Solid State Module Spring Plate Compression Allowances under Cycling
Solid state spring plate allowances absorb 10 to 18 percent cell volumetric strain while bounding contact pressure between 1.0 and 4.0 MPa across cell life.
Stress Relaxation Rate
Meaning
The speed at which a material loses its internal resistive force over time under a constant strain determines the long-term tightness of compressed joints and seals. In battery pack assembly, the stress relaxation rate of elastomeric pads dictates how quickly the holding pressure on the cell stack will decrease. It is a critical factor for ensuring that the cells remain securely clamped throughout their lifetime.
Relaxation Behavior
Viscoelastic properties govern how a material reacts to a fixed deformation over years of service. A polymer with a high stress relaxation rate will quickly lose its sealing force, which can lead to leaks in the coolant system or loose electrical connections. This decay must be modeled to predict the end-of-life behavior of the module.
Longterm Performance
Clamping pressure must stay above a minimum threshold to prevent cell swelling and subsequent delamination of the electrode layers. If the stress relaxation rate is too rapid, the pack will suffer from premature degradation because the loose cells are free to expand during high-current charging. This expansion causes accelerated capacity loss.
Materials Procurement
Quality specifications for seals and spacers require that suppliers provide stress relaxation data at the maximum operating temperature of the pack. Sourcing teams compare the stress relaxation rate of silicone and polyurethane foams to choose the material that offers the longest service life. This selection helps prevent warranty claims and field failures related to loose components or coolant leaks.
It also ensures that the chosen materials comply with the rugged performance requirements of electric vehicles.