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How Long Can a Car Battery Sit Unused?

Owning a car comes with its own set of facilities as well as drawbacks. A car battery can sit unused for many days depending on the type of your car, the weather, etc. In order to keep your car and its battery in good health, you must drive it on a regular basis. Otherwise, with time, the battery will lose its charge which will result in the engine not starting when you try to drive the car. But why does this happen? And, what’s the exact time by which your car’s battery won’t have any charge left if the car left unused?

Where Does the Charge in a Car Battery Come From?

The radio, alarm system, GPS, and all other electrical gadgets in your car directly drain power from the battery. The battery, on the other hand, produces power from the alternator/generator when you drive the car. The generator, while the car’s on the move, supplies the charge to the battery pack to keep the electrical components of the car running.

From the regular construction of batteries, we know that the electrolyte in the battery cells supply the negative and positive ions to the electrodes and keep the electrons moving inside the cells so that charges get stored in the plates. This process gets slow when your car is parked, or not in use.

So, you see, the charge in your car’s batteries generates mainly when you drive it.

How Does the Charge in a Car Battery Decrease?

The electrical devices in your car- the radio, clock, the engine computer, alarm system, etc. operate with the power of your car’s battery. Even when the car is not in use, these devices still function while draining the power from the batteries.

Therefore, the decrease in the charge of the battery depends on the devices of your car that keep functioning when the car is parked. The temperature of the surrounding also affects the battery charge. In winter, the car battery loses its charge faster than in summer. That’s because many people use car heaters in winters which uses up some extra charge. Also, people tend to drive less in winters. As a result, the battery doesn’t get a chance to charge up from the generator.

In summary, the built-in electrical devices in the car make the charge in a car battery decrease. You cannot prevent this from happening, but you certainly can take some measures to keep the battery alive for a long time.

How Long a Car Battery Can Sit Unused?

This depends on the type of your car. High-end car batteries might live up to only two weeks, while others might elongate that period to two months when not in use. You can calculate the time by which your car’s battery will lose all of its charges. For this, you need to know your car battery’s capacity.

A normal car’s battery generally loses 2% of its charge each day when parked and not being used. This measurement would be higher for high-tech cars. So, depending on the battery’s capacity, you can have an idea of how many days you can leave the car in the garage without any worries.

For example, if your car’s battery has a capacity of 40A/h, the charge below which the engine won’t turn on would be 40/3.3 which equals 12.12A. The battery has to lose 40-12.12= 27.87 A/h to reach that level. Let’s suppose, the regular leakage current of a car battery I 10mAh. Then, the battery will survive for 27.87/0.01 =2787 hours which is equal to 116 days. That’s a lot of days, isn’t it? But, did you notice that we only calculated the leakage current here? We didn’t calculate the charge that the radio, the dash clock, the alarm system, etc consumes.

The number of days significantly decreases when the battery is still in your car and you’re not using it. In the winter season, this period can be only 10 days to 14 at max. And for summers, it can be 20 to 30 days.

Saving Battery Life

If you want to save the battery from losing its charge and not planning to drive your car for a long time, I’ll suggest you store your battery separately or buy a battery maintainer or a smart charger. Storing the car detached from your car is a whole different thing and requires you to be very cautious about how and where you put it.

On the other hand, a battery maintainer or a smart charger keeps things simple for you. You connect it to your car battery and can keep it right there forever. It’ll recharge the battery whenever the battery needs it to. It won’t overcharge the battery; just sufficiently charge it. It keeps the battery safe when you keep it parked for days. So, you better start looking for a smart car charger if you’re planning to not use your car for a long period.


It’s not wise to keep your car unused for long. Driving the car on a regular basis elongates battery life. A car battery will sit unused for days but eventually start degrading. Therefore, you either should store it safely somewhere else or get a battery maintainer for the days when you don’t drive your car.

Read here best car battery

Angela E. Bouchard
Angela E. Bouchard

Angela E. Bouchard is a writer and blogger as well as the chief editor of Route Vibes. She was grown up in a small neighborhood of Linden Avenue, Orlando, FL. From childhood, she has developed a keen interest to know about everything. Such characteristic helped her to become a passionate writer as she grows up. Before starting at the Route Vibes project, Angela E. Bouchard worked as writer and editor at multiple top-notch blogs and magazines. You can follow her on different social media, including Twitter, Instagram, Facebook, and Instagram, to know more about his work.

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