How to Test LiFePO4 Battery Capacity?

LiFePO4 or Lithium Iron Phosphate batteries have become a popular choice. They are known for their high energy density, better efficiency, shorter charging time, long cycle life, and superior safety, compared to other lithium-ion or lead-acid batteries.


However, to ensure optimal performance, it is essential to test the capacity of LiFePO4 batteries accurately. Testing the capacity of a LiFePO4 battery will help you better understand its compatibility with your power requirements. But how to test LiFePO4 battery capacity? In this article, we will guide you through the process of testing LiFePO4 battery capacity effectively.

What is LiFePO4 Battery Capacity?

The capacity of LiFePO4 battery refers to the amount of charge a battery can store and deliver. The capacity of a battery is measured in ampere-hours (Ah) or milliampere-hours (mAh). Testing the battery capacity allows you to determine its state of health, verify manufacturer specifications, and assess its overall performance.

How to test LiFePO4 Battery Capacity?

Preparing for Testing

Before starting the testing process fully charge the LiFePO4 battery. To charge the battery use a dedicated charger designed specifically for LiFePO4 batteries to achieve accurate results. Verify the battery's nominal voltage and capacity from the manufacturer's specifications.

1.Constant Current Discharge Test

Constant Current Discharge Test is the most common method to test LiFePO4 battery capacity. In this test, a constant current is drawn from the battery until its voltage reaches a specified cutoff point. The time taken for the discharge is then used for calculating the capacity of the battery.

Capacity Calculation

To calculate the capacity of the LiFePO4 battery, multiply the average discharge current (in amperes) by the discharge time (in hours). For example, if the average discharge current is 1.5A and the discharge time is 10 hours, the calculated capacity would be 15Ah. However, it is essential to note that the actual usable capacity may be slightly lower due to voltage sag and other factors. This is one of the most accurate methods of calculating the capacity of a battery.

2.Meter Measurement

Another method to test the LiFePO4 battery capacity is to use a voltage or current meter. This is the digital measuring process and saves you the trouble of manual calculations. To measure the capacity of the battery with a digital meter, fully charge the battery and complete the circuit with a multimeter. The meter will show the result when the battery reaches the cutoff voltage.

Additional Considerations

To ensure accurate results, it is recommended to repeat the capacity test multiple times and calculate the average capacity. Also, consider the battery's temperature during testing, as extreme temperatures can affect the battery's performance and capacity. Perform the test in a controlled environment with stable temperatures.


Testing the capacity of a LiFePO4 battery helps you access the health and performance of the battery. By following the steps outlined in this guide, you can accurately determine the battery's capacity and ensure it meets your specific requirements. You can choose the constant current method or a multimeter for testing the capacity of a LiFePO4 battery. Regular capacity testing will help you monitor the battery's condition and optimize its usage for various applications.

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