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Ask the Mechanic: Discussing vehicle battery maintenance and failure

By: Chris Bradford
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Before we talk about battery failure, let’s talk about the battery itself. Everything electrical in a vehicle is supplied by current from the battery. The battery is one of the most important parts of a vehicle because it is the heart of the electrical system. The primary purpose of an automotive battery is to provide a source of electrical power for starting and for electrical demands that exceed alternator output. The battery also acts as a voltage stabilizer for the entire electrical system. It acts as a voltage stabilizer because the battery is a reservoir where large amounts of current can be utilized quickly during starting, and then replaced by the alternator. There are two types of batteries. A lead-acid battery is also known as a flooded cell, and a low water-loss battery is known as a maintenance-free battery. They both use electrolyte, which is a solution of 36 percent sulfuric acid and 64 percent water. Flooded cell batteries have inspection covers that can be removed to inspect the electrolyte levels of all six cells, while maintenance-free batteries provide a built-in state of charge indicator. These state of charge indicators only tests one of six cells and may not always be accurate. The voltage of a fully charged battery should be 12.6 volts or higher. That is considered 100 percent charged. A battery that tests at 11.9 volts or lower is considered a discharge or bad battery. As you can see, there isn’t much voltage between a good and bad battery. Here are some symptoms of a battery that is starting to fail: Your headlights are dimmer than normal; you hear a click or rapid clicking when attempting to start the engine — a battery with approximately 10 volts will cause this condition; if the engine is slow in cranking; your battery connections have excessive corrosion, or the battery is low on water then you need to have your battery checked. These are the most common failures. Every automotive battery has a limited service life of approximately 3 to 7 years. Keeping your battery clean and charged will maximize the life of your battery. Chris Bradford is the shop foreman at Magnussen’s Auburn Toyota, 800 Nevada St., Auburn. He can be reached at (530) 885-8484.