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Native Simulink Battery 2RC Model

This example generates an inspectable Simulink block diagram for the existing two-RC battery reference. It independently integrates fast and slow polarization states while reusing the validated current, parameter, SOC, and OCV preprocessing pipeline.

Engineering Question

Can a generated Simulink diagram preserve both battery recovery time scales and reproduce the exact two-RC MATLAB reference over pulse-current profiles?

Block Structure

The model uses the repository's positive-discharge convention. A zero-order held current source drives native gain, sum, integrator, and lookup blocks:

dSOC/dt  = -I / (3600 * Q_Ah)
dVrc1/dt = I / C1 - Vrc1 / (R1 * C1)
dVrc2/dt = I / C2 - Vrc2 / (R2 * C2)
Vterminal = OCV(SOC) - R0 * I - Vrc1 - Vrc2

The generated diagram exposes current, SOC, OCV, both branch voltages, total polarization, and terminal voltage as logged outputs. Its SOC integrator is limited to [0, 1], and the OCV lookup uses linear interpolation with clipped extrapolation.

Input Preprocessing

build_battery_2rc_simulink_model calls the exact MATLAB two-RC solver first. That call validates the profile, timestamps, parameters, OCV data, optional uniform resampling, and SOC-feasible interval current. The resulting applied current is embedded directly in the generated .slx file.

Simulink then independently integrates SOC and both RC states and reconstructs all voltage outputs. Keeping the boundary-current policy in one validated location avoids two subtly different limiters while still testing the native dynamic diagram.

Starter Parameters

Parameter Value Unit
Capacity 50 Ah
Initial SOC 0.80 -
Ohmic resistance R0 4 mOhm
Fast resistance R1 1.5 mOhm
Fast capacitance C1 1200 F
Fast time constant 1.8 s
Slow resistance R2 2.5 mOhm
Slow capacitance C2 12000 F
Slow time constant 30 s
Canonical profile duration 600 s
Canonical output interval 1 s

Requirements

  • MATLAB R2026a is the verified release.
  • Simulink is required to build and run the block diagram.
  • No battery, power-electronics, control, or testing toolbox is required.

Run

Generate the model in a temporary workspace, simulate the canonical pulse profile, plot both branch states, and open the diagram:

run_battery_2rc_simulink_model

Generate a persistent copy in a directory of your choice:

build_battery_2rc_simulink_model('generated-models')

Run the no-plot regression check:

check_battery_2rc_simulink_model

Expected summary:

Native Simulink battery 2RC check passed.
Final SOC: 0.767
Voltage range: 3.325 V to 3.925 V

The check verifies every state-path block, key connection, branch gain, zero-order-held input, SOC bound, and lookup method. It compares all seven logged signals with the exact MATLAB solver for both the canonical case and a custom case with different branch time constants and a nonlinear OCV table. Generated models are removed after validation.

Explicit Limitations

  • The current trace is prevalidated and SOC-limited by the MATLAB reference; the diagram does not implement current, voltage, thermal, or power limits.
  • Both RC branches start from a rested zero-polarization state.
  • Parameters and OCV data are educational placeholders, not a fitted cell.
  • Continuous Simulink states use numerical integration, while the MATLAB reference uses exact interval updates.
  • OCV hysteresis, ageing, thermal feedback, self-discharge, and cell variation are excluded.
  • A second branch adds response flexibility but does not prove parameter identifiability or predictive accuracy without held-out measured data.