Battery Capacity Test

To perform this test, use a high rate discharge tester, Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent, in conjunction with Rotunda 73 Digital Multimeter 105-R0051 or equivalent.
1. Turn the control knob on the ARBST to the OFF position.
2. Turn the multimeter selector switch to the DV volt position.
3. Connect ARBST 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 ARBST tester clips. Unless this is done, the actual battery terminal voltage will not be indicated.
4. Turn the load control knob in a clockwise direction until the ammeter reads approximately half of the cold cranking amps of the battery.
5. With the ammeter reading the required load for 15 seconds, note the multimeter reading. Avoid leaving the high discharge load on the battery for periods longer than 15 seconds.
6. 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.
7. If the voltage reading obtained during the capacity test is below 9.6 volts at 21°C (70°F), and the battery is fully charged, the battery is defective and must be replaced. If unsure about the battery's state of charge, charge the battery.
8. After the battery has been charged, repeat the capacity test. If the capacity test battery voltage is still less than 9.6 volts at 21°C (70°F), replace the battery. If the voltage is 9.6 or more at 21°C (70°F), the battery is satisfactory for service.
9. If the battery is found to be discharged only, check for a loose drive belt, loose electrical connection, charging system performance, and perform battery drain testing. [1][2]Drain Test