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The vast majority of passenger vehicles on the road today have only a single, large battery. It’s generally located under the hood, although some makes and models have the primary battery in the trunk, near the spare tire. This battery’s job is simple – it provides the electricity needed to start the engine. All other power generated during operation to power the radio, signal lights, and other accessories comes from the alternator.
However, some vehicles (notably higher-end European imports) have more than one battery. There’s the primary battery under the hood, but there’s also an auxiliary battery. These are used to power other systems on the car that require 12 volts of power, and which the alternator is not capable of powering directly. In these instances, the alternator is responsible for charging both the primary and the auxiliary battery. The primary battery delivers voltage during cranking, and the auxiliary battery runs some or most of the car’s accessories.
Like all batteries, auxiliary batteries will eventually wear out or fail. When this happens, they’ll need to be replaced.
Over time and through normal use, your battery deteriorates. Eventually, it will fail completely. Most have a lifespan of about five to seven years, but this is only an estimate. Once your auxiliary battery fails, it puts a strain on the rest of your system, and some of your accessories may not operate properly or at all. Have the problem professionally diagnosed by one of our expert mechanics as electrical issues can stem from many different problems, not just battery failure.
While a failed auxiliary battery will not prevent your vehicle from driving, it can cause significant complications, including important accessories malfunctioning or not working at all. It can also put additional strain on the rest of your charging system components. Have the auxiliary battery replaced as soon as possible.