This is my first Arduino project, so I'm still learning a lot
I have four 3-6V motors and to L298N motor drivers with an Uno Rev3. I was wondering if one 9V battery would be enough for this?
Thanks:)
no. 9v battery is not sufficient. use 6xAA cells or wall power. Arduino is NOT a power supply.
Do you know how much power will be going to each motor? I don't need it to go very fast but have some speed
The 9v PP3 more or less guarantees the answer will be "no", and you should put it back into the smoke detector you stole it from before your mother finds out. Pretty well anything you can think of will be a better choice. Perhaps 2x 18650, or even one. Note that the regulators on your Uno are pretty poor and those on the motor drivers may be no better. You may be a lot better off with a separate and more efficient 5v converter driving everything. Note that Bluetooth is 3.3v and it is good practice to have a 1k/2k divider on Arduino tx line. You may already be aware that you will also need to disconnect Bluetooth while uploading your programme.
Ok I'll get it back in the smoke detector quick 
. So 2x18650 would be enough for all the components? I'm guessing the more power I push through the hotter the regulators get?
Also I am quite new to electronics sorry, is it a 1/2k voltage divider? Would this just lower the voltage going to the BT module?
I will look into a 5V converter also, would this connect from the battery to the Arduino directly and nothing else I assume?
Thanks:)
You can't use the 5V from the L298 to power the Arduino, instead connect the Vin pin directly to the batteries
Oh ok, I think I saw somewhere that that was possibly, would a 9v battery be ok directly connected to the arduino?
To the Vin pin, Yes.
Vin needs to be between 7v and 12V
If you are using the two 18650 batteries in series to power the motors, you can connect that to Vin
Would two 18650 batteries be enough for the motors and the board?
Yes
Awesome, like Nick suggested, would I want a separate 5V converter instead of using the regulators on the drivers and arduino?
The best way to answer that question would be to measure the current the entire prototype project consumes with a DMM or an AMP meter.
Let's say your project is using a 9V supply and requires 5 amps (4 motors plus power for the rest of the system), 9X5=45 watts. Now lets say you want to power the system for 24 hours. A 9V, 5Ah battery would last one hour. You'd want a big battery to last 24 hours.
BTW, What is the purpose of the project?
No, as I said DO NOT use the regulators on the L298 to power the Arduino, connect Vin directly to the batteries.
This is a work project I have been set, to create a functional RC car. We're currently in the design stage and we aren't actually able to have any of the components atm:/
I think we're only concerned with having the car last for 1-2hours, would that denote only a 9v battery then?
I misunderstood that sorry:) So the batterys to the arduino vin and to both the driver 12v's?
Try not to exceed 10 volts directly to the Arduino.
There have been many cases where exceeding that eventually blew the boards regulator.
AA battery packs are usually considered fine for most simple purposes.
Lifespans of battery packs will vary on the motor load.
Those appear to be GEARED so you may find it a little shorter.
LIPO of similar such as your 18650 will give you a better life and are at least rechargeable.
A 9V battery like one of these,
The C rating or charge rating let you know, basically, how much current the battery can consume and supply.
Ah I see, so the voltage might be enough but the current is no where near what I want
Correct.
We could know for sure if you could post a data sheet for the motors or a link to a website
