12vdc to 18vdc 2.3 A

Discussion in 'General Electronics Chat' started by 55 dude, Aug 16, 2013.

  1. 55 dude

    Thread Starter New Member

    Aug 16, 2013
    Hello guys i'm new to the forum. I found on a google search and what i'm wanting to do is buy/build a converter for my sleep apnea machine so I can use it in my car when I travel. Its normally plugged into 110vac and transformed to 18vdc at 2.3A , guys i'm a novice at best electronic buff and do have some understanding of it and any help would be great. Thanks in advance.
  2. ian field

    Distinguished Member

    Oct 27, 2012
    Most discount stores these days have low power inverters (12V to mains) but unless you pay a fair bit for them, they're likely to be pretty much square-wave output - check your machine can work with that before paying out.

    At the current you want 18V at, stepping up from 12V isn't trivial, but there are some chips that can take the edge off it from the likes of LT & Maxim. The real hard work is designing the inductor.

    You could always contact the manufacturer and ask whether it would come to any harm if you tried it on 12V.
  3. #12


    Nov 30, 2010
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
  5. crutschow


    Mar 14, 2008
    So you are planning on sleeping in your car? I hope it's not while you are driving. :rolleyes:
  6. SgtWookie


    Jul 17, 2007
    18v @ 2.3A is 41.4 Watts; with 75% conversion efficiency translates to about 55 Watts of input power, or approximately equivalent to operating one halogen headlamp. If you used a 12v to 120VAC inverter to power your supply, you'd get another 80% to 75% efficiency hit on top of your supply, so around 74 Watts of input power would be required. Attempting to operate your C-PAP machine for any extended period of time will leave your battery too discharged to start your engine again; at the least will be very hard on it. Automotive batteries fall apart quickly if they are deeply discharged.
  7. Ramussons

    Active Member

    May 3, 2013
    You may be able to get a Laptop Power Adapter for Car Use that gives 18 V DC.