The new automotive architectures will require high-voltage, high-power batteries that are completely different from existing 12 V flooded lead-acid products. Battery requirements for these applications are reviewed first from the standpoint of the vehicle, and then from an electrochemical/thermal performance perspective. Design and performance characteristics are then critically evaluated for the three major candidates for the new 36/42 V systems, namely: valve-regulated lead-acid (VRLA), nickel-metal-hydride (Ni-MH), and lithium-ion (Li-ion). Design and manufacturing requirements, performance strengths and weaknesses, reliability issues, markets and pricing are then examined for the VRLA battery, which appears to be the leading candidate at this time.