Understanding the Internal Resistance of Lithium-Ion Batteries
Charging Lithium-Ion Batteries: A Crucial Factor
When it comes to charging lithium-ion batteries, understanding their internal resistance is vital. Internal resistance is a key indicator of a battery's charge transfer and ion migration capabilities. It influences charging lithium-ion batteries efficiency, power output, thermal management, and longevity.
Methods for Measuring Internal Resistance
Direct Current Internal Resistance (DCIR)
The DCIR method is commonly used for quickly assessing internal resistance and the health of batteries. By applying short high-rate current pulses, measuring voltage changes before and after the pulses, and using Ohm's law (I=V/R), DCIR is determined. When charging lithium-ion batteries, DCIR is calculated with the formula: DCIR=(V1-V2)/(I2-I1). Following the IEC 61960 standard, a 0.2C discharge pulse followed by a 1C discharge pulse helps derive these values.
Alternating Current Internal Resistance (ACIR)
ACIR involves applying a small amplitude AC signal to the battery, allowing measurement of the impedance modulus and phase angle. Typically conducted at 1kHz for indicative impedance data, the true part of impedance, Vac/IAC, simplifies to ACIR. It's important to note that when charging lithium-ion batteries, a sinusoidal current load of 1kHz is impractical, meaning ACIR might not fully reflect battery behavior in real-world applications.
Electrochemical Impedance Spectroscopy (EIS)
While not as frequently mentioned as DCIR and ACIR, EIS is a comprehensive method for examining battery impedance across a spectrum of frequencies and can offer deeper insights, aiding understanding of how charging lithium-ion batteries might affect performance over time.
Having detailed knowledge of these methods greatly assists in optimizing charging lithium-ion batteries effectively.