Laptop motherboard question; Failed BIOS battery = no video?

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Laptop motherboard question; Failed BIOS battery = no video?

Postby FiberBundle » Tue Sep 15, 2009 11:31 am

I am drifting ever more heavily into servicing old laptops and I'm pleased to report that the similiarities between laptop motherboards and desktop motherboards are many.

The BIOS on the motherboard uses a button battery just like on desktops and they also fail. But getting at them is a little more complicated than your average desktop.

I have a Toshiba L25-1193 laptop and the thing boots up sounding like it is POSTing (fan starts), but nothing shows on the video. I have checked out the BIOS (CMOS?) battery and found that it is dead. It is a ML1225 rather than a CR1225 and this means that it is rechargeable.

A couple questions that I'm sure apply to motherboards generally:

Can I replace this rechargeable battery with a regular nonchargeable battery?

Could this failed battery have anything to do with the lack of video? There is the onboard video (of course) and also the external video and neither one shows any display.

Any and all tips and clues would be appreciated.
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Postby Copper » Tue Sep 15, 2009 1:24 pm

Can I replace this rechargeable battery with a regular nonchargeable battery


NO it will explode, because the laptop will try to recharge it

it is possible the problem with the video is caused by the battery failing
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Postby FiberBundle » Wed Sep 16, 2009 12:40 pm

Copper wrote:
Can I replace this rechargeable battery with a regular nonchargeable battery


NO it will explode, because the laptop will try to recharge it

it is possible the problem with the video is caused by the battery failing


Are both observations consistant with your experience with desktops, or do you have some laptop experience? I have never seen a desktop motherboard with a rechargeable battery, they have all been the classic CR2032. And I've always seen a POST, even when the CMOS battery is dead on a desktop, but my experience is limited to 300Mhz CPU's and above. I remember seeing only one or two plug in type batteries on a desktop motherboard and never attempted to get such boards going.

Anyone else care to comment?
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Postby evasive » Thu Sep 17, 2009 1:07 am

Some desktops will not boot at all with a dead cmos battery these days. Many laptops will not boot at all if the cmos battery is dead.

So, in short: get a new ML1225 even if it is more expensive and harder to find. It costs less than a new L25-1193 laptop i think.
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Postby c327 » Tue Dec 01, 2009 3:54 am

Wouldn't the laptop battery be special and need to be had from the lappy manufacturer? If that is the case the cost will be way more than if it could have been purchased from a local store.
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Postby TriAngle » Mon Dec 14, 2009 2:13 pm

Yes, they are quite pricey.
I have ordered several of these rechargeable laptop batteries from VIVO Technologies, as I can't locate them locally:
NEW Maxell ML1220 CMOS M-Board Battery AHL03014003
$5.98 plus S/H = $11.83

* This is a ML1220, not a ML1225 I am referring to.

The ML1225 is very hard to find; non on Amazon or eBay.
Check with Toshiba.

I have also noticed that some laptops have a rechargeable CMOS battery that slips into a connector, and, also, they have a 2 or 3 battery pack that connects with a connector to the motherboard.
Go figure.

Be sure to check that your laptop doesn't have both types installed.
Replacing just one may not get the job done.
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