Failure is due to battery failure caused by mobile phones. AT & T used cell phone battery is not original, but they are worthy of 3.6V/270mA businesses nickel-cadmium rechargeable batteries, poor quality, will fail after about a year to use. Battery failure is usually a battery pack in one or two cell battery internal resistance increases, while measuring the voltage across the battery pack is normal, but the area of ​​the load, the voltage will quickly fall, the phone automatically turns off. I had to combine the two into a damaged battery intact battery pack. AT & T has the phone clear instructions

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