The Battery Dies

How Long Can a Car Sit Before The Battery Dies

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When we moved into our new condo near the CBD, we realized that location was so convenient that we seldom needed to use our car when getting to work. To save on gas expenses and avoid traffic issues, we decided to rely on public transportation and instead park our car in the garage since it wasn’t used often enough. After a month of busy office work, my husband and I decided to take our kids for a tour. With everyone ready for this long-awaited day, I was shocked to realize that our one-year-old car couldn’t start. Not only was it horrifying but it was also a tense moment as we were wondering what could have happened to our dear auto. It wasn’t long before my husband searched online about how long can a car sit before the battery dies.

The information we found in searching was very helpful and it confirmed the main reason why our car couldn’t start after being left in the garage for so long. After lengthy research both on the internet and information provided to us by our car mechanic, we realized that your car’s battery can easily be depleted if your car sits unused for a period exceeding two months. Since there’s a lot of information we would like to share, we decided to compose this step-by-step guide to give you everything you’d like to know regarding your car’s battery.


How Long Can a Car Sit Before The Battery Dies: Step by Step Guide


If you’re reading this post, then it’s likely you’ve faced such a predicament at one point in life. You see, most people think that a car is just an ordinary toy that holds its battery charge for long as long as it’s not being used. What you fail to understand is that your car comprises of many electrical components most of which are attached to your car’s onboard computer.

For instance, there’s the radio, dashboard clock, automatic seat adjusters, the alarm system, the headlights, and the door lock system among other alert systems. Now, imagine you’ve packed your car in the subway station or at the airport for a two months’ vacation then accidentally, you forget to switch off the headlights or lock one of the doors.

Obviously, your car’s battery will be depleted within a week right? Supposing you’re too careful this time round and you leave everything in perfect order. Although the battery will not be depleted rapidly like before, it will still lose its charge and die eventually due to something called “parasitic drain”. Parasitic drain is a phenomenal where your car’s electrical components draw power slowly by slowly until the battery gives up eventually.

In the case of BMW vehicles, such manufacturers warn that the longest the battery can survive before dying is a month. Other manufacturers talk about 2 ½ months on average. However, most of these manufacturers still mention that the longevity of your car’s battery life greatly depends on several factors.

One of those factors is the electrical components that are still operating even when the car is parked. Another factor is the condition of the battery. So, if you have a new fully charged battery, then it will last longer than an old one.


What’s the Role of Your Battery?

Now, a battery plays a very critical role in your auto. It’s actually the one responsible for translating chemical energy into electrical energy which can be used to power the engine and other electrical components in the car. Most cars rely on the lead-acid batteries that fall in the SLI category. Now, the SLI batteries consist of six cells with each cell consisting of two plates made of lead and lead dioxide. Each cell is capable of producing 2 volts of energy making the total energy produced by the battery to be 12 volts.

The two plates, lead and lead dioxide, are submerged in acid inside the battery to trigger a chemical reaction. This reaction causes the lead dioxide plate to produce ions and lead sulfate. These ions then react with the adjacent (lead) plate to produce hydrogen and lead sulfate. A chemical reaction is then generated in the process that produces electrons. Now, the electrons generated in this chemistry are the ones that accumulate around the plates to generate electrical energy.

Lastly, the electricity generated here flows through the terminals to start your car’s engine as well as power the rest of your car’s electrical components. Now, with this in mind, you must be asking yourself the reason why the battery dies even when the car is parked right? What actually happens is that the chemical reaction in the battery doesn’t stop simply because your car is packed. The battery actually continues to transfer power which is consumed by some of your car’s electrical components in a process referred to as parasitic drain.


Which Factors Can Cause Your Car’s Battery to Drain?

Now that you’re aware of how a car’s lead-acid battery works, we will move ahead to discuss some of the factors that can cause your car’s battery to die. Although you can easily jump-start your vehicle to revive the battery after being dead, it’s important you understand some of these phenomena that can kill your battery when your car sits for too long without being used.

  • Leaving the Headlights: One of the major culprits that can kill your battery prematurely is forgetting to turn off the headlights. Although most newer cars are fitted with a memory feature that turns off the lights automatically, those that don’t have this feature will end up draining the battery completely within a very short time.
  • Using Electrical Components With the Car Off: Now, if you’re used to leaving your car in your apartment’s parking lot, there are chances that you or your kids might be using the car’s electrical components (such as the radio) without turning the engine on. If that’s the case, then the battery is likely to die rather quickly.
  • Temperature Fluctuations: If you happen to leave your car packed for too long during freezing winter or hot summer seasons, then there’s a great chance that your battery might be weakened by these extreme temperature fluctuations. This can cause your car’s battery to die prematurely.
  • Faulty Alternator: The alternator is responsible for two things. The first one is charging your battery and the second is supplying electrical power to your car’s electrical components. Now, if the alternator is faulty, then it means you’ll be driving your car without the battery getting charged. Since the alternator is already damaged, it won’t supply electrical power to your car’s components. As a result, the battery will be used to supply power instead causing it to get overworked and die eventually.
  • Parasitic Draw: Although we’ve already discussed this factor several times already, it’s good to know that your battery experiences some electrical “whoopsies” when it’s packed. During this time, the engine is off meaning the alternator is unable to charge the battery. Since most of the electrical components are drawing power from the battery continuously, its juice is likely to last for a few weeks before it drains out completely.


