What is a Motherboard Battery?
A motherboard battery, also called a CMOS battery, is a small lithium coin cell battery that provides power to the CMOS (Complementary Metal Oxide Semiconductor) chip on the motherboard when the computer is turned off.
The CMOS chip stores your computer’s BIOS settings, date, time and other configuration data. When your computer is turned off, the CMOS battery provides just enough power to keep this data saved. Without a working CMOS battery, your BIOS settings and clock will reset every time you turn off the computer.
Some common signs your motherboard battery may be dead or weak include:
- The clock resets every time you turn off or restart your PC
- You get a “CMOS checksum error” on bootup
- BIOS settings reset to defaults when power is removed
So replacing the CMOS battery is important to restore normal functionality.
Why Do Motherboard Batteries Fail?
There are a few reasons why a CMOS battery might fail or die over time:
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Old age – Most CMOS batteries last 3-5 years before needing replacement. The shelf life decreases over time.
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High temperatures – Heat can accelerate battery discharge. Poor case airflow and hot components like the CPU can expose the battery to high temps.
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Poor connection – Vibration or damage to the battery holder/socket can disrupt the connection and drain the battery prematurely.
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Manufacturing defects – In rare cases, a small percentage of batteries may be defective right from the start.
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Power surges – Power spikes from unstable electrical supply, lightning strikes, etc can damage the CMOS battery. Surge protectors help prevent this.
So in most cases, the CMOS battery eventually fails simply due to old age and normal wear and tear. Higher than normal heat exposure can accelerate the aging process.
How to Replace a Motherboard Battery
Replacing a CMOS battery is a very simple process, usually only taking a few minutes. Here are step-by-step instructions:
1. Turn off and unplug your computer
First turn off and unplug the power cable from your computer. Pushing the power button to drain residual power after unplugging. This prevents electric shock.
2. Open the case
Open up your computer case so you can access the motherboard. Refer to your computer or motherboard manual if needed.
3. Locate the CMOS battery
Look for a coin cell battery, usually the size of a nickel or quarter, on the motherboard surface. It should be in a battery holder or socket. See your manual for the exact location.
4. Remove the old CMOS battery
Carefully pry or push the old battery out of the holder. A flathead screwdriver works well for gently prying it loose.
5. Insert the new battery
Place the new CR2032 lithium coin cell battery into the holder with the positive + side facing up. Match the original orientation. Push in firmly so it clicks into place.
6. Close up and test
Put the case covers back on, reconnect power, and boot up to confirm normal operation. You may need to go into BIOS and reconfigure lost settings.
And that’s it! With the new battery installed, your motherboard should go back to keeping clock settings for years before you need to replace the battery again. Taking 5 minutes to swap in a new battery can save you future hassles.
CR2032 vs BR2032 Batteries
When buying a replacement CMOS battery, you’ll typically see two main options:
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CR2032 – The most common style used on motherboards. 3V voltage. Should work for most CMOS battery applications.
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BR2032 – Alternative 3V lithium battery. Also interchangeable in most cases. BR style might be used in some specialty industrial boards.
Either CR2032 or BR2032 should work fine for a standard motherboard replacement. Check for a model number or voltage markings on the old battery if you want to match exactly, but usually the basic CR2032 is perfectly compatible. Stick with reputable battery brands for longevity.
Buying a Replacement CMOS Battery
Replacing a dead CMOS battery is very cheap – expect to pay around $5-10 for a multi-pack of good brand name CR2032 or BR2032 coin cell batteries. Here are some options:
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Local electronics stores – Check electronics and battery reseller shops for individual replacement batteries.
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Online – Amazon, Newegg and other e-tailers carry CMOS batteries for very cheap. Energizer and Panasonic batteries recommended.
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Computer shops – Brick and mortar computer repair stores usually stock CMOS batteries for sale.
Look for name brand batteries from Energizer, Panasonic or other major manufacturers. Avoid no-name generic batteries which tend to have shorter lifespans. Stick with reputable battery brands for longer reliability.
Troubleshooting CMOS Battery Issues
If you’ve replaced your motherboard battery but are still having issues, here are some things to check:
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Battery polarity – Make sure the + and – sides are aligned properly in the holder.
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Battery holder – Check for any dirt, damage or bent pins in the battery socket. Clean with isopropyl alcohol if needed.
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Motherboard connections – Reseat RAM, cables and boards in case of a connection issue.
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Reset BIOS – After replacing the battery, enter BIOS setup to Load Optimized Defaults or reset CMOS.
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Battery voltage – Test the new battery with a voltmeter. It should show 3V.
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CMOS chip – In rare cases, the CMOS chip itself could be damaged and may need replacement.
If you still have problems after replacing the battery and troubleshooting connections, a motherboard failure may be to blame. Contact your system manufacturer or replace the motherboard if needed.
Conclusion
A dead CMOS battery is a common and inexpensive issue to fix when your computer is losing BIOS settings. Replacing the small lithium coin cell battery only takes a few minutes. Look for CR2032 or BR2032 models from reputable brands for the best longevity.
Follow proper anti-static precautions, match the original battery orientation, and double check connections. Test afterwards and reset BIOS if needed. With a fresh battery installed, your motherboard should reliably store settings and clock data again.
