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Testing Automotive Batteries and Starters

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Update time : 2020-02-20 15:53:10

MODERN STARTER TESTING

Although modern engine starters are generally permanent-magnet, reduction-gear designs, many older vehicles are equipped with field coil starters. To illustrate, a 3.0 L V6 equipped with a permanent magnet starter in good condition was tested. Its new battery is rated at 650 CCA and tested at 842 CCA with 3.82m ohms plate impedance.
 

The initial battery voltage was 12.51 volts and at a 50-amp draw, the voltage dropped to 12.15 volts. The average cranking voltage was 11.28 volts, with the minimum at 11.16 volts. The maximum initial cranking amperage was 161.0 amperes with an average of 114 amperes during a 7-second extended cranking test.
 

Next, a 2.8 L V6 equipped with a field coil starter in good condition was tested. The battery had been in service 18 months, rated at 500 CCA, and tests at 640 CCA with an impedance of 5.00m ohms. Initial voltage was 12.48 volts and, after a 50-amp load, dropped to 12.10 volts. The average cranking voltage was 10.87 volts with the minimum at 10.84 volts. Maximum cranking amperage was 205.0 amps and the average was 180 amps during a 7-second extended cranking test.
 

In conclusion, the field coil starter was drawing nearly 150% more amperage than the permanent magnet starter. Note: the larger engine displacements and higher compression ratios will increase cranking amperage. Most important, neither minimum cranking voltage fell below 10.0 volts. Only a battery and starter in good condition will maintain the high cranking voltages needed to maintain a full range of PCM functions.


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