# Where is CMOS battery located on my emachines D520?



## gumbyy (Mar 11, 2009)

I have the service manual for my Emachines D520 laptop and it doesn't say where the CMOS battery is located nor how to access it. 

My laptop is 5 years old and I think I should replace the CMOS battery. I emailed Emachines (Acer) about this and they wouldn't tell me the CMOS battery location, saying they can't provide support for some reason. Can you help?

I read somewhere that laptop CMOS batteries are rechargeable and might not need replacing. Is that true? I have wondered why it still works after 5 years, using the computer 8 hours plus everyday.

Thanks for any help.


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## Wrench97 (May 10, 2008)

The CMOS battery is only used to retain the date, time and any changes you made to the CMOS default settings whan the laptop is turned off and the main battery is disconnected or discharged. 
It's most likely soldered to the motherboard. 
It's not unusual to see them last 10+ years


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## joeten (Dec 4, 2008)

Hi look at pages 77 and 102 I believe you can see it there


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## gumbyy (Mar 11, 2009)

Wrench97 said:


> The CMOS battery is only used to retain the date, time and any changes you made to the CMOS default settings whan the laptop is turned off and the main battery is disconnected or discharged.
> It's most likely soldered to the motherboard.
> It's not unusual to see them last 10+ years


Thanks for this info. I just unplugged my laptop and removed the main battery for about 10 minutes. Then put the battery back in and booted. Time and date were same as before, current and accurate. Does this mean that the CMOS battery is definitely still good, wherever it may be hiding?

Underneath the main battery I saw a disc shaped thing that looked a bit like a CMOS battery. It had words inscribed "FG 18LIB. 4Ω 2W with - and + symbols at bottom. Could this be the CMOS battery? 

It isn't accessible from where I saw it under the main battery, but looks like it would be accessible from underneath the switch cover (the panel to the north of the keyboard, where the computer meets the LCD). But I couldn't find any hits when i googled FG 18LIB. 4Ω 2W. Maybe it's the back of a speaker or something.


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## joeten (Dec 4, 2008)

I had a look and like you found nothing on it, but that appears to be it from your description.


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## greenbrucelee (Apr 24, 2007)

the cmos battery looks like a battery you would get for a watch but is bigger. Have a look at this picture.


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## gumbyy (Mar 11, 2009)

Thanks. yes, I remember replacing a CR2032 in my previous Compaq laptop. I think CR2032 is pretty much standard for CMOS batteries, isn't it? CR2032 says 3 volts. The disc I found says 4 ohms and 2 watts. Isn't that speaker terminology?


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## greenbrucelee (Apr 24, 2007)

yeah pretty much.


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## gumbyy (Mar 11, 2009)

joeten said:


> Hi look at pages 77 and 102 I believe you can see it there


Didn't see anything that looked like it on p. 77. On p. 102 [Replacing the ODD Module] I see a picture of the disc I described that's under the main battery. Is that what you were referring to? (I assume you mean pages 77 and 102 as printed on the pages themselves, not the PDF reader program's pagination which assigns them different page numbers because of the un-numbered pages in the beginning of the file)


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## joeten (Dec 4, 2008)

OOps my bad, time to go take a rest should have seen that


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## joeten (Dec 4, 2008)

That was the nearest thing to a cmos I saw on those pages, granted 1 pic is only a little better than the other.Still pretty hard to see clearly.


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## gumbyy (Mar 11, 2009)

greenbrucelee said:


> yeah pretty much.


I think it's the back of one of the speakers, which are in that same position on the top of the laptop.


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## Wrench97 (May 10, 2008)

Yea 4 ohms is not a battery.
A lot of the eMachines models I've seem are pretty well buried almost to the point of complete disassembly to get to it.

If it held the date and time with the battery removed it's still good.


