DC Box Thermal Modeling: The Component That Gets Forgotten Until It Fails
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. ...