Functional Input Parameters

Overview

In BattMo, several key input parameters—such as open-circuit voltage (OCV) curves, electrolyte diffusivity, and conductivity—can vary based on material properties and operating conditions like concentration and temperature. To allow flexibility, these parameters can be specified in one of three supported formats: real number, string-based expression, or dictionary-based arrays.

This page outlines how each type is used and can be specified within a JSON cell parameter set using the diffusion coefficient of the electrolyte as an example.

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Supported Parameter Types

1. Real — Constant Value

A single numeric value is interpreted as a constant, independent of state-of-charge (SOC), concentration (c), temperature (T), etc.

Example:

"DiffusionCoefficient": 2.5e-10

2. String — Expression-Based Function

String parameters represent mathematical expressions that may depend on:

• c – Local concentration

• cmax – Maximum concentration

• T – Temperature (K)

• refT – Reference temperature (K)

The string is parsed into a function during initialization and can be evaluated dynamically.

Example:

"DiffusionCoefficient": "8.794*10^(-11)*(c/1000)^2 - 3.972*10^(-10)*(c/1000) + 4.862*10^(-10)"

Supported variables:

Parameter	Supported variable order	Battery component
OpenCircuitPotential	c,T,refT,cmax	ActiveMaterial
DiffusionCoefficient	c,T,refT,cmax	ActiveMaterial
ReactionRateCoefficient	c,T,refT,cmax	ActiveMaterial
IonicConductivity	c,T	Electrolyte
DiffusionCoefficient	c,T	Electrolyte

3. Dict — Julia Function

The parameter can aslo be provided as a function. The function can be passed to BattMo by either importing the function into the main script and writing down the function name within the input dict:

Example:

function calculate_diffusion_coefficient(c,T,refT,cmax)
    return diff_coeff_interpolation(c,T,refT,cmax)
end

"DiffusionCoefficient": {
    "FunctionName": "calculate_diffusion_coefficient"
}

or write the julia function in a separate Julia script and pass both the function name and the file path relative to the json input file within the input file:

"DiffusionCoefficient": {
    "FunctionName": "calculate_diffusion_coefficient",
    "FilePath": "diffusion_coefficient_function.jl"
}

Supported variables:

Parameter	Supported variable order	Battery component
OpenCircuitPotential	c,T,refT,cmax	ActiveMaterial
DiffusionCoefficient	c,T,refT,cmax	ActiveMaterial
ReactionRateCoefficient	c,T,refT,cmax	ActiveMaterial
IonicConductivity	c,T	Electrolyte
DiffusionCoefficient	c,T	Electrolyte

4. Dict — Tabular Data

For parameters like OCV curves, a dictionary with pre-tabulated data can be used. The dictionary must contain two keys:

• x – Representing the data of the dependent variable

• y – Representing the data of the input parameter

Example:

"DiffusionCoefficient": {
    "x": [0.01, 0.05, 0.10, 0.15, 0.20],
    "y": [0.0, 0.25, 0.5, 0.75, 1.0]}

The simulation uses interpolation to evaluate the y-quantity at any given x during the run.

Note: Ensure that both arrays are of equal length.

Supported data:

Parameter	Supported x data	Battery component
OpenCircuitPotential	StoichiometricCoefficient	ActiveMaterial
DiffusionCoefficient	StoichiometricCoefficient	ActiveMaterial
ReactionRateCoefficient	StoichiometricCoefficient	ActiveMaterial
IonicConductivity	Concentration	Electrolyte
DiffusionCoefficient	Concentration	Electrolyte