Have an issue with your computer booting up? Do you sometimes have to boot it twice to get to behave? Does your clock have an issue keeping time? The culprit could be a weak CMOS battery.  Now, I’m not talking about a laptop battery, but a tiny little battery inside your laptop or desktop that allows your PC to remember setting or the time even when it is turned off.

It looks like this:

The CMOS ( complementary metal oxide semiconductor) battery  maintains time, date and your hard disk and configuration settings. They are attached directly to the motherboard and cannot be changed without opening up your PC.

When the CMOS battery goes bad you may find that the date and time settings keep changing. Sometimes it will reset to the original manufacture date of your motherboard. Your Bios settings may also change and that can prevent your PC from booting or cause you to have to boot it multiple times until it finally comes up. On some PCs, you may hear a constant beeping sound. Or it may just not book up at all. Sometimes when it appears that a PC is dead, the issue is really just the CMOS battery.

There’s a possibility you may see a CMOS error when you boot up.  There may be an easy fix for this. Try leaving your PC on for a day or so to recharge the battery. If you don’t use your PC frequently and turn it off between uses, the battery may not be receiving enough of a charge.

If that doesn’t help, it’s time to have a professional look at your device to see if the battery is the issue. The battery itself is inexpensive (less than $5), but the labor might be expensive depending on the place you go to. If you’re tech-savvy, you could attempt to open up the PC to change it yourself (be careful, that may void any warranty on your device). And always make sure to unplug your PC before working on it.

Your user’s manual should show you the location of the CMOS battery. But unless you are really comfortable opening up a PC, I’d probably leave it to a professional.