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Battery Cable. |
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Battery cable, like its spark plug wire cousins, is a fat wire. However, the bulk in a battery cable is in its metal, not in its insulation.
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| Fig. 13 |
Battery cable takes low voltages (battery voltages of 13.2 volts on modern cars) and supplies massive quantities of electrons to the starter motor at this low voltage pressure. Thus, in order to move many electrons, the battery cable has a lot of metal on which the electrons can move. (See Fig. 13)
What makes a battery cable good? |
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A good battery cable is one which allows maximum electron flow for starting the car under all typical operating conditions. A good cable has the following qualities:
1.) the right kind of conductor material to permit maximum electrical amperage;
2.) battery connectors which permit maximum flow and suffer minimum attack by battery acid corrosion;
3.) connectors with maximum strength to allow a tight connection on the battery terminal;
4.) correct minimum length for the application to route conveniently to the various components, thereby minimizing total cable resistance;
5.) cable flexibility to permit ease of installation; and
6.) construction features to give expectation of long service life.
Within these performance limits, there is a surprisingly small number of variations which still enable the cable to meet the design criteria.
Gauge and material controls flow. |
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There are two factors which control the flow of electrons in any wire: 1.) the size or gauge of the wire; and 2.) the material from which the wire is made. (The flow of electrons into the wire from the voltage source and out of the wire into the starter motor or other electrical load is also governed by the type and quality of termination and connection. Right now, however, we are only concerned about the conducting wire itself.)
The larger the diameter of wire, the greater the number of electrons able to flow. This explains why large diameter wires are used for large amperage or volume flow, even at very low voltage pressures.
When you want a large amount of flow, the first reaction is to "over design" for the application and use a very large conductor. However, in terms of battery cable, this would make for an excessively large cable that is too inflexible for easy installation. A compromise between low resistance and flexibility requirements is needed.
Materials. |
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There are a number of materials used for automotive amperage cables. In terms of conductivity -- rating the wire's ability to conduct electrons -- there are several materials that make good conductors. (See Fig. 14).
| Relative Conductivity of Metals | ||||||||||||
| Silver |  |
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| Copper | | |||||||||||
| Gold | | |||||||||||
| Alumn. | | |||||||||||
| Zinc | | |||||||||||
| BRASS | | 25% | ||||||||||
| Iron | | |||||||||||
| Nickel | | |||||||||||
| Tin | | |||||||||||
| LEAD | | 7.8% | ||||||||||
| Antimony | | |||||||||||
| Mercury | | |||||||||||
| 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | |
| Percent | ||||||||||||
As shown in the chart, you can see that gold and silver are by far the materials of choice for conductivity. However, they are clearly too expensive for all but the most high-tech (computer and aerospace type) applications. The materials of choice in the automotive business are copper, aluminum, and copper clad aluminum. Copper is the conductor of choice based on experience and experimental results. We do not offer an aluminum or copper plated aluminum for battery cable in our lines.
| Gauge. |
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The typical 12-volt starting/charging system uses 4-gauge battery cable, although this varies from one car maker to another. Remember, car makers are specifying for a car which is supposed to work correctly through warranty. In the aftermarket, we need to consider that cars are seldom well maintained. Thus, more electron flow may be needed in an aging car. If you are going to vary from OE specs, it is best to go larger in gauge.
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Pay attention to gauge. |
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How big a conductor do you need to do the job correctly? Our cables are sized to do the job properly based upon OE specifications for engine size, type, battery size and power, and cable length. They are sized using the American Wire Gauge (AWG) sizing method, which is used by the automakers. The typical size we use for battery cables is 4-gauge for an OE length of cable.
Beware! There are more than a few companies who are selling cables which are "cheaters."
They use a much smaller conductor (even a plain aluminum conductor), make the cable larger
by using thicker insulation, and sell the cable as "4-gauge style." (See figure 15.)
Four-gauge style?? Plenty of battery manufacturers will be happy to tell you that some of their tech reps who troubleshoot so-called battery problems in the field take a pocket knife, cut through the soft insulation and aluminum cable to expose the cheap, low-capacity conductor. Then, they replace it with a copper cable to eliminate the "battery" problem.
Of course, it is often the repair shop that gets cheated here. They buy a new battery because the old one is bad or marginal, only to discover that they need new cables. And then the new cables are cheap aluminum and can't move the electrons needed to crank the car properly. How can you tell what you are getting? How can you tell what you are selling? You can either cut open the insulation to the cable and look, or you can ask the manufacturer. All of our battery cables use 100% copper conductors.
Other cheapening. |
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Another method of cutting cost is to use fewer strands of larger diameter wire. The reason for stranding is to make the cable more flexible so that it is easier to handle when routing to the battery and starter. A small number of larger strands makes the cable more stiff and difficult to work with. Not only does it flow less electricity, but it makes the technician's job more difficult.
