A couple of times, I have let the TC75 run out of power and left it dead for a day or two. And both times I had difficulty getting the TC75 to power on again.  I plugged the TC75 in and it would not turn on.  By the time I checked it, the battery was 100% charged, I removed the power cord and tried to turn on the device. It would not power on. They only way it would power on is if I removed the battery and put it back in.