Motherbaord Battery

if there is an app, then it likely keeps tabs on the system clock and if it is consistently off and inaccurate, then its time to change the motherboard battery, also known as the cmos battery.

to this end, you can monitor the clock yourself, instead of downloading some kind of program that may or may not work, may or may not be spyware, may or may not be a bot.

The battery does two things, it keeps the real-time-clock (RTC) oscillator oscillating and supplies enough power so the CMOS settings are saved in SRAM (on most motherboards).

More commonly today the bios settings are saved in NVRAM and the battery just keeps the RTC working. In many laptops, the battery has been replaced by an ultra-capacitor since it's cheaper to do that.

On some PCs the CMOS passwords are stored in SRAM, so therefore the battery effectively saves the password. (most modern laptops use NVRAM and an encryption chip to store power-on password, but I digress)

Since the battery is typically a lithium cell, with a life of usually 3-10 years, there really is no need to monitor the voltage, as in most modern PCs, a dead battery just means the time is wrong upon reboot, but the OS will fix that itself, usually.

There is no indication that a battery is going flat, nor does it affect anything.

Either there is a 'setup-error press F1' on boot or incorrect time/date at bootup, or not.

The only possible indication would be if you noticed the clock was losing time after a long power-off duration, then perhaps the battery is a bit weak. While you could remove the cell and measure it, it's just as easy to swap it out.

It is generally a CR2032 3v Coin Battery which costs a few $.

Assuming that you have a ATX M'Board here these generally speaking do not go flat unless you turn the power off at the wall or unplug the unit. While the Computer is plugged in and not running the ATX Power Supplies enough Current to keep the Real Time Clock running and the saved settings in the CMOS from being lost.

This also doubles as what is required to turn the computer on as it causes a Ripple to appear on the 3v Line which depending on the state of the unit either turns the system off or on.

The symptoms that you will see when this battery is flat will be error messages telling you to press F1 to continue or whatever to enter Setup because the Real Time Clock has stopped/changed time dramatically and the settings in the CMOS have been lost.

If you are getting Error Messages like that replace the battery.

Col

You can change the CMOS battery and not loose any data or even clock cycles.

On a desktop system, the 5 volt standby power from the power supply maintains the CMOS and clock as long as the power supply is plugged in and the rear panel power switch (if present) is turned on.

Just open the case and change the battery.

While few monitor utilities check the CMOS battery, most of the BIOS PC Health screens will show the battery voltage.

As stated, the first indication of a weak CMOS battery is usually lost time after a power outage or after unplugging the computer. But, I have seen a number of systems with weak CMOS batteries that develop unusual hardware symptoms on bootup. When I see a system acting "strange" on boot, the first thing I check is the CMOS battery voltage.

Chas