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Cable & Wiring Questions

Some of the most common questions I get asked are things like, “what type of wire do you use to build the cables?” and “What size cable should I use for my vehicle?”

Below are some descriptions of what we use, information on the types of wire and when to use it and some other technical charts to use.  I’ll even give you my opinion about if you should be using marine grade wire on your Dodge Dart…..

Different Types of Wire and Use:

SGT Battery Cable: 

We generally use SAE (Society of Automotive Engineers) SGT battery cable.  SGT designates the type of insulation.  For example ‘THHN” is probably what you have for wiring your house (THHN stands for “Thermoplastic High Heat-resistant Nylon-coated).  SGT is a thermoplastic PVC insulation rated at 50 volts. It’s typically rated for 85 or 105 degrees C.  This is the lowest cost wire of the 3 wire types discussed here and it does the job just fine.  It usually has a fairly low strand count (meaning the strands are larger), making the wire stiff enough to stay where you put it but is still flexible enough to bend around tight corners.

Pros: Lowest cost, SAE rating

Cons: Lowest temp rating (as low as 85C, about 185F)

SGX Battery Cable:

Sometimes we use SGX battery cable. SGX uses a high-grade XLP (Cross-Linked Polyethylene) insulation which has a higher temperature rating. The trade-off is the insulation is thicker and stiffer.  Often it has a higher strand count to make it flexible to help offset the stiffer insulation. It also costs a little more. If you need the higher temp rating, it might be a good solution.

Pros: SAE rating. Higher temp rating (125C)

Cons: Stiffer, might be harder to route. More expensive.

Marine Grade:

There are several types of “Marine” wire. It’s usually rated for a higher temperature and “wet” (think submerged) applications. It also has a requirement that it be “self-extinguishing”. That is extremely important on a boat in the middle of nowhere.  SGT-M is SGT battery cable rated for marine use and is only a little more expensive that SFT. Some marine grade wire is “tinned” (plated) to help reduce corrosion and has a high strand count like welding cable. It can get very expensive (twice as much).

There was a time when I was grumpier if I was asked for a marine cable for a car that I would answer “Are you going to be taking your Taurus out to sea??”. I thought it was a waste of time, money and energy. I still do in most cases. Then a friend pointed out that perhaps marine cable would help if one lived somewhere near the ocean and a salt atmosphere, or maybe salt on the roads. Or perhaps the self-extinguishing characteristic was of critical importance to the customer. I guess that might be true. I live in the desert, so I don’t have any personal experience with such things. However, I can tell you that once we install the lugs, terminals and the heat shrink is applied, no copper is exposed so I honestly doubt it actually makes much difference in automotive applications.

Because of the high cost I only stock small quantities of marine cable but if I don’t have it, I can order it. Expect it to take a few days longer.

I absolutely believe that it must be used on boats. After all, that’s what it’s made for. I will not build a cable intended for marine use out of automotive wire. Don’t bother asking.

Pros: High temp, flexibility (sometimes), corrosion resistant, wet applications, self-extinguishing

Cons: Expensive, sometimes hard to get out here in the middle of the Arizona desert

Fuse Link or Fusible Link:

Fuse link wire is a special wire that is intended to act as a fuse. It has special very high temp insulation that won’t burn even if the wire becomes so hot that it fuses open. It’s most common use is in alternator wires. It protects the electrical system from a catastrophic failure of the alternator where the alternator shorts to ground. Without the fuse link, the alternator wire would melt or burn, possibly starting an under hood fire. It’s usually a 6 to 9-inch piece two wire sizes smaller than the wire it is protecting. For example, a 4 gauge wire would use a piece of 8 gauge fuse link. It is hard to find fuse link larger than 6 gauge. To purchase: Order Wire

Welding Cable:

Welding cable is built to be flexible so the welder does not have to work hard to drag the wires around. It usually has a high temp rating and a soft flexible insulation. I have seen it swell up when exposed to oil; do NOT use it in an application where it will get oily. For that reason, I do NOT recommend it for automotive applications. Welding cable tends to be large gauge wire so I think the guys that claim welding cable is the very best stuff to use do so because they are comparing very large 2/0 welding cable to a small #2 battery cable. They don’t really understand why it’s better. If they compared apples to apples, a 2/0 welding cable to a 2/0 battery cable in an oily under-hood application, they would agree the SGT/SGX batter cable is a better choice. I do NOT stock welding cable but I can order it. It does work well as a booster cable where the ability to roll it up and put it behind the seat is important.

