Battery knowledge · Units and electrical basics
Internal resistance
The resistance a cell presents to current, from its foils, electrolyte, interfaces and the reactions themselves. It converts part of the delivered energy into heat, sets the voltage drop under load, and rises as the cell ages; a large automotive cell has about a milliohm, a small cylindrical cell tens. [1]
- Abbreviation
- IR
- Also called
- DC resistance, DCIR
- 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
Lemonergy Studio blocks
AC current source worked example
Analytic sinusoidal current, positive from p to n
Blocks to use
- AC current source
Conserving component solved simultaneously with the connected network. Analytic sinusoidal current, positive from p to n
Inputs & settings
- Use the block reference for settings and connections.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the interface, units and model limits.
- Open the Studio example and run its bundled model.
- Compare outputs with the numerical checks; change one input and run again.
Example. Editable first-party network. load: resistanceOhm=4. Checks below were verified in the native execution engine.
Observe. Inspect the output channels and checks on the block reference page.
Analytic sinusoidal current, positive from p to n Demonstration parameters are not calibrated hardware data. Singular or incompatible ideal constraints and unsupported state ranges stop the run.
Open Studio example →Lemonergy Studio blocks
AC voltage source worked example
Analytic sinusoidal voltage p minus n
Blocks to use
- AC voltage source
Conserving component solved simultaneously with the connected network. Analytic sinusoidal voltage p minus n
Inputs & settings
- Use the block reference for settings and connections.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the interface, units and model limits.
- Open the Studio example and run its bundled model.
- Compare outputs with the numerical checks; change one input and run again.
Example. Editable first-party network. load: resistanceOhm=4. Checks below were verified in the native execution engine.
Observe. Inspect the output channels and checks on the block reference page.
Analytic sinusoidal voltage p minus n Demonstration parameters are not calibrated hardware data. Singular or incompatible ideal constraints and unsupported state ranges stop the run.
Open Studio example →Lemonergy Studio blocks
Capacity health index worked example
Endpoint-normalized health index with raw value and out-of-reference flag.
Blocks to use
- Capacity health index
Maps a measured capacity or resistance between user-selected fresh and end-of-life endpoints. It returns a clipped health index, the raw index and a flag for values outside the reference interval.
Inputs & settings
- Use the parameter values in the block reference.
- Bundled example verified on the production release of 28 October 2026.
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Review the block inputs, units and model limits.
- Open the Studio example and run its bundled model.
- Compare the output channels with the numerical checks; change one input and run again.
Example. Use the defaults below with Measured capacity (Ah) = 1.8 Ah. At 0 s, Clipped health index is 0.5 1 (fraction). Additional checks are listed below.
Observe. Inspect the outputs and numerical checks on the block reference page.
This endpoint-normalized index is not the same quantity as capacity retention. The endpoint choice determines its interpretation. The example verifies numerical behavior for synthetic parameters. Cell characterization and validation for an intended use are separate tasks.
Open Studio example →Learn it in Lesson 0 · Battery basics →
All connected Lemonergy block references
- AC current source
- AC voltage source
- Capacity health index
- Pulse power capability
- Resistance health index
- Current-controlled current source
- Piecewise-linear diode
- Electrical gyrator
- Controlled electrical switch
- Capacitive floating reference
- Ideal transformer
- Open branch with initial voltage target
- Ideal linear motor coupler
- Bounded drift memristor
- Coupled inductors
- Open electrical port
- Finite-gain operational amplifier
- Ideal rotational motor coupler
- Voltage-controlled current source
- Current-controlled voltage source
- Controlled resistor
- Voltage-controlled voltage source
- Battery with SOC-dependent OCV
- Electrical reference
- Regulated CC/CV charger
Studio interfaces connected to this concept
These components declare this quantity or operation. Their individual pages distinguish authoring metadata from numerical verification.
References & further reading
Technical references
- Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification
Gregory L. Plett · Journal of Power Sources · 2004
Technical reference · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- The International System of Units (SI), 9th edition
Bureau International des Poids et Mesures · 2026
Topic background · Definitions of SI units and coherent derived units; 2026 revision.