I'm fairly sure that Lithium-Ion batteries (the modern kind that is used literally on every device) are designed in a way that you can charge the batteries as many times as you want without automatically counting a cycle. If you charge the battery from 80% to 100%, only about the 4th or 5th time will it be the same as if you charged from 0% to 100%. I recommend charging as soon as you come home that way the battery won't drain when it's sitting at home. Also, the phone won't charge more if it's already charged, so don't worry about that.