Can a Car Battery Die If Not Used? [Here’s What to Know!]

Last year, my car would have trouble starting, especially when it was sitting for too long. That made me wonder whether a car battery can die if not used for some time!

A car battery can die or lose charge significantly if a car has been sitting for too long. A car battery depends on the alternator to charge itself. If you don’t use your car often, it is advisable to start the car at idle for 15-30 minutes once every few days to keep the battery charged.

Eventually, I ended up replacing my car battery. But, in the process, I learned a lot about this topic! In this article, I’ll share everything that I’ve learned along the way so that you can fix or even prevent the issue if you are facing a similar situation!

So, let’s get started!

Can a Car Battery Die If the Car Sits Too Long?

There are occasions when you don’t get to start your car for a long time. Either you have multiple cars at home, or perhaps you just don’t need to take your car out! 

Whatever the scenario, in such situations, chances are your car battery will lose charge as it doesn’t get an opportunity to charge itself.

But why exactly does this happen and how long can a car sit before its battery dies? Let’s understand these aspects in further detail.

Why Does a Car Battery Die When Your Car Has Been Sitting?

A mechanic holding a car battery

The primary reason for the car battery to die when the car has been sitting for too long is the power consumed by instruments such as clocks, infotainment presets, security systems, etc. Other reasons include a bad battery, bad alternator, human error, etc.

Many of us are not aware that the car battery is in use even when the car is completely turned off. 

Instruments such as your infotainment system need to remember your presets, the clock needs to keep updating the time and your car’s central locking and alarm system need the power to lock or unlock your car! 

Other features like computer systems, climate control, and other electrical features are also powered by the car battery thereby discharging the battery in the process.

Thus, your car battery can die when the car has been sitting for too long as power from the car battery is consumed even when your car is turned off. 

Furthermore, since the car is stationary, the alternator, which essentially acts as the power source for charging the car battery, doesn’t come into action. This prevents the car battery from getting charged all the while it is losing power.

That said, there are actually quite a few other factors also involved in your car battery losing power when your car has been sitting too long.

1. Human Error

One of the most common reasons for the battery to die when your car has been sitting is human error. 

Perhaps you forgot to turn the headlights off, or the lights in the central dome inside the car. This can easily drain the car battery much faster than usual.

But, how long can a car battery really last if you forgot to turn off your car lights? Check out my other article on “Can a Car Battery Die from Leaving the Lights On?” where I provide complete details on the various factors that affect how long can a battery last with the car lights on!

It is always a good practice to check your car once after you’ve locked it. Check to see if all the lights and other systems are off

2. Bad Alternator

Another factor that can impact the capacity of your car battery is a faulty alternator. 

Since the alternator in the car is the main power source for charging the car battery, a bad alternator can mean that your car battery is either not able to charge enough or not charging at all!

This can lead to undercharging of the battery. If a battery is not getting charged adequately, you will notice corrosion on the negative terminal of the battery. 

One thing to remember is that the corrosion on the negative terminal doesn’t always mean that the alternator has gone bad, but it surely is one of the possible factors.

A bad alternator can mean that your car battery doesn’t last as long as it should when the car is sitting. It can also mean that your car battery can die even when you are driving the car! If this issue is not fixed in time, it can ultimately lead to a shorter lifespan of your car battery.

In such a scenario, it is best to reach out to a car mechanic and have him or her take a look at the issue at hand.

3. Bad Battery

This might seem like an obvious reason for a car battery to die when your car has been sitting; sometimes even for a short while!

But, many people are often not aware when they have a bad car battery. 

A car battery can be considered bad or faulty when it can not be charged to its full potential even after providing enough time to charge!

There are several reasons and signs of a bad car battery. The most common reason, however, is lack of maintenance during the course of normal usage. 

The easiest way to detect whether your car battery is faulty is to charge it fully and use a voltmeter to check the voltage on the battery. You can easily buy a voltmeter on Amazon like this one for as little as $12.

With all that being said, if you have a bad car battery, you might notice that your car battery dies more often than usual when your car is sitting.

4. Current Leakage

Another factor albeit less common is when there is a leakage of current from the battery into some part of the car.

This probably needs no further explanation. Current leakage can mean that the amount of current consumed from your car battery is higher than what the usual instruments consume when your car is turned off.

This in turn leads to a faster discharge of current from your car battery and, as a result, the car battery dies much faster than usual when your car is parked. 

Fixing this problem can get quite complex as it is not easy to figure out the leak without checking the complete wiring system in your car. 

For a permanent fix, you will need to pay a visit to your car mechanic and get your car’s electric and wiring systems checked.

5. Corrosion on Battery Terminals

Another possible factor is the corrosion on the battery terminals. Most car batteries experience some corrosion on their terminals if they are not regularly maintained. 

This corrosion can be detrimental to the battery’s performance as it creates a resistive force in the flowing current.

