can i use a 9v battery as an external power supply for arduino , which controls 4 dc motors , six sensors
If you mean one of those little rectangular things, then I wouldn't recommend it.
btw i have two external rechargeable batteries of 12volts each and im only using the 9volts one only to power up the arduino board , is this possible>>>???
The 9 volt can supply he arduino alone. The other batteries should power the motors. The 9 volt will not be enough to poer both.