How Long Do Car Batteries Last?

Due to variances in quality, type, usage and care, there is no set life span for a car battery. However, as a general rule of thumb, many sources quote three to five years as an average, though some car batteries have been known to last 10 years.

That’s quite a span. Let’s take a closer look at some of those “variances” that can affect how long a battery lasts.

Related: How to Change a Car Battery

Quality of Car Batteries

As with many items, some batteries are better than others. In the case of car batteries, some of that has to do with the battery’s quality, which we’ll get into in a bit, as well as its cold crank amps rating.

Batteries lose quite a bit of their power as the temperature drops, so their CCA rating is important because it’s measured at 0 degrees Fahrenheit (where a battery typically has lost about 60% of its peak starting power) and thus represents sort of a worst-case scenario for the battery. Since batteries also tend to lose power over time, one offering more CCA when new can lose some and still have the power to start your car, whereas one purchased at the same time but carrying a lower CCA rating may have deteriorated to a point where it can’t do its job.

Also, as batteries lose some of their life just by sitting, it’s possible the battery you bought “new” had actually been built months before and spent the intervening time degrading on a shelf.

Types of Car Batteries

The common car battery has long been what’s called a lead-acid battery, which primarily contains lead plates immersed in sulphuric acid. But in recent years, another type that has come into use is called an absorbed (or absorbent) glass mat battery. It works on the same principle, but instead of being in liquid form, the acid is contained in fiberglass mats that surround the lead plates. These batteries are more expensive, but they tend to have a higher power density, can go through more charge and discharge cycles, aren’t as sensitive to being deeply discharged, don’t leak, charge faster and are less vulnerable to vibration.

AGM batteries are often found as original equipment in cars that use stop-start technology to save fuel, in which the engine automatically shuts off when you come to a stop, then automatically starts when you release the brake. Since starting the engine requires an extremely high power draw and wear on a battery, these frequent engine starts would likely kill a normal battery in rather short order.

If your car doesn’t have stop-start technology — or didn’t come with an AGM battery — you might be able to upgrade to one. However, it will cost more, and you have to make sure your car is compatible; for instance, your alternator might be putting out too much power, which can kill an AGM battery. Therefore, it’s a good idea to have the battery professionally installed by someone who acknowledges that they need to check such things as alternator output first.

Battery Usage

As hard as starting an engine is, letting the car sit isn’t good for the battery, either. Part of that is because a battery will naturally discharge over time, and starting the car activates the alternator, which recharges the battery as you drive. (Note that the alternator also has to power all the devices used when your car is running, and as the alternator doesn’t put out much, if any, power when the engine is idling, it won’t recharge the battery much on a short drive.) But on modern cars, there’s another problem.

There are many computers and electronic devices in newer cars that require battery power to keep their memories alive, and they draw power even when the car is “off.” For instance, for in-car equipped with remote locks, there’s a little receiver that’s constantly “listening” for a radio signal from your key fob, and that receiver draws its power from the battery. All of this is why the battery can go dead just from the car sitting — as has happened in recent years when people have suddenly been working from home and rarely going out.

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Car Battery Care

It’s not good for a normal lead-acid battery to be kept in a discharged state (though AGMs aren’t as sensitive to this), so even if the battery isn’t “dead” when you try to start your car after a long period of sitting, it wears on the battery. If the vehicle has been sitting for a long time, try to drive it awhile — ideally on the highway — to fully recharge it.

If your car often goes unused for long periods, you might consider using what’s called a battery maintainer or“battery tender, which hooks up like a battery charger but is designed not to overcharge the battery — which a battery charger can do if you leave it on too long. Note that a maintainer is not good for charging up a low battery; it only keeps a fully charged one at its peak.

Extreme temperatures also affect a battery’s life. While we often think of cold weather as being hard on a battery, and it does indeed reduce its power, heat is actually worse for longevity. Keeping your car in the shade during the summer (or garaged year-round, ideally) is an advantage.

Signs of a Dying Battery

Slow cranking of the engine or odd electrical problems are usually an early tip-off that your battery might be on its last legs. The latter includes headlights or cabin lights that flicker at idle after starting, the engine running roughly for a few seconds after starting, and the car losing your Bluetooth or radio settings. The battery’s case bulging out at the sides is another indication of a dying battery.

Best, however, is to have your battery tested. While it doesn’t necessarily extend the life of your battery, having the battery tested periodically can help keep it from being dead at an inopportune time — which is just about any time. After the battery is a couple of years old, it’s often recommended that it be tested at every change of seasons, or at least at every oil change. If the battery is shown to be at less than its best, a good charge might help, but it’s really more of a warning that you might want to get a new battery before the next really cold spell.

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