Computer battery

[#1]

As the time and date on my desktop computer are constantly wrong despite me entering the correct information I am assuming the battery needs changing.

OK simple enough job but how important is it to change it ?

Exactly what else of importance, if anything is this battery keeping charged up ?

[#2 · Accepted solution]

see http://www.makeuseof.com/tag/why-does-my-motherboard-have-a-battery/

[#3]

The battery is used to persist settings in the CMOS along with the system clock. It can get to the point that the PC will fail to boot due to issues with the CMOS so changing it is recommended and you don't have to do it at every boot up. In addition to that the clock needs to be quite accurate when using some secure services such as HTTPS, so that certificate(s) can be validated correctly.

[#4]

Most modern motherboards use a CR2032 lithium button cell which is located in a battery holder on the board. Its as simple as popping the old one out, maybe with the help of a small screw drive and pushing the new one in.

Some cheaper OEM boards have the battery soldered onto the board, but you would have to be really unlucky to have one of these.

These should do the job:

http://www.screwfix.com/p/coin-cell-batteries-cr2032-pack-of-2/4059k

[#5]

Yes,

Depending on where you live, there is a local hardware store near me.
They do a pack of batteries for about a £1 (a pound shop). They have CR2032's in them.

[#6]

I am sometimes called to see computer that will not load certain websites.  The most frequent cause of this problem is that the system date is badly wrong and the most frequent cause of that is a failed or failing battery.

Other than the need to maintain the correct date I'm not sure if the CMOS battery serves much practical purpose most of the time.  99% of computers use the default CMOS settings or would work perfectly well using them.  So if lack of battery causes these settings to revert to their default values then there is no change or no great harm, other than the time and date being wrong.

[#7]

@gleneagles wrote:

 Exactly what else of importance, if anything is this battery keeping charged up ?

 Well PCs will often lock up for a few seconds when the battery needs replacing. I've had a couple of friends with PCs that would randomly freeze and then continue working, solved by replacing the cmos battery on the mobo.

My current machine keeps randomly freezing for a few seconds and in that time the CPU graph on task manager also freezes so it is indicating that i need to replace the battery too.

[#8]

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@ReedRichards wrote:

I am sometimes called to see computer that will not load certain websites. 

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On a similar note, if you ever have glitches with old versions of IE not working on some sites you'll probably find its to do with the SSL support. Older versions of IE only have 256bit support but from 8 onwards (iirc) it supports 512bits hence old versions of IE fail miserably on SSL sites.

Took me a while to get to the bottom of thata few years back when IE suddenly stopped working on all of our machines..

[#9]

I've never had to replace a battery in a period of 30 years, covering hundreds of PC's.

So you are rather unlucky.

[#10]

If you have had hundreds of PCs over 30 years that might imply that you never keep a PC long enough to need to replace the battery.  I presume that's not what you mean to imply but more information as to the average working life of those PCs would give a much better context for your remark.  

I think that keeping a PC plugged in to the mains when switched off may prolong the life of the battery - this certainly works where the battery is near to end-of-life.

[#11]

I had a HP Proliant Server a couple of years back that just 'failed' when trying to run DFS.  Took days to finally 'twig' that the root cause was a dead CMOS battery!

[#12]

I had an old PC which I had to change the battery.

Keeping time on the PC never bothered me it was the infernal boot option that started popping up and having to keep choosing the default settings.

As said it was just a case of locating the battery.

[#13]

Thanks for the replies.

It's a fairly old desktop PC which gets very little use.

I do have the correct battery, amazing how many things take this size of battery.

[#14]

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@ReedRichards wrote:

I think that keeping a PC plugged in to the mains when switched off may prolong the life of the battery - this certainly works where the battery is near to end-of-life.

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That does seem to be the case. The machine i'm using now was packed away for a year or two and unused however now its back in use it does freeze randomly for a few seconds at a time which is rather annoying. I have batteries floating around too i just keep forgetting to deal with it.

@VileReynard 30 years ago few computers even used batteries. In the last 20 odd years yes the PC and similar hardware seems to carry a clock on board and I do actually remember an Atari 1040 that had a plug in clock (the owner was very chuffed to be showing that off in the late 80s!) - what the point of that was is beyond me.

As Reed says, I reckon you've got through a lot of machines or worked with other techs that have dealt with things like this (or the machines were just plugged in most of the time). As i understand it the battery is only there as a backup.

What i've never quite grasped is the RPi thing.. they come with no RTC and get it from the web on booting but what if you've got no internet connection?

[#15]

If the RPi is not connected to the internet, does it really need to know the time?