I believe it is because they used they own quick charging technology instead of the proven Qualcomm 3.0 technology. While driving to the A&M football game I used a Qualcomm quick charger 3.0 in my car. I noticed about half there my phone was not really charging much on the car display. So I reached down to pick up the phone it wasn't charging and was so hot it was almost untouchable. I placed in front of the air conditioner vent and it comes down quickly. I then used the Samsung quick charger and it charged rapidly with no heat at all. My phone had never over heated or had any trouble but this was the first time in 2 weeks I charged it with another brand of charger other then the Samsung charger. It appears the decision to attempt to use a different quick charging technology is causing the battery to over heat to me. Which also explains why they didn't notice it in trials because I am relatively sure the people using the phone prior to its release where likely using Samsung chargers so it never over heated. Hopefully it is just the battery as they believe because I love this phone. Unfortunately I am nervous it could be related to the charger more then the battery. Let's go hope they can do some type of firmware update to enable Qualcomm quick charging in the future.