Using CPAP machine on battery power

PB from AB

New member
I am trying to figure out what size inverter to use to power a CPAP machine when boondocking. We have a 2008 Winnebago View 24J with 250 watts solar. I am awaiting my new Progressive Dynamics PD9245CV 45 amp power converter and will be installing 2 new Trojan T105 AGM 6 volt batteries. We don't really plan on using the inverter for much else, maybe a hair dryer but certainly not at the same time. I was thinking about the plug in style inverter, not hard wired in. Anyone have any experience with a CPAP. It says it draws 1-1.5 amps.
 

smiller

2008 View J (2007 NCV3 3500)
1.5 amps @ 120 volts is 180 watts so allowing some safety room a 250-watt or higher inverter would run the CPAP, and for this type of device you should probably get a true sine wave converter (somewhat more expensive but a good idea for certain types of devices.) The hair dryer will draw much more current (> 1000 watts) and it probably wouldn't be a good idea to get an inverter sized for the hair dryer if the primary purpose will be for the CPAP, the reason being the larger inverter will not only be much more expensive but it will also likely be less efficient powering small loads.

Regarding plug-in or hardwired, even a 250-watt inverter will draw more than most cigarette lighter plugs can supply (safely at least) so hard-wired is really the way to go, and of course it would be mandatory for a larger inverter. You will want to use a wire gauge large enough to run the inverter with a minimal voltage drop and you can use an online calculator to tell you what size you need (depends on distance from the power source.) You should size it for 15-20 amps and ideally you don't want to drop more than a few tenths of a volt.

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Hosh

Navion 2018 24J
If your CPAP machine has a humidifier and a heated hose, you'll save lots of battery by turning the humidifier off.
 

sprint2freedom

2008 NCV3 170ext
There are a few possible cases here:

Case a) If the amperage you're quoting is at 120V, then your CPAP machine draws 120V * 1A~1.5A = 120~180 watts.

Case b) If the amperage is at 12V, then your CPAP machine draws 12V * 1A~1.5A = 12~18 watts. That's a pretty significant difference.

A cigarette lighter plug-in style inverter will be limited to drawing about 15 amps at 12 volts, which is 180W. With case a), you're right at the limit for using that type of connection. In either case a hair dryer is simply not an option unless the inverter is hard-wired.

As mentioned, your CPAP will very likely require a pure sine-wave inverter. Something like this would be a good choice:
https://www.amazon.com/Samlex-Solar-PST-300-12-Pure-Inverter/dp/B00H8N97E2

For case a), running a 120~180 watt appliance for 8 hours overnight would require between 0.96 and 1.44 kWh. That's a fair amount of power. A pair of T-105s taken from 100% to 50% SoC over ten hours is good for about 187 Ah, or 1.12 kWh.

While you may be able to run a hair dryer for brief use from those batteries with a large enough inverter, most people here would recommend against it as the inverter and wiring would be a large investment (hundreds of dollars) for a single purpose use.

I don't have a CPAP but from reading about them, the humidifier is the largest current draw, and it may not be running continously so the numbers on the nameplate may not be reflective of actual power consumption.
 

Kevsuda

Active member
I built a power station box for a buddy to use his CPAP while camping. I had him buy the 12V adapter instead of going the inverter route. A 35 AH battery gets him through the night (just barely) without the humidifier on. He bought a flexible 50 watt solar panel to charge it throughout the day. He was super concerned about needing the humidifier, but the first night he only lasted about 3 hours before it shut down from low voltage. After that he was willing to try without the humidifier and it got him through the night and he had no physical issues without it. I believe most of these machines are 19-ish volts which you can buy a converter for. That would be my first suggestion and would be much cheaper and likely more efficient.
 

sprint2freedom

2008 NCV3 170ext
I believe most of these machines are 19-ish volts which you can buy a converter for. That would be my first suggestion and would be much cheaper and likely more efficient.
It's a good suggestion but I would only do so with great care- don't try powering it in a way you don't fully understand. These machines are a lifeline for their users and if damaged can be very expensive (financially and in terms of lost sleep) to replace.
 

Old Crows

Calypso 2014 View Profile
You might like to grab your VIN # and call WBGO to find out exactly what you have as an inverter. Here's an '09 brochure..... inverters were optional in 09, and I suspect optional in 08s. Could be you have the option.... if OEM it would be 300W.

