Dielectric foams can accommodate the dimensional changes and variances of the battery cells but deliver enough pressure to the cell package to prevent misshaping and disconnections. The foam has a spring-like characteristic, but is in fact better than a spring. The more a spring deflects, the higher the potential return energy. But foams can be engineered to deliver the same, consistent return energy across a wide range of compression amounts, a property known as compression force deflection (CFD). Springs are also thermally and electrically conductive and can create hard spots in the battery.