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Charging System Troubleshooting Part 3

How to test your vehicles charging system and what to look for.
» Part 1: Charging System
» Part 2: Battery Diagnosis
» Part 3: Battery Capacity
» Part 4: Drain Testing
» Part 5: Alternator Testing

Battery Capacity Test

To carry Out this test, use a high rate discharge tester, Battery Tester, in conjunction with a Digital Multimeter.

  1. Turn the tester to the OFF position.
  2. Turn the multimeter selector switch to the DV volt position.
  3. Connect the tester and multimeter positive test leads to the positive battery post and both negative test leads to the negative battery post. The multimeter clips must contact the battery posts and not the tester clips. Unless this is done, the actual battery terminal voltage will not be indicated.
  1. Turn the load control knob in a clockwise direction until the ammeter reads approximately half of the cold cranking amps of the battery.
  2. With the ammeter reading the required load for 15 seconds , note the multimeter reading.
    • If the multimeter reading is 9.6 volts at 21°C (70°F) or more, the battery has a good output capacity and will readily accept a charge, if required.
    • If the voltage reading is below 9.6 volts at 21°C (70°F) and the battery is fully charged, the battery is damaged and a new battery must be installed. If you are unsure about the battery's state of charge, charge the battery.
  3. After the battery has been charged, repeat the Battery Capacity Test.
    • If the capacity test battery voltage is still less than 9.6 volts at 21°C (70°F), install a new battery.
    • If the voltage is 9.6 or more at 21°C (70°F), the battery is satisfactory for service.
    • If the battery is found to be discharged only, check for a loose drive belt, loose electrical connection, charging system performance, and carry out the Battery Drain Testing.
» Part 1       » Part 2       » Part 3       » Part 4
Part 5
Additional Information provided courtesy of and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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