How Long Will a Car Battery Last If Disconnected? (Explained)

Car batteries typically last long when connected to the engine. The reason is that they gather power as the engine runs. With this in mind, you’ll know batteries can last for years. However, you may wonder how long will it last if it’s not connected. Thus, you may ask:

How long will a car battery last if disconnected? A disconnected battery can last for six weeks to six months. If you do so, you may need to keep recharging it over time. It would be a good idea for you to charge your battery every 12 weeks if you have it disconnected. This way, you can keep it in good condition, ready for future usage.

At some point, you may find the need to disconnect your car battery for a variety of reasons. Once you do, you must know what to do to maintain the battery’s condition, preserving it for future use.

In this article, we’ll cover everything you need to do about this matter. This way, you can keep your battery in a good and usable condition.

Without further ado, let’s get into it!

How Long Will a Car Battery Last If Disconnected

If I Disconnect My Car Battery Will It Stay Charged?

Disconnecting a car battery is the only way to keep it going without putting in a lot of effort. However, you need to do it right to preserve it.

For instance, you need to disconnect the negative part for the batter to stay charged.

One of the common questions typical drivers ask is if a car battery would drain its power if it gets disconnected.

The short answer to this is no. It won’t drain, especially overnight, even if you disconnect the positive lead.

Still, experts don’t recommend such and call it a bad practice for your car and your battery’s health. This concept applies to batteries assuming the car is negative earth or ground.

As I said earlier, you may need to disconnect your car batteries for some reason. If it happens, it would be best to ask an automotive expert’s opinion.

This way, you’ll have a better perspective on how to preserve your car battery.

Will a Car Battery Go Flat If Disconnected?

In general, a typical car battery won’t go flat if disconnected. Thus, you don’t need to worry about this matter should you ever find the need to do so.

As you disconnect your car battery, it helps prevent the electrical systems from draining completely. Such a system includes the clock and on-board computer system.

Thus, if you leave the car battery unattended for an extended period, you may end up damaging it. If such happens, you may have to replace the battery, which can cost you more.

With this in mind, always take it as a rule of thumb to disconnect your battery only when it’s essential.

How Do You Keep a Car Battery From Dying When Disconnected?

To disconnect the battery, you need to remove the cable from the negative port. One thing to remember is not to let the negative and positive cables touch each other at all times.

Now, to keep your car battery from dying, you may need to charge it regularly. This way, you’ll avoid draining its power and preserve it for future use.

If you would do so in a secure garage, disengage the security system to preserve the battery. You can also charge it once a week by driving your car for at least half an hour.

Further, you can disconnect the negative battery terminal. This method will also help your battery to remain in good condition.

Lastly, you can get a portable jump-starter in case you need to use it for your battery.

Should I Disconnect Battery if Car Parked Long-Term?

Many automotive experts recommend disconnecting the battery if you would leave your car idle for months.

The only thing to remember is that doing so would reset all electronic systems and settings in your car.

For this reason, you’ll need to spare some time in reconfiguring such settings once you would drive your car again.

With such a long time, no memory saver can help you retain such settings. In short, you will need to reconfigure all the settings on your own.

disconnected car battery

Why Does Car Battery Drain When Not in Use?

Car batteries drain when not in use due to the reaction that keeps on happening.

Take note that the battery drains slowly, but it does so to the extent that it will die.

It’s for this reason that alternators work. This tool maintains the battery’s charge. At the same time, it helps produce extra power for accessories such as lights, radio, and other electrical gadgets in the car.


While not all, some people find it necessary to disconnect the car battery from their car to preserve it. Such a necessity happens to those who won’t use their car for a long time.

Maintaining a car battery isn’t a simple task. Thus, it requires understanding and proper care. Without such, you won’t be able to preserve it for future use.

As always, battery preservation saves you a lot from buying a replacement. Thus, it’s all worth putting in an effort, especially if you will not use your car for a while.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more