Resistance and impedance both oppose electric current, but they are not the same thing. In batteries, understanding the difference helps you monitor health and predict failures.
What is Resistance?
Resistance (R) is the opposition to direct current (DC). It is a constant value (for a given temperature) and causes energy loss as heat. Battery internal resistance is a key DC parameter that increases as the battery ages.
What is Impedance?
Impedance (Z) is the opposition to alternating current (AC). It includes resistance (R) plus reactance (X), which depends on frequency. Impedance is measured by applying a small AC signal to the battery.
Why Does It Matter for Battery Health?
- Internal resistance (DC) rises due to sulfation, corrosion, or drying out. Tracking it helps predict end of life.
- Impedance (AC) is often measured by battery monitoring systems because it can be done online without discharging the battery.
- Both metrics are useful, but standards like IEEE 1188 recommend using internal resistance trends for maintenance decisions.
Next Step
Now that you understand impedance vs resistance, learn how DFUN’s battery monitoring system measures these parameters in real time to prevent unexpected failures.
Read our detailed guide on internal resistance vs impedance →
Or explore DFUN’s BMS solutions for live monitoring.
