How do you simulate EV battery pack thermal behavior across a drive cycle?

By coupling cell-level electrochemical-thermal simulation in STAR-CCM+ with system-level pack, cooling loop and vehicle duty-cycle simulation in Amesim, so transient loads like fast charge and regenerative braking are represented, not just steady-state conditions.

How is inverter power module reliability tested for EV applications?

Power modules are power-cycled under Simcenter Micred Power Tester against the AQG 324 qualification framework, with Simcenter Micred T3Ster characterizing the module's thermal path before and after cycling to quantify degradation.

Why do cells in a pack age at different rates?

Pack-level thermal gradients mean cells at different positions experience different temperatures across the duty cycle, and because aging accelerates with temperature, small gradients compound into meaningfully different degradation rates over vehicle life.

01EV Battery Thermal Management

How do I design a battery pack cooling system that holds up across the full duty cycle, not just the datasheet condition?

Cell-to-pack-to-vehicle thermal simulation connected to inverter reliability testing.

02The problem

A cell-level thermal model looks fine in isolation, but pack-level temperature gradients between cells drive uneven aging, and a cooling loop sized against a steady-state assumption struggles with the transient loads of real drive cycles — fast charging, regenerative braking, and sustained highway load in hot ambient.

Separately, the inverter and power modules sitting next to that battery pack face their own thermal reliability question under repeated power cycling, and teams often qualify the pack thermal design and the power electronics reliability as two unconnected programs.

Why it's hard

Electrochemical heat generation inside a cell is nonuniform and depends on state of charge, C-rate and aging — not a fixed heat flux
Pack-level thermal gradients between cells drive divergent aging rates that are difficult to predict from a single-cell model
Cooling loop performance under transient duty cycles (fast charge, regen, sustained load) differs substantially from steady-state design points
BMS thermal control strategy has to be validated against the same plant model used for the physical cooling design, or the two diverge over the program
Power module reliability under thermal cycling is a separate qualification discipline that is frequently disconnected from the pack thermal design effort

03How we solve it

Predict — simulation

Model electrochemical-thermal behavior at the cell level in STAR-CCM+ to resolve heat generation and internal gradients under charge and discharge
Carry cell behavior up to pack and vehicle duty-cycle simulation in Amesim, including the cooling loop and control strategy
Develop and test BMS thermal control strategy against the same plant model via hardware- and software-in-the-loop testing in Amesim

Measure — hardware

Characterize inverter SiC or IGBT power modules with Simcenter Micred T3Ster before and after cycling
Qualify power module reliability under real duty-cycle power cycling with Simcenter Micred Power Tester

Correlate — close the loop

Use measured module degradation data to set aging assumptions in the pack and vehicle thermal simulation, so end-of-life design margin is based on real degradation, not a fixed derating factor
Feed cell and pack simulation results back to validate the assumptions used when sizing the power-cycling qualification test

04Tools applied

STAR-CCM+

Electrochemical-thermal battery coupling, cell to pack

Amesim

System simulation for pack, cooling loop and vehicle duty cycle, plus BMS HIL/SIL

Simcenter Micred Power Tester

Power cycling reliability qualification for inverter modules

Simcenter Micred T3Ster

Power module characterization before and after cycling

05Standards in scope