cmos not holding memory even after new battery is installed

June 29, 2016 at 16:17:59
Specs: Windows 7, 4GB
My HP small form factor pc won't hold cmos settings even after replacing with 2 new cmos batteries. I would make settings, save and exit and after a reboot would notice that the cmos checksum is invalid and all the settings lost. What could be the problem and solution please? I double-checked also to make sure the batteries were well-seated, yet nothing comes of it. Thanks

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#1
June 29, 2016 at 17:45:29
Presumably the CMOS battery polarity was correct (yeah, silly question I know).

You could try this:
Turn off, remove domestic power, remove main battery if at all possible. Hold power off-on button down for 20 seconds to discharge the motherboard components. Restart and put settings right, See if a further restart keeps the settings. Bit of a long shot but at least it is easy to try.

Always pop back and let us know the outcome - thanks


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#2
June 29, 2016 at 17:57:19
When changing the battery, you should always unplug the power cord 1st. Make sure it's the correct one - CR2032 is the most common (20mm diameter x 3.2mm thick). There are other similar batteries that are the same diameter - CR2025 or CR2016 for example - but the thickness is different (2.5mm & 1.6mm). If you use the wrong battery, it may not make good contact with the socket.

Did you check the batteries with a voltmeter to make sure they're good (3v)?


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#3
June 29, 2016 at 21:32:03
Sometimes solder joints break. If that happened with the battery holder it wouldn't charge the cmos circuitry. I don't know how old your computer is but that's more likely to happen with age.

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Related Solutions

#4
June 29, 2016 at 23:37:03
Is there any jumper to "Clear CMOS/Password" on the MB?
Is it in the correct position or accidentally removed?

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#5
June 30, 2016 at 05:58:14
Unfortunately checking battery voltages with a voltmeter off load doesn't tell you very much. When a load is applied to a poor battery they can then fall to a very low voltage.

For the above reason I always check flash lamp 1.5V batteries (for example) with a bulb applied whilst I'm taking the reading. Dud ones often show the full voltage when off load because with no appreciable current flowing there is no voltage drop across their internal impedance either.

Always pop back and let us know the outcome - thanks


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