Connecting 12V DC Motor to Two 9V Batteries

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Discussion Overview

The discussion centers around the feasibility of connecting a 12V DC motor to two 9V batteries in series, resulting in an 18V output. Participants explore the implications of this setup, including potential risks and alternatives, within the context of practical applications and motor specifications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants suggest that connecting a 12V motor to an 18V supply is generally not advisable, but there may be exceptions depending on the motor's specifications.
  • One participant inquires about the motor's specification sheet and its rated current, indicating that this information is crucial for determining compatibility.
  • It is noted that the motor is rated for 3V to 12V and operates at 15,000 RPM, with its application being an air blower.
  • Another participant points out that running the motor at 18V could cause it to attempt to operate at 22,500 RPM, which may exceed its power rating significantly.
  • Concerns are raised about overheating if the motor is run continuously at 18V, suggesting that a PWM control system could mitigate this by averaging the voltage to around 12V.
  • One participant questions the necessity of using two 9V batteries, proposing that a single 9V battery could suffice given the motor's voltage range.

Areas of Agreement / Disagreement

Participants express differing views on the safety and practicality of connecting the motor to an 18V supply. While some caution against it, others suggest potential methods to manage the situation, indicating that no consensus has been reached.

Contextual Notes

The discussion highlights the importance of motor specifications and the potential risks of operating outside recommended voltage ranges. There are unresolved questions regarding the specific current rating and duty cycle of the motor.

Who May Find This Useful

This discussion may be useful for hobbyists, engineers, or students interested in motor applications, battery configurations, and the implications of operating electrical components outside their rated specifications.

cyril joel
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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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cyril joel said:
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? :smile:
 
berkeman said:
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? :smile:
The motor is rated 3v to 12 v 15000 RPM and medium size the application is an air blower
 
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.
 
cyril joel said:
i have to connect a 12v dc motor can i connect it to two 9v batteries in series

cyril joel said:
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?
 

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