I got home from a trip today, where my phone had been sitting at a low charge for a bit. I managed to get it a high enough charge to hold out, but it died by the time I was in my house and hooked it up to the charged. The Amber LED is not lighting up like it is charging, which has me worried. I have switched between different USB cables, and also from the wall to a USB. Is it normal for the LED to not light up if the battery is absolutely drained? Also, any USB mini cable should work, correct?