Car Batteries

What Can Drain A Car Battery? 8 Common Things You Should Know

Mike Cross
Updated Oct 26, 2021

Nothing is more frustrating than heading out to your car, only to find out that the battery is dead. To be sure, the battery does need to be replaced from time to time. But, if it should still have plenty of juice left, you may be wondering what exactly happened?

If you are sure that your battery is new enough and should have plenty of juice left in it, you may be wondering what could have drained the battery and was there anything you could have done to prevent it from happening?

There are actually a few things that could have drained the battery in your car. Let’s take a look at some of those issues and see what you can do differently once you have a working battery again.

What Can Drain A Car Battery

What Can Drain A Car Battery

1. Parasitic drain

Parasitic drain is what happens to your battery after the key is switched to off-some components in your vehicle may continue to run. To clarify, some parasitic drain is normal, the battery will always deliver enough power to keep things, like your clock, radio presets, and security alarm operating at all times. If there is an electrical problem, such as faulty wiring, poor installation, or defective fuses – parasitic drain might exceed normal usage and drain the battery.

2. Human error

This is what happens when you come home from work after a long day and you accidentally left the headlights on, did not close the trunk all the way, or you even forgot to turn off an internal light that you turned on. This will drain your battery overnight. Some new cars will alert you if you have left some lights on.

3. Faulty charging

If the electrical charging system is not working properly, your car battery can drain even while you are driving. Most cars power their lights, radio, and other systems from the alternator. If there is a charging issue, this can make the battery drain more drastic. You should check to see if the alternator has loose belts that are keeping it from working properly.

4. Problem with the alternator

A car alternator is responsible for recharging the battery, as well as powering certain electrical systems like lights, radio, air-conditioning, and automatic windows. If the car’s alternator has a bad diode, it will cause the battery to drain. A faulty alternator diode can cause the circuit to charge even when the engine is shut off, and you wake up in the morning with a car that will not start.

5. Temperature extremes

Keep in mind that extremely hot temperatures of over 100 degrees or bitterly cold such as under 10 degrees, can cause lead sulfate crystals to build-up. When a car is left in these extreme conditions for too long, the sulfate buildup can damage the long-term battery life. It may also make it nearly impossible for your battery to charge in these conditions, especially if you only drive it short distances.

6. Lots of really short drives

Your car battery may wear out before its time if you take a lot of short rides. The battery in a car uses the most power when starting up the car. When you drive really short distances, you end up shutting off your vehicle before the alternator has had a chance to recharge. This could be a reason why your battery seems to die out quickly.

7. Bad battery cables

When you drive your car, it charges the battery. The charging system cannot top off your battery while driving if the cables have become corroded. The cables should be checked for dirt or signs of corrosion. Then they should be cleaned using a cloth or a toothbrush. Loose battery cables make it very difficult to start the engine too, since they are not able to transfer the electrical current efficiently.

8.Older battery

If your battery has not been replaced in quite some time, it is likely old and weak. In this state it will not be able to hold a full charge. If your car always has problems starting up, it is possible that the battery is worn out. You should generally replace your car’s battery every 3-4 years.

Your next steps

Once you notice that your battery is having trouble keeping a charge or dying out, you need to figure out why. If your battery is having trouble because of human error, that is an easy fix. Make sure to charge up your battery and then be careful not to leave lights on overnight in the future.

If you cannot remember the last time you replaced your car battery, then it might be time to replace it. A quick trip to your local auto parts store is all you need. Replace the older battery with a new one and you should be all set.

Since the battery issues could also be caused by excessive amounts of short drives, be mindful of your driving habits. Try to plan trips and errands out so that your car will get ample time to recharge the battery. And if you will not be driving your car for some time during brutal cold or hot temperatures, consider removing the battery.

If you need more help

If you replace your battery and it is still dying out quickly, you may have an electrical problem. If you are handy under the hood and have a scanner, you can use that tool to narrow down the problem. If you are not comfortable doing this yourself, make an appointment with your local mechanic. They can check the electrical system and check for corrosion.


It can be inconvenient and frustrating to have a dead car battery. You can take steps to help prevent this. Make sure that you always double check that you have turned off headlights and completely closed doors and trunks. It is also a smart idea to replace your car’s battery every 3-4 years. And make sure to have routine maintenance done on your car, as this is a good way to catch problems before they become big ones.

Mike Cross
Life is too short to drive with stock audio

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