Author Options:

How to wire 12v dc case fan to 1x9v and 2xAA batteries? Answered

Hi there!

I'm planning a project using a 12vdc case fan to inflate a plastic bag for a school project.

I have located a 9v battery clip and a 2xAA battery holder and was wondering how i'd go on with wiring them together.

I was also wondering if it was possible to reverse the polarity, thus creating a vacuum effect. If so i'd like to have a 3 prong switch to control the case fan.

I appreciate any help you could provide me. Thanks!



Best Answer 6 years ago

I worry the 9V in series to the 3V to equal to 12V will have the power to inflate
a large plastic bag.
You need a Double Pole Double Throw switch to reverse the fan.
See the circuit.... Hope this helps. . . . . . A

Thanks for your reply!

I've done some more research and I've ended up connecting the 12v dc fan to an ac-dc adapter and it's working out good. In reversing the fan would i also need a double pole double throw switch in this case?

Also, would connecting another fan decrease the speeds of both? The one i have now is 0.1A and the ac-dc adapter is 1000mAh. Thanks!

Yes.....Always need a DPDT switch for reversing a DC device.

No problem adding a second fan to a 1A ( 1000ma ) wall wart.
Two fans only use 20% of the adapter power.


A case fan is rather weedy for suck/blow functions - you'd better have a very light & thin bag for this to work.
A 9V and AAs shouldn't be mixed, use all the same type in a pack.


Thanks for your reply!

Yes I will be using a very thin plastic bag. similar to the type that you use to bag produce at the grocery store. I'm going to experiment with other thicknesses also. Is there any other low cost fans that you could recommend? I just used a case fan because it was readily available. I've switched from batteries to an ac-dc adapter. Any concerns with this method?

You should look at the fans/blowers intended to inflate air mattresses. It would fit your purpose better, and they usually can be found in 12 volt versions.

The adapter is a good move, but suck/blow is usually on the powerful side if it's not weedy.