How Long Can a Car Battery Sit Unused? How to Avoid a Dead Battery and Save Money

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How Long Can a Car Battery Sit Unused

How Long Can a Car Battery Sit Unused, and what are the best practices to maintain it? This article will answer all your questions and more.

One of the biggest concerns that car owners have is: how long will my car battery last if I don’t drive it for a while? Maybe you have a car that you rarely use or a car that you keep for the summer. Maybe you’re away for a long time or stuck at home. Whatever the case, you don’t want to find a dead car battery when you need it.

But how long can a car battery sit unused? The answer is that a car battery can sit unused for around 20 to 60 days under ideal conditions. But that’s not the final word. There are a lot of factors that can affect the lifespan of your car battery. These include the climate, age, type, and parasitic drain. I’ll explain how these factors affect the time your car battery can sit unused.

I will also discuss what you can do to prevent the battery from dying.

Let’s dive right in and see how long we can make your battery last.

Key Takeaways

  • Under ideal conditions, a car battery can sit unused for around 20 to 60 days.
  • Factors like climate and battery type affect how long a battery can remain unused.
  • Disconnecting the battery can help extend its life when the car sits idle for long periods.

How Long Can a Car Battery Sit Unused?

Let’s get down to the facts.

General Timeframe Before Battery Loses Charge

TemperatureDischarge Rate
10°C (50°F)0.25% per day
Room (25°C/77°F)1% per day
30°C (86°F)1.5% per day

An unused car battery can last between 20 to 60 days before it goes flat. But, remember that this timeframe is just a rough estimation, it’s not set in stone. Factors like temperature or the condition of the battery can affect how long it holds its charge.

All batteries eventually drain themselves over time, even if not connected. This phenomenon is known as self-discharge. The discharge speed varies depending on the battery’s chemistry and storage temperature. It also depends on other factors.

For instance, a flooded lead acid battery will drain at a rate of about 1% per day when kept at room temperature. It will drain only 0.25% per day when stored at 10°C (50°F). In contrast, the rate of discharge is significantly higher in temperate climates. At 30°C (86°F) it will drain rapidly, at 1.5% per day. 

The battery will, therefore, still have roughly 50% of its capacity after six months. Calcium-lead batteries can self-discharge at a rate of less than 2% per day. Low-maintenance and sealed batteries have an even lower discharge rate, less than 0.5% per day.

By disconnecting the negative terminal of your car’s battery, you can slow down the discharge rate to around five percent per month.

Recommended Recharge Frequency

To keep your battery in good shape, driving the car and recharging it regularly is best. If you can’t drive it, then using a trickle charger or a battery maintainer can help maintain its charge.

Tips for Preventing Battery Drain

  • Drive your car regularly: This helps recharge the battery.
  • Disconnect the battery. If you’re not using the car for a month or more, consider removing and storing the battery away.
  • Use a trickle charger or battery maintainer. These devices can keep your battery charged while it’s not in use.

Factors Affecting Battery Life

Let me tell you about some factors that affect the life of a car battery when it sits unused. The factors are:

  • Age
  • Condition
  • Temperature
  • Humidity
  • Electrical components draining power

Age and Condition of Battery

The age of the battery plays an important role in how long it can sit unused. An older battery may not last as long compared to a newer one. The condition of the battery also matters. If I keep my battery clean and free from corrosion, it’ll have a longer lifespan. Batteries degrade over time, so it’s wise to keep an eye on their health.

Temperature and Humidity

Weather conditions are another factor to consider. Extreme temperature fluctuations and high humidity can negatively affect the battery life. In the winter, cold weather can slow down battery reactions and reduce the available power output. Hot weather can accelerate these reactions, leading to a shorter battery life and increasing the rate of self-discharge and evaporation of the electrolyte.

Electrical Components Draining Power

Car batteries face a continuous drain from a number of electrical components. These include the radio, headlights, and security systems, even when the car is not running. This power consumption is also known as a parasitic drain.

Make sure that all electrical components in the car are properly turned off. If you plan on not using your car for a while, disconnect the battery to prevent it from draining.

Disconnecting the Battery

I mentioned earlier that disconnecting the battery can reduce the discharge rate. But when should you disconnect it?

Let’s take a look!

When to Disconnect the Battery

So, you may ask, when do I need to disconnect my car battery? The answer is simple. If you plan to leave your car unused for extended periods of time, it’s smart to disconnect the battery. This can prevent the battery from draining. Not being used for 20 to 60 days is going to make it go flat. Before disconnecting the battery, make sure you understand the necessary steps.

Steps for Disconnecting the Battery

Here’s how:

  1. Turn off the car: Make sure your car is entirely switched off before you begin working on the battery.
  2. Locate the battery terminals: Find the positive and negative battery terminals. The positive terminal is typically marked with a “+” sign (red cable), while the negative terminal has a “-” sign (black cable).
  3. Disconnect the negative terminal first: Use a wrench to loosen the nut on the negative terminal and carefully remove the cable from the terminal.
  4. Disconnect the positive terminal: Repeat the process for the positive terminal.

Tips for Storing the Battery

Now that you’ve removed the battery, you’re probably wondering how to store it, right?

This is how:

  • Storage location: Store the battery in a cool, dry place like a garage or basement. Avoid placing it directly on the floor or on a metal surface.
  • Charge level: Keep the battery fully charged. Charge it every couple of months if possible.
  • Cleanliness: Remove any corrosion or dirt from the battery terminals before storing it.

Following these tips can help extend your car battery’s life while it’s disconnected. Remember, proper care and maintenance are essential for a healthy battery.

Before You Go…

Preventing your car battery from dying while sitting unused is a great skill, but there’s more to learn. Do you know how long your car battery can last in total? The lifespan of a car battery varies based on many factors. These factors include the type, quality, usage, and maintenance. If you want to learn how to measure and improve the lifespan of your car battery, you need to read my next article.

It is titled “Can a car battery last 20 years?”. You’ll discover the facts and the myths about car battery life. You’ll also learn the difference between conventional and electric car batteries. This is essential information for any car owner. Don’t miss this chance to learn more!

Frequently Asked Questions

Here’s the FAQs

How long before a battery dies if not used?

If a car battery is not used, it can last between two to four weeks without a charge. Several factors, like battery health, age, and ambient temperature, affect this time.

Can sitting too long damage a car battery?

Yes, it can. Batteries discharge over time when not in use. So, if a car sits unused for too long, it can kill the battery. This is especially true for older batteries, around three or more years old.

What can prevent a battery from dying when unused?

To prevent a battery from dying when unused, follow these tips:

  1. Disconnect the battery to stop power drainage.
  2. Use a battery maintainer to keep it charged.
  3. Run the car for 15-20 minutes every couple of weeks.

How many days can a car sit before the battery dies?

Generally, a car battery can last about 21 days without needing a charge. But, this time can vary based on several factors I mentioned earlier.

Does using the radio affect car battery life?

Yes, using the radio when the car engine is off can drain the battery. So, avoid using the radio for extended periods without running the engine.

What is the longest time a new car battery can be stored?

A new, unused car battery has a shorter lifespan if not recharged often. When connected and driven regularly, however, new car batteries last three to four years. Their lifespan is shorter when stored. Check out this article for more information.

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Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life. Follow him on Twitter: @batterycharge1

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