# Dc motor

Hello i am abeginer i have to connect a 12v dc motor can i connect it to two 9v batteries in series meabs a total output of 18V.

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berkeman
Mentor
Hello i am abeginer i have to connect a 12v dc motor can i connect it to two 9v batteries in series meabs a total output of 18V.
Welcome to the PF.

In general, the answer would be no. But in some cases it might be okay. Do you have the specification sheet for the 12V DC motor?

Also, you can buy modules to convert your 18V supply down to the 12V needed for the motor. What current is the motor rated for? What is the application?

Welcome to the PF.

In general, the answer would be no. But in some cases it might be okay. Do you have the specification sheet for the 12V DC motor?

Also, you can buy modules to convert your 18V supply down to the 12V needed for the motor. What current is the motor rated for? What is the application?
The motor is rated 3v to 12 v 15000 RPM and medium size the application is an air blower

CWatters
Homework Helper
Gold Member
The motor would try to run 50% faster on 18V than 12V. So it might try and go 22,500rpm

The power absorbed by a propeller is proportional to rpm cubed (http://www.eaa62.org/technotes/prop.htm) so unless you reduce the size of the load (fan) you might be asking the motor to deliver more than three times it's rated power...

(22500)3/(15000)3 = 3.4

If it's an intermittent duty cycle, it might work, but any extended run it'll probably suffer from overheating.... Depending on the control system you have for it, you could run a PWM (Pulse width modulation) at about 66%, and it would give you an average of 12V.

If you're thinking of the typical 9V battery in most multimeters and electronics, etc, I think battery life would be very short too.

i have to connect a 12v dc motor can i connect it to two 9v batteries in series

The motor is rated 3v to 12 v 15000 RPM and medium size the application is an air blower

So your really hooking up a 3-12v motor? Why not just use one 9v battery?