Quick post for something to add to your toolkits. Occasionally a CMOS battery will go out, especially on an old machine that’s been sitting around a while. They last several years but not forever. I’ve seen some ancient machines that use some weird battery packs but most motherboards use plain old ‘CR2032’ lithium batteries. You can be a sucker and go buy them locally for way more than what they’re worth or get a few dozen of them now for about fifty cents each if you need one.
The above link has ten packs, twenty packs, and fifty packs. If you look around you can find them in hundred piece blister packs. Personally I wouldn’t buy that many unless you work with a lot of old computers. They do go bad, not quickly but they do.
They’re also handy to have around for other things. Small kitchen scales, alarm clocks and other devices use them either as their power source or as a memory backup. You can also replace old gameboy game cartridge batteries with them.
Just had to use one for a computer I ‘refurbished’ for a ClearOS server build I just did. Don’t get caught unprepared!