Also, the power output depends on battery capacity and their state of health. Theoretically, you probably have enough power to last 8 hours (or what ever) if you don't have any battery uses. YMMV.
 

NYBobbo

Member
for what it's worth:
I use a CPAP, depending upon weather conditions I use a heated hose, I always use the humidification which is adjusted to what I like (like a thermostat it only turns on when needed). I think using a CPAP or any other medical device should be a priority for those that need it. In the past I have woken early to turn on the gen because the house battery was projected to be getting low, or ran the gen all night.

There are self contained battery packs made for CPAP machines but the cost (3-4 hundred) is crazy considering we have batteries and generators already.

My OEM batteries have gone to crap in 1.5 years and I'm putting in Lifeline AGM 6 volt 220amp hr in the very near future. The largest demand I have figured is my CPAP and the propane heater running through the night. The OEM batteries never really had the reserve needed to do this.

For me I feel that I needed to have a working solution. If it's for a friend visiting, guess it depends on how good a friend they are< lol
 

autostaretx

Erratic Member
If the CPAP is vital, i'd carry along a second (perhaps not pure sine) inverter in case the main inverter failed.

... and forget the hair drier until you've got shore power. Towels (and air-dry) work.

--dick
 
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Kevsuda

Active member
It's a good suggestion but I would only do so with great care- don't try powering it in a way you don't fully understand. These machines are a lifeline for their users and if damaged can be very expensive (financially and in terms of lost sleep) to replace.
This adapter he purchased was from a CPAP company and specifically listed as compatible with his machine. It was this one. https://www.cpap.com/productpage/resmed-airsense-aircurve-10-external-power-supply-cord.html And I may have some of my terms wrong. I know he was still using water, so maybe it was the heater turned off and not the humidifier. The instructions in the optional $450 battery pack he could of purchased also instructed to turn off the function for the pack to power the machine through the night. It has worked for a couple trips now without issue.
 
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SailingOn

New member
My experience:
A 300 watt inverter, plugged into a 12v outlet in the bedroom, would not run a 100 watt fan more than a few seconds.
Placed near the battery, with a short length of heavy gauge wire, then a long extension cord (110v section) to the bedroom, the same inverter runs two 100 watt fans and a small TV reliably.
There's an elegant explanation for this, but the point is
you'll want to keep the 12v supply short if you're going to plug anything important into the inverter.
 
I am trying to figure out what size inverter to use to power a CPAP machine when boondocking. We have a 2008 Winnebago View 24J with 250 watts solar. I am awaiting my new Progressive Dynamics PD9245CV 45 amp power converter and will be installing 2 new Trojan T105 AGM 6 volt batteries. We don't really plan on using the inverter for much else, maybe a hair dryer but certainly not at the same time. I was thinking about the plug in style inverter, not hard wired in. Anyone have any experience with a CPAP. It says it draws 1-1.5 amps.
Lots of threads about this on Expedition Portal forum...I'd suggest searching that forum via Google.
 

PB from AB

New member
Thanks for all the useful info on using my CPAP machine with an inverter. I have lots to think about now. Also have definitely decided not to even think about using a hair dryer with inverter.
 

HarryN

Well-known member
Medical devices bring up interesting discussions about reliability and redundancy.

While perhaps not ideal, you RV has a generator, so worst case you "could" run off of it for a night or two if the inverter fails and it is really needed.

I am not sure about your particular unit, but some generators can be setup to auto-start to replenish the battery pack if it runs below a predetermined voltage. Even a 30 minute quick charge (in the bulk mode) during the night might be enough to get you by if the pack is running low. It isn't ideal, but not the end of the world either.

Lifeline batteries can accept fairly high charge currents during the bulk stage - don't be afraid to install a 75 amp or larger charger.
 
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cacaw

Well-known member
If the CPAP is vital, i'd carry along a second (perhaps not pure sine) inverter in case the main inverter failed.
I was thinking along the same lines. For a mission-critical appliance, I'd be tempted to invest in one of the Goal-Zero or Anker battery banks. They consist of a full-sized lithium battery and are self-contained with both 12V and 120V outlets and can be recharged in many ways.

Budgeting for electrical power, I'm not sure that I'd want to mix my crucial medical-support power in with my inconsequential entertainment and comfort power.
 

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