NOVELTY - The system (52) has first and second batteries non-voltage matched such that voltage range of the second battery is greater than voltage range of the first battery. The first battery steers power generated during regenerative braking to the second battery using internal resistance of the first battery to enable the second battery to capture majority of the power generated during regenerative braking. The second battery provides power to an electrical system due to higher voltage range of the second battery when the second battery comprises positive state of charge.    USE - 12 volt automotive battery system e.g. semi-passive battery systems and passive battery systems such as single 12 volt lead-acid battery, for use in vehicular contexts and energy storage/expending applications for supplying power to components of a vehicle electrical system in a vehicle e.g. micro-hybrid vehicle. Uses include but are not limited to radiator cooling fans, climate control system, electric power steering systems, active suspension systems, auto park systems, electric oil pumps, electric super/turbochargers, electric water pumps, heated windscreen/defrosters, window lift motors, vanity lights, tire pressure monitoring systems, sunroof motor controls, power seats, alarm systems, infotainment systems, navigation features, lane departure warning systems, electric parking brakes, external lights.    ADVANTAGE - The system increases fuel economy and/or reduces undesirable emissions compared to traditional gas-powered vehicles. The system can continuously supply power to a vehicle's electrical system by utilizing generated electrical power, where the generated electrical power is utilized to stabilize voltage during high demand in regenerative storage systems. The system improves efficiency of a power storage in the battery system and efficiency of power distribution to a vehicle's electrical system while largely conforming with existing vehicle electrical systems.    DETAILED DESCRIPTION - The battery is a LTO/LMO battery (32) and lead-acid battery (30). The voltage range of the first battery is in range of 11.2 to 12.9 volts when first battery chemistry is lead-acid. The voltage range of the second battery is from 13.2 to 16.4 volts when second battery chemistry is lithium nickel manganese cobalt oxide. The first battery chemistry is lead-acid. The second battery chemistry is lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese cobalt oxide- lithium nickel cobalt aluminum oxide. An INDEPENDENT CLAIM is also included for a method for operating a 12 volt automotive battery system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a passive battery architecture.    Lead-acid battery (30)    LTO/LMO battery (32)    12 volt automotive battery system (52)    Starter (62)    Alternator (64)