How Long Can A Car Battery Sit Unused? [Explained Detailed with Preventive Measures]

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this...Read more

While planning a long trip, one of the most significant things to consider is storing your car. Since the battery can be flat if not used for a long time, it is common to worry while storing the car.

In that case, a question may arise in your mind: How long can a car battery sit unused? Typically, the battery is considered the heart of any car, which helps to start the car and function other electronics properly.

If you don’t use your car for a long time, the battery’s self-discharging nature will lead to sitting it. In general, a car battery can last around two to four weeks when unused, depending on several factors, including your battery’s health, age, and ambient temperature.

Read the entire context to grab more information about the car battery’s sitting duration.

Why Does a Car Battery Go Flat?

Self-discharging is the natural characteristic of batteries which is internal chemical reactions. This chemical reaction reduces the stored charge gradually without any outside connection. Although almost all batteries undergo self-discharge, car batteries, especially lead-acid batteries, survive much.

For that, if the battery is left unused for a long time, the self-discharge will slowly finish the entire charge, resulting in a flat battery. The same goes for cars’ lead-acid batteries.

Why Does a Car Battery Go Flat

If you leave your car unused for a long time, the battery wouldn’t recharge by the car’s alternator, causing a flat battery. Basically, this problem can happen for many reasons, but the most common are:

  • Your car doesn’t use for a longer time.
  • The lights of your car are left on.
  • Using faulty components or devices in your car.
  • If your car’s alternator has any issue that resists charging the battery.
  • Having a faulty battery in your car.

How Long Can A Car Battery Sit Unused?

This is a common question among car owners, especially when storing the car. Several factors actually contribute to how long a car battery can sit unused.

how long can a car battery sit unused

However, two to four weeks is the average lifespan of a car battery for being able to sit unused. Besides, if the car is stored in a colder ambiance, the battery will dry faster than if stored in room-temperature weather.

This is because temperature enhances the rate of the self-discharging character of batteries. So, if your car’s ignition does not turn on for a longer time, your car’s battery will be flattered gradually, causing you to be unable to start the car. A car usually needs to have at least 11.8V (50%) of battery charge to start.

What Factors Contribute To How Long Can A Car Battery Sit Unused?

As we said earlier, various factors are related to how long can a car battery sit unused. Here we have discussed some common factors that contribute to car batteries’ self-discharging nature.

What Factors Contribute To How Long Can A Car Battery Sit Unused

Battery Health

Every car battery has a specific lifetime. After being used, the efficiency of the battery degrades gradually. So, if your car has a poor-health battery, it will discharge faster than a new one.

For example, the charge degrading process speeds up when the battery health is down to 50%. In contrast, if your car battery has good health, the charge degrading process will be slower, making the battery last longer unused.

Battery Type

Most cars are equipped with lead-acid batteries, which are not powerful enough to hold a charge for a long time. These types of batteries can’t endure deep charge, which makes them not stand for a long time when not used.

In contrast, AGM car batteries provide a long service life with a low self-discharge rate. Although these batteries are costlier than lead-acid batteries, the batteries won’t go flat faster when unused.

Ambient Temperature

Car batteries react negatively to cold weather, another reason the battery discharges faster. Although storing your car in the garage or closed area might help, the battery can still self-discharge. Typically, the self-charge character of car batteries remains stable in a dry environment at room temperature.

Charge Level

Charge level is also a factor in getting the battery to sit unused for a shorter time. Having a 50% or 60 % charge on your car battery will go flat faster than a fully charged battery. So, if you store your car with a fully charged battery, it will be going to sit unused slowly.

How To Keep Your Car Battery From Going Flat When Not In Use?

You might have understood the factors related to car batteries going flat when unused. Now you may be looking for ways to prevent your car battery from going flat. If so, follow the techniques discussed below.

How To Keep Your Car Battery From Going Flat When Not In Use

Fully Charged The Battery

Before storing your car battery, make sure the battery is fully charged. You can easily monitor the battery charge status through the battery level indicator on your car. If your car doesn’t have a battery indicator, you should install one, so you can check the battery charge level. This will prevent your car battery from self-discharging.

Clean The Battery

Sometimes corrosion on the battery’s connectors makes the car battery go flat faster. So, you should keep your car battery’s connectors clean. To clean the connectors, you will need a solution made of Vinegar and baking soda and a scrubbing brush. However, while cleaning the connectors, it is better to wipe down the entire battery case.

Store The Battery Warm Location

While storing your car battery, you should choose a dry and well-ventilated area. In that case, it is better to prefer an area where the temperature remains around 26.7 degrees Celsius or 80 degrees Fahrenheit.

Avoid areas that are too hot or cold, as these can make the car battery discharge faster. Additionally, keep your battery away from excess humidity, which can cause corrosion on your battery.

Use Battery Maintainer

Using a battery maintainer is the easiest way to make any car battery last a few years. Typically, it is a small battery charger that supplies a constant and small amount of charge to the connected battery.

There are usually two types of battery maintainers you will find: traditional float and fully automatic chargers. You can use any of these chargers to prevent your car battery’s discharge when stored.

Recharge The Battery Frequently

If you don’t want to use a battery maintainer, you can manually monitor your car battery to maximize its life. In that case, you have to charge your car battery at least every two weeks (the more often, the better).

If possible, you can use a Voltmeter to check the voltage of your car battery to know how much charge your battery requires.

Some Frequently Asked Questions

Some questions are answered here that are asked by people all over the world. For any queries you are looking for, check the section; you might get your desired answer here.

What To Do If My Car Battery Is Sited?

If your car doesn’t start due to a flat battery, you have to first check whether the battery is connected to the car properly. Then, examine the wheels to ensure they are not jammed against the kerb.

If everything is ok, try jump-starting your vehicle. Even if it doesn’t work, you will need to replace your car battery.

How To Store A Car Battery Properly?

While storing your car battery for a long time, you should be very careful. Otherwise, the battery can discharge gradually, causing a flat battery. In that case, you can check the battery-storing process discussed below.

  • Charge the battery fully if necessary, and then unplug the battery connectors – first the negative (black) and then the positive (red) one.
  • If the battery’s connectors have any corrosion, clean them properly.
  • Now store the battery in a cool and dry area where there is no excess humidity. If you have a battery maintainer, connect it to the battery.

How To Know If I Have A Flat Car Battery?

Through some simple symptoms, you can easily determine whether your car has a flat or a nearly dead battery. Below, we have pointed out these symptoms.

  • Your car headlights will be dimmer than usual.
  • When you turn the ignition on, nothing will happen.
  • Struggling to start the car in the morning.
  • The battery of your car is corroded visibly.
  • Radio and other electronic devices won’t turn on.


Self-discharging is a common nature of batteries that leads to going flat. In general, if you do not use the battery, the self-discharging character finishes the entire charge without any external connections.

You might have already figured out how long can a car battery sit unused, after reading the entire context. Typically, two to four weeks is the average time for most car batteries to be flat.

However, the time can be shorter or longer depending on the battery health, charge level, stored weather, etc. The good thing is following the techniques discussed above; you can prevent your car battery from going flat.

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this site Batteryquery to help people purchase the right battery for their vehicles. The reason behind creating this site is to help my customers purchase the right car battery who often purchase the wrong one due to their lack of knowledge.

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