Battery knowledge · Testing methods
DC internal resistance
Internal resistance measured from the voltage change during a current pulse of defined length, usually 10 s or 18 s. It is larger than the AC value because it includes charge-transfer and some diffusion, and it depends on SOC, temperature and pulse duration. [1]
- Abbreviation
- DCIR
- Also called
- DC-IR, pulse resistance
- Unit
- mΩ
Example
Voltage under load
5 A through 20 mΩ gives 0.1 V ohmic drop.
Chosen OCV curve; no chemistry calibration, hysteresis or voltage cutoff.
Explore the graph
Discharge current creates an ohmic drop below open-circuit voltage.
5 A through 20 mΩ gives 0.1 V ohmic drop.
V_terminal = OCV − I_discharge R
Illustrative model. Chosen OCV curve; no chemistry calibration, hysteresis or voltage cutoff.
Use in Lemonergy
Design protocol or analysis tool
Inspect pulse characterization
HPPC alternates pulses, moves SOC and includes long rests.
Equation or tool to use
- Rest
Allows relaxation
Inputs & settings
- s
- Pulse
Excites charge/discharge
Inputs & settings
- a
- pulseS / restS
- Repeat
Repeats SOC points
Inputs & settings
- count
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
Example. 0.2 V change after a 10 A step gives 20 mΩ by ΔV/ΔI on the same cell/pack basis.
Observe. Long rests differ from the immediate resistive jump.
The estimate depends on timing, temperature and state; this is not AC impedance spectroscopy.
Open Design → Protocol bench →References & further reading
Technical references
- Battery Test Manual For Electric Vehicles, Revision 3
Jon P. Christopherson · Idaho National Laboratory · 2015
Technical reference · Performance characterization, pulse resistance/power, life testing and reference performance tests; historical 2015 edition.