The Most Common Reasons for 12 Volt Car Battery Drain

May 23, 2018

The Most Common Reasons for 12 Volt Car Battery Drain


Ever looked for jumper cables? Or begged for a jump-start on the side of the road like a hitchhiker? You are not the only one. Most car owners will experience this at least once.

One of the most overlooked parts of any car, at least until it stops working, is the battery. Without the battery working properly, a car may not be able to start, making it a bit difficult to make it go. So it can be important to recognize things that may cause a car battery to drain. By doing so, drivers can avoid those inconvenient instances when their car doesn’t start while also getting the most out of their car battery. (A typical 12V can cost anywhere from $60 to $125. Not necessarily devastating, but why pay for something before you have to?)


Leaving A Light On


Human error is the most common cause of a drained battery. When car owners forget to switch their headlights off or mistakenly leave the trunk open, it can drain the battery overnight so that it won’t start the next day. Playing the radio for long periods while the car is sitting in park can have a similar effect. The good news is that a quick jumpstart can usually fix the problem. Such a problem can also be avoided by double checking that the headlights and internal lights are off when the car is off.


Bad Alternator



A car’s alternator is tasked with powering things like the car’s windows, radio, and air-conditioning. But it also re-charges the battery while the car is being driven. If there’s a problem with the alternator diode, the battery could be drained while the car is off. Outside of human error, a bad alternator is the most common reason why a battery is drained. If a battery drains overnight even when all the interior lights and functions are turned off, the car should get check out, especially if it's a newer battery.


Extreme Hot and Cold


Cars that operate in a climate that experiences extreme temperatures one way or another can be more susceptible to drained batteries. When temperatures climb over 100 degrees or drop below 10 degrees Fahrenheit, it can damage the battery due to the build-up of lead sulfate crystals. These kinds of weather conditions can drain a battery and take it longer to re-charge. Also, with cars that are only used for short drives and spend long periods sitting in extreme hot or cold temperatures, the battery will drain much quicker than it would in a more moderate climate.


Parasitic Drain


"Parasitic drain" refers to certain components of a car that continue to run after the ignition is off, draining the battery in the process. For things like a car’s clock, this is normal, but it shouldn’t be enough to drain the battery. It’s important for car owners to check to see if the light in the glove box or trunk remain on when the car is off. These are some of the more common causes of a parasitic drain, which usually points toward a larger electrical problem with a car.


Corroded Battery Connections



The usual wear a car takes on over time can lead to loose or corroded battery cables. This will keep a car battery from receiving a full recharge, eventually draining the battery to the point that it prevents the car from starting. Of course, it’s easy to clean car battery terminals, and plenty of YouTube video tutorials exist to show car owners how to do it themselves.


Old Age


Finally, a classic case of old age can cause a car battery to drain. Eventually, batteries simply aren’t able to hold their charge anymore. This is why car batteries should usually be replaced every three to five years. However, without regular maintenance on the car, there’s a good chance the battery will need to be replaced sooner than three years' time. That being said, even with cars that are well maintained, batteries should be replaced every five years, just to be safe. 


There are numerous reason why car batteries die out. Good maintenance will ensure a longer lifetime. But please take note that a car battery is a wear and tear products which need replacing every few years.

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