Recently, one of my computers was giving me trouble after some rolling blackouts from the summer heat. Density keeps increasing with all the condos/apartments being built and rebates are being given out to promote electric cars. Meanwhile the grid is not being improved, so the system cannot take much additional load.
Anyway, my computer was turning itself on when it was plugged into power and I was getting setup errors about the time not being set correctly. I had always heard and read that your computers CMOS battery is how your PC keeps track of time when you turn it off. So it seemed pretty obvious to me that it had a dead CMOS battery. But the interesting part was when I observed that if it remained plugged in, it started up normally and kept the correct time. So then the light bulb went off in my head that when the PC is connected to power, the battery is not necessary even if the PC is not running.
When I Googled my realization, I discovered that my new understanding was correct. Even when the PC is turned off, it still draws a small amount of current to keep track of time and other settings. This is similar to the way some electronics draw a small amount of current to power a LED light even when the unit is off. It you never unplugged your computer and you never had a power outage, you could just as well run your computer without a battery installed.
It’s cool that after all the years of being around computers, I could learn something new that is so basic. It goes to show you that sometimes in life generalizations and learning without doing are not good enough.