SM-T320 randomly fatal crashes then bootloops for a bit
You are right about the battery connection; try this trick: 1. Hold down power button for 10-15 sec while keeping it plugged in 2. When the tablet powers down and shows charging indicator, remove the cable and it should simulate removing the battery.

There was a constant error with sec_fuelgauge which is a process that regulates battery on hardware level. Check to see error at line 955 and so on later.