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Batteries are a mystery to many drivers. If you ask 100 people off the street how batteries work, you would probably get 100 different answers, and maybe 1 or 2 of them would be close to the truth.

Batteries are as ubiquitous as they are mysterious. Without getting too technical or scientific, let’s take some of the mystery out of the battery that 'powers' your car or truck.

Why Does My Car Have a Battery if it Runs on Gas?

  • Despite technological advancement in vehicle technology, most vehicles are still powered by gasoline or diesel fuel engines. In the early days of the automobile, engines had to be hand-cranked to get them started. Manufacturers added electric starters to make starting automobile engines easier, which necessitated a battery.

  • The primary function of the battery is to help you start the engine by powering the electric starter. After you turn your key and start your engine, the alternator ensures the battery stays charged. The battery also provides electric power to your car’s engine control unit (ECU), its ignition system, as well as all the interior accessories that require electric power, like the radio.

Your Battery and Your Alternator

  • Without getting too technical, your car or truck’s battery is a device for storing electricity. Like all batteries, it uses a cathode and an anode along with an acid solution carried in a plastic housing to store the electricity your car or truck needs to start and run properly. The battery itself gets its charge from the alternator.

  • If your alternator breaks or malfunctions, your car or truck will continue to run until there’s not enough electricity in the battery to power the ECU. At that point, the vehicle will stop running. It won’t restart because there isn’t enough electricity to turn the starter. If you attempt to jump-start the car, it may start and run, however, it will likely stop running shortly after you remove the cables. Even if you install a fresh battery, while it may get you home, your car or truck will neither start nor run after a short time in the absence of a functioning alternator.

  • Before you replace your battery, be sure to check your charging system. It’s a good idea to have your battery and charging system tested before you replace any parts. If you’re not sure how to do that, you can get your battery tested for free at Pep Boys. So if you notice your car or truck becoming harder to start, don’t hesitate bringing it to your local Pep Boys.
  • Why Batteries Wear Out and Go 'Flat'

  • As soon as the battery is discharged, even in the slightest, the metal plates inside begin to oxidize. Although your car or truck’s battery is designed to start your car repeatedly and store electricity from the alternator, the oxidation that occurs is a matter of physics, not design. If engineers could design around this inconvenience, batteries would last forever and you would never have to replace them.

  • Eventually, after you’ve used the battery to start the engine for a couple of years, the oxidation inside of it gets to a point where the battery will no longer take a charge, no matter how much electricity the alternator supplies to it.

  • Extremely cold climates are tough on batteries too. Batteries simply don’t work as well when they’re cold compared to when they’re warm. If you live in an area where it regularly dips below 20 degrees Fahrenheit, installing and using a block heater can take some of the strain off your car’s starter, battery, and electrical system.
  • Average Car Battery Life

    In theory, the life of a car battery is determined by a variety of factors, many of which rarely come to full fruition. Under normal circumstances, a car battery has a lifespan of about four years. For a car battery to make it to this average life, it’s under the assumption that it is under the following conditions:
    • Goes through full charge cycles
    • Does not get subjected to extreme cold or heat
    • Connected to a reliable charging system
    • Does not power accessories
    Most automotive batteries don’t live in these 'normal' or 'ideal' circumstances. In reality, batteries are subjected to temperature extremes in the winter and summer months. Starting your car takes a large surge of electricity from the battery, which means the charging system then kicks in to replenish it. Short trips often mean that the battery does not receive a full charge.

    Accessories that rely on the car battery for power can also shorten the lifespan of the battery, as it requires more juice to power items such as phones, MP3 players, and GPS Units, on top of providing power for the vehicle itself.

    Replacing Your Old Battery

    • The first step is to choose a battery. There are a variety of types available, and the friendly parts professionals at your local Pep Boys can help you decide on an appropriate replacement battery.

    • Note that there is absolutely nothing wrong with conventional, maintenance free, lead acid type batteries. These batteries are economical to purchase and last at least 2 years.

    • Absorbent glass mat (AGM) batteries often last much longer, but they can also be a more expensive investment.


    There’s no reason to let a failing battery sneak up on you. If you notice your car or truck is becoming more difficult to start, head to your local Pep Boys and have us run a test on your battery and charging system for free!