Pros: High temp; very flexible

Cons: Expensive; soft insulation; limited abrasion resistance; not oil resistant. Not SAE approved.

High Strand Count:

Some folks are looking for high strand count battery cable.  Perhaps they have heard it’s somehow “better”. Other folks think that carries more power due to “skin effect”. That is just plain false. Skin effect is a high-frequency phenomenon (think radio frequency or microwave) and is nonexistent at 12V DC. The high strand count is more flexible but in an automotive application, the cables get installed once and hopefully they never move again! So, flexibility isn’t really a huge issue.

OFC (Oxygen Free Copper):

Don’t waste your money. This stuff is just another way for stereo salesmen to get more of your hard-earned money.  OFC (Oxygen Free Copper) wire is a type of wire that often gets sold by stereo shops as the best stuff to hook up speakers or a high power amp. I occasionally get asked about it.  I’ve had folks ask if I can make battery cables out of it. 

What’s different about it?

As the name suggests the copper used in the wire is “oxygen free”, almost.  It’s not really “oxygen free”, it has less oxygen.  When copper is smelted oxygen is added to help remove the other impurities.  OFC adds another step by adding phosphorous to remove the oxygen.  Standard wire is AT LEAST 99.90% pure copper.  OFC is 99.95% pure copper.   An extra 0.05% copper sounds good.  What’s the downside?  COST.  OFC is often TWICE the price for the same size of standard cable. So you are paying DOUBLE for 0.05% more copper.  There is NO measurable electric difference (source Wikipedia 


For automotive cables, I like the SAE rated SGT or SGX battery cable. It works great for automotive applications at a fair price. Do NOT use welding cable for under hood applications.

For boats, you have got to have “marine”. I’m no legal expert, but isn’t that a Coast Guard rule?

Welding cable makes great booster cables or portable inverter cabling. Nice and flexible for when you roll them up and put them back in the trunk.

What size Cable do I need?

6 Gauge

6 Gauge works for accessory leads and most stock alternators. Battery cables for small engines (like ATVs and sub-compacts). Some stock golf cart wiring.

4 Gauge

4 gauge wire makes great accessory leads and alternator wiring (up to about 180A).  Many cars use this as battery cable. Some electric ATVs use #4 for the battery banks. It also makes very good automotive booster cables.

2 Gauge

We recommend #2 wire for 4 cylinder and small 6 cylinder automotive engines, hi-power accessories (like winches, power converters) and alternators over 180A.  Also works great for high-performance golf cart battery banks.  Recommended for professional heavy-duty,  booster cable (jumper cable) kits.

1/0 Gauge

1/0 makes great battery cable for large or hi-performance 6 cylinder engines and stock V8s.

2/0 Gauge

Use 2/0 for hard to crank engines (like high compression, big blocks, or diesel engines), electric vehicle battery banks (depending on controller amperage), and large RV power converters house batteries..

3/0 and 4/0

are for very large marine or heavy equipment engines and high power alternative energy battery banks.

Long runs:

For very long cables (for example 15-foot long battery cables to relocate your battery) go one size larger.

Go Big.

I recommend building cables larger than stock.  Most of the cost is the ends and labor.  Going up a size or 2 is worth it in the long run.  The manufacturers make stock battery cables as small as possible but still get the job done. Copper is expensive, about $3.10 as I write this. The manufacturer saves a few bucks on millions of cars and it adds up to real money. I recommend using cables larger than the factory because I believe they will work better and last longer. Isn’t that what you want for your car or truck? Something that will work better and last longer.

Just how big is that 2/0 cable? Check out the information in the charts below.

Technical Data and Wire Gauge Charts:

Note: this information comes from a variety of sources and it is used for reference only.  We have not personally verified all the data shown.

Don’t see the cable you wanted here?  Custom Battery Cables be happy to build a custom cable to your specifications.  Go to the Custom Orders page for more information.

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