November 27, 2022

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Automotive to Us

How Long Do Car Batteries Last?

It always seems to happen at the worst possible time. You turn the key and—nothing. Dead battery. You think, “Didn’t we just replace the battery a couple of years ago?” Unfortunately, few people think about their car’s battery until it leaves them stranded.

It wasn’t that long ago that car battery makers marketed their products as 48-, 60-, 72- or 84-month batteries as a universal indicator of the expected durability. In more recent times, they’ve backed away from that because it was never a reliable predictor of how long a battery would last. There are too many environmental and use factors at play. Far too many post-purchase variables affect the life of a vehicle battery to label them universally.

You’ll still see those phrases, but with the word “warranty” afterward, not “battery.” And really, that’s how it always was.

There are some differences in the quality and relative lifespan of batteries. Still, instead of attaching a misleading number to the product, most manufacturers have settled on something along the lines of a “good, better, best” marketing strategy and aligned their warranties accordingly.

On average, no matter the warranty, a traditional car battery has a reliable and trouble-free lifespan of about three years—36 months. While many batteries last much longer, that’s the point where a measurable decrease in performance can be detected. Unfortunately, few car batteries ever see five years of service, much less six or seven; those that do last that long operate at a significantly reduced capacity. But if you pay for a 60-month battery and it fails in regular use before that, you’ll get some money toward a new battery on a pro-rated basis.  

When it’s time to replace your car battery, check your owner’s manual for the proper group size and other pertinent specifications. Many auto parts retailers will install a new battery for free or for a small fee if purchased from them. Getty


Types of Car Batteries

Although there are numerous types of automotive batteries on the market, most batteries designed for starting internal combustion vehicles and powering the electrical system generally fall into one of the following two categories: A traditional wet cell or flooded battery that can require periodic maintenance, or a sealed, low maintenance version, sometimes called a Valve Regulated Lead Acid (VRLA) battery.

Additionally, there are a variety of sub-variations of the two primary types. The Enhanced Flooded Battery (EFB) and the Absorbent Glass Mat Battery (AGM) are two of the most prominent. Both types are designed to provide robust specifications and improved longevity. EVs and hybrid vehicles use much larger and highly specialized battery packs not covered here.

Why Don’t Car Batteries Last Longer?

In the simplest terms, a traditional wet cell or flooded car battery consists of lead and other metallic plates in a solution of two-thirds water and one-third sulfuric acid. The formula stores electricity, but over time, the caustic mix tends to eat itself, weakening the battery.

Besides time, heat is a huge enemy of battery life. If you live in a hotter than average climate, say a desert city where triple-digit temperatures are a given for many months out of the year, expect even shorter than average car battery life. That heat is causing the solution inside your battery to evaporate. And even in more temperate climates, the temperatures underhood can be extreme under heavy use.

Also attacking your battery from within is vibration. It causes the plates inside the battery case—the ones sitting in an acid bath—to break down even more quickly.

Any charging system issues that go undiagnosed such as a bad alternator, worn, poorly adjusted or broken belts or regulator and electrical faults can also shorten the lifespan of a car battery.

And then there are the “oops” moments. For example, even though many modern vehicles have built-in safeguards, it’s still possible to leave the headlights or interior lights on in a parked car, causing the battery to go dead. Most often, a jump start will get the car moving again, but repeated full discharges of this type shorten the battery’s life.  

If your battery terminals are excessively corroded, it can be a sign of a bigger problem. Check them occasionally for condition and tightness for the best performance. Getty

Can I Help My Car Battery Last Longer?

Not much can be done about the weather, but cars with the battery mounted remotely instead of in the engine compartment have an advantage. Common remote locations include the trunk or under the rear seat, both of which will reduce the heat exposure somewhat.

Proper maintenance, however, can help a battery last longer. Check to be sure the battery is securely fastened in the battery tray to prevent excess vibration. Make sure the charging system, including the alternator and belts, are in good condition. If the battery is easily visible, occasionally check the terminals for tightness and buildup of corrosion. The terminals should be snug but resist the urge to overtighten them.   

And if you have a car that doesn’t automatically turn off headlights and interior lights after the engine’s been shut off, take the time to double-check those things when you park. If you’re leaving a car to sit for a long time or don’t regularly use your car, a battery tender or charger can prolong its life and prevent it from going flat.

Unless you buy a new car every two years, sooner or later, you’ll deal with a dead or weak battery—the trick is to keep an eye on an older battery and replace it before it leaves you stranded. Then, when it does come time to replace it, shop for the best price on a warranty that makes sense for your car and how long you plan to keep it.

This article, How Long Do Car Batteries Last?, originally appeared on Forbes Advisor.