How to test a car battery

The battery is the most important part of your car to start the engine, without a healthy battery you can not start your car and can get into trouble. In this guide, we will discuss how you can test your car battery’s health.

Bad Battery symptoms

  1. Slow Engine crank sound
  2. Longer time to start the engine
  3. Delay in response for electrical items like power windows, headlights
  4. The battery does not store charge longer

Six Easy tests to check battery health

You can perform some or all battery tests as listed below to get the battery health of your car so that you can decide if you need to replace the current battery or not.

Safety First

Before starting any battery test you must ensure your safety. Use gloves and safety glasses. Also, make sure that your hands are dry and then you can start the tests.

1. Visual Inspection

Car battery terminal having scaling

Open the bonnet of your car and locate the battery which is in most cases on the right side. Start by visually inspecting the battery. Look for any signs of corrosion, leaks, or damage to the terminals. Corrosion or white powdery substance around the terminals indicates acid leakage and could affect the battery’s performance.

If the battery has any signs of corrosion do not worry just clean them gently with a wet soft brush. Make sure you are using the gloves. Once the terminals get cleaned you can add a small amount of grease on the terminals with the help of a soft brush to minimize the corrosion effect.

2. Ignition off voltage test

Battery voltage test image using multimeter

For this purpose, you need a multimeter to get accurate voltage readings across the battery terminals. Turn the engine and ignition off and make sure all the electrical components of the car are switched off. Now set the multimeter to DC voltage and place the red probe of the meter to the positive terminal of the battery and black to the negative end.

With the ignition off and no electrical loads, a fully charged battery should have 12.6 to 12.7 volts. Anything lower indicates a discharged or weak battery that may need to be fixed.

3. Load voltage test

Car battery test with load image

Keep the engine, ignition off, and turn on some electrical parts like headlights, and note down the voltage reading through the multimeter. If the voltage drops significantly under load, it indicates that you may have a weak battery.

4. Starting voltage test

Turn off all electrical loads, including headlights and air conditioning. Then slowly, crank the engine and observe the voltage across the battery terminals while the starter motor is engaged. A healthy battery should have a voltage of around 9.6 volts or higher during cranking. If a battery voltage drops below 9.6 volts then it shows weak battery health.

5. Charging system test

Turn the ignition on and start the engine. Observe the voltage across the battery terminals after the engine starts. When the engine is running the voltage should be higher than the battery’s resting voltage, if it is around 14.4 volts then it is normal. If the voltage is too low or too high, it indicates a problem with the charging system or the car’s alterator needs to be checked.

You can also press the race pedal and observe a spike in the voltage value for a quick time, which indicates that the charging system is working perfectly.

6. Voltage hold test

Multimeter reading image

If you park your car for 2-3 days and you get trouble in starting then it means the car’s battery is unable to hold the charge for longer intervals of time. There could be two reasons for that. You may have a weak battery that needs to be replaced and another possibility could be there may be some electrical part that could be draining the battery.

You can simply test if any electrical part is draining the idle battery. To do so you need to remove the negative terminal of the battery. Wait for a few minutes for the vehicle’s electronic systems to power down and enter sleep mode. Some vehicles may take longer than others, so you can consult the vehicle’s manual for specific instructions. Now simply add a multimeter in series with the negative terminal and the removed point of the battery and note down the current value. A small amount of current drawn is normal to power functions like the clock and security system, but if the amount of current drawn is excessive that is over 1 ampere then it indicates a problem, and you need to identify that electrical part and fix it.

Conclusion

Testing your car battery 1-2 times a month is enough to maintain the car battery and so the car’s performance. By following our testing methods, you can assess the health of your battery and charging system, ensuring you do not get into any trouble due to a dead battery. Remember, if you’re unsure about the results or need assistance, consult a professional mechanic near you for further evaluation and necessary repairs.

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