If you are receiving unplug detection event at the moment of ignition it could indicate that device is not properly installed since unplug detection is triggered when device does not detect external voltage. We would recommend verifying the connection as the device should not be losing external power source at the moment of ignition.
Is also possible to read vehicle battery
If you are referring to battery capacity (%) of the non electric vehicle, then no, it is not possible to read such parameter.
But regarding electric vehicles, depending on the model it is possible to receive parameters Battery Level on ALLCAN300 adapter.