Have you ever wondered what keeps the time ticking in your computer even when you have completely shut it down? The reason why your PC seems to keep the correct time and date, even after you have not used it for weeks is that it has a 3 volts Lithium battery on the motherboard. Often called CMOS battery, this small coin battery keeps the real-time clock of your computer’s motherboard working in all conditions. But this is an ordinary Lithium battery cell and it runs out of charge in around a year or so. After it is completely drained, you start to experience strange things in your PC.
The first sign of a dead CMOS battery is that your PC cannot keep the correct date and time. It gets stuck with the time of the last PC shutdown. So if you shutdown your PC at 9:00 PM on Monday and start it again on Tuesday to find that it is showing 9:05 PM Monday as the time, then in all possibility the CMOS battery is dead. The second thing you would notice is the appearance of strange messages on the boot up screen. For example, it might say – “CMOS checksum failure, press F1 to continue”.
In all these situations the only remedy is to replace the CMOS battery and here is how you can do it:
- First of all, get a replacement battery from your local computer hardware shop or shopping center. You can also order it online. What you are looking for is a CR2032 Lithium 3 Volt battery. You can get cheap ones that cost less than a dollar for 5 cells, or you can get ones from reputed brands like Sony that last much longer.
- Turn off your PC and detach all the power cords from the power outlets going into your PC. Open up the PC cabinet by unscrewing the screws from behind (you will need a Phillips screw-driver for this). When the cabinet is open, you will see all the components housed inside like the hard disk, SSD, motherboard, power supply unit etc.
- Find the small coin battery on the motherboard and apply gentle pressure on the lever that is holding it in place inside the battery socket. The battery should pop out of the socket without much trouble.
- Use a cotton swab dabbed in very small amount of rubbing alcohol (the one that doctors use to clean a patient’s arm before giving a shot) and clean the metallic contacts that touch the battery terminals. Wait for the remaining rubbing alcohol to evaporate.
- Take a brand new CR2032 battery and gently push it into the battery socket, keeping the positive (+) terminal on the top. You should be able to see the labels like CR2032 written on the battery when it is in place.
- That’s it. Now you can close the PC cabinet, close the cabinet cover back in place, put the screws back carefully and re-attach the power cords. As you start your PC, you may still see the CMOS data error message one more time again, but that is normal after replacing the CMOS battery.