I'm not sure of the definitive answer but you are using power just displaying light/clock or when phone is in sleep mode as phone is still connecting to mobile towers etc. You will only have no drain if you power off using "slide to power off".I generally go through 1 charge per day on my phone . If you turn phone off completely following a full charge and you have a drain on the battery then I think you'll need to check your soldering job- sometimes there's just a little touching from one lead to the next.