Powering a CPAP

I'm estimating about 9 amps input at 12V for 8 hours is about 72 amp-hours consumed overnight.

Average single 100 amp-hour second battery would give you one night only.

Due to lead-acid inefficiencies, you need to put about 90 amp-hours in to replace the 72 out.

Getting 90 amp-hours in in a day's driving depends on your charging system and the driving time. A 25 amp dc-dc charger may do it, but typically they taper off as the battery comes up, so maybe not 4 hours driving as the numbers suggest, but perhaps 6 hours.

Depending on chosen battery, a higher amperage dc-dc charger could be used, eg 40 amp, but not all batteries can take 40 amps charge. If you can use a 40 amp charger then clearly charging (driving) time would be less.

Depending on your alternator (temp compensated, ECU controlled or plain vanilla) and auxiliary electrical system (cabling size) maybe less driving time, maybe more. HKB Electronics can advise more on that.

Cheers

Anthony
Res Med have a unit called a 90W DC Converter which you run off 12v. It steps your 12v supply up to 24v to run the CPAP. My wife requires a CPAP and we the converter when travelling and I have found that she can use it without the humidifier without getting dry a throat and it only draws about 1 amp(1 amp 8 hours sleep= 8ah). With the humidifier connected it draws 6 amp (48ah per night) and runs my 100ah right down over night. Without the humidifier I have no problems even with the frig and lights running.
We got ours from the chemist where she brought the Res Med CPAP from and I think it was about $150 and money well spent as on longer chasing 240v.
Tell your mate to check their web site as I recon that its a lot better way of going than using a 240v inverter
Murray

Most manage without using the humidifier when travelling at a great power saving.

Hi Anthony,

Firstly, I'm not a tech guru - just an experienced CPAP user. By the look of the power pack it looks like your mate's machine may be a S9 or S10. These devices do NOT require a PSW inverter, so your mate might be able to save some loot there. If it is an S8, it DOES require a PSW.

Battery usage will vary considerably, and is dependent on a few variables, such as room temp, humidity, whether the humidifier or climateline (heated hose) are on, and their settings. Also, of a lesser concern is the actual pressure and ancillary settings of the CPAP itself.

Here's a rough guide for my machine: Pressure=auto, EPR=2, Climateline=25 degrees, Humidifier=5.0.

In winter, camper temperature 20 degrees uses 45-50Ah.

I can't use my machine (S9) without the humidifier because my throat dries out too much. I can do without the Climateline, but get rainout if I don't use it.

I use the 12-24 converter when camping.

My husband uses a ResMed CPAP machine and a ResMed Humidifier. It is possible to buy a ResMed converter the plugs directly into a 12V outlet and steps the power up to the 24V requirement. He often uses it without the humidifier when we are away. He also uses an 300watt pure sinewave inverter at times. We have found that it makes very little difference to our stored power. Remember it is 24V. He uses the batteries in our camper or caravan. Visit the ResMed shop and they will be able to help too.

Di

I've been using a S9 CPAP for 5 years now and camp quite often and remain independent of 240volts. I use the 12/24volts converter mentioned earlier which incidentally comes with its own Cig Lighter with switch. I connect it to a 35 Amp hour AGM battery (cost $110) I attached a female Cig Lighter socket put it all into a soft esky type bag which keeps everything nice and tight. I then have freedom to 'sleep' where ever I like in the tent. (I also take it into motels/hotels as well, without worrying about how far the powerpoint is from the bed) Also no problem running long leads from the car to the tent

This system will last me 3 nights say 9 hours per night without re charging the battery. I then simply connect the battery to via a cig socket, drive thru the day say 5-6 hours and the battery is fully charges. Works a treat.

I agree with Murry but I do get the dry throat problem but you can buy a dry throat spray at the chemist & that works great & if you use the dry throat tooth paste that also helps

Thanks to all who have taken time to reply.

I can't truly appreciate the debilitating effects that sleep apnoea has on people as I'm not a sufferer. Not just the person with it, but also those that live with them.

My mate said "if I can't get this sorted, I can't go - I just won't be able to stay awake!" Apparently, he is at the extreme range of the condition.

Hopefully the info provided will help others who are hoping to go camping with their machines.

Cheers

Anthony

I recently purchased a DeVilbiss auto cpap sleep cube that works off 12v or 240v

I'm on a mobile so can't print specs but I operate it off our vans single 100 amp sealed battery without problems. It doesn't seem to use much power.

On 12v though the humidifier won't work. I don't use that anyway.

HI Anthony, my wife has a cpap machine - we just purchased the 12v power unit for camping - has been excellent - looks like there are plenty of optioned resmed brand on the web. Ps it was cheaper than buying the inverter. Regards Chris

I found the humidifier generally to be a PITA. The water has to be emptied out and refilled each setup, and if some gets splashed into the tube the gurgle will keep you awake all night. I just got used to operating without it to reduce the power consumption, as shown above. To use the convertor in place of the AC unit is a must for reasons already covered.
Just make sure he is comfortable with the setup and isn't tempted to skip using it...would spoil the trip if he had a stroke or didn't wake up!