There are two ways to plug this unit in while driving. one is to directly connect the charger to the unit's AC port.  the other is to connect the charger to the main cable.

 

the manual said to use the second method (charger to cable, cable to mount). But by doing so, I can't do anything while the unit is plugged in (e.g. enter addresses...etc), since I did not do any bypass.

 

Is it really harmful to directly connect the charger to the unit while traveling?