Absorptive glass mat (AGM) is commonly used as a separator in valve-regulated lead acid (VRLA) batteries because of its high porosity (~ 92%) that can accommodate oxygen transport and recombination, low impedance, excellent oxidation resistance, and ability to immobilize sulfuric acid. The latter results in non-spillable batteries that can be positioned in many different areas of an ICE or electric vehicle. In this paper, we briefly review the influence of fiber type, fiber diameter, surface area, and process conditions on key AGM characteristics. We examine all-glass and organic fiber-glass hybrid compositions to better understand differences in porosity, wicking rate, and compression-recovery in both a “wet” and “dry” state.

Finally, we investigate X-ray tomography as a tool to evaluate the homogeneity of AGM. Initial results show differences not only in the wire-side and top-side of the product, but also evidence of trapped air and other gradients within the wetted bulk structure.