Corrosion on the positive terminal indicates that the battery is being overcharged. Whereas, corrosion on the negative terminal indicates that the battery is not getting charged enough.

You can sand the corrosion on the car battery terminal using Battery Terminal Cleaners like this one on Amazon. This can improve the battery’s lifespan. The complete process and other measures you can take actually deserve an article of their own.

If you see corrosion on your car battery, just know that this could be one of the many possibilities of why your car battery dies when your car is sitting! 

6. Extreme Temperatures

Another common factor for a car battery to die is when your car is exposed to extreme temperatures, particularly cold weather!

In cold weather, your car batteries can freeze especially when it is not adequately charged. When the battery output voltage is on the lower side, there is an increase in the water content inside the car battery output thereby increasing the freezing temperature of the battery!

I’ve written an entire article on this topic “Can a Car Battery Freeze?”. Make sure you check out that article to know the complete details!

It is best to use a battery blanket like this one on Amazon to prevent your car battery from dying due to freezing temperatures!

How Long Can a Car Sit Before Its Battery Dies?

A fully charged new car battery can last up to 2 months before it dies when the car is sitting for too long. A moderately used battery should last at least 2 weeks before it dies from not being charged. 

How long it takes for a car battery to die when a car is sitting depends on several factors including age, health, and charge of the battery.

That said, the primary factor is the charge left in the battery.

When a battery becomes old, it gradually loses the ability to charge to its maximum capacity. Likewise, if the battery health is affected by any of the reasons mentioned in the previous section, it again won’t be able to hold a full charge.

If the battery is unable to charge to its full capacity, it is more likely to die in a shorter duration of time if the car sits for too long. 

To give you an indication, a car consumes 10-20 mAh at any given point even when the car is turned off. This can vary based on your car’s make and model. 

Most car batteries come in the range of 44 Ah – 88 Ah capacity (again, depending on the car brand and size). Assuming that a car consumes 20 mAh at any point, a fully charged new 44 Ah car battery will take a little over 2 months to reach about a third of its capacity (minimum capacity required to start a car).

Cars with a bigger battery are also likely to have a proportionately higher power consumption. So, even if your car has a new 88 Ah capacity, the overall time it can last while your car sits can is about the same i.e. 2 months.

However, as the battery ages and its capacity decreases, the same car battery may end up lasting for 2 weeks or less when the car is sitting.

How to Keep the Car Battery From Dying When the Car is Not in Use?

There are a few things you can do to keep your battery from dying when your car is not in use for long periods of time –

  1. Start your car at idle for 10-15 minutes once every week. This will help charge your car battery and prevent it from losing all its charge.
  2. You can also remove the car battery and keep it in a safe place either in your garage or in your house. This will ensure that the battery doesn’t lose charge. Keeping your car battery outside your in a warm place can be especially effective when you want to prevent your car battery from freezing!
  1. Another thing you can do is simply remove the cable on the “Positive” terminal of the battery on your car. This method is especially effective when your car battery is leaking current and you can’t seem to figure out why!
  2. Use a trickle charger or battery tender [on Amazon] to keep charging your battery at a slow rate over a long period of time. This can also help maintain the temperature of your car battery; another effective method against cold weather conditions!

How to Start Your Car When Your Battery is Dead?

There are a few things you can do to start your car when your battery is dead. I intend to write an extensive article around this topic with a step-by-step guide. But, in the meanwhile, here are a few things you can do –

  1. Jump start your car using jumper cables – If you have access to another person’s car who is generous enough to let you jump start your car, then you can easily plug your car battery into their car battery using a set of jumper cables [on Amazon].

    In fact, I recommend buying this NOCO Boost Plus Battery Starter Box [on Amazon]. It comes with a power bank and a set of jumper cables attached. It is slightly more expensive than a simple jumper cables but the best part of this jumper set is that you don’t need to depend on any other car battery to jump start your car!
  2. Push-start your car – If your car won’t start due to a dead battery and you don’t have access to a jumper cable set, you can use some muscle power to crank your car!

    You will need 2 or 3 friends who can push your car. Before they start pushing, put the car in the first gear and release the handbrake. Press and hold the footpadle for your clutch and ask your friends to start pushing the car. Once the car reaches certain momentum, release the clutch. This will start the car engine.
  3. Charge your battery outside your car if at home – If you car has battery has been dead from your car sitting at home for a long time, one of the best ways to revive your car battery is to use charge them!

    You can easily buy a car battery tender like this one [on Amazon] to connect with your car battery and charge the car. A battery tender will ensure that your car battery gets fully charged and ready to go when you are. You don’t need to remove the battery out of your car with this battery charger.
  1. Call for road-side assistance – If none of these are options for you and your car battery died in the middle of the road while you were driving (which is entirely possible as it has happened to me once!), the best option would be to call for roadside assistance offered by your car servicing company.

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