Battery Testing

Visual inspection alone is insufficient to determine the battery's overall health.

Specific Gravity Test

DO NOT ADD WATER BEFORE TESTING (Flooded batteries only)

  1. Fill and drain the hydrometer 2 to 4 times before pulling out a sample.
  2. The hydrometer should have enough sample electrolytes to support the float completely.
  3. Record a reading, and return the electrolyte to the cell.
  4. The OCV of the tested cell will be the specific gravity reading + .84
  • Example 1.22 s.g. + .84 = 2.06V
  1. To check another cell, repeat steps 1 thru 3 above.
  2. Check all cells in the battery.
  3. Replace the vent caps and wipe off any electrolytes that might have been spilled.
  4. Correct the readings to 80°F:
  • Add .004 to readings for every 10° above 80°F, ( 6o above 26°C)
  • Subtract .004 for every 10° below 80°F, ( 6o below 26°C)
  1. Compare the readings.
  2. Check the state of charge using “Open Circuit Voltage” table below.
  3. The OCV of the tested cell will be the specific gravity reading + .84
  • Example 1.22 s.g. + .84 = 2.06V

The readings should be at or above the factory specification or 1.280 ± .005. If any specific gravity readings register low, then follow the steps below:

  1. Check and record voltage level(s).
  2. Put battery(s) on a complete charge.
  3. Retake specific gravity readings.

If any specific gravity readings still register low, then follow the steps below:

  1. Check voltage level(s).
  2. Perform equalization charge. Refer to the Equalizing section for the proper procedure.
  3. Retake specific gravity readings.

If any specific gravity reading still registers lower than the factory specification or 1.280 ± .005, then one or more of the following conditions may exist:

  1. The battery is old and approaching the end of its life.
  2. The battery was left in a state of discharge for too long.
  3. The electrolyte was lost due to spillage or overflow.
  4. A weak or bad cell is developing.
  5. The battery was overwatered previous to testing.
  6. Batteries in conditions 1 - 4 should be taken to a specialist for further evaluation or retired from service.

Open-Circuit Voltage Test

For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 8 hours, preferably 24 hrs.

  1. Disconnect all loads from the batteries.
  2. Test specific gravity if possible. The OCV of the tested cell will be the specific gravity reading + .84 • Example 1.22 s.g. + .84 = 2.06V.
  3. Measure the voltage using a DC voltmeter.
  4. Check the state of charge with the Table below.
  5. Charge the battery if it registers 0% to 75 % charged.

After the charge, if the battery registers below the Temperature Compensated values illustrated in “How can you tell if a battery is fully charged” or “How can I measure my battery's State of Charge,” the following conditions may exist:

  1. The battery was left in a state of discharge for too long.
  2. The battery has a bad cell.

Batteries in these conditions should be taken to a specialist for further evaluation or retired from service.

Load Testing

Use this same procedure for VRLA DRY CELL batteries and flooded batteries:

  1. Recharge if the open circuit voltage is below 75%.
  2. If you have an adjustable load tester, set the load at 3 to 3.5 times the 20-hour rate.
  3. Apply the load for 15 seconds. The voltage should stabilize above 9.6 volts while on load.
  4. If the battery has a CCA rating, you can apply a load equal to ½ the rating for 15 seconds. The voltage should stabilize above 9.6 volts while on load.
  5. To apply a more determined test, you may apply a load equal to 100% of the rated CCA or 5 to 6 times the 20-hour rate for 30 seconds. The voltage should stabilize above 7.2 volts while on load.
  6. If below 9.6 volts (7.2 volts for the 100% CCA test), recharge and repeat the test. If below 9.6 volts (7.2 volts for the 100% CCA test) again, replace the battery.

Specific Gravity Test

DO NOT ADD WATER BEFORE TESTING (Flooded batteries only)

  1. Fill and drain the hydrometer 2 to 4 times before pulling out a sample.
  2. The hydrometer should have enough sample electrolytes to support the float completely.
  3. Record a reading, and return the electrolyte to the cell.
  4. The OCV of the tested cell will be the specific gravity reading + .84
  • Example 1.22 s.g. + .84 = 2.06V
  1. To check another cell, repeat steps 1 thru 3 above.
  2. Check all cells in the battery.
  3. Replace the vent caps and wipe off any electrolytes that might have been spilled.
  4. Correct the readings to 80°F:
  • Add .004 to readings for every 10° above 80°F, ( 6° above 26°C)
  • Subtract .004 for every 10° below 80°F, ( 6° below 26°C)
  1. Compare the readings.

Check the state of charge using the “Open Circuit Voltage” table below.

The OCV of the tested cell will be the specific gravity reading + .84

  • Example 1.22 s.g. + .84 = 2.06V

The readings should be at or above the factory specification or 1.280 ± .005. If any specific gravity readings register low, then follow the steps below:

  1. Check and record voltage level(s).
  2. Put battery(s) on a complete charge.
  3. Retake specific gravity readings.

If any specific gravity readings still register low, then follow the steps below:

  1. Check voltage level(s).
  2. Perform equalization charge. Refer to the Equalizing section for the proper procedure.
  3. Retake specific gravity readings.

If any specific gravity reading still registers lower than the factory specification or 1.280 ± .005, then one or more of the following conditions may exist:

  1. The battery is old and approaching the end of its life.
  2. The battery was left in a state of discharge for too long.
  3. The electrolyte was lost due to spillage or overflow.
  4. A weak or bad cell is developing.
  5. The battery was overwatered previous to testing.
  6. Batteries in conditions 1 - 4 should be taken to a specialist for further evaluation or retired from service.

Open-Circuit Voltage Test

For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 8 hours, preferably 24 hrs.

  1. Disconnect all loads from the batteries.
  2. Test specific gravity if possible. The OCV of the tested cell will be the specific gravity reading + .84
  • Example 1.22 s.g. + .84 = 2.06V 3. Measure the voltage using a DC voltmeter.
  1. Check the state of charge with the Table below.
  2. Charge the battery if it registers 0% to 75 % charged.

After the charge, if the battery registers below the Temperature Compensated values illustrated in “How can you tell if a battery is fully charged” or “How can I measure my battery's State of Charge,” the following conditions may exist:

  1. The battery was left in a state of discharge for too long.
  2. The battery has a bad cell.

Batteries in these conditions should be taken to a specialist for further evaluation or retired from service.

Load Testing

  1. Use this same procedure for VRLA DRY CELL batteries and flooded batteries:
  2. Recharge if the open circuit voltage is below 75%.
  3. If you have an adjustable load tester, set the load at 3 to 3.5 times the 20-hour rate.
  4. Apply the load for 15 seconds. The voltage should stabilize above 9.6 volts while on load.
  5. If the battery has a CCA rating, you can apply a load equal to ½ the rating for 15 seconds. The voltage should stabilize above 9.6 volts while on load.
  6. To apply a more determined test, you may apply a load equal to 100% of the rated CCA or 5 to 6 times the 20-hour rate for 30 seconds. The voltage should stabilize above 7.2 volts while on load.
  7. If below 9.6 volts (7.2 volts for the 100% CCA test), recharge and repeat the test. If below 9.6 volts (7.2 volts for the 100% CCA test) again, replace the battery.

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