Replace the bios battery?

By altitune ·
On 09/28/2007 ThumbsUp2 wrote this:
"On some laptops, the battery needs to be charged before they will boot and they run down when not used. BIOS may run off the laptop battery or at least the BIOS battery won't charge unless the laptop battery is charged."

Can anyone advice me if the safe thing to do is to replace the Bios battery on my old Best 3100 from 2000. After a period of inactivity it has stared to not recognise the date, keyboard, hard disk, and give bad checksums. I have given it to a friend with not much money.

Or will regular charging of the main battery hold the problem at bay?

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All Answers

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It may help but I would suggest replacing the BIOS Battery

by OH Smeg In reply to Replace the bios battery?

If the NB comes from the 2000 era they tend to have a coin sized BIOS battery that is the same one used in Desktop computers. A 2032 Type Battery and these only cost a few $ to replace.

I don't think that the BIOS will run off the NB battery on a NB of this age but it never hurts to keep the NB's Batteries charged.

edited because this Dyslexic Keyboard mixed up the Battery Type.

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The bios battery is not rechargeable, just replace it

by robo_dev In reply to Replace the bios battery?

The bios battery is typically either a simple snap-in 3V CR2032 coin cell, or else a laptop-specific part (many compaq laptops used a Cr2032 with a two wire conector soldered to it). On compaqs, you had to take out three screws and the cmos batt is under the keyboard, then carefully solder the wires to the CR2032 without overheating it.

Having a dead cmos battery won't hurt anything, it's just annoying when it needs to re-learn everything and the date is 1/1/1980. (And web sites like Banks will give you certificate errors since your machine thinks it's 1980, and the certificate was issued in 2006.)

Typically when the laptop is completely off, the CMOS battery is the only thing keeping the date and config settings, not the laptop main battery. But I suppose this could vary by model.

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Follow-up: Replace the bios battery

by altitune In reply to Replace the bios battery?

Thanks for your replies, I will follow them. One last question:

Somewhere I have read that the bios battery must be replaced while the computer is powered up.

If it is replaced while the computer is powered DOWN, the bios will loose all information and the computer will be a vegetable, totally and irreversible junked.

Is there any truth in this?

Stockholm, Sweden

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No, the computer is smarter than that

by robo_dev In reply to Follow-up: Replace the bi ...

If the bios battery is removed (or is dead) the PC will need to spend an extra few seconds identifying the hard-drive and other similar devices, and the date will be set to something like 1/1/1980.

I've never seen any sort of issue with losing bios setup information, other than any special changes made to the bios configuration will be lost.

If anything, replacing the CMOS battery with the computer on would be risky....if you drop the battery it may short out something or fall into the processor fan. Normally you should not plug or unlpug anything from the system board of a computer while it's running.

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The Battery must

by cmiller5400 In reply to Follow-up: Replace the bi ...

The battery must be replaced with the machine powered OFF. If you do it on, you risk shorting out the motherboard and trashing the machine. If you have any encryption setup in the BIOS, make sure that you have a copy of the encryption key so that you can restore it if it is lost during the swap.

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Most defiantly NO!

by OH Smeg In reply to Follow-up: Replace the bi ...

BIOS Batteries should be replaced with no power applied. It will wipe the BIOS but as this is already happening there will be no difference.

What you need do after you have replaced the Battery is to open BIOS up and reset the Date & Time, it may also be necessary to set the Defaults but most NB's don't have this options they run a cut down BIOS set.

When people replace the battery with the unit powered up I've seen numerous cases where the battery gets dropped and fries the M'Board because the metal case creates several short circuits. While I like people paying me to fix their computers jobs like this are always a No Win Situation as the customer always seems to think that you are doing unnecessary work and charging them to repair their computer.


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