Alternator swaps and general charging system performance Part 1- GM This article is an attempt to sort out some of the confusion arising when swapping engines and powertrains into older cars, while at the sane time maintaining or improving electrical system performance, which is often lacking in performance vehicles and hot rods. I would also like to make one point about modern automotive electrical systems that seems to be misunderstood by some. Prevailing thought seems to place the battery at the center of the automotive electrical system. In the days of the DC generator, this was partially true, but in modern vehicles, with electric power demands ten-fold or higher than the typical 1950s vehicle, this is not true. The alternator supplies all the power for operating the powertrain and accessories, while the battery is present primarily for cranking the engine and providing auxiliary power for accessories until the engine is runni...