Your car's battery has three important jobs: Starting, lighting, and ignition. Once your car battery starts the engine, the alternator takes over and charges the battery so that the next time you need to start your car, it's recharged and ready to go. A bad battery means that your car can't start, which can be frustrating, especially if you don't know what caused it to die.

Most car battery deaths can be traced to five common causes: Cold weather, time, corrosion, electronic drain, and parasitic drains. The last two are closely related, but while one can be controlled the other is harder to detect. If you're struggling with a battery that seemingly can't hold a charge, these are the five things to check first and what you can do about each of them.

Cold Weather Causes Battery Failure

Cold weather is the number one reason why car batteries die. Weather doesn’t have to be particularly extreme to cause a car’s battery to weaken. Even at a mild 32 degrees, a battery is 35% weaker. At 0 degrees, it plummets to 60% weaker. When a battery is that weak even your interior lights become a challenge, forget about starting your car. There's a reason most people associate dead car batteries with winter, and that's because it's when most batteries that were in marginal condition give up and die.

This one can be hard to fix. Obviously, you can't change the weather, and not everyone has easy access to a parking garage or carport. Really, the only thing you can do is be aware that your battery is more likely to die during winter and make the required preparations.

Keep an eye out for symptoms that your battery may be losing steam. If you notice your headlights dimming while your car idles or hear a strange clicking sound when you start your vehicle, that's a good indicator that your battery is on its last legs. To affirm that it's getting close to its last start, you can either test the battery yourself or go to a nearby auto shop where they'll be able to test your battery for you. Many states require this as part of the inspection process as well, which is a good time to make note of your battery's expected life.

You can’t change the weather, but you can prepare for the worst.

Batteries Die Over Time

Time, not surprisingly, is also a top car battery killer. Just like the batteries in your remote, eventually, there is just no juice left and no amount of cajoling or jumping will bring your battery back to life. The average car battery dies after three to five years. Car batteries have a shorter lifespan if you’re in an area prone to especially cold winters. Keep an eye on your battery’s ‘birthdays’ and looking for the warning signs of battery failure. Don’t forget to test your battery regularly.

The other way time affects car batteries is "time unused." The longer you go in between drives, the less likely your car is to start up. Car batteries are charged by the alternator, which only turns if the car is running. If you’re not able to drive your car for a while, it’s worthwhile to invest in a battery tender. Battery tenders act as a charging system for your battery, making sure it stays fully charged without overcharging.

Much like cold weather, time isn't something you can actually change. But by keeping track of it and being observant, you can be prepared for the worst and reduce the chances of it happening while you're unprepared.

Corrosion Can Cause Battery Death

Battery acid is corrosive. That might sound obvious, but one of the other reasons why car batteries repeatedly die is due to corrosion at the connections. Check under your hood. The battery terminals are the points of contact on the top of your battery, one is marked with a positive, the other a negative. These are the points that you use to jump your car, and they're also the way your battery is able to be charged by your alternator. If your connection is gunked up, your alternator may not be doing an adequate job of recharging your battery.

If you see blue or green growths hanging off your battery terminals, that’s a sure sign that your battery has been slightly damaged by corrosion. Corrosion can also look like a thin white powdery substance, almost as if your battery has a bad case of dandruff. Though this is a perfectly natural and expected process, it isn’t doing your battery any favors and by improving the connection you can improve your car’s ability to charge your battery.

If there isn't much corrosion, you can use a dry rag to wipe away dirt and grime. If that doesn't do the trick then use a stiff wire brush to clean this corrosion off (carefully of course). In no time your connections will be shiny and clean and your battery will have an easier time charging.

Human Error and Batteries

We've all accidentally left our headlights on and killed a battery. It's practically a right of passage. And that's one of the many reasons why human error is a top battery killer. Everyone makes mistakes that can lead to battery death.

One of the more common mistakes we make is forgetting exactly how much we've started expecting batteries to do. Car batteries are really pretty amazing. They power everything in the car, and over time that’s expanded into digital navigation systems and displays. Add to that people charging their phones, tablets, computers, and mobile entertainment centers on the go and you have a very overtaxed battery system.

This isn't an easy one to fix. Obviously, you can firmly resolve to always turn your headlights off when you leave the vehicle, but it's not like anyone intends to forget something. Even if you do a perfect job of unplugging your devices and turning off your headlights, the car battery doesn’t actually get a break. Instead, it’s hard at work powering the anti-theft system and keeping the time on your clock.

Make sure to give your car a break when you can by unplugging your charging cables at home. Also, obviously, make sure that your lights are off when you turn the car off. Just changing your parking angle so that you can see the headlights from your front door can make a big difference in how easy it is to forget to turn off your lights.

Electronic Parasites

Electronic parasites aren’t as predictable as the other reasons car batteries die. One of the most frequent parasites is a bad alternator. Your battery relies on your alternator in order to recharge. If the alternator isn’t pulling its weight, your battery may die frequently even when you know the weather is lovely and you haven’t been draining the battery. Sometimes a broken fuse can drain a battery, even when your car is off. For electrical problems, you’ll want to get a skilled mechanic involved. Though the voltage produced by a car battery isn’t enough to kill a person, there are other hidden dangers that can physically wound you and total your car.

Be Prepared

Ultimately, the best thing you can do to help yourself deal with the probability of an eventual dead battery is to be prepared. Portable jumpstart units are inexpensive and can be a lifesaver in unexpectedly cold weather. You can even purchase a nitrous themed jumpstarter if you so desire. Jumper cables, of course, are the old standby and they work fantastically. Keep them in a cable bag in your trunk and relax a little with that piece of mind.

Jumping a car is easy. With both vehicles in park or neutral, attach the cables in the following sequence: Red Bad, Red Good, Black Good, and then ground it on any unpainted metal surface in your car. To elaborate a bit, you attach the red cable to the bad battery, then attach the red cable to the good battery, and then attach the black cable to the negative terminal of the good battery. The last clip goes on any unpainted metal surface. A lot of people go for the struts, which is a good choice. Then turn on the good car. When it's been running for a couple of minutes, try to turn on the car with the dead battery. It should turn on immediately, if it doesn't, give it another five minutes and then try again. If that doesn't do it, you may need a new battery.

Just make sure that after jumping your car you drive it for a while before powering it off. That will give the alternator time to recharge your car’s battery.

Take care of your car’s battery, prepare for the worst, and stay safe out there.