You need at least a 7v for most fans. Some will work will 5v though. Most requir 7 to start spinning. Don't see the point in a 9v baterry. Why not use a computer psu?
kryptobs2000 Reviewed by kryptobs2000 on . computer fan question I got 2 computer fans, and I powered them up with gameboy 6 v adapter. but most people say that you need a computer power suply to power them. so is adapter not suitable for this ? will adapter overheat and burn if it'll be ON for 24/7 ? Rating: 5