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Can you power a 12v case fan with a 9v battery? Answered

If you can't, then where can you find a 12v battery connector ? I looked everywhere and couldn't find it.
BTW, I am trying to build this https://www.instructables.com/id/Simple-Bots-Scrub/?



No problem at all - The Instructable is using 'computer fans' which would normally be powered off the 12V line of a PC, so that's what the author's doing.
Some fans have an extra wire which would be used for speed sensing. If yours have, just ignore it.

Many small DC motors will run on less than the rated voltage, though not as fast nor with as much torque. I have a 180VDC motor that would turn when connected to a 12v car battery. Hook up the motor temporarily with a 9v battery and a couple of wires. If it spins fast enough for the application, go for it.