How Can You Tell if Your Car’s Battery is About to Die?

Although we’ve discussed some factors that can cause your car’s battery to drain prematurely, there are other things you need to be aware of regarding your car’s battery. One of those is detecting when your car’s battery is almost giving up. Although your mechanic will assist you in detecting most of these symptoms, learning a few of these tricks is really important as they can prove helpful in case of an emergency.

  • Cranking of the Engine: One of the common signs of a dying battery is the cranking of the engine. When you start the car, the engine pulls amperage from the battery. In case the battery is struggling, then it will fail to provide sufficient power to the engine leading to cranking or rather a slow engine start.
  • Dimming Headlights: Another clear sign of a dying battery is the frequent malfunctioning of your car’s components. These include the radio, the wipers, headlights, power doors, windows, and all lights inside the car. Since all these components rely on the same battery for power, frequent malfunctioning might be evidenced with the battery being at fault.
  • Clicking Noise: This sign is usually evident when you’re trying to turn the car on. What happens is that a clicking sound is heard that’s usually very different from the normal cranking of the engine. So, if you happen to hear an abnormal sound when turning your car on, then just know the problem is caused by a struggling battery.
  • A Foul Smell: The last obvious sign of a dying battery is a foul smell that resembles that of rotten eggs or burning wires. This smell is usually caused by a mixture of sulfuric acid and water vapor that tend to evaporate from the battery once it begins to overheat. Since this reaction only occurs when the battery is completely worn out, it’s a clear sign that your current battery is nearing its final stages.


How Can You Save Your Car’s Battery From Dying When Your Car is Not Being Used?

Having discussed key factors that cause your battery to die, our next discussion will be providing an answer on what should be done to preserve your car’s battery from dying prematurely. So, in this last section, we will be discussing several tips you can consider to ensure that your car’s battery stays in great shape even when your car is unused for a long time.

  1. Rev the Engine Frequently

Earlier on, we discussed how a lead-acid battery works. In most cases, the battery is likely to lose some power when the car sits for too long due to parasitic draw. So, to compensate for this loss of power, it’s recommended that you rev the engine for at least 5-10 minutes to recharge the battery. To do this, you only need to start the engine then put the car in neutral. From there, accelerate the car until it reaches at least 1,000 RPM.

By doing this at least once every week, you’ll give the alternator ample time to recharge the battery to compensate for the power it has lost over that period.

  1. Remove the Battery

Let’s assume your busy working or studying schedule will not allow you to drive a few minutes weekly or rev the engine routinely to maintain battery power. In that case, our second trick can be the perfect option. Here, you need to remove the battery completely to store it in a safe place.

But, what’s the safest place? Well, in this case, your battery should be away from kids in a location that has a dry and moderate temperature. The battery should be placed in an elevated place but not directly on the floor to avoid any contact with water.

  1. Disconnect the Negative Terminal

Supposing you’re planning to go out on a vacation and you’ll not be available to tend to your car. In this case, cutting down on car battery drain is the only logical option. But how do you do this? Well, it’s pretty simple. All you need is to disconnect your battery’s negative terminal to disable your car’s onboard computer from draining the battery. Remember, the onboard computer is the one responsible for controlling most of your car’s electrical components. By disconnecting it, you’re actually disallowing these components from conducting a parasitic drain.

  1. Get a Car Battery Charger

The last option you can consider, especially if you’re planning for a vacation, is getting a battery charger. Now, there are two types of battery chargers I’ll recommend you to get. The first is a solar-powered charger and the second is a smart battery charger. The solar-powered battery charger is designed to be inserted on the cigarette lighter to burn the battery to keep it juiced up.

The second one is the smart charger or a battery maintainer. This one is useful if you have an AC outlet in your garage. By attaching it to the battery and the AC outlet, this smart charger will be topping up your car’s battery whenever it detects a reduction in battery voltage.



So, there you have it all. As you can see, there are many reasons that can force you to abandon your dear auto for several weeks. Maybe it’s during the winter season, a vacation; schooling, or maybe you’ve decided to rely on public transportation. No matter the case, knowing the steps you need to consider to preserve your battery is very important.

In this guide, we’ve discussed several tricks you can consider, and most of all, we’ve discussed those factors that drain your battery prematurely. So, with such solid information, answering the preposition of how long can a car sit before the battery dies will be much easier.

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