I was at work, minding my business, and then, around 10:00, I hear...
Yes, the beep that alerts me to the fact that the current battery has about 15 minutes of life left in it before I am completely dependent on the 25% hearing that's left in my right ear for all sound.
Normally, I would just replace the battery. But the other battery, for some reason, has decided Not To Charge anymore. So I have one decent battery. Which is now charging beside me--at home.