I don't know when you wake up but that could be like 14 - 15 hours that you mentioned which possibly isn't all that bad (plus the extra 10% you had remaining). Personally I want to see what it's like when you unplug it at 8am, not at 5pm the night before since I can't see any good reason not to leave the phone charging over night anyway.
If you then manage to get about 10 to 12 hours or so then there probably isn't much issue. Granted you weren't using it while asleep so the battery shouldn't drain overly quick but I wouldn't want to use your test as an example of a days use.
Thanks for the info but. If I was you I'd just have a car charger too if you like to use GPS...I can't see any reason not to.
The GPS thing in the car was only to do a quick test, literally 10 mins. I need to buy a new car charger with micro USB, but I just made a note that I had done this because I knew it would affect the battery.
Anyway, we'll see what today brings.