Many cars will soon have 48-volt electrical systems. They’ll power stop-start motors, hybrid motors, and turbochargers, allowing for smaller engines with better fuel economy and performance. These systems use battery packs with multiple cells that must be kept stable under challenging-use conditions. When developing a 48-volt lithium-ion battery pack for a stop- start system, designers at a European automotive supplier were seeking a high-performance foam cushion to keep the battery pack in place. The stack of battery cells would be continuously in motion, charging and de-charging, meaning that its dimensions would be continuously changing. In addition, the cells could grow over their lifetime by as much as 8%. How could designers ensure that the battery stack would remain stable under these conditions while keeping continuously in contact with vital cooling fins? They would need a foam material that could put consistent tension on the stack, holding it in place, despite changes in thickness tolerances in the cell and housing over the life of the battery pack. If the foam relaxed over time, it could cause the battery to fail - not an option as it could endanger passengers and lead to costly quality recalls. Reliable compression set resistance and stress relaxation performance over a broad range of temperatures and conditions would be critical to the battery cushion’s performance.
Rogers’ European automotive sales team recommended PORON® 4701-50, a firm, microcellular polyurethane ideally suited for providing consistent force or tension despite variances in thickness, temperature, or compression. Key to this critical application, the PORON® material offered the superior compression set resistance needed to enable long- term performance. The high-performance foam is also low-outgassing and non-fogging, containing no plasticizers or residual chemicals to contaminate the vehicle. It does not become brittle and crumble, is non-corrosive to metal, and is inherently flame retardant without the use of additives. Also key to this application, the material passed stringent energy storage conditions testing based on OEM specifications that simulated a 10-year life.
The battery designers chose Rogers’ PORON® 4701-50 polyurethane over all other material options. After stringent testing, they knew they could count on PORON® polyurethane material to handle the continuous motion, changing dimensions, and changing compression of the foam inherent in the function of these battery packs. When stability, reliability, and consistency are needed, PORON® polyurethanes deliver non-stop performance.