Charging it for 15 hours is crazy! Why do that when it will be charged fully in a hours or so?
When I took mine out of the box it had like 70% and I just used it and charged it that night while sleeping.
Do not let the battery and charging interfere with your enjoyment of the device , just use it and charge when you want to do so. No need to dwell on the battery or charging.
It's not necessary to charge 10-15 hours when first used. Unlike common Ni-CD or Ni-MH batteries, most lithium ion batteries are activated before leaving the factory. Due to their low self-discharge, it’s unnecessary to charge lithium ion batteries for such a long time when new. Lithium ion batteries are ready for use when the charger indicates so, and they will reach their best capacity after 3 or 5 cycles.
It's not necessary to charge 10-15 hours when first used. Unlike common Ni-CD or Ni-MH batteries, most lithium ion batteries are activated before leaving the factory. Due to their low self-discharge, it’s unnecessary to charge lithium ion batteries for such a long time when new. Lithium ion batteries are ready for use when the charger indicates so, and they will reach their best capacity after 3 or 5 cycles.
Most iDevices I receive have about 80 on them anyway. I just start using them and then charge overnight. These batteries can't be hurt from what I've read.