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How to replace the CMOS battery?

Posted By : Student of Katharine Gibbs School - New York on March 8, 2004

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My computer will not keep the current time. It loses about 30 minutes per day. What could be causing this?

Thanks -

This question was answered on March 8, 2004. Much of the information contained herein may have changed since posting.

You have to change the CMOS battery

Computer Clock Batteries

Computer clock CMOS batteries are used in virtually all desktop and laptop computer systems that use CMOS memory to retain the date, time and configuration information when the power is off The types of devices used vary greatly depending on the manufacturer and the application Most desktop systems use a single device while laptops may contain a clock/CMOS battery and a resume battery to retain RAM memory information in the event the system battery loses power For detailed information about the types of devices used, please see: "Computer Clock Battery Types."

Here are some instructions how to replace the battery.

CMOS Battery, Replacing

If your computer is more than two or three years old, a safe bet is that your CMOS battery is losing power

(Time-out: CMOS refers to a chip that contains vital information about your computer's configuration and how it should boot up The chip can hold onto this information only as long as its battery has power.)

The good news is that the battery is very similar to the lithium batteries that power digital watches

Unplug and open your PC Look for the battery, note what voltage it is and which side is up Don't take it out yet

Buy a replacement

After you have discharged yourself of static electricity or have put on an anti-static wristband, replace the battery

If you have been efficient - and even if you have not but own a fairly new-model computer - the next time you boot up, the CMOS chip will automatically regenerate the information it needs about your PC

But there is a very small chance that it will not

So, before you change the battery, boot the computer

Watch the bottom of the screen for a message telling you which key to press to enter "Setup" - probably the "Del" or "Esc" or one of the F keys - and press the key before Windows starts

Once the CMOS file is open, go through all its sections and write down all the settings

After you have changed the battery, reboot, go into Setup again, and make the appropriate entries if your CMOS chip has not done so

Of course, if you have a maintenance utility such as Norton Utilities, you can use it to back up and restore your CMOS settings

One other thing: If your computer is more than five or six years old, you may find that the CMOS battery looks like a teeny flashlight battery and is soldered to the motherboard Replacing it will mean a trip to the computer repair shop

I hope this will help you Enjoy

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Posted by Student of Katharine Gibbs School - New York on March 8, 2004

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