Over 70 per cent of all new vehicles will be fitted with an engine start/stop function, in order to achieve the CO2 limitation targets set by the EU by means of sustained fuel consumptionsavings and emission reductions. In general, two differing starter battery types are employed in these environment-friendly vehicles, consisting of the absorbent glass mat (AGM) and the enhanced flooded battery (EFB) systems. The use of the appropriate technology depends largely on the fuel and CO2 savings that can be attained. Above all, AGM batteries are utilised for start/stop systems with braking energy recuperation in mid-range and premium class vehicles.