A lot of research has been done on internal combustion engine to reduce fuel consumption and emission. One field is being researched today is to recuperate from kinetic energy to electric energy as a vehicle deceleration status. More energy recuperation can be reduced fuel consumption. To recuperate the more electric energy, this study was applied to the high power alternator and AGM battery device and optimized voltage control. This kind of system is new generation alternator management system. The result of fuel economy test for this system showed an about 0.8~4% improvement effect.