It took me half a day to get mostly dead RTC and RAM backup batteries from two desktop and six notebook computers. In 50% of cases the batteries already started leaking so they would soon kill the computer.
I didn’t replace the batteries with new ones as I don’t need another ticking bomb in my old machines. Now I have to access BIOS setup every time I want to use the computer. That’s the only drawback but I can live with it.