Understanding the Qualities and Strength of Battery and Starter Cables for Automotive Use

17 May 2019

Maintenance-conscious car owners know a little about car battery cables. The red and black wires are as thick as an adult’s pinky finger. They’re made of stranded copper, which can be bent back easily when a new battery is installed. It’s the same with the engine starter, whose job it is to provide initial turning force. They’re large, these electrical cables, but there’s a reason for that big cross-sectional area.

The Rudiments of Car Engine Starting

Car batteries generally deliver a 12-Volt power supply. That’s a relatively small voltage, especially when compared against a small portable appliance. Just like a car, these handheld devices often use a 12-Volt battery supply. Why, then, can’t we simply place a few soda can-sized power cells in a car? If they ever needed replacing, to do so would only require a visit to a local store. Clearly, that’s not an option. Car batteries need to have large capacities, which explains their dimensions, and they also need to output large electrical currents. That means over 100-Amps of current zaps through the battery cables, although that flow only lasts for a few seconds. After the engine starts, the car starter and battery have done their job.

Understanding Car Battery and Starter Cables

So, what can be taken away from the principles described above? Well, it takes a lot of mechanical energy to “crank” an engine. In order to generate that energy, the vehicle starter needs to draw lots of electrical current, which is then converted into pure mechanical torque. As the flow of energy increases, it encounters resistance. That’s okay, though, because the large cross-sectional area cabling allows the higher current to flow easily. Like a pressurized water pipe, the wider channel eases the flow. A narrower pipe would cause a nasty system bottleneck. It’s the same with the copper strands. Too thin, the system bottleneck would cause resistive heat and system losses. At best, the car wouldn’t start or the battery would go flat after a few attempts at starting the car. At worst, the heat generated by the skinny wiring would cause an engine compartment fire.

Dependent on the size of a vehicle’s engine, its car battery cables and starter cable cross-sectional areas vary proportionally. The accepted sizing standard measures cable size using the “gauge” scale. For example, 6-gauge is a common car battery cable size, although larger vehicles would likely use 8 or 10-gauge wiring. Thickly insulated in red or black engineering plastics, the rubberized polymers resist the chemicals and oils that leak from vehicle compartments. Finally, and perhaps most importantly, multi-stranded, low-impedance, high-quality copper wires connect to the battery or starter via a series of end-terminating electrical lugs.

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