do have to give, besides not listening to my advice?

The only time IMO that oversized cables are going to help the starter much is at initial spin up, The battery to block ground carries more Amps generally.

And lastly, I tend to double cables, instead of pulling them and up sizing, whenever possible anyway. The reason is simple, redundancy works. The battery I have in my XJ has four poles.

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I see six cores (bad eyes ?) Maybe the table I used was the wrong table, anything is possible. Anyhow I figure the guys at Mil Spec, Chrysler and Ford may be smarter than me and chose this strand/core configuration, oil resistance and temperature range wire for a reason. How big you want to upgrade is a matter of opinion. I usually upgrade cables that show heat damage or use the finger test and check for heat. Heat equals resistance, in most cases less resistance in the cables is a plus and larger cables make better heat sinks. And like I said there can be a point of diminishing returns, the cable ends and connections may be a choke point.

I'm finished being windy, now it is your turn to try and give the poster some useful advice.

Ooops, double post.

Those are not six core wires. When you read "core", think "conductors". Typical home wiring isn't done conductor-by-conductor. You by a roll of Romex with two conductors in it, each insulated from each other, but wrapped in a common paper jacket. The thing is, this outer jacket acts as an insulating layer - so more cores build up more heat, which can become dangerous.

To the OP...
If you really want to, buy battery cable one size up from the factory junk & solder on some ends. Then heat shrink it.
What I've done was this: go to the JY. Find cars that have the battery in the trunk (newer Volvo stuff comes to mind) & "harvest" all that thick-gauge factory quality stuff. Buy a few cable lugs & make something happen.

yossarian19 said:

Those are not six core wires. When you read "core", think "conductors". Typical home wiring isn't done conductor-by-conductor. You by a roll of Romex with two conductors in it, each insulated from each other, but wrapped in a common paper jacket. The thing is, this outer jacket acts as an insulating layer - so more cores build up more heat, which can become dangerous.

To the OP...
If you really want to, buy battery cable one size up from the factory junk & solder on some ends. Then heat shrink it.
What I've done was this: go to the JY. Find cars that have the battery in the trunk (newer Volvo stuff comes to mind) & "harvest" all that thick-gauge factory quality stuff. Buy a few cable lugs & make something happen.

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Thanks for the clarification, disregard my cores table.

We use something like Romex here, but it is plastic insulated wire inside another plastic sheath. I think they call them cores also, ground, common, phase and they add wires (cores) for additional phases and reverse polarity switches. Sometimes things get lost in translation.

Back in my racing days I bought a bunch of battery to trunk relocation kits. They had them on sale at Summit, Summit brand. AWG 2 (I think? maybe AWG 1). The battery clamps are already on there. I've got one of those big mother crimpers for the cable lugs, I still wrap the insulation in a wet rag and solder the ends after crimping.

I've been using a hammer style crimper, then blowtorching & piling solder into the ends. Not elegant but it is in my budget and seems totally effective. Add heat shrink to conceal your shame, and you've got custom cables.

yossarian19 said:

I've been using a hammer style crimper, then blowtorching & piling solder into the ends. Not elegant but it is in my budget and seems totally effective. Add heat shrink to conceal your shame, and you've got custom cables.

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The only real test is if it works or not. If it works your good to go.