Testing the internal resistance of battery pack using small DC discharge method
The following are the general and specific steps for measuring the internal resistance of battery modules using the small DC discharge method:
1. Preparation work:
Ensure that the battery module is in a relatively stable state, such as standing in a suitable temperature environment for a period of time to allow its internal state to reach relative equilibrium.
Prepare a small DC discharge device that can accurately control the output DC current and measure parameters such as voltage at both ends of the battery module. At the same time, it is necessary to ensure that the accuracy and stability of the equipment meet the measurement requirements.
Connect the measurement circuit, correctly connect the positive and negative poles of the discharge device to the positive and negative poles of the battery module, and pay attention to the connection being firm and reliable to avoid poor contact that may affect the measurement results.
2. Set discharge parameters:
Determine the appropriate small DC discharge current value based on the type, specifications, and measurement purpose of the battery module. Generally speaking, the discharge current should not be too high to avoid excessive damage to the battery module, but it is also necessary to ensure that measurable voltage changes can be generated within a reasonable time. For example, for some small battery modules, a discharge current of several amperes or even smaller may be chosen; For larger capacity battery modules, the discharge current can be appropriately increased, but it is usually controlled within tens of amperes.
Setting the discharge time not only ensures that sufficient data can be obtained during the discharge period to accurately calculate the internal resistance, but also prevents unnecessary damage or impact on the subsequent performance of the battery module caused by excessive discharge time. The common discharge time may range from a few seconds to several tens of seconds.
3. Start discharge and measurement:
Start the small DC discharge device and allow the set DC current to pass through the battery module. During the discharge process, monitor and record the voltage changes at both ends of the battery module in real-time. Data recording can be achieved through the device's built-in data recording function or by connecting to external data collection devices.
Observe the performance of the battery module during discharge, such as abnormal heating, smoking, deformation, etc. If there is any abnormality, stop discharging immediately and check the cause.
4. Data processing and internal resistance calculation:
Based on the recorded discharge current and corresponding voltage change data, use Ohm's law (where is internal resistance, is voltage change value, and is discharge current) to calculate the internal resistance of the battery module. Usually, data from the relatively stable voltage stage during the discharge process is selected for calculation to improve the accuracy of internal resistance calculation.
Analyze and process the results of multiple measurements, such as calculating the mean and standard deviation, to evaluate the stability and consistency of the internal resistance of the battery module.
5. End operation:
After the discharge is completed, turn off the small DC discharge device and disconnect it from the battery module.
Organize and archive the measured data for subsequent analysis and reference.
Different types and specifications of battery modules may have differences in specific operational details, and in practical applications, the influence of measurement equipment characteristics, environmental factors, and other factors on measurement results also needs to be considered. If measuring the internal resistance of a specific battery module, it is recommended to refer to the relevant equipment manual and professional technical data to ensure the accuracy and safety of operation.
