Car batteries are essential for starting your vehicle. While most drivers know a dead battery prevents their car from starting, understanding the individual battery cell and how to address its issues is less common. This guide from Car Repair Online will explain car battery cells, how to identify problems, and provide step-by-step instructions on how to repair a car battery cell yourself.
Understanding Car Battery Cells and Their Location
Modern cars primarily use lead-acid batteries. These batteries function by converting chemical energy into electrical energy, a process made possible by battery cells. These cells store energy until your car needs it to start or power electrical components. In almost every vehicle, the car battery is located under the hood, usually in one of the front corners of the engine bay.
A typical car battery contains six cells arranged in a row within a plastic case. Each cell houses a lead dioxide plate and a lead plate. Each pair of plates generates approximately two volts, which is why car batteries are commonly known as 12-volt batteries. The cells are immersed in sulfuric acid, facilitating the necessary chemical reaction between the plates [1].
For a car battery to function correctly and deliver the required 12 volts for smooth vehicle operation, all six cells must be in good working order.
Recognizing Signs of a Failing Battery Cell
Cell failure is a frequent cause of battery problems. Factors like age and excessive heat can lead to cell degradation [2]. Here are some common indicators of a failing car battery cell:
- Dim or Weak Electrical Components: Noticeably weaker performance from components like your dashboard lights or headlights can indicate a battery cell issue.
- Clicking Noises When Starting: Hearing a distinct clicking sound when you turn the ignition key, but the engine doesn’t crank, is a classic sign.
- Slow Engine Cranking: The engine turns over slowly or struggles to start, often described as a slow crank.
- Engine Backfiring: In some cases, a failing battery can cause the car to backfire [3].
Alt text: Car battery located in the engine bay, showing terminals and cables.
Furthermore, general neglect and dirt accumulation on the battery can lead to rust and corrosion, affecting cell performance. Regular car maintenance should include battery cleaning to prevent such issues.
Step-by-Step Guide: How to Repair a Car Battery Cell
Repairing a car battery cell involves restoring the chemical balance necessary for energy generation. While complex car repairs should be left to professionals, you can check and potentially fix a battery cell issue yourself if it’s a minor problem. However, you’ll need specific tools and safety precautions.
Tools and Materials Needed:
- Voltmeter: To test battery voltage.
- Battery Hydrometer: To measure electrolyte specific gravity.
- Distilled Water: Specifically for battery top-up.
- Battery Acid (Sulfuric Acid): For adjusting electrolyte levels (handle with extreme care).
- Large Screwdriver: For removing battery caps.
- Torch/Flashlight: To inspect cell fluid levels.
- Protective Gear: Including safety goggles and acid-resistant gloves [4].
- Battery Charger: To recharge the battery after repair.
Repair Procedure:
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Test Battery Voltage with a Voltmeter [5].
- Use a digital voltmeter for accurate readings. Connect the red (positive) voltmeter lead to the positive battery terminal and the black (negative) lead to the negative terminal.
- A healthy battery should read approximately 12.6 volts or higher when fully charged and at rest. A reading below 12.4 volts indicates a discharged or potentially failing battery [6]. Note the voltage reading for later comparison after potential repair.
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Clean the Battery Top.
- Before proceeding, ensure the vehicle is turned off and the parking brake is engaged.
- Use a dry cloth to carefully clean any dirt, grease, or corrosion from the top of the battery, especially around the vent caps.
- Using the screwdriver, carefully unscrew and remove all cell vent caps. Place them aside in a clean, safe location.
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Inspect Electrolyte Fluid Levels.
- Use the torch to look into each cell and check the electrolyte level. The fluid should be visibly covering the lead plates, ideally about 6-7 mm (approximately 1/4 inch) above the plates.
- If the fluid level is low in one or more cells, top up these cells with distilled water only. Avoid overfilling.
- Reinstall the vent caps securely after topping up.
- Wait for about 12 hours, then re-test the battery voltage with the voltmeter. If the voltage has improved, the issue might have been low electrolyte levels.
Alt text: Inspecting car battery cell electrolyte level with a flashlight, showing low fluid.
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Check Specific Gravity with a Battery Hydrometer (If Step 3 is Insufficient).
- Safety First: Perform this step in a well-ventilated area. Wear safety goggles and acid-resistant gloves as battery acid is corrosive and dangerous.
- Use a battery hydrometer to measure the specific gravity of the electrolyte in each cell. Draw a small amount of electrolyte from each cell into the hydrometer.
- A fully charged battery should ideally have a specific gravity reading of around 1.265. Crucially, the specific gravity readings between cells should not vary by more than 0.05. Significant variations can indicate a problem cell.
- If a cell’s specific gravity is significantly low, carefully add battery acid (sulfuric acid) to that specific cell to adjust the level. Add acid cautiously and re-measure after small additions until the specific gravity is within the acceptable range and closer to the other cells. Note: Adding battery acid is generally only recommended if distilled water alone didn’t resolve the issue and should be done with extreme caution. In many cases, if distilled water doesn’t work, the cell might be irreversibly damaged.
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Recharge and Re-test the Battery.
- After completing steps 3 or 4, recharge the battery using a battery charger. Follow the charger’s instructions for proper charging.
- Once fully charged, re-test the battery voltage with the voltmeter. If the battery still shows low voltage or fails to hold a charge, it’s likely that the cell is sulfated or internally damaged beyond repair [8].
When to Consult a Mechanic: If these steps do not restore your battery, or if you are uncomfortable performing them, it’s best to consult a qualified mechanic. They can accurately diagnose the battery issue and advise on repair or replacement.
Cost of Car Battery Cell Repair vs. Replacement
If DIY car battery cell repair seems daunting, professional help is readily available. However, it’s important to note that mechanics typically replace the entire battery rather than individual cells, as cell-level repairs are often not cost-effective or reliably long-lasting.
In Australia, the average car battery replacement cost ranges from $150 to $350 [9], including the new battery and labor. Battery inspections alone can cost around $80 [10]. The final price depends on your vehicle’s make, model, battery type, and the mechanic’s labor rates.
Conclusion: Act Promptly on Battery Issues
Don’t ignore the warning signs of a weak car battery. Addressing battery problems early can prevent you from being stranded with a completely dead battery. If you suspect a battery cell issue, follow the steps outlined to attempt a repair, or use Car Repair Online to find trusted local mechanics for battery testing and replacement services. Remember, proactive maintenance is key to ensuring your vehicle’s reliability.
[1] Continental Battery. How Does a Car Battery Work?
[2] Sydney Battery. 8 Common Reasons Why Car Batteries Fail.
[3] Tires Plus. 5 Unmistakable Signs Your Car Battery is Failing.
[4] 365 Days of Motoring. Fix Dead Cell Car Battery.
[5] It Still Runs. Symptoms of a Dead Cell Car Battery.
[6] BatteryStuff.com. How to Tell If Your Motorcycle Battery Is Bad.
[8] Car Also. How to Fix a Dead Cell in a Car Battery?
[9] Oneflare. Car Battery Replacement Cost in 2024.
[10] AutoGuru. Battery Inspection and Replacement Service.
