L298N with two 9V

So, I'm trying to use an L298N to operate 4 motors, a single 9V doesn't give me the power that I need so I want to know if there is any risk in connecting a second battery in series. I'm also using the driver to power up the arduino using the 5V port.
Specs:

Chuck the 9V battery in the bin and use six AAs.

Better still, ditch the 298 and get a FET bridge.

^^^ 'wot he said.

Except the bit about chucking them in the bin.

Put those 9V batteries back in the smoke alarms where they belong.
Or recycle them responsibly.

Lol whats the problem with 9Vs?

Only suitable for very low power circuits. Anything with motors is not a low power circuit.

No problem with them, where they're suited, like powering smoke alarms, or 1970s pocket radios.

The L298 is an ancient and inefficient motor driver. 2 to over 4 Volts of your battery voltage will be wasted as heat.

Pololu makes a wide line of modern MOSFET output motor drivers. Get a driver that will handle the stall current of your motor.

What is the advantage of AA over 9V?

More current

Ok, thank you. I will try that.

Way more current... 9V PP3-sized batteries are good to 50mA before they start to
droop, most AA's can handle 1A. Good branded rechargable AA's can handle even
more, and LiPo packs can handle way more than that (10 .. 200A).

Motors use lots of current, it seems to always confuse newcomers that different
things require different amounts of power (think bike v. car v. train - lots of orders
of magnitude variation is commonplace in electronics, you need to do the maths
every time...)