Tech News Today
  • Hardware
    • Motherboards
    • CPUs
    • Graphic Cards
    • RAM
    • SSDs
    • Computer Cases
    • Monitors
    • Peripherals
    • Power Supply Unit
    • PC Builds
    • Computer Tips
  • Software
  • Operating System
    • Windows
    • Mac
    • Linux
  • Gaming
  • Mobile
  • Console
  • More
    • Internet
    • Networking
    • Security
    • Buyer’s Guide
    • Gadgets
    • Laptops
    • Reviews
    • How To
    • News
Facebook Twitter Instagram
Tech News Today
  • Hardware
    • Motherboards
    • CPUs
    • Graphic Cards
    • RAM
    • SSDs
    • Computer Cases
    • Monitors
    • Peripherals
    • Power Supply Unit
    • PC Builds
    • Computer Tips
  • Software
  • Operating System
    • Windows
    • Mac
    • Linux
  • Gaming
  • Mobile
  • Console
  • More
    • Internet
    • Networking
    • Security
    • Buyer’s Guide
    • Gadgets
    • Laptops
    • Reviews
    • How To
    • News
Tech News Today
Home»Hardware»How Long Does a CMOS Battery Last

How Long Does a CMOS Battery Last

Deep ShresthaBy Deep ShresthaJanuary 25, 2023
how long does a cmos battery last

The CMOS battery supplies power to the CMOS chip so that the system can remember all your BIOS configurations even after the system turns off.

One major variable that determines the lifespan of a CMOS battery is its current voltage. The CMOS battery becomes useless once it reaches a point where the battery fails to supply the minimum required voltage for the CMOS chip.

Once the battery dies, any data saved on the CMOS chip will be set to its default value. This data includes all your BIOS settings and the system clock. So if you see that the BIOS or the system clock resets every time you turn on the system, you might need to replace the CMOS battery in your system.

Table of Contents

  • How Long Does CMOS Battery Last?
  • How to Know if Your CMOS Battery is Dying?
    • Incorrect Date and Time
    • BIOS Settings Keep Resetting
    • POST Error Message
    • Check for Visible Damages
    • Check CMOS Battery Voltage
  • What to Do if the CMOS Battery is Dead?
    • Remove PC Side Panel
    • Locate CMOS Battery
    • Replace CMOS Battery
  • How to Increase CMOS Battery Lifespan?

How Long Does CMOS Battery Last?

The CMOS battery can last three to ten years depending on the CMOS battery charge capacity, the system’s uptime, the standby current of the motherboard, and many other factors.

The voltage on a CMOS battery decreases gradually if it is not in use. Therefore if you leave your PC turned off, the system constantly uses the CMOS battery and hence will deplete over time. In such a case, the battery may not last more than four years.

On the other hand, the system does not use the CMOS battery when you turn it on. So if you constantly use the PC, the CMOS battery may even last up to ten years.

How to Know if Your CMOS Battery is Dying?

The CMOS chip holds all your BIOS settings and Real Time Clock (RTC). All these configurations will be reset once the CMOS battery stops functioning. Some motherboards even have features that let you know when to replace the CMOS battery. Some motherboards even have features that display a message when the CMOS battery runs out.

Here are some ways you can determine if you have a dead CMOS battery.

Incorrect Date and Time

incorrect date and time cmos battery

Your motherboard keeps track of time using the RTC (Real-time Clock) chip. But the RTC chip requires constant power to function. When you turn off the system, the RTC uses the CMOS battery as the power source. And if the CMOS battery is not functional, your system time will reset every time you turn off the computer.

If you have not synced your time computer to an internet time server, you will notice that your computer time is not accurate.

If you have not synced your time computer to a time server, you will notice that your computer time is not accurate.

BIOS Settings Keep Resetting

All your motherboard configurations are saved on a CMOS chip. These include RAM’s XMP, hardware frequency in which it operates, and all other configurable settings in BIOS. 

Similar to the RTC chip, the CMOS chip also stores all its data as long as it has constant power to it. When you turn off the system, the CMOS chip uses the CMOS battery as the power source.

So when the CMOS battery dies, all your BIOS configurations will reset once you turn off the system. You will especially notice this if you have changed the settings in the BIOS. Besides the BIOS settings, you may also run into CMOS checksum error or System battery voltage is low error.

POST Error Message

post error cmos battery

When you turn on your system, the motherboard first runs a POST. During POST the system checks crucial hardware components. POST also detects any data mismatch in the CMOS chip. These errors in the CMOS chip might be indicating a possible CMOS battery failure.

Check for Visible Damages

You can physically check your CMOS battery for damages. Your motherboard has a dedicated slot for the CMOS battery. Any visible damage to the CMOS battery might hint at a dead battery. These damages could be a swollen or corroded battery.

Check CMOS Battery Voltage

You can check the CMOS battery’s voltage using a voltmeter if you want to get accurate data. 

