Not having any luck at all on the net finding the information I needed to build a cable, I’ve finally broken down and paid £26.00 (including shipping) to buy one.  I’ve wanted a DC cable mostly so that I could a) go camping without the need to have a tent pitch that was powered (extra cost), and b) be able to power my CPAP should we have a prolonged power outage at home (fairly low risk of this, but a risk none the less).

Click on the image below to see the full sized one.  This is a page from the manual that came with my cable.

Basically, should someone have posted something like:

To make your own Respironics Shielded DC Cord, Part number 1001956, you will need the following:

• 1 x 2.1mm (5.5mm outside) X 15mm Coaxial DC plug
  Such as: Maplin’s Part number HH61R (www.maplin.co.uk)
• 2-3m of suitable wire for a max of 7amp DC (depending on your CPAP model)
• 2-4 Clip on Ferrite suppressors, such as Maplin’s part N89AB
• 1 x 12VDC cigarette plug, suitable for upto 7amp DC

The construction of a DIY Respironics CPAP DC Cable, model number 1001956 is quite simple.  Wire up the cigarette plug to the DC plug that will go to the CPAP, be sure to wire the tip of the cigarette plug (Positive 12V, I suggest a multi-meter to confirm this in your car or battery pack you intend to use) to the centre connector of the 2.1mm DC plug.  Wire the negative to the other remaining connections. 

At both ends of the cable, as close as possible to each of the plugs, leave not much more then 3-4cm of cable “exposed” put a couple of the clip on ferrite RF suppressors.  These are quite important as they will ensure the dc is free of RF (Radio Frequency) or Electromagnetic noise.  These, should they get into the machine, could cause damage.  You can likely get away without them, but frankly for the extra £5 it will cost for these it’s worth saving your £500+ CPAP.

That’s all there is to it.  I really hope people find this useful, for some reason there has been a black hole of info about these cables, and I’m not sure why.

**DISCLAIMER** This information has been provided purely for theoretical and personal information.  I will not, nor can not, be held responsible if you are not competent enough to build this simple cable and end up damaging or destroying your CPAP.  I’m pretty sure in the wonderful lawsuit happy world we  live in it’s also most likely a violation of your warranty to attach a home made DC cable to your CPAP machine.  You have been warned, don’t come crying to me if you blow something up, also, don’t ask me to make one for you.  These are beyond simple to make.