This phone ticks me off, it stops charging when it reaches 100% and does not resume charging unless the phone is un pluged and then reconnected. I plug the dam thing in to charge over night and when I wake up it says "100%" and when I unplug the charger it imediately drops to critical orange. Once the phone reaches 100% it stops monitoring the battery and the battery discharges without any concern that the charge had droped off. Some greeny programer thinks I should wake up in the middle of the night and unplug the dam phone to reduce my carbon footprint. Idiot doesn't realize I am not his his grid and my solar panels don't produce any6 carbon. Anyhow the firmware for charging the phone needs updated to continue monitoring the battery after full charge and resume charging. Samsung says that Google writes the program for charging and nobody at Verizon or Samsung would admit any problem at all but this is my second |tratosphere and both phones did the same thing.
While I don't argue that it would be nice if it recharged after the level went down while still plugged in I would wonder if you need a new battery as battery gets fully charged (you say it shows 100% charged when you first check it) and when unplugged it shows critical orange. Have you noted how long a charge lasts when it's not plugged in? If it only lasts a couple of hours (about how long it would take from when it reaches full charge to when you wake up) I would try a new battery. If the charge lasts longer perhaps charging at a different time (such as during the day or the evening) and then unplugging it when full might be a better idea.
mine is always at 100% when i unplug it in the morning after waking up, i plug it in around 1100pm and wake up between 8 and 9 am, it ALWAYS reads 100% when i wake up, this makes me think that the phone firmware does do this and as suggested above you simply have a piece of bad hardware be it the phone (unlikely at this point since you have had it replaced already) or the battery (last time i had a warranty replacement it did not include the battery, i would expect that policy to be the same now) or maybe even the charger.
