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More often than not, batteries die at the most inopportune times. Sometimes you get the usual warning signs for a weak car battery, like an engine that’s slow to turn over or an illuminated check engine light. Sometimes, though, you get no signs at all, so it’s always a good idea to have your battery frequently tested, and it also may help to have a jump-starter on hand as an extra precaution.

If your battery is older than 3 years, then it might not be a surprise when it’s time for a new one, but what if it’s not old? Once you rule out obvious causes like an open trunk lid, glove box or car door, then you have to dig deeper. Here are three unusual reasons why your car battery might die.

1. Car Alarm

Car alarms installed by the automaker don’t usually cause trouble, but aftermarket car alarms are a different story. Installed correctly, they draw a small amount of power and won’t drain your battery. Installed incorrectly, they can suck the power right out of your battery.

If you have an aftermarket car alarm, then this is one of the first things to check when you have a draining car battery. It could be as simple as a frayed wire touching a metal part and causing an intermittent connection. If the aftermarket alarm system is new, then it might be a more complex installation problem that needs double-checking by the installer.

2. Stereo System

A car stereo may also be the culprit when your battery dies. Once again, it’s not usually those installed by the automaker that will drain your battery. It’s the aftermarket systems that produce the kind of sound people can hear three cars ahead of you in traffic that can be trouble. The larger and more powerful the system, the greater the potential for battery drain.

A simple check is to disconnect your stereo system and see if that fixes your battery woes. This will prove the stereo is the issue, but diagnosing how to fix it can be challenging. It all depends on how your stereo was installed, and you may need the help of an experienced technician to fix the problem.

3. Car Key

Once upon a time, car keys were metal things you put into a slot and turned to unlock the doors. Some cars still have traditional keys, but many have proximity keys. These let you walk up to the car to automatically unlock the doors. It’s a handy feature when your arms are full and your key is stuffed in your pocket, but one that can also cause battery issues.

A receiver in your car is constantly searching for your proximity key’s frequency. Whenever it finds that frequency, it checks to see if it’s an exact match to your car. Any proximity key wakes things up. If you’re parked next to the entrance of a parking structure where everyone is walking by with proximity keys in their pockets and you happen to leave your car for an extended period, then your car battery can drain. It won’t be an issue for every car, but particularly in hybrids, it might be your problem.

It can be frustrating trying to figure out what went wrong when a car battery drains. Looking at these three unusual reasons right from the start will help limit that frustration and get you back on your way.

Check out all the electrical system products available on NAPA online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on reasons your car battery might die, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

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