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Hi guys, as its mostly us guys who use these machines,

I am glad to say that my CPAP unit, supplied by the NHS is a Remstar and not Resmed as luckly there is a fairly simple 12 volt DC lead available for about 20 quid. However, whilst I was searching for details of it I came across an article by someone who had just bought one. He found that there wasn't a lot to it and all the component parts could be bought from Maplins, he even listed their part numbers and how to do it. I bought and assembled them and now use it in the van. I am lucky to be in the electronics game but there is only a modicum of electrical knowledge required.

The main thing with this lead is that although its a straight 12 volt DC supply, you need to eliminate any electrical interference getting into the CPAP unit and so it utilises ferrite beads on both ends of both wires to do so.

Should anyone else be interested I will see if I can get the details agaim.

Dave

There are a number of CPAP Forums that suggest that because ResMed is an Australian Company, the 12v DC Cable is Positive Earth and that all that is required is to take a standard 12v lead, cut the wire and reverse it.

I have seen a number of photos showing ResMed CPAP Units being used this way. However, as the machine is not my own and the proper 12v cable is only £49, two weeks without EHU at £3.50 per night has paid for this cable.

From what I read on the ResMed Website, their 12v cable reduces or raises the output voltage to 12.5v, no matter what the input voltage is.

Actually, from experience of some busy campsites and their electrical mains packing up, sometimes overnight, I personally have more confidence in my own 110Ah battery than any caravan park's set up.

Hi Lobey,

If I had a ResMed I think like you I would opt fot the safest option. Their DC power supply lead seams a bit more involved that the Respironics (REMstar) that I have.

The people who should be able to give you advice are the Tech Bods who Service them every year at your local Department of Respiritary Medcine or such like.

Dave

Hi Dave, Our puppy pulled my CPAP off the bedside table and it stopped working, so I took it back to the Respiritory Technician who told me it would have to go back to the UK Suppliers.

Anywhere I have looked for information on the ResMed DC side of things, there is no mention of the polarity. The only place where I have seen information was on a American Sleep Apnoea Website Forum but now that I want it again, I cannot find it. Typicle!!!

Like I said thougfh, there is very little difference between the power usage through an inverter and through a 12v Converter.

For my S8 Escape, using a Converter Cable (12v) at a treatment pressure of 6cm H2O and a current draw of 12V DC, it would use 10Ah over an 8 hour period.

For the S8 Escape, using an Inverter at a treatment pressure of 6cm H2O and a current draw of 12V DC, it would use 12Ah over an 8 hour period.But that includes a 50% Safety Margin.

So I could possibly use less power through an Inverter than through the Converter but my Inverter is not a Sine Wave one as recommended by ResMed and I would be loathed to invest in a sine wave inverter just for the CPAP.

Hi Lobey, I too wasn't sure what the polarity was to my machine so I cheched the output of the mains unit with my multimeter, job done -  Live to the centre and negative to tho outside terminal. Yours may well be different but a multimeter that you could use is only £6.99 from Maplins, and similar ones I've seen for even less these days.

Dave.

Hi Dave, I have a multimeter, but I got all the information I needed for my CPAP Machine on a CPAP Forum like this one.

They have a lot of members using different machines, that go camping and sailing and therefore need 12v power to use their machines.

I think that the only downside to using a CPAP when away on tour is that you cannot use the Humidifier part as 12v is simply not powerful enough.