The Impala has had kind of an odd life. Since its debut in 1958 as the top trim level of the Bel Air, the Impala has gone through 10 generations of changes in appearance, engines, style and purpose. From stock car dominator to boulevard bruiser to the modern interpretation of a speedy, Euro-style sedan, very few threads have truly carried through the car's life span. Few, that is, aside from a penchant for power and speed.
The 3.4-liter, 60-degree GM V-6 was the base engine in eighth-generation, 1999-to-2005 Impalas, offering 180 horsepower to base-model buyers. The stock replacement battery in this car is a Battery Group Size 78. It measures 10 3/4 inches long, 6 7/8 inches wide and 7 1/4 inches tall. It's a standard top post battery with 775 cold cranking amps, 995 cranking amps and 120 minutes of reserve capacity -- 55 amp-hours of capacity. That would give you about 5 1/2 hours with a 10-amp radio running, or about 2 1/2 hours with the headlights on. Those living in more extreme environments can, as of 2013, acquire batteries that will fit this chassis and have upward of 850 cold cranking amps and 1,020 cranking amps. However, the trade-off is about 5 amp-hours of storage capacity, which means that the battery will die a bit quicker if you leave the headlights or radio on.
