My laptop Samsung bought in 2010 (and still going strong) at boot up toggled F2 at start up, selected 80% max charge, at times it lights a light when off line. Discharges battery and charges again when back to mains power, this happens about twice per month. One day I'm going (F2) to give it a real boost and see how long the batteries last without mains power.
Never happened with my Commodore 64