20% to 80% Charging

When I look up 20% to 80% charging, I get pages of distractions.  This happens these days with just about any subject I try to look up so I am not surprised.  What I am interested in is charging something like an iPad to less than its full capacity.  A while back, I read a couple of articles about how the batteries in a tablet can last longer if they are not charged to 100%. When I try some search programs, I get pages of irrelevant links.  That is not just with searching about ways to limit the charge.  I often get links to music and maybe concert appearances of a band or musician with that name.  I can sometimes improve my wording to focus more on what I am looking for.