Two 300RPM 12V DC motors connected to arduino motor shield r3 power supply

Other Hardware Motors, Mechanics, Power and CNC
1

I have two 300RPM 12V DC motors connected to arduino motor shield r3 that is mounted on arduino uno board.
Problem is my motors runs very slow some times not even running.

After googling I found I need to use external power supply. I did supplied 9 volt dc power to arduino motor shield r3.
But still motor is running very slow what could be the issue.

My other questions.

When supplying power to arduino motor shield r3 via external power supply pins do I need still need to provide separate power to arduino uno board via power jack.

Can I use 9 volt dc for arduino uno board and another 9 volt batter to arduino motor shield r3.

Is single 9 volt batter enough for running two 300RPM 12 dc motor.

My circuit.

2

Is single 9 volt batter enough for running two 300RPM 12 dc motor

I think you've already found the answer to that question.

To cope with voltage drops on the shield, you'll need about a 15 volt supply, at whatever current the motors need when stalled.

3

I have two 300RPM 12V DC motors connected to arduino motor shield r3 that is mounted on arduino uno board.
Problem is my motors runs very slow some times not even running.

After googling I found I need to use external power supply. I did supplied 9 volt dc power to arduino motor shield r3.
But still motor is running very slow what could be the issue.

My other questions.

When supplying power to arduino motor shield r3 via external power supply pins do I need still need to provide separate power to arduino uno board via power jack.

Can I use 9 volt dc for arduino uno board and another 9 volt batter to arduino motor shield r3.

Is single 9 volt batter enough for running two 300RPM 12 dc motor.

My circuit.

4

A battery pack of 6 AA or C batteries should work.

5

Why mess with batteries at all? Get a good 15V@5A wall wart that can run your motors. The UNO is rated at 20V input max so you should be OK with 15V. https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2078320_-1

6
7

You have told us nothing about the motors that's useful other than they are 12V.

We need to know the stall current rating, and preferably the full rated load current/power
too. Any information please, even a photo would help to see how big they are.

If they are 12V why are you thinking of using 9V at all?

Small 9V batteries cannot power motors or servos, they just cannot produce
enough current, give up on the 9V battery notion completely!

8

If they are 12V why are you thinking of using 9V at all?

FYI,
3S is 12.54V fully charged
2S is 8.74 V fully charged.

I don't know why he was using a smoke alarm 9V PP3 battery. That's way off in left field.