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How to replace a dead CMOS battery

The CMOS battery is a small battery found in all computers, both laptops and desktops. You may not know this, but the computer’s CMOS takes care of storing some data, such as hardware settings, system time and date, and some settings needed to start the machine. The CMOS battery provides power to the CMOS chip even when the system is turned off: in particular, it retains the settings, but – if it does not receive the necessary power – it returns to the original factory settings.

As you may have guessed, the CMOS battery is indeed essential for the computer to function properly. What to do then if downloaded? In this guide, we explain how to replace the CMOS battery when it is low.

What is a CMOS battery?

Replace CMOS battery

Before explaining how to solve the problem of low battery, let’s try to understand what a CMOS battery is and what its role is in a computer. This battery is the main part of the motherboard and can certainly be defined as the backup power component for the motherboard. The CMOS battery is also used:

  • Digital logic circuits;
  • microcontrollers;
  • microprocessors;
  • Static RAM (SRAM);

What happens when the CMOS battery runs out?

When the CMOS battery runs out, it is important for the machine to work properly and it can cause the following problems:

  • You will see the wrong date and time on your computer.
  • BIOS passwords will be reset.
  • Some drivers may not work correctly or even be missing.
  • You will see a startup error on your computer.
  • Computer peripherals (such as keyboard and mouse) may not work properly.

In addition, if the CMOS battery is dead, you will also not be able to view certain websites or access certain services: this is because the system detects the wrong date and time. Of course, even if your internet connection does not depend on the date and time detected by the PC (in fact, it is still connected via Ethernet, USB key or Wi-Fi), you will not be able to connect to certain sites, because many programs use data and time as an important part of the security check. And also let’s not forget that the system storage of date and time can protect files, notes and documents. The wrong date can cause missed appointments, lost files, and many other problems.

Finally, another consequence of a low CMOS battery can be a constant beep emitted by the system to indicate that the CMOS battery is dead or low.

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How is a CMOS battery made and how long does it last?

replace cmos battery

If you know the CMOS battery better, it will be easier for you to replace it and solve all problems. So, what does it look like and how to recognize it among the many PC components?

Well, a CMOS battery is a lithium battery with a very coin-like appearance: it is located on the computer motherboard and has low static power consumption. This particular battery can last around 3-4 years: some types are even rated to last around 10 years. These are, in particular, new generation CMOS batteries that can last the lifetime of the motherboard, even if they may sometimes need to be replaced a little earlier.

As you may have guessed, the CMOS battery is not rechargeable, and if it fails or runs out of power, your computer may end up with a blank, blue, or black screen. Finally, most CMOS batteries are rated at 3V, although some computers may require a 5V battery.

Can a computer run without a CMOS battery?

The answer to that question is yes – your computer can definitely run even without a CMOS battery. This is because it does not power the entire computer, but only the CMOS when the computer is turned off.

In any case, without a CMOS battery, you will have to reset the clock every time you turn on your computer. In addition, every time you start or turn off your computer, the BIOS can restore the original factory settings. In this case, your computer will continue to work, but everything will be reset in the BIOS, such as boot order, time, date, and many other functions.

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How to change the CMOS battery in a laptop

Replacing the CMOS battery in your laptop is a very simple operation that only takes a few minutes. Below we will explain how to do this.

To get started, place the laptop in a suitable location: remember that one of the machine’s components can be easily damaged by electrostatic discharge. That’s why we recommend doing this on a flat pad of conductive foam rubber. Also, before doing anything else, gently rub your hands on a metal object to remove any static charge. You can also use an antistatic wrist strap.

Once the laptop is placed on the correct surface, turn off the laptop and unplug it from the power source. Disconnect all cables and accessories from the laptop, including peripherals. At this point, turn the laptop over and use a Phillips screwdriver to remove all screws. Now carefully remove the outside of the laptop and locate the coin-shaped lithium battery. Once you have located the CMOS battery, remove it from its holder, but be very careful when handling the motherboard: it is still the most important part of your laptop!

Before you remove the battery, we advise you to take a picture of it: this way you will know how to position it and how to properly orient it in the case. It’s time to put the new battery in the laptop: I recommend installing it in the same orientation as the one you replaced. Then tighten all screws again to install the laptop.

You are ready to test your new CMOS battery! Connect the laptop to the power cable and turn it on – you may need to set the date and time again. That’s it – you have replaced the dead CMOS battery with a new one. Obviously, be very careful when doing this, as you can seriously damage the motherboard.

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How to replace the CMOS battery in a desktop computer

We have shown how to replace the CMOS battery in a laptop computer: instead, in this paragraph, we explain how to replace it in a desktop computer. Let’s start!

First, disconnect all cables from the computer except the power cable. Write down the location of each cable so you can connect them correctly when you’re done. Now also unplug the power cord and press the power button on your PC – this will remove any current flowing from your PC components. Then remove all screws from the PC side panel and carefully remove it.

At this point, locate the CMOS battery on the motherboard and remove it with a screwdriver. Before doing this, make a note of the direction in which the battery was installed so that you do not make a mistake later. Now replace it with a new CMOS battery, installing it in the same orientation as the old one. Install the side panel on the PC by fixing it with screws, connect all the cables and turn on the PC: as the last step, you will need to set the correct time and date.

Replace the CMOS battery to avoid losing all PC settings.

The CMOS battery powers the BIOS firmware and is responsible for booting the system. When it fails or fails, it needs to be replaced: in this guide, we saw how easy it is to do and how much replacing it yourself can save you time and money.

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