Rick's Free Auto Repair Advice

How long does a car battery last

How long does a car battery last?

The average life of a car battery

Car batteries last about 3 to 4 years. That’s less than in the past when car batteries lasted 4-5 years. In fact, battery manufacturers tell us that only 30% of batteries sold reach the 48-month mark. 80% of early battery failures are due to battery plate sulfation caused by short drives and long periods of non-use.

Heat is the #1 killer of car batteries

Late-model cars and trucks have a packed engine bay. Plus, many engines are powered by a turbo and those suckers generate a lot of heat. A car battery works by creating electricity through a chemical reaction. Increase the temperature and you increase the rate of the chemical reaction. Heat (and running out of space under the hood) is one reason why car makers are moving batteries under the back seat and in the truck.

More power accessories cause more stress on the car battery, causing them to fail sooner

GPS navigation systems, cellular phones, collision avoidance cameras, radar and lasers, heated mirrors and seats, video screens, high-powered sound systems, WiFi, and additional power ports equal more power usage. A typical automotive alternator can only produce about 30% of its maximum rated capacity at idle, so the rest of the power comes from your battery. Idle for a long time with lots of power accessories running and you stress the battery.

Parasitic battery drain kills your car battery

All vehicle computer modules draw power. When you shut off your car, computer modules are supposed to go into sleep mode to reduce power draw.If a module doesn’t shut down and continues to draw too much power it can drain your battery.

Not driving your vehicle can kill your car battery

A car battery’s self-discharge rate of 1% per day combined with the power draw from your car’s computers can drain your battery in 4-6 weeks of non-use. If you start your car, turn the AC or heat on full blast, run seat heaters and drive a few blocks to the convenience store and then return home, you’re pulling far more power out of your battery than you’re putting back in. Do that several times per week with no other driving in between and you’ll severely discharge your battery and reduce its life.

What are the latest technological car battery trends? Read this

Replace your battery if it’s more than four years old

If your battery is approaching the four-year mark, have it tested now so you get a read on its condition. Otherwise, it can leave you stranded.

Car battery testing is easy

The old-school way to test a battery was to perform a stress test where the battery is loaded to half of its rated Cold Cranking Amps (CCA) for 15-secs. prepare your car for winter, test car batteryIf the battery voltage stayed above 9.6 volts during that period, it passed the test. But that same battery could fail the day after from causes that can’t be spotted by the stress test.

Modern battery testers conduct a simulated stress test, as well as internal resistance tests that can spot weak connections between the bus bar and plates and plate sulfation. Modern battery testers are far more accurate at predicting future battery life, so you should ask the shop to conduct the test at least once a year.

Here’s how car batteries get ruined

The car battery sits unused too long between charging in hot weather

The car battery sits unused too long between charging in extremely cold weather

The battery is run down by extended cranking (cranking but the engine won’t fire up) without immediate recharging with a battery charger.

Used in a high heat environment—the underhood temperature of 100°F increases internal self-discharge.

Low electrolyte level kills your car battery

Improper charging. Using a cheap battery charger can do more harm than good. Recharging a battery requires a specific charging procedure depending on the battery condition. Newer chargers can assess the condition of the battery and apply the correct charging protocol.

Cold weather. Cold weather slows down the chemical reaction that produces power.

Parasitic battery drain. All late-model cars draw computer current even when the engine is off. If all computers go into sleep mode, the draw is low (less than 50mA). However, even when all computers are in sleep mode, a 50mA draw can completely discharge a battery in 30-days. If a computer doesn’t enter sleep mode the parasitic draw can discharge a battery within hours. To find the source of a parasitic battery draw, read this article.

Dirty battery cables can kill your battery

Dirty/corroded battery terminals dramatically

coroded battery terminals

These corroded battery terminals are killing this battery

reduce the amount of current available to start the engine AND reduces the amount of recharging current needed to recharge the battery.

For tips on buying the best car battery, read this article.

If you own a 2000 or newer vehicle, the techniques for installing a new battery have changed. If you don’t follow the proper installation practices, your car may not run at all or may run poorly after a battery change. Read this post on how to install a new battery.

©, 2015 Rick Muscoplat

Posted on by Rick Muscoplat


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