Transportation Science

What's inside a car battery?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. The standard lead-acid battery hasn't changed much over the past 100 years. The car battery usually is encased in a plastic box (some also have insulation sleeves to protect against extreme temperatures). Plates of lead and lead dioxide are inside the battery. The plates are suspended in a liquid mixture of water and sulfuric acid, which creates an electrolyte solution. The solution allows electrons to flow between the lead plates and produce electricity.

    If your battery never gets fully charged, a state called acid stratification can result. Acid stratification is when the electrolyte solution in your car battery separates into two distinct halves: heavy acid settles at the bottom and light acid rises to the top. The consequences for your car battery are that the light acid will start to corrode the plates, and the heavier acid then has to work harder to compensate -- harder than the battery is designed to work. The corrosion and undue drain shorten your battery's life.

    All of this is pretty standard in batteries, because these functions are necessary for a battery to work. When purchasing a battery, however, you should be aware of its cold-cranking amps and reserve capacity before automatically opting for lower price. As with any purchase, you might pay less up front, but end up replacing the battery more often, which costs you more over time. Cold-cranking amps (CCA) are the maximum number of amperes a battery can store. This is critical to starting the car, especially when the outside temperature is cold. Your car manufacturer should provide a recommended level of CCA; don't go below that or too high (about 200 amps) over it. Reserve capacity is how many amps it can sore for an hour before dying; shoot for the highest reserve capacity you can get in the model that fits your car and for your budget [sources: MSN, CarsDirect.com].

    Of course, this all assumes the car you're driving is a traditional, fossil-fuel powered vehicle. Today's electric and hybrid cars still are researching the best battery technology to hold power for the longest time (and driving distance) possible without adding energy-wasting weight to the cars. These batteries may have cathodes made of materials such as lithium, cobalt and nickel [source: Zyga]. Or they might run on "goo," an electrically conductive waste product of fuel [source: Danigelis].

    More answers from Science Channel »



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