Hello,
I am working on a science fair project where I'm supposed to build and code an arduino 4 wheel car.I'm using 4 DC Motors ( 3V-->6V ) , Arduino Mega,Arduino L293D Motor Driver Shield and 4 AA Batteries.
I am having trouble with the motor driver shield :
1-I am not sure where I'm supposed to connect my 4 DC Motors
2-Is my battery source enough
3-Should I connect another battery source for my Arduino since it is not booting from the motor shield.
Thanks 
4 x AA batteries is not enough to drive any motors with an L293D. 6 x AAs might do it but that will depend on what motors you're trying to use.
The motors connect to the terminal pairs marked M1, M2, M3 and M4.
Steve
Look at the DRV8841 Dual H-Bridge Driver IC, it is a nice chip but needs about 8 volts or so to operate. There are many others. Look for a MOSFET H bridge chip and you will be surprised how many there are. The reason for the MOSFET output is there is minimal voltage drop and less heating. You could build one from discrete components if you like. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
Are 2 Lethium Batteries 18650 Enough (3.7V) each ?
2 x 18650s in series to give 7.4V is worth a try. But the L293 still can't drive much current and you still haven't said what motors you are trying to use.
Steve
hey steve,
I already stated im using 4 DC Motors that can operate on 3 to 6 Volts

LearningArduino30:
hey steve,
I already stated im using 4 DC Motors that can operate on 3 to 6 Volts

But I (and the L293D) want to know how much CURRENT they need. Too much CURRENT is what will ruin the motor driver and/or battery.
Steve