Battery

Most battery models fail not because the equations are wrong — but because the assumptions smuggled in with them are wrong. Fifteen years working with battery models across the stack: from ECM spreadsheets that needed to survive a BMS real-time loop, to full electrochemical models trying to capture what actually happens inside the cell during a fast charge. The gap between “runs on paper” and “works in a vehicle” is where most of the interesting problems live. ...

GitHub Repository CFD-based battery simulation is powerful and routinely impractical. OpenFOAM can model the coupled thermal-flow behavior of a battery pack in detail that lumped models can’t touch. It can resolve cell-to-cell temperature gradients, coolant channel flow distribution, and transient heat propagation through complex pack geometries. It can also take an experienced CFD engineer a day to set up a single case, another day to run it, and significant effort to extract anything useful from the output. ...

Most battery simulation work happens inside large OEM simulation frameworks — tools with hundreds of subsystems, long setup times, and infrastructure built for full-vehicle analysis. Useful when you need the full vehicle. Counterproductive when you need to iterate quickly on battery-specific questions. At Volvo Trucks, the problem was clear: the battery and BMS teams needed a simulation environment they could actually use — fast iteration, battery-focused, not dragging a full vehicle model along for every run. ...

The EV marketing spec says “0 to 80% in 22 minutes.” It rarely says how long 80 to 100% takes. The omission is deliberate — and it reveals something fundamental about how lithium-ion cells actually work. The CC-CV Profile and Why the Transition Matters Lithium-ion charging follows a two-phase profile, not because someone decided it was a good idea, but because cell physics demands it. Constant Current (CC) phase: You push current in at a fixed rate. The cell voltage rises as SoC increases. This phase is efficient — you’re putting energy into the cell at the maximum rate the chemistry allows without exceeding the voltage limit or driving electrochemical side reactions. ...

In battery development, the cell you’re simulating is rarely the cell you have test data for. A customer RFI comes in specifying a 60 Ah prismatic. Your characterisation data is for a 40 Ah cylindrical from the same chemistry family. The programme timeline doesn’t allow for a full test campaign on the new cell before the simulation deliverable is due. This is the normal situation — not the edge case. ...

A battery’s safe operating envelope is not a fixed number. It’s a surface — varying continuously with temperature, state of charge, state of health, and operating history. Getting it wrong in the conservative direction costs performance and range. Getting it wrong in the aggressive direction costs cell life, and at the extreme, safety. The Current Limits Generator was built to define that surface correctly — from physics, not from conservative blanket rules. ...

Most thermal modelling projects in automotive spend the majority of their time not solving physics — but configuring it. Setting up geometry representations, mapping cell sensor signals to Simulink ports, assigning material properties, wiring the cooling boundary conditions from CFD into the thermal solver. The same steps, repeated for every new battery variant, every new pack geometry, every new cooling configuration. The Battery Thermal Model Configurator was built to eliminate that overhead — and to produce something better than what the manual process was generating. ...

An EV thermal management system is not one problem. It’s eight problems that happen to share coolant. The battery wants to stay between 15 and 35°C. The power electronics want active cooling at high load. The cabin wants heat in winter and cooling in summer, and it’s competing for the same refrigerant circuit the battery uses. The motor generates heat during aggressive driving. The DC-DC converter has its own overtemperature failure mode. All of these are connected — through coolant loops, refrigerant circuits, and control logic — and all of them interact dynamically. ...