Help with 4wd rc car

I’m new to arduino and am trying to make an RC car with mecanum wheels, I have each wheel attached to a DC motor using the tamiya twin motor gearbox kit ( and if I just wire them directly to a battery (9v) it works fine, but when I attach it via the arduino uno and the adafruit motorshield, it just budges a little (wheels completely off the ground floating so the only resistance is the weight of the wheels), if I attach an external power to it via the “ext power” ports on the motorshield, I still only just budge off of the 9v battery, so I decided to up it to a higher power source, a battery to my dewalt drill, 18v (I have no idea about milliamp hours or even what milliamp hours even means regarding this, but with the 18v battery it still only JUST moves when it’s on the ground, and I know this must be bad for the arduino/motorshield/everything, but I was really curious. Why can’t I get this thing rolling?

Are you running it from the Arduino power port or the EXT port? Also what does your code look like?

I have the power running from a 9v battery into to the power on the arduino (the barrel plug or whatever it’s appropriate name is) and then I’ve been plugging in other power sources to the EXT port on the shield. The code is very preliminary as I just wanted to test out that everything worked before I started trying to figure other things out. Also, is it damaging the equipment if I use my 18v battery through the shield? I ordered a 9.6v battery ( that I’d like to run the dc’s off of, I assume that the 9.6v wouldn’t damage anything and should run everything fine right?

#include <AFMotor.h>

AF_DCMotor motor1(1); //creates motor 1
AF_DCMotor motor2(2);
AF_DCMotor motor3(3);
AF_DCMotor motor4(4);
void setup()
  motor1.setSpeed(1000); //originally I had this set at 255 because I thought that was the max, but then I saw
  motor2.setSpeed(1000); // a video where a guy had his at 1000 so I figured, more is better in this case

void loop()

Hi, a circuit diagram will help and if possible a picture of your project. The diagram can be as simple as a scan or picture of a hand drawn if you don't have a cad drawing. Show us in particular your power connections to arduino and shield.

Tom.. hope to help... :)

Here's an image of my little car attached to the 18v dewalt battery, it's VERY simplistic, just the DC motors going to motor 1-4 on the shield and then the dewalt battery going to the EXT power on the shield, and my 9v battery to the arduino.

Is that motor library up to date? Also set speed has a range from 0-255.

I had it at 255, but that wasn't working so I moved it to 1000 because I saw a video on youtube while trying to look up how to use it where a guy had his at 1000, I'll put it back to 255, but that still doesn't fix my problem. And as for the library, I got it from adafruits website yesterday so I'm assuming it's up to date.

Edit: moved it back to 255 but still nothing, I did notice that if it's plugged into the computer it has more power though, I've also stopped using the dewalt battery because each time I test it with that the h-bridges get REALLY hot and I know it can't be good for it. If I have it plugged in via USB and have the 9v battery powering the Uno it seems to spin the wheels fine until there is any resistance, such as placing it down.

That's a bad idea, don't have both battery power and the USB plugged in, it could damage the arduino. You might have a bad motor driver.

Added: I did some reading on the adafruit website, and it turns out regular 9V batteries are no good, they are ok for the Arduino, but not the motor shield. You can use your other power supply to power the motors, just be sure to take off the jumper on the motor shield.

sorry to be dumb but: what does it mean to take the jumper off the motor shield and how do I do that? I hate not knowing what people mean on this forum! hopefully I'll be up there one of these days talking with the big dogs, understanding the arduino/electrical lingo.

The jumper is the blue tab under the middle chip.