The voltage does not need to drop to zero for it to become useless. Depending on your CMOS chip, the minimum voltage required for it to function may vary. 

  1. Turn on your multimeter and set it to read voltage from a DC source.
    set multimeter to read volt
  2. Touch the red lead to one side of the CMOS battery. And touch the black lead to the other side of the CMOS battery. The voltmeter should display the reading on the display panel.
    voltmeter CMOS reading

What to Do if the CMOS Battery is Dead?

Once you are certain that the CMOS battery is dead, the first thing to do is replace it.

Since the CMOS battery slot is embedded into the motherboard, you will need to access the motherboard first in order to remove the CMOS battery.

Remove PC Side Panel

  1. Turn off your computer and unplug the PSU from any wall outlet.
    remove pc from wall outlet
  2. Press the power button for a few seconds to discharge the residual charge on the capacitors.
    press and hold power button cmos battery lifespan
  3. Unscrew all the screws on one side of the CPU case to remove the side panel.
    remove side panel cmos battery life span

Locate CMOS Battery

cmos battery location in motherboard

The CMOS battery connects to the motherboard. For desktop PCs, you will find a separate circular slot in the motherboard that holds the CMOS battery. As for laptops, they may have a separate slot on the motherboard, just like the motherboards on desktop PCs. 

If the laptop’s motherboard does not have a separate slot, CMOS should be connected to one of the ports on the laptop motherboard with a short cable. In that case, the CMOS battery will be wrapped with electrical tape.

Note: Depending on the motherboard manufacturer, the CMOS battery could be located anywhere on the motherboard. Please refer to the motherboard user manual if you have issues locating the CMOS battery.

Replace CMOS Battery

  1. Press the lock that holds the CMOS battery in place to pop the battery out of the socket.
    how long does cmos last remove cmos battery
  2. Take the fresh CMOS battery and insert it into the CMOS battery slot on your motherboard. Ensure that you insert the battery such that the + sign faces up.
    insert cmos battery how long does cmos battery last
  3. Insert the side panel and connect all the screws that you previously removed.
  4. Once you put everything together, turn on your system.

How to Increase CMOS Battery Lifespan?

The CMOS battery loses the charge stored inside it if not in use for a long time. When this happens, the battery fails to deliver the minimum voltage required for the CMOS chip.

When you constantly turn on the system, it does not use the CMOS battery. Therefore, if you want to increase the life span of a CMOS battery, we recommend that you use your computer regularly.

Question
Deep Shrestha
  • Twitter
  • LinkedIn

Deep Shrestha works as a computer hardware writer at TechNewsToday with several hardware and programming certifications. Although he has been writing technical content for more than a year, his interest in hardware components started at a very young age ever since he heard about PC building. Pursuing his passion, he has assembled several desktop computers. Besides building desktop PCs, Deep also has hands-on experience fixing software and hardware issues on laptops and desktop computers. Using all this knowledge and skills about computer hardware, he's on a quest to make content that's easy to read and understand for everyone. You can contact him at deep@technewstoday.com

Related Posts

aio vs air cooler

AIO Vs Air Cooler(Detailed Comparision)

February 15, 2023
power bank not charging

Power Bank Not Charging? Here’re 6 Ways to Fix It

February 8, 2023
usb a vs usb c

USB A Vs USB C – What’s the Difference?

January 31, 2023
AIO Pump Not Working

AIO Pump Not Working? Here’s How to Fix It

January 29, 2023
How to clean usb port 1

How to Clean USB Port on PC (Comprehensive Guide)

January 27, 2023
thunderbolt vs usb c

Thunderbolt Vs USB C: What’s the Difference

January 25, 2023
Add A Comment

Leave A Reply Cancel Reply

Latest Posts
Memory-Compression

What is Memory Compression in Windows? Should You Enable or Disable It

March 1, 2023
dism-vs-sfc-vs-chdsk

DISM, SFC, CHKDSK: What’s the Difference

February 28, 2023
bios-settings-for-gaming

Best BIOS Settings for Gaming

February 16, 2023
You may also like
how-to-clean-hp-printer-rollers

How to Clean HP Printer Rollers

March 3, 2023
keyboard input lag

9 Ways to Fix Keyboard Input Lag

March 3, 2023
keyboard key is stuck

How to Fix a Stuck Key on a Keyboard

March 3, 2023
Recommended
Cookie Clicker Garden Guide

Cookie Clicker Garden Guide to Unlocking Every Seed

September 26, 2021
monitor no signal

Computer Turns On But Monitor Says No Signal (9 Ways To Fix)

November 10, 2022
Facebook Twitter Pinterest
  • Home
  • About Us
  • Our Team
  • Editorial Guidelines
  • Privacy Policy
  • Affiliate Disclosure
© 2023 TechNewsToday, editor@technewstoday.com | Tech Central Pvt. Ltd.

Type above and press Enter to search. Press Esc to cancel.