How to Troubleshoot a Battery Charge

Troubleshooting a battery charge goes beyond checking the presence of 12.4 volts or more, which tells you the condition of its electrolyte and internal plates. Maintenance-free batteries use an indicator to let you know the battery's charge status. But for those requiring maintenance, there is a way to confirm the battery's internal condition and what corrective action--if any--you should take. Here we will follow simple steps to confirm whether your battery has a good charge, needs a charge or is defective.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• 2 combination wrenches
• Safety goggles
• Rubber gloves
• Screwdriver
• Needle thermometer
• Hydrometer

1. Open the hood of your vehicle and disconnect the negative cable from the battery terminal using a pair of combination wrenches.

2. Put on your safety goggles and rubber gloves; remove the caps off the top of the battery using a screwdriver--make sure the top of the battery is clean before removing the caps.

3. Verify the electrolyte is at the proper level--up to the split ring at the bottom of the vent hole. If it's not, refill with distilled water. If you need to add water, wait at least 24 hours before proceeding with this test to allow the water and electrolyte to mix thoroughly.

4. Insert a regular needle thermometer inside the battery and make a note of the electrolyte’s temperature.

5. Squeeze the hydrometer’s rubber bulb and submerge the unit’s tube into the electrolyte, maintaining a vertical position at all times.

6. Allow the bulb to expand and draw electrolyte into the hydrometer’s tube.

7. Lift the hydrometer to eye level, look at the intersection point of the float inside the tube and the printed scale on the unit and make a note of your reading.

8. Squeeze the electrolyte back into its appropriate cell and repeat Steps 5 to 7 for the remaining battery vent holes.

9. Make the appropriate adjustments to your readings. For every 10 degrees above 80 degrees F of the temperature taken in Step 4, add 0.04 to every reading. For every 10 degrees bellow 80 degrees F of the temperature reading in Step 4, subtract 0.04 from every reading.

10. Compare your results. If any cell reading is bellow 1.265, the battery needs to be recharged. Note that an undercharged battery may indicate a problem in the charging, starting system or cable connections. If any of your cell reading varies between 0.025 to 0.050 points from any of the other cell readings, the battery has internal damage or is near the end of its service life, and you need to replace it.

Tips & Warnings

• If you do not own one, you can buy a cheap hydrometer at any auto parts store. Follow the manufacturer's instructions.
• Always wear safety goggles and rubber gloves when handling battery electrolyte, which is highly corrosive and may cause severe damage to the eyes and skin.
• Make sure you are in a well-ventilated area, away from appliances with open flames like gas-operated dryers or water heaters, and do not allow smoking in the area. A car battery generates hydrogen gas, which is highly explosive.

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