Meaning
Structural bending of the cold plate in a battery thermal management system occurs due to internal coolant pressure or external cell expansion forces. This cooling plate flexure alters the spatial distribution of the contact force between the cells and the cooling surface. It can lead to uneven temperature distribution and localized cell degradation if not managed.
Thermal Contact
Bending of the plate creates physical gaps where the air acting as an insulator restricts heat transfer. Because thermal grease or gap fillers can only bridge limited distances, a deflected plate reduces the cooling efficiency of the system. The cells closest to the center of the deflection run hotter than those near the supported edges.
Strain Accumulation
Repetitive temperature cycling and pressure pulses from the coolant pump cause cyclic loading of the plate structure. This stress leads to fatigue cracks, especially around soldered or brazed joints where the cooling channels meet the manifold. Solid bracket attachments and ribbed stiffeners are needed to limit the deflection to sub-millimeter levels.
Design Adaptation
Finite element analysis guides the placement of internal columns and flow channel walls to increase the plate stiffness without adding excess weight. Increasing the thickness of the plate is often avoided to prevent adding mass to the vehicle. Extruded aluminum channels provide a high strength-to-weight ratio while maintaining thin walls for optimal heat conduction.
Designers can also specify variable-thickness baseplates that are thicker in high-stress regions and thinner where the cells exert less mechanical pressure.
