How to test car battery cells with multimeter

The car battery is one of the essential parts of the vehicle that provides electrical energy to other components such as the starter motor, headlights, and other accessories. Over time, the car battery may lose its effectiveness and cause several issues such as difficulty in starting the engine, dimming headlights, and more. To diagnose the problem, you’ll need to test the battery cells with a multimeter.

A multimeter is an electronic device that measures current, voltage, and resistance. It’s an essential tool that every car owner should have to diagnose electrical faults in the vehicle. In this article, we’ll explain how to test car battery cells with a multimeter step by step.

Before testing the car battery cells with a multimeter, you need to ensure that the battery is fully charged. If it’s not fully charged, you can use a battery charger to recharge it. Once the battery is fully charged, you can use a multimeter to test its cells.

How to Test Car Battery Cells with Multimeter

Step 1: Safety First

Before testing the car battery, it’s important to take the necessary safety precautions. This includes wearing safety glasses, gloves, and ensuring that the car engine is turned off. Make sure that you’re working in a well-ventilated area to avoid inhaling any harmful gases.

Step 2: Set the Multimeter

Set the multimeter to the DC voltage setting, usually marked as “V” with a straight line and dotted line above it. Set the range to at least 15V.

Step 3: Test Battery Voltage

To check the overall voltage of the car battery, place the multimeter leads on the appropriate battery terminals. The red lead goes on the positive (+) terminal, and the black lead goes on the negative (-) terminal. If the voltage reading is below 12.4 volts, the battery might need to be charged or replaced.

Step 4: Test Individual Cells

If the battery voltage is below 12.4 volts, it’s time to test each individual cell in the battery. First, remove the battery caps to expose the cells. Then, place the multimeter leads onto each cell’s terminal, making sure that the red lead is on the positive (+) and the black lead is on the negative (-).

Each cell should have a voltage around 2 volts or higher. If one cell is significantly lower in voltage than the others, it’s likely that cell is damaged and needs to be replaced.

Step 5: Re-test Battery Voltage

After testing each individual cell, re-test the overall voltage of the battery. If each cell is in good condition, the battery voltage should be above 12.4 volts. If the voltage is still low, the battery might need to be charged or replaced entirely.

Note: Always follow the manufacturer’s instructions for your specific multimeter when performing the test.

Preparing for the Test

Gather Necessary Tools

Before starting the test, make sure you have all the necessary tools. You will need a multimeter, safety goggles, gloves, and a cleaning cloth. It is important to wear goggles and gloves to ensure safety and avoid any potential hazards.

Ensure Safety

Before testing the battery cells, ensure that the car is turned off and all the electronic devices are turned off. Also, check if any of the battery cells are corroded or damaged. If you find any, clean them before testing to make sure you get an accurate result.

Locate the Battery Cells

Locate the battery cells on your car. Most cars have their battery located in the engine compartment, but some may have it elsewhere. You may need to consult your car manual to find the exact location of the battery.

Familiarize Yourself with the Multimeter

Before testing the battery, you should familiarize yourself with the multimeter. Read the user manual carefully to understand how to select the right range and set up the device. It is important to choose the right range for accurate results.

Testing the Battery

Step 1: Prepare your multimeter

Before testing the battery, make sure your multimeter is set to DC voltage mode. This can be identified by a letter V with a straight line and three dots above it. Ensure that the multimeter probes are in good condition and that they are connected firmly to the multimeter.

Step 2: Test the battery voltage

To test the battery voltage, turn off the engine and all electrical appliances in the car. Connect the red (positive) probe of the multimeter to the positive terminal of the battery and the black (negative) probe to the negative terminal of the battery.

Step 3: Read the multimeter measurement

The multimeter will display the voltage measurement of the battery. A fully charged battery should read around 12.6 volts. If the reading is low, charge the battery or replace it if it cannot be recharged.

Step 4: Test the battery cells

If the battery voltage is low, it may be due to a bad battery cell. To test the battery cells, set the multimeter to resistance mode (Ohm) and connect the probes to each battery cell’s positive and negative terminals. A good battery cell should display a low resistance reading, while a bad cell should display a high resistance reading.

Step 5: Determine the health of the battery

If the battery cells are all good, the battery may still be weak due to other factors such as sulfation or a bad alternator. To determine the overall health of the battery, use a battery load tester or take the battery to a professional for testing.

Interpreting the Results

Healthy Battery Cells

If the voltage reading of each cell is between 1.26V and 1.28V, this indicates that the battery cells are healthy and fully charged. The total voltage of the battery will be approximately 12.6V to 12.8V, which is considered a good reading.

A healthy battery should maintain a steady voltage even when a load is applied to it. If the voltage drops significantly when a load is applied, it may indicate that the battery has a weak cell or is starting to fail.

Weak or Failing Battery Cells

If one or more cells are reading a voltage below 1.26V, it indicates that the cells are weak and may need to be replaced. This can cause the battery to lose power and reduce its overall performance.

If the voltage in one or more cells is significantly different from the others, for example, if one cell is reading 1.25V and another is reading 1.3V, it may indicate that one of the cells is failing and needs to be replaced.

If all cells read low voltage or there is a significant drop in voltage when a load is applied, it may indicate a completely dead or failed battery that needs to be replaced.

Battery Cell Voltage Interpretation

Cell Voltage Reading	Battery Cell Health
1.26V – 1.28V	Healthy/Fully Charged
1.23V – 1.25V	Weak/Needs Replacement
Below 1.23V	Failed/Needs Replacement