It is now two months that I have this external battery. I bought it to recharge Mount HTC ONE M7 when I travel on my vacation, but I was never able to carry two full charges when the phone battery is only 2300mAh. I will however be able to do a little more than two full recharges. Initially I thought maybe the external battery required a time calibration / break but now I tell myself rather than either I received a defective model that quickly runs alone or no 5200mAh . The best I managed to get a full charge is more a refill to about 60% knowing that there remained about 15% of the phone battery charging. Note that I always fully recharge the external battery before use (to extinction of 4 LEDs). If the product is practical, so I am a bit disappointed with his performance.