Battery on CMOS fault

[steve wilson]

Hi,
I have a computer at work and the battery keeps failing on the CMOS. I've replaced twice in the space of a year. Is it most likely a faulty motherboard?

 

[Steltek]

Could be.

Probably a stupid question, but were are you getting your replacement batteries? Have you tried a different brand?

 

[steve wilson]

I got the batteries from a local jeweler. But the original battery in their came with the computer and that must of been from a different supplier (well 99.9999% sure). This will be the 4th different battery going in.

 

[sm625]

If you could insert an ammeter in series with the battery, you can find out if too much current is being pulled from it.

How much time does this computer spend without power?

 

[steve wilson]

If you could insert an ammeter in series with the battery, you can find out if too much current is being pulled from it.

How much time does this computer spend without power?

It is always plugged into the mains, but the computer is probably switched on for around 2-4 hours a day, Monday to Friday.

I have no experience with an ammeter ... how would I go about that?

 

[sm625]

If it is always plugged into the mains then it shouldnt matter. Even when the PC is off, the standby circuit should be providing power from the mains. The mains power should be setting and holding the voltage at the battery terminal, preventing the battery from discharging at all.

 

[Steltek]

If it is always plugged into the mains then it shouldnt matter. Even when the PC is off, the standby circuit should be providing power from the mains. The mains power should be setting and holding the voltage at the battery terminal, preventing the battery from discharging at all.

True. It makes me wonder if the power supply might be malfunctioning.

 

[steve wilson]

True. It makes me wonder if the power supply might be malfunctioning.

Since the rest of the computer is working fine, is it not more likely the mobo?

 

[sm625]

I'm not sure how it could malfunction to produce such a failure. Even if the powered on voltage to the cmos circuit was lower than the battery voltage, the battery would jsut discharge until the voltages equalized. We know this voltage cannot be too low or else it wouldnt work at all. If the power supply to cmos was too low then the computer would cease functioning as soon as you pulled the battery out or until the battery died.

 

[mlc]

if you've gone through several batteries, and they always fail shortly after putting them in... and assuming they are the correct type of battery, then i would think one of 2 things to be the problem

1) motherboard circuitry at fault... how old in the board? do you see signs of age (bulging caps, etc?)

2) there is a short between the board and the case standoff... pull the board and make sure they all line up with the install holes, etc..

 

[steve wilson]

OK thanks for the advice... will try that out.