Troubleshooting Guide: Car Runs But Battery Won’t Charge – DIY Tests & Solutions

Ever wondered why your car runs fine, but the battery just won’t charge up? Picture this: you’re all set to hit the road, but your battery seems to have other plans. Frustrating, right? Don’t worry, we’ve got your back! In this article, we’ll unravel the mystery behind your battery not charging while your car keeps on cruising.

Common Causes of Battery Not Charging

When your car runs fine but the battery doesn’t charge, it can be perplexing. Let’s dive into some common reasons behind this issue:

  • Faulty Alternator: One of the primary causes is a faulty alternator. This component is responsible for charging the battery as you drive. If it malfunctions, your battery won’t charge properly.
  • Broken Belt: The alternator is belt-driven in many vehicles. A broken or slipping belt can prevent the alternator from doing its job effectively, leading to a lack of proper battery charging.
  • Corroded Battery Terminals: Corroded battery terminals can disrupt the flow of electricity between the battery and the charging system. It’s essential to keep these terminals clean and free of corrosion.
  • Faulty Voltage Regulator: The voltage regulator controls the amount of charge the alternator sends to the battery. If it’s faulty, your battery may not receive the correct charge, resulting in a battery not charging issue.
  • Wiring Issues: Faulty wiring or loose connections between the alternator, battery, and starter can also be culprits. Ensure all connections are secure and free of damage.

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70% of alternator failures are due to a faulty voltage regulator.
25% of cases of a battery not charging are caused by broken belts.
20% of vehicles with battery charging issues have corroded battery terminals.

Signs of a Battery Issue

If your car is running fine but the battery is not charging, there are several signs indicating a potential battery issue. Here are some common indications that you might have a problem with your battery:

  • Dimming headlights when starting the car.
  • Slow cranking or difficulty starting the engine.
  • Dashboard warning lights related to the battery.
  • Corrosion on the battery terminals.

When you notice any of these signs, it’s important to address the battery issue promptly to avoid further complications with your vehicle.

DIY Tests to Determine the Problem

If you suspect your car’s battery isn’t charging properly, there are a few DIY tests you can perform to pinpoint the issue. Here are some practical steps to help you identify the problem without advanced tools or professional assistance:

  • Check the Battery Voltage: Use a multimeter to measure the battery voltage. A fully charged battery should read around 12.6 volts.
  • Inspect the Charging System: Start the car and rev the engine while someone observes the volts on the multimeter. The voltage should increase as the engine revs.
  • Examine the Alternator Belt: Ensure the alternator belt is not loose, damaged, or slipping. A faulty belt can affect the alternator’s ability to charge the battery.
  • Look for Corrosion: Inspect the battery terminals for corrosion. Corrosion can impede the flow of electricity between the battery and the charging system.

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Performing these tests can provide valuable insights into why your battery is not charging properly when your car is running.

Potential Solutions for Charging Issue

When facing a situation where your car runs but the battery is not charging, it can be frustrating. To help you troubleshoot this issue, here are some potential solutions you can explore:

  • Check the Battery Connections:

  • Inspect the battery terminals for corrosion. Clean off any buildup with a mixture of baking soda and water. Ensure the connections are tight and secure.
  • Assess the Alternator Belt:

  • Examine the alternator belt for signs of wear or damage. A worn-out belt can prevent the alternator from charging the battery effectively. If necessary, replace the belt.
  • Test the Alternator Output:

  • Use a multimeter to measure the alternator’s output. A healthy alternator should produce a voltage of around 13.5 to 14.5 volts when the car is running.
  • Inspect the Charging System:

  • Rev the engine and observe if the battery warning light on the dashboard illuminates. If it does not, there might be an issue with the alternator or the charging system.
  • If the issue persists after trying these solutions, consider seeking assistance from a qualified mechanic. They can conduct a more in-depth analysis of the charging system.

Remember, addressing the charging issue promptly can prevent more significant problems down the road. Taking proactive steps to troubleshoot and resolve the issue can ensure your car’s battery remains in optimal condition.


You’ve now learned some handy DIY tests and solutions to tackle your car’s battery charging problem. By following these steps, such as checking the battery voltage and inspecting the charging system, you can troubleshoot and potentially resolve the issue. Remember to clean any corrosion off the terminals and assess the alternator belt for wear. Testing the alternator output with a multimeter and keeping an eye on the battery warning light while revving the engine are also crucial steps. If the problem persists, it’s best to seek assistance from a mechanic to ensure your battery stays in top-notch condition. Happy driving!

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Frequently Asked Questions

How can I determine if my car’s battery is not charging properly?

Inspect the battery voltage with a multimeter to verify if it is within the recommended range. Additionally, examine the alternator belt for signs of wear and test the alternator output using a multimeter.

What should I do if my battery terminals have corrosion?

Clean the terminals with a solution of baking soda and water or a commercial battery terminal cleaner. After cleaning, apply a thin layer of dielectric grease to prevent future corrosion build-up.

Why is it essential to address a car’s charging issue promptly?

A malfunctioning charging system can lead to a dead battery, stalling, or even damage to the car’s electrical components. Prompt action helps prevent further complications and ensures the battery’s longevity.

When should I seek professional help for battery charging issues?

If DIY tests and solutions do not resolve the problem, it is advisable to consult a mechanic promptly to prevent any further damage to the battery or the vehicle’s electrical system.

Battery industry professional with 5+ years of experience. Bachelor of Science in Electrical Engineering from Georgia Tech. Specializes in power systems and renewable energy.

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