Phillips and Devilbiss, the latter no longer made unfortunately both work on direct 12v.
Resmed use 24v so need a special cord/step up power supply to run on 12v and in doing so use more power than a native 12v unit. Running a small inverter to supply 240v may be an alternative. Also be aware that Resmed an Australian Company has an agreement with the ACCC or whatever its called now to allow price fixing for its products in Oz. You can buy Resmed machines, accessories and spares cheaper overseas than here in Oz.
There may be other smaller brands that run directly on 12v but I'm not aware of them.
I have found the most power efficient method is to charge via 240 volt inverter. The cpap needs 12v not 13.5 so the 12 volt device still has to do transformation of voltage. With an efficient 240 inverter I found it used half the amp of the 12 volt connection.
That is my experience , and as you probably already have a 240 inverter I would be saving you the cost of the 12 volt adapter.
I dont have a CPAP but have a friend that does. If you give us the make and model then we can see whether it is 240v or 12v and advise you appropriately. If it is 240v then you may need to run an inverter. Somewhere on the machine it will indicate the power usage in watts but generally they seem to use about 50W. Allowing for inefficiencies in the inverter that equates to about 5A so if you use it for say 7 hours then you will have used 35Ah from your battery that you will need to replace. Plus of course the power from your lighting etc. So unless you have a generator you will need appropriate sized batteries and a method of recharging them.
A 100W inverter should be ample and turn it off when not in use as they draw power even though not being used.
My other half uses a Cpap, a Resmed brand. As yet, I have not worked out its power usage because we have mostly travelled in hot weather and used 240V power for aircon, or freecamped just overnight where our batteries have coped with the Cpap use. This Cpap has come with an adaptor to run from a 12V plug. This Resmed Cpap has a humidifier which requires power as well. The operating instructions state to not use the humidifier if running from 12V power, which has been our experience.
I have a Devilbiss Blue (DV64) - runs natively on 12v & also came with an adaptor to run on 240v which is handy when house sitting/caretaking. Uses very little power even wth it's humidifier. It is now 6 years old & still going strong. When I heard they were ceasing production to focus upon oxygen machines during covid, I bought another the same for when this one eventually dies. If you were to find one languishing on a chemists shelf somewhere you could do a lot worse for a great machine for an RV and/or at home.
Like you, and others above, I have a Resmed 10, and as you know it runs on 24V internally and comes as standard with a 240v AC to 24v DC power adapter.
If you don't have a 240v supply available the options are to run it using the normal 240v power supply via an inverter, or buy their optional 12v to 24v converter. At $180 the DC converter is ridiculously expensive like all CPAP stuff, but I bought it anyway for the sake of getting the most out of my limited battery capacity, because using an inverter involves converting 12v DC to 240v AC and back to 24v DC, so more than double the losses of a simple step up from 12v DC to 24v DC. Note also the higher consumption on standby as below.
Having limited battery capacity (100Ah Lithium) I was interested to see how much my CPAP used so I did some measurements, all at 12v DC nominal.
Standby (on DC adapter): 0.4A Standby (on AC adapter and 600W Inverter): 1.1A Fan only: 1.5A Fan and humidifier: 4.5A Fan and heated tube: 5.5A Fan, heated tube and humidifier: 6.0A
Things to note about these results are: 1. If used for eight hours a night with full function it will use approx. 48Ah of battery capacity, but on fan only 12Ah. 2. By far the most power is taken by the heated tube and humidifier (itself a heater), neither of which are essential to the basic operation and are comfort features, so switching one or both of these off can save up to 75% of the power consumption. 3. If left in standby for the rest of the day it'll consume another 6.4Ah of my valuable battery capacity if on the DC power supply, or 17.6Ah if run through an inverter, so worth completely unplugging it when not using it, no matter which option you use.
Hope that gives you some food for thought...
-- Edited by Mamil on Tuesday 2nd of May 2023 10:58:37 PM
I had a philips, went in to get and adaptor, it was 8 years old, they said there is a recall. I looked into it and had a new one within 6 months. not bad. the new one takes the adaptor. so have a brand new one now for nothing really.
