how to calculate internal resistance of a battery


Battery internal resistance refers to the resistance between the internal components of the battery and the electrolyte, which affects factors such as heat generation, energy conversion efficiency, and lifespan. Accurate measurement of battery internal resistance is crucial for assessing battery performance and lifespan. Here are several commonly used methods for detecting battery internal resistance:

  1. Open Circuit Voltage Method:
    • Place the battery in a test state and disconnect the circuit to make the battery open circuit.
    • Measure the open circuit voltage of the battery and record it.
    • Connect the battery to a load resistor and measure the voltage change across the load resistor.
    • Calculate the internal resistance of the battery based on the voltage change.
  2. Constant Current Discharge Method:
    • Set a constant current and discharge the battery to a certain extent.
    • Measure the voltage change of the battery during discharge and record it.
    • Calculate the internal resistance of the battery based on the rate of voltage change during discharge.
  3. AC Internal Resistance Method:
    • This method is specifically used for detecting the internal resistance of large-capacity batteries.
    • Use an AC signal as an excitation signal.
    • Measure the phase difference and amplitude difference between the battery output voltage and current.
    • Calculate the internal resistance of the battery based on these measurements.
  4. Electrochemical Impedance Spectroscopy (EIS) Method:
    • This method is based on electrochemical principles.
    • Apply an AC signal with a certain frequency and amplitude to the battery.
    • Measure the impedance spectrum of the battery and convert it into a complex impedance diagram.
    • Analyze the features of the complex impedance diagram to calculate the internal resistance and other electrochemical parameters of the battery.

Battery internal resistance is a crucial indicator for evaluating battery performance and lifespan. The choice of a specific method depends on practical requirements and conditions. Selecting the appropriate method for battery internal resistance detection can help assess battery performance and lifespan more effectively.

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