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## gumbyy (Mar 11, 2009)

Wrench97 said:


> Yea 4 ohms is not a battery.
> A lot of the eMachines models I've seem are pretty well buried almost to the point of complete disassembly to get to it.
> 
> If it held the date and time with the battery removed it's still good.


That's scary if true of my laptop. Maybe Emachines didn't show it in the service manual because it's so deeply buried that nobody could ever service it.

I just wanted to make sure the laptop was still viable before I buy a new hard drive for it. If the CMOS battery dies, does that make the computer totally unusable, or could I still maintain the date and time just by never removing the main battery? (I almost never do, anyway, because I almost always use the machine plugged into AC power, with the battery inside. But if there's a power outage, that means my date and time get screwed? Hmm... not if there's still a charge in the main battery, I'm guessing...


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## Wrench97 (May 10, 2008)

It'll be fine, if the battery fails the bios will go back to default settings(most likely is on default now) and the date and time will revert back to when the bios was first written, you'll just need to reset it.


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## roodap (Mar 2, 2012)

if you can identify the bios chip look for 3V powerline when both battery and mains removed. you must find the cmos battery located close to the bios chip.


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## gumbyy (Mar 11, 2009)

Wrench97 said:


> It'll be fine, if the battery fails the bios will go back to default settings(most likely is on default now) and the date and time will revert back to when the bios was first written, you'll just need to reset it.


But will existing files retain their dates? If they lost their dates it would be chaos trying to backup.

And if the CMOS battery fails but the main battery (the rechargeable lithium ion battery) still has a charge, the date and time will remain current and accurate?


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## roodap (Mar 2, 2012)

usually it will show the bios setup screen at the start if the cmos battery is in trouble or if date time and all varies considerably from last settings when powered off.


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## gumbyy (Mar 11, 2009)

roodap said:


> if you can identify the bios chip look for 3V powerline when both battery and mains removed. you must find the cmos battery located close to the bios chip.


Thanks, but I'm not capable of taking apart the whole laptop and putting it back together again. If it's not easy to access I won't even attempt it.


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## roodap (Mar 2, 2012)

it is not easy to dissemble the laptop and put it back together.
do not attempt it.
you probably don't need to open out whole laptop. 
eMachines D520 | eMachines D720/D520 Series Service Guide
service manual for your laptop is there in the link.
read it . yo will get idea how to replace /find the cmos batery


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## joeten (Dec 4, 2008)

This is what I find as the motherboard and in the picture (enlarged) there is what would be the cmos battery as far as I can make out Acer MB.N0902.001 motherboard - $195.00 : Buy motherboard, Laptop motherboard replacement shop!Beyond Tech please note I posted this purely for the picture.


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## gumbyy (Mar 11, 2009)

roodap said:


> it is not easy to dissemble the laptop and put it back together.
> do not attempt it.
> you probably don't need to open out whole laptop.
> eMachines D520 | eMachines D720/D520 Series Service Guide
> ...


Thanks, but my whole problem, the reason why I posted, is because I already read the service manual and it doesn't tell you or show you where the CMOS battery is located.


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## koala (Mar 27, 2005)

gumbyy said:


> But will existing files retain their dates? If they lost their dates it would be chaos trying to backup.


The existing files on your hard drive won't be affected. Any files created _after_ the BIOS reverts to its original date will be incorrect though.


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## gumbyy (Mar 11, 2009)

joeten said:


> This is what I find as the motherboard and in the picture (enlarged) there is what would be the cmos battery as far as I can make out Acer MB.N0902.001 motherboard - $195.00 : Buy motherboard, Laptop motherboard replacement shop!Beyond Tech please note I posted this purely for the picture.


Hey, thanks for that motherboard pic, Joeten. Sorry I haven't been back to this thread for a while. I guess it would be pretty difficult to get to the motherboard to replace the battery.


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## gumbyy (Mar 11, 2009)

koala said:


> The existing files on your hard drive won't be affected. Any files created _after_ the BIOS reverts to its original date will be incorrect though.


Thanks Koala.


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