Will a 12v car battery safely work for 9V 3.5A device?
No, a 12V car battery will not safely work for a 9V 3.5A device.
The device requires a voltage of 9V and a current of 3.5A, while the battery provides 12V. Connecting a device designed for 9V to a 12V power source can potentially damage the device due to overvoltage.