Powering a 24v fan with a 9v battery using a voltage multiplier

Discussion in 'The Projects Forum' started by Rudy Melo, Jun 3, 2015.

  1. Rudy Melo

    Thread Starter New Member

    Jun 3, 2015
    Hello, this is my first post and my electronics knowledge is limited. Is it possible for me to power a small fan rated at 24V 0.14A with just one 9V battery and without a transformer. I've been learning about voltage multipliers and have somewhat successfully turned 9v dc into more voltage but I've been told that once the output is hooked up to a load the voltage drops a lot...is this true and does that mean it couldn't work? Would the battery run out faster than usually. Also, what is the best way to turn a small voltage dc into an ac square wave?
    Thank you for time
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Please post a schematic of your "somewhat" successful cicuit so we can see what you have done. One way to boost battery output voltage is with a power oscillator (usually squarewave) driving a few stages of a Cockroft-Walton voltage multiplier. With only a 9V input, this will not be a very efficient circuit.

    Why do you want to do this? You are correct, increasing the voltage means the battery will be drained much faster. Power equals volts times amps, so you fan is drawing 3.36 watts. At 9 V, you would need 0.373 A for the same power level, plus more power to cover the inefficiency of the conversion circuit.

    planeguy67 likes this.
  3. SgtWookie


    Jul 17, 2007
    9V "transistor" batteries would be a very expensive and inefficient way to power a 24v fan; inside these batteries there are actually six (seven for some "industrial" batteries) 1.5v cells that have a relatively high internal resistance, wired in series.

    You'd be much better off to simply use a bunch (16) AA batteries wired in series. Radio Shack stores used to sell a battery holder that would take 8 AA cells for 12v output; two of those filled with fresh batteries would power your fan for a reasonable amount of time; roughly 10 to 12 hours.
  4. Rudy Melo

    Thread Starter New Member

    Jun 3, 2015
    Thank you for your replies. I used a 555 timer in astable mode and set the output square wave through a simple RC differentiator. At first I was just getting the usually sharp peaks jumping from positive to negative voltage but after messing around and checking again with my oscilloscope, somehow I ended up with a fairly clean square wave that was about 3.76V max, -3.76v min, 7.52 Vpp. I used a cockcroft-walton multiplier and after cascading three multiplying stages using whatever diodes and caps I could find I got about 11.5V DC. I know there were way better ways of doing this and my reasoning for wanting to power this fan is simply that I had it lying around my parts and I thought I could learn some knew concepts by trying to power it from something such as a 9V. On EEVBlog (youtube), I just saw how dave uses a microcontroller in a voltage doubler circuit and I found some schematic for 555 voltage doublers that make way more sense