The balance of end-user requirements which result in multiple design options will ultimately define the configuration of 36-/42-V lead–acid batteries used in future vehicles. Analysis of the driving forces, i.e. high power output, space and weight minimization, and especially cost/benefit considerations, reveal a high probability for a 36-V flooded, prismatic, battery design. The main requirements on the separator will be superior oxidation stability and high puncture strength, i.e. to levels far beyond what are achievable today.