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How Long Does a Car Battery Last?

Learn the signs of battery decay

When does a car battery die? At the worst possible moment. The vehicle system's heart is its battery. If the battery is not functioning, the car or truck will simply not start.

The battery life of a vehicle lasts anywhere from 4 to 7 years. Typically, it's time to start watching for signs of malfunction around 4 years. One person's typical battery lifespan is another person's dead battery. This is due to the fact that batteries are affected by things like change in temperature, vibrations, trip duration and the number of electronic devices that are being charged.

Car batteries are traditional lead acid based. The technology and manufacturing of these batteries has not changed very much over the years. These batteries are in such high demand that they add 92,000 jobs in the USA, with a 26.3 billion dollar impact to the economy.

Lead acid batteries work via a simple chemical reaction. If you look inside a battery, you will find a liquid solution and metal plates. The plates are usually made of lead (the lead part of the lead acid battery). Those plates are suspended in a water/sulfuric acid solution. Electrons flow between the acid solution and the lead plates creating electricity.

With this in mind, it's easy to see how different driving conditions could affect the car's battery life. In warmer areas of the country like the southeast, the heat causes the chemical reaction within the battery to speed up, shortening the lifespan of the battery. On rough road surfaces, there is more vibration on the battery. This could shake the lead plates out of their suspended positions, weakening the flow of electrons. 

The biggest shock to the battery comes with starting the vehicle. Once the battery is used, it needs to recharge, which it does while the car is being driven. A delivery truck making frequent starts and stops with a short driving duration between stops would have a shorter batter life since the battery doesn’t have time to fully charge after the truck is cranked.

Signs of Battery Decay

The most obvious sign that the battery is bad is during ignition the car doesn’t crank. The battery is simply dead. At this point, the only thing you can do is replace the battery. The bad news is, you are left with a vehicle that will not start and have to inconvenience yourself and someone else to help you get to the auto parts store to buy a replacement.

Prior to the point of a dead battery, there are warning signs that the battery is nearing its end. Knowing these signs will help you prepare and buy a replacement battery while the battery still runs. A lot of auto parts stores will replace the battery for you…assuming you can get the car to the store. Which means it is in your best interest to preserve the life of the battery and replace it before it completely dies.

Long Engine Turnover Time

If your engine takes a long time to turn over, this could point to an issue with the battery. A weak battery will have a more difficult time creating the electricity needed to turn over the engine and start the car.

Interior Lights Dimming

If the interior lights are dim, or begin to dim while driving or starting the car, this is a sign that the battery is having issues. The battery is not supplying enough power to meet the needs of the vehicle's electrical system.

Swollen Battery Case

If the battery case is swollen, there is an expansion of gasses inside the battery. This is usually a sign of overcharging and can be dangerous. Lead acid batteries can have slight swelling due to their chemical composition, but a visibly swollen battery should be replaced.

Rotten Egg Smell

The presence of a rotten egg type smell is usually an indicator that the battery is overheating. Since lead acid batteries contain sulfuric acid (which smells like rotten eggs), overheating or boiling of the acid will produce the nasty odor. If this smell is present, the battery likely needs to be replaced immediately

Testing the Car Battery

If you experience any mechanical or electrical issues, the best way to know if the problem is the battery versus another component of the vehicle is to use a battery tester. Using a battery tester, a 12 volt battery should maintain at least 12.6 volts. You can also perform a load test. This requires the battery to maintain 9.6 volts for 15 seconds. For this test, a carbon pile load tester is needed.

By knowing your driving habits, climate and road conditions, you can understand the "typical" battery life of your vehicle. Determining where you are in that 4 to 7 year range can help you to know when to look for warning signs that the battery might be going dead. Knowing these warning signs and replacing your battery early will help ensure you do not end up stranded with a dead battery.

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