Battery Wire & Cable Questions

SGT Battery Cable: 

We generally use SAE (Society of Automotive Engineers) SGT battery cable.  SGT designates the type of insulation.  (Wire is rated by several characteristics but most commonly its insulation type.  For example ‘THHN” is probably what you have for the wiring in your house.  THHN stands for “Thermoplastic High Heat-resistant Nylon-coated). SGT is a thermoplastic PVC (polyvinyl chloride) insulation rated at 50 volts. It’s typically rated for 85 or 105 degrees C.  

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.

Buy SGT Battery Cable

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 and is more abrasion-resistant. The trade-off is the insulation is thicker and stiffer.  Often it has a higher strand count. If you need a higher temp rating, it’s a good choice.

Buy SGX Battery Cable

Marine Battery Cable:

There are several types of “Marine” wire. It’s usually rated for higher temperatures and “wet” (think submerged) applications. It also has a requirement that it must be “self-extinguishing”. The marine rating is a Coast Guard legal requirement for marine applications.  Do not build a cable intended for marine use out of wire that does not have a marine rating. 

Most of the SGT we sell also carry a marine rating (BC-2 rating)

Get all of the Marine Battery Cable specs here.

Fuse Link or Fusible Link:

Think of a fuse link as a very slow-acting (“slow-blow”) fuse that looks like a piece of wire.  Fuse link wire 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 diodes.  Without the fuse link, the alternator wire would melt or burn, possibly starting an underhood fire.  Other common applications are the wires going to glow plug or intake grid heater relays on diesel engines.

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.

Buy Fuse Link Wire

OFC (Oxygen Free Copper):

OFC (Oxygen Free Copper) wire often gets sold by stereo shops to hook up speakers or a high-power amp. Don’t waste your money. This stuff is just another way for slick salesmen to get more of your hard-earned money.

What’s different about it?  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). 

CCA (Copper Clad Aluminum):

Just say “no”. Copper clad is nothing more than copper-plated aluminum.  Aluminum has 60% of the conductivity of copper so a CCA wire will need to be roughly 2 sizes larger to have the same conductivity.  In other words, a CCA wire would need to be 2 gauge to do the work of a 6 ga copper. Just buy copper wire.

For more info see Wikipedia. 

Summary: 

For automotive cables, use SAE-rated SGT or SGX battery cable. It works great for automotive applications at a fair price. Do NOT use welding cable, OFC or CCA for underhood applications.

For boats, you must use “marine” rated wire.