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Do You Need To Test Your Battery? What Causes It To Fail?

American Government Special Collections Reference Desk

Do You Need To Test Your Battery? What Causes It To Fail?

Elliott Turner
2 October 2008


A battery is a series of two or more connected cells, which changes chemical energy into electrical energy. A lead-acid battery contains plates made of lead and lead dioxide. They are submerged in sulfuric acid mixed with water, which makes the electrolyte. An automotive battery is a lead-acid battery, which is used mainly to start the engine of the automobile. The only other function of the battery is to keep the clock running and the alarm system functioning while the engine if off. The capacity of the battery is measured in ampere-hours. A maintenance free battery is usually a sealed lead-acid battery. Small amounts of calcium and silver are added to the lead plates in order to reduce water loss from the electrolyte.

We have a tendency to throw away our batteries too soon because sulfation occurs. The battery will normally discharge for longer periods of time than it will charge. Face it, our cars sit parked for longer amounts of time than we are in it driving. While the car is sitting, lead sulfate is being produced faster than it can be turned back into lead, lead dioxide, and water.

As the car sits idling, the lead sulfate is left sitting, the spongy lead sulfate hardens and form crystals. While the spongy lead sulfate can be reverted back to active material, lead and lead dioxide, the crystals cannot be changed back into active material. The more crystals form on the lead plates, the less active material is left to be changed back into its original state. A battery is dead when there is not enough material left to start a vehicle.

The leading cause of batteries to fail before their designated lifetime, is when the lead sulfates turn into crystals. So how long should you let your vehicle stay parked? The amount of time you are referring to, would be how long it can stay parked in an airport parking lot, sitting in your garage, or placed in storage. The length of time will depend on the battery�s State of Charge, the reserve capacity, the amount of normal self-discharging and the functions requiring battery power to continue running when the engine is off such as the clock settings, the radio setting and the car alarm, also the temperature of the battery and the battery type.

Car manufacturers normally allow for 14 days or more for airport time. This time frame is based on a fully charged battery in good condition: moderate temperatures in the weather, no additional after market add ons, which use battery power when the engine is off. When a battery�s state-of-charge drops below 100% and is left sitting, sulfation starts and will slowly increase until it kills the battery.

Testing your battery with an accurate battery health analyzer can mean the difference between a quick solution, or time consuming and frustrating problem. Do it right the first time, use proven equipment and you�ll be better off.

For more information on what type of battery tester you should be using to get it right the first time, visit the Battery research center.

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