When car batteries are new they are capable of putting out some 500-700 peak amps. When this sort of amperage hits the starter, your engine will crank over nice and fast, even when it's cold out. When a battery gets older, it can't put out the amperage that a new one does and your engine simply won't crank as fast.  And, especially when it's cold out, you might not be able to start your car. Most drivers have a horror story or so about an engine that won't start when they are a long way from home. It's not a fun predicament to be in.

A natural question, then, would be: "Should I replace my car battery before it reaches that point?" The service manager at Patrick Dealer Group of Schaumburg, IL, a BMW, Hyundai, Cadillac, MINI and Volvo dealer, told us that a rough rule of thumb is that a car battery lasts about four, maybe five, years, under "normal conditions."  If your battery is that old, it may be a good idea to replace the battery before it lets you down.

Normal conditions?

"Normal conditions" refers to a number of factors. Normally a car battery isn't subjected to extreme temperatures (high and low), isn't jostled about, and is attached to a properly functioning charging system. In the real world, however, things happen. For example, if you live in Arizona, your battery is going to get really hot on some days; if your battery isn't held down with a battery strap, it's going to bounce around; and sometimes charging systems don't put out enough power to charge a battery. Bottom line: rarely do batteries operate under "normal conditions."

What's inside

Let's take a look inside a typical lead-acid car battery and get a better idea of what can go wrong. Inside the plastic battery box are a series of lead plates arranged in rows. These plates are suspended in a mix of water and sulfuric acid.  These metal plates are built to be strong but there are factors that can break the internal structure. For example, rough travel without a battery strapped down can shake loose or weaken the lead plates. Extreme heat during the summer can accelerate the chemical reactions inside a battery which can shorten its life too.

Short trips

This may be a surprise but if you have a short commute or take lots of brief trips, this can harm your battery too. It's because the battery never gets fully charged and this results in "acid stratification" which shortens the battery's life because the plates are damaged.

Symptoms that the end may be near

The most obvious sign of a battery that is nearing the end of its lifespan is that when it is fully charged (say after a long trip), that it cranks the engine slowly.  This can also be attributed to the vehicle's charging system too so this should be checked out.  Any mechanic can do this. However, if the charging system checks out, it's likely that the battery is bad. You may also know that the battery is just simply old and, as we explained above, they only last 4-5 years at the most.


Batteries are so reliable that drivers have a tendency to forget that they do age and should be replaced. If you pay attention to the age of your car's battery, you'll reduce your risk of being stranded on the road.  As we mentioned, if your car turns over slowly and its fully charged, it might be because your battery needs replacement. When in doubt, have a mechanic check it out. Then you are assured of reliability and full cranking power for years to come.

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