Yes what we talking, car battery? phone battery? toothbrush battery?
If its a pc cmos battery then its easy just unplug pc, remove side panel, you will see a small circular batter, pop it out with a small screw driver, replace with new battery, done.
If its a laptop batter, then it just unclips at the back and new one clips in.
If its laptop cmos, then you have the nice task of taking the laptop appart.