18650 Lithium Battery Internal Resistance Test Guide: Evaluate Battery Health And Predict Lifespan

18650 lithium battery internal resistance test guide: evaluate battery health and predict lifespan

As a high energy density energy storage device, 18650 lithium battery is widely used in various electronic products and power tools. However, as the use time increases, the internal resistance of the battery will gradually increase, affecting its performance and lifespan. Therefore, regular internal resistance testing, evaluating battery health, and predicting its remaining lifespan are essential to ensure the normal operation of the equipment and avoid safety hazards.

1. Internal resistance: the "barometer" of battery health

Internal resistance refers to the resistance encountered when the current passes through the inside of the battery, and is one of the important indicators for measuring battery performance. The size of the internal resistance directly affects the discharge capacity, temperature rise and lifespan of the battery:

Discharge capacity: The larger the internal resistance, the greater the voltage drop generated when the battery is discharged, the lower the output voltage, and the weaker the discharge capacity.

Temperature rise: The larger the internal resistance, the more heat generated when the battery is discharged, the higher the temperature rise, and the greater the safety hazard.

Lifespan: The increase in internal resistance will accelerate battery aging and shorten its service life.

2. Internal resistance test method: accurate measurement, scientific evaluation

At present, there are two main methods for testing the internal resistance of 18650 lithium batteries:

AC internal resistance test method: This method injects an AC signal of a certain frequency into the battery, measures the voltage and current at both ends of the battery, and calculates the internal resistance of the battery. The AC internal resistance test method has the advantages of fast measurement speed and high accuracy, but requires professional testing equipment.

DC internal resistance test method: This method applies a short DC pulse to the battery, measures the voltage change at both ends of the battery, and calculates the internal resistance of the battery. The DC internal resistance test method is simple to operate, but the measurement accuracy is relatively low.

3. Internal resistance test steps: standardize operation to ensure accuracy

In order to obtain accurate internal resistance test results, it is necessary to follow the following steps to standardize the operation:

Preparation: Select appropriate test equipment and test methods, and ensure that the test environment temperature is suitable (generally around 25°C).

Battery charging: Charge the battery to full power and let it stand for a while to stabilize the battery voltage.

Connect the test equipment: According to the instructions of the test equipment, correctly connect the battery and the test equipment.

Start the test: Start the test equipment and record the test results.

Data analysis: Compare the test results with the internal resistance value in the battery specification to evaluate the battery health.

IV. Internal resistance and life: predict the remaining battery life

The internal resistance of the battery is closely related to its life. Generally speaking, the internal resistance of the battery will gradually increase with the increase of usage time. When the internal resistance of the battery increases to 1.5-2 times the initial value, the capacity of the battery will decrease significantly, and it is necessary to consider replacing the battery.

By regularly performing internal resistance tests, a curve of the change of battery internal resistance over time can be established, thereby predicting the remaining life of the battery. For example, if the internal resistance of a certain brand of 18650 lithium battery increases by 5% per year under normal use conditions, then when the internal resistance of the battery is measured to increase by 20%, it can be predicted that its remaining life is about 4 years.

5. Precautions: Safety first, standard operation

When conducting the internal resistance test of 18650 lithium battery, the following matters need to be noted:

Safety first: Avoid short circuit, overcharge, over discharge and other operations during the test to prevent the battery from heating, leaking or even catching fire and exploding.

Standard operation: Strictly follow the instructions of the test equipment to ensure the accuracy of the test results.

Ambient temperature: The test environment temperature should be kept at around 25℃ to avoid the influence of high or low temperature environment on the test results.

Battery status: Before the test, ensure that the battery is fully charged and let it stand for a period of time to stabilize the battery voltage.

6. Conclusion

The internal resistance test of 18650 lithium battery is an important means to evaluate the health of the battery and predict its remaining life. By regularly conducting internal resistance tests, the trend of battery performance degradation can be discovered in time, and corresponding measures can be taken to ensure the normal operation of the equipment and extend the battery life. I hope that the guide provided in this article can help you better understand and apply the internal resistance test technology of 18650 lithium battery.