solved this already, it seems TA who sent me this unit had it flashed with wrong Images. so FYI  if  DVT unit is flashed with  MVT 19.0  OS version the following behavior  can be observed. when device has totally empty battery it will say first " battery too low , shutdown device " if you leave it on AC charger it will end with  "Charger Disabled" resolution is to  reflash  with DVT 19.0 Only images and then the device will be able to charge a totally empty  battery. adviced TA to not reflash the device anymore as well :-)