Changing CMOS Battery help please

  14all 11:23 28 Aug 2006

My Clock looses time when turned off over night which seems to point to changing the CMOS battery on my motherboard.

I have searched through these forums and others to find out the correct procedure to carry this out, but none seem to go into detail on how you save your BIOS settings.

Do you have to write down all the settings in the BIOS?
I started, but gave up as there are so many advanced menus that I was loosing track of what was going on. I tried the print screen button to print the menu’s off but that didn’t work, so down to writing the lot down,

Could someone give me an idea of how much info you have to copy before changing the battery?

  rodriguez 11:30 28 Aug 2006

click here try this one. It will save your CMOS settings to a floppy so they don't reset when you take your battery out. However if the battery is completely dead, the settings may have already been lost and set to default anyway but it's worth a try.

  14all 11:42 28 Aug 2006


Thank you I will give it a go.

  14all 12:14 28 Aug 2006

For some reason that didn’t work, probably down to me.

I wish someone would write this procedure down in plain English, lets face it I’m only replacing a darn battery, why make so complicated?

  VoG II 12:19 28 Aug 2006

click here

I would take digital photos of each BIOS screen.

  14all 13:45 28 Aug 2006

Thanks VOG but my print screen button doesn’t produce anything.

Am I right in saying that when the computer is shut down and the main supply is still connect to the computer, that the battery isn’t in use? Therefore if I’m very careful I could change the battery without loosing any settings.

  Eric10 13:54 28 Aug 2006

VoG™ means to use a digital camera to take the photographs and that is the advice I would have given. Please do NOT try to change the battery with the PC still connected to the mains as parts of the motherboard are still live and one slip could be disastrous giving you a much bigger problem than you have now.

  DieSse 13:54 28 Aug 2006

Don't try touching anything inside the PC while tha mains power is still on. It's not dangerous to you, but can be disasterous for your system.

Either take a (digital) photo of each screen - or write down the settings is best.

There is a "Set to ..." function inside most BIOSes to enable you to do a basic setting.

Unfortunately, when you've seen symptoms that prompt you to change a battery, then the settings at least must by definition be suspect. You should always use the jumper provided to do a "CMOS Reset" when changing a battery, just to avoid any possible corrupt settings.

Best to make a picture or note of the settings when the system is working correctly, then store them somewhere sdafe for when the day comes...

  14all 17:33 28 Aug 2006

Thanks for all your responses, I finally copied all the BIOS settings by hand turned the power off, replaced the battery and booted back up.

Surprisingly the BIOS settings remained unchanged, either that was a one off or I was so quick at changing the battery the computer didn’t have time to realise I changed it. ;-)

  Stuartli 17:38 28 Aug 2006

Providing the battery is changed reasonably quickly then the settings should have been saved - it normally takes several minutes for the settings to be cleared if the jumper method is used.

  rodriguez 00:10 29 Aug 2006

When the battery's unplugged it usually takes about 10 to 15 mins before the CMOS settings are wiped. Also, as DieSse said, you shouldn't try and change the battery or any other component with the battery still plugged in. You won't get a serious shock because everything past the PSU operates at about 12 volts. However if you accidentally short something then it could damage the components as a lot of computer components imploy microchips and these are easily damaged by things such as sparks and static electricity. Also if you want to repair anything other than a computer, then your last choice would be a TV set or CRT monitor. These are lethal because of the capacitors that have to power the tube. They're also radioactive, so if yours breaks down, throw it out and get a nice TFT rather then repair it. ;-)

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