A 36-V valve-regulated lead-acid (VRLA) battery used in a 42-V power system has been developed for the Toyota Hybrid System-Mild (THS-M) vehicle to meet the large electrical power requirements of hybrid electric vehicles (HEVs) and the increasing power demands on modern automobile electrical systems. The battery has a longer cycle-life in HEV use through the application of ultra high-density active-material and an anti-corrosive grid alloy for the positive plates, special additives for the negative plates, and absorbent glass mat with less contraction for the separators.