Sorry I'm sure this has been asked before but I always charge to 80% unless I'm going on a long journey. Recently I had an epiphany. the car has 10% battery reserve (21.5 KWh useable) it doesn't use so is there any need to charge at 80%? why is the option there? manufacturer must think it's necessary? anyone cleverer than me have an informed opinion? am i wasting my time?