The AC conductance method reads CCA by injecting a single frequency of 80–90 hertz to the battery. This test method is fast and convenient, but it does not estimate capacity. Ohm’s law calculates the internal resistance on hand of the induced voltage drop, and the device provides a CCA-equivalent reading. Mechanics prefer small sizes and device manufactures have developed handheld testers, which induce a momentary high-current pulse that corresponds to the entered CCA value. The carbon pile simulates real-life cranking conditions while observing the voltage, but this method cannot estimate capacity. Colder temperatures will cause the voltage to drop further. As an example, a 500 CCA battery will discharge at 250A for 15s, and the battery passes if the voltage stays above 9.6V. It is then loaded with half the rated CCA for 15 seconds at a temperature of 10º C (50º F) and higher. To test the CCA with a carbon pile, a battery that must have an SoC of 70 to 100 percent. Since current flow relates to ohmic value, most CCA testers measure the internal battery resistance. (See SAE J537 in Glossary)Ī variety of battery testers have emerged that read CCA. The methods differ in the length of discharge and the cut-off voltages. Table 1: CCA test methods of SAE, IEC and DIN (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 9V for 30s and 6V for 150s. While at subfreezing temperature, apply a discharge current equal to the specified CCA. To SAE J537 and cool to -18☌ (0☏) for 24 hours. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 8.4V for 60 seconds. While at subfreezing temperature, applyĪ discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 7.2V (1.2V/cell) for 30 seconds. The methods are similar and only differ in the length of discharge and the cut-off voltages. Table 1 illustrates the test procedures according to SAE J537, IEC and DIN. To test CCA, apply different discharge currents to see which amperage keeps the battery above a set voltage while cold. A full CCA test is tedious and is seldom done. SAE J537 specifies that a battery with a CCA reading of 500A can deliver 500A at –18☌ (0☏) for 30 seconds without dropping below 7.2 volts.ĬCA cannot be “measured,” but it can be “estimated” and the process can take a week per battery. Typical CCA readings for a car range from 350 to 600A and higher for trucks. CCA measurements assure that the battery has sufficient power to crank the engine, especially when cold. Ever since Cadillac invented the starter motor in 1912, car mechanics have explored ways to measure cold cranking amps (CCA).
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