The typical life span of a car battery is 3 to 5 years, though some variables can shorten its life. A well-maintained battery, on the other hand, can last far beyond its limited warranty. To properly maintain a car battery, you should have the terminal ends inspected and cleaned and the battery tested for cold-cranking amp output at least once a year. This will help you monitor the life left in the battery.

The Battery

A battery's task is to produce enough cold-cranking amps to ignite the starter. The portable power to the starter brings life to the engine. Once the starter powers the engine crank and the engine is running, the alternator takes over and recharges the spent amps back to the battery. At this point, any other power demand in the car comes from the battery: lights, radio, blower motor and any other electrical options. Again, the alternator restores the charge back to the battery. However, the alternator does not fully recharge the battery, it simply restores it. Over time, the battery's output capacity loses its effectiveness. A typical fully charged and new battery has about three to four times the necessary cold-cranking amps to start the engine. However, some variables can compromise this.

Battery Variables

Extreme cold weather is one of the leading causes of battery failure when a battery has reached a certain age. The battery should be tested every year near the end of autumn to determine its cold-cranking amp output. The colder the temperature outside, the fewer cold-cranking amps the battery can produce. The older the battery, the fewer cold-cranking amps are restored to it from the alternator. Leaving lights or other power sources on in the car can drain the battery and significantly reduce its life. Simple maintenance, such as cleaning terminals, cables and posts, can significantly improve the battery's ability to provide enough portable power to start the engine.

Date Codes

Even a new battery sitting on a display shelf will slowly lose its effectiveness. It's not uncommon for a place that sells batteries to charge them up before selling them. Batteries have date codes stamped on the outside housing that show when they were manufactured. Although a battery will still come with its limited warranty no matter when it is sold, a fresher battery is a better option. Eventually, if the batteries expire on the store shelf, they're sent back to the manufacturer for inspection, recharged and then recycled back out to the field. Most batteries have 60-month warranties. The warranty starts the day you buy the battery. The battery itself gets prorated as time passes. In other words, the closer the battery gets to the end of its warranty, the less its value would be in the event it failed. Some batteries have warranties of 72 months or more. These batteries are usually slightly larger and can produce more cold-cranking amps than are necessary to start the car. This is why they can last longer. Always check the date of the battery before purchasing one. Have the battery checked right before winter each year to determine its cold-cranking amp output. Many service stations and auto parts stores have portable battery testers and will do the service for free with the understanding that you'll purchase the battery from them or have it installed there if you need one.

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