FitEquivalentCircuitModel

Equivalent circuit model for fitting parameters from time-based pulse power characterization data

Since R2025a

Description

Use FitEquivalentCircuitModel to create a fit equivalent circuit model (ECM) object. Use this object to fit battery ECM parameters from time-based battery pulse power characterization data.

You can obtain the pulse power data at different battery operating conditions, such as different states of charge, temperature, load currents, and current directionality. The preferred technique for the impedance measurement of batteries is hybrid pulse power characterization (HPPC). To specify the ECM topology used to fit the data, set the ECM property. You can specify the desired fitting algorithm by defining the FittingMethod property.

Note

To perform impedance parameter estimation for a battery ECM object from time-based hybrid pulse power characterization data, use the fitECM function instead.

Creation

Description

Note

To use this object, at the MATLAB^® Command Window, run this command at least once each MATLAB session:

import simscape.battery.parameters.*; 

All properties are exposed as name-value arguments in this object.

fitBatteryEcm = FitEquivalentCircuitModel creates a FitEquivalentCircuitModel object with default property values.

fitBatteryEcm = FitEquivalentCircuitModel(PropertyName=Value) creates a FitEquivalentCircuitModel object and sets Properties using one or more name-value arguments.

Properties

ECM — Equivalent circuit model used to fit pulse power characterization data

ECM object (default)

Equivalent circuit model used to fit the pulse power characterization data, specified as an ECM object.

SegmentToFit — Segment of pulse to fit

"Load" (default) | "LoadAndRelaxation" | "Relaxation"

Segment or section of the pulse to fit, specified as "Load", "LoadAndRelaxation", or "Relaxation".

Data Types: char | string

RelaxationSegmentFitTime — Time duration of relaxation to add to fit

10 (default) | positive scalar

Time duration of the relaxation to add to the fit, specified as a positive scalar.

Data Types: double

ThresholdForR0 — Time frame at which to calculate instantaneous resistance

0.1 (default) | positive scalar

Time frame at which to calculate the instantaneous resistance R0, specified as a positive scalar. This threshold serves as the definition for the value of R0.

Data Types: double

FittingMethod — Fitting method used to find ECM parameters that best fit time-based impedance data

"fminsearch" (default) | "tfest" | "curvefit" | "mbc"

Optimization or fitting method used to find the parameters of the ECM that best fit the time-based impedance data, specified as "fminsearch", "tfest", "curvefit", or "mbc".

The "tfest" option requires a license for the System Identification Toolbox™.

The "curvefit" option requires a license for the Curve Fitting Toolbox™.

The "mbc" option requires a license for the Model-Based Calibration Toolbox™.

Data Types: char | string

CurrentSignConvention — Sign convention of input current during discharge

"negativeDischarge" (default) | "positiveDischarge"

Sign convention of the input current during a discharge, specified as "negativeDischarge" or "positiveDischarge".

Data Types: char | string

CurrentOnTreshold — Threshold current that indicates whether charge or discharge is occurring

0 (default) | nonnegative scalar

Threshold current value that indicates whether a charge or discharge is occurring, specified as a scalar.

Data Types: double

InitialParameterEstimate — Initial parameter values of ECM used in first iteration of fitting method

[0.0250 0.0250 10 0.0125 100] (default) | vector of nonnegative elements

Initial parameter values of the ECM used in the first iteration of the fitting method, specified as a vector of nonnegative elements.

Data Types: double

LowerParametersBounds — Lower parameter bounds of equivalent circuit parameters in fitting method

[0 0 0 0 0] (default) | vector of nonnegative elements

Lower parameter bounds of the equivalent circuit parameters used in the fitting method, specified as a vector of nonnegative elements.

Data Types: double

UpperParameterBounds — Upper parameter bounds of equivalent circuit parameters in fitting method

[250 250 100000 125 1000000] (default) | vector of nonnegative elements

Upper parameter bounds of the equivalent circuit parameters used in the fitting method, specified as a vector of nonnegative elements.

Data Types: double

Options — Fitting options

"optimset" (default) | "fitoptions" | "idoptions.tfest"

Fitting options for the method you specify in the FittingMethod property, specified as "fitoptions", ""idoptions.tfest", or "optimset".

Data Types: string | char

TimeStep — Time step to use for input data

0.1 (default) | positive scalar

Time step to use for the input data when the input data has a variable time step sampling, specified as a positive scalar.

Data Types: double

VoltageDetrend — Voltage detrending strategy

"constantOCV" (default) | "hppcTestOCV"

Voltage detrending strategy when you set the FittingMethod property to "tfest", specified as "constantOCV" or "hppcTestOCV".

Data Types: string | char

OpenCircuitVoltage — Open-circuit voltage variable

zeros(0,1) (default) | table | timetable

Open-circuit voltage variable, specified as vector, table, or timetable.

Data Types: double | table | timetable

TimeVariable — Name of time variable

"Time" (default) | string scalar | character vector

Name of the time variable, specified as a string scalar or character vector.

Data Types: string | char

VoltageVariable — Name of voltage variable

"Voltage" (default) | string scalar | character vector

Name of the voltage variable, specified as a string scalar or character vector.

Data Types: string | char

CurrentVariable — Name of current variable

"Current" (default) | string scalar | character vector

Name of the current variable, specified as a string scalar or character vector.

Data Types: string | char

OpenCircuitVoltageVariable — Name of open-circuit voltage variable

"OpenCircuitVoltage" (default) | string scalar | character vector

Name of the open-circuit voltage variable, specified as a string scalar or character vector.

Data Types: string | char

Object Functions

fitecm	Estimate parameters of battery equivalent circuit model for constant current pulse
fitecmToHppcTest	Estimate parameters of battery equivalent circuit model from HPPCTest object
fitecmToHppcTestSuite	Estimate parameters of battery equivalent circuit model from HPPCTestSuite object

Version History

Introduced in R2025a