Mercedes-Benz

The DC junction box doesn’t get much attention in EV thermal discussions. People focus on the battery pack, the inverter, the motor. The junction box is a metal enclosure with some contactors, fuses, and busbars — it switches current and protects the circuit. How hot can it get? Hotter than you expect, under the conditions that matter most. Why the Junction Box Gets Hot The DC box carries the full HV current whenever the vehicle is driving or charging. The heating is straightforward: I²R losses in the busbars and contactors. At peak power — high speed driving or DC fast charge — this current is large. ...

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. ...