Operating on DC while camping

[archangle]

If you'll tolerate one more question, do these units handle fluctuating power very well? I've noticed some fairly large voltage swings when I'm in RV parks, and have even had to repair my fridge once when the power "sagged" too much. I suspect a lot of RV parks don't really have the wiring to handle the new 50 amp crowd when they're full. My RV provides a 12V outlet (powered by the house batteries, which are automatically charged in the park). I suspect it might be wise to power my unit via 12V in the parks as well. Any opinions? In my experience, the state parks have reliable power. It's the private ones that'll fry your appliances.

Well, I'm not going to buy you a new CPAP if it blows up, but I'd expect the M-series blower to be very resistant to voltage fluctuations. The brick is rated 100-240V 50/60 Hz, and external power bricks of that vintage tend to handle weird voltages pretty well. A surge protector wouldn't hurt.

If you really need a humidifier, get one of the external ones and set it lower than the blower unit so the water would have to run uphill. https://www.cpap.com/productpage/fisher ... ifier.html or one of the unheated Respironics units.

[Guest]

My RV provides a 12V outlet (powered by the house batteries, which are automatically charged in the park). I suspect it might be wise to power my unit via 12V in the parks as well. Any opinions?

yes use the 12 v power whenever possible but wait til rightangle approves it

[Guest]

archangle wrote:
Pay no attention to the troll with no userid.



I'm not. When someone starts ragging on another's post, no useful information follows (and I skip on to the next).

i guess thats not considered ragging on anothers post

[Super Iridium]

I just finished using my CPAP on a two-day camping trip, and I noticed two things.

First, there is no problem at all using the blower on DC without a humidifier -- mostly because you have no idea how moist the air gets inside an enclosed space like a tent with two or three people breathing in it all night. Even with the fall weather and the outside air being relatively dry, I didn't notice any dryness in the air going into my nose from the machine.

Second, once you remove the humidifier AND power the blower with DC current directly, you will find that you get a LOT of hours of use from a deep-cycle battery. I have a 35 Ah battery, which is a decent size for my purposes (camping, back-up at home). I had no idea that they put a battery as large as 600 Ah into a boat (or is it actually more like a yacht?!), but a battery that large should honestly last you for weeks of use without a recharge.

Good luck!

[emt_271]

OK, here is the math that one needs to calculate how long something runs on the battery:

Lets start with the 200watt inverter - not that I'm advocating it here, since the Respironics power supply is a switcher, and probably wont like the MSW power. All of the inverter calculations assume a max 200 watt load to get the minimum time. A lower load WILL result in longer run times.

Take 200watts, at 12 volts is 16.67 amps of draw on the 12 volt batteries (200 watts divided by 12volts), 16.67 amps will run 5.4 hours on a fully charged 90 ah deep cycle battery (90 divided by 16.67). I would expect the inverter to drop out somewhere about 5.2 hours on low volts though.

I cant seem to find a spec on the M series power supply, but the math above works either way. Just plug in your numbers. The M series 120v converter will have it's output power rating listed on the outside of the brick. Deep cycle batteries, unlike a car battery provide a steady 12v dc almost to full discharge (thats why they are really costly for a given size).

[JohnBFisher]

To borrow from a previous post ...

If you (or someone you know) can use a few tools, you might find the following Battery Backup Design helpful to create your own battery backup system:

viewtopic.php?p=449334

This design puts the battery in a battery box, it keeps things securely fastened, it includes a float charger, and makes the whole arrangement much safer. You can then connect battery to a power inverter and plug the CPAP into the inverter.

By the way, if you have a Resmed system you will probably want an inverter. The Respironics systems can run off DC with just a special cable. Yes, yes, there is a DC converter for the S9, but's it's pretty pricey:

https://www.cpap.com/productpage/DC-Con ... hines.html

This arrangement is good for a home battery backup system. It's portable enough for car/trailer/RV camping. It's as good as a portable system, such as for air travel. But it does get the job done at home. And it keeps the cost down, while keeping the whole arrangement as safe as possible.

Hope that helps.

[Guest]

search for a post titled another battery option
no tools or assembly are required

[archangle]

By the way, if you have a Resmed system you will probably want an inverter.

However, if you have a ResMed S8 system, an inverter may damage the humidifier, so be careful. S8 humidifiers can't take a MSW waveform from an inverter.

[Guest]

By the way, if you have a Resmed system you will probably want an inverter.

However, if you have a ResMed S8 system, an inverter may damage the humidifier, so be careful. S8 humidifiers can't take a MSW waveform from an inverter.

doesnt the s8 run on 12v

[BudSky]

By the way, if you have a Resmed system you will probably want an inverter. The Respironics systems can run off DC with just a special cable. Yes, yes, there is a DC converter for the S9, but's it's pretty pricey:

https://www.cpap.com/productpage/DC-Con ... hines.html

At $85 the ResMed DC convertor is really not that bad- is is very similar to many laptop DC convertors and they are typically in the same price range or more.

I have a lot of experience with invertors and can say the pure sine wave ones are the best in many cases. I have noticed many electronic devices do not work properly off modified sine wave invertors. For example- I have a huge assortment of Ryobi 18V cordless tools at my camp, which has no commercial AC. When I charge the Ryobi batteries off an MSW invertor they take about twice as long as they do off my pure sine wave invertor to get to full charge. Likewise a microwave oven takes a lot longer to warm something off MSW. They both "work" but don't work well. The Visio tv at camp seems not to care either way what sort of AC powers it. I do think there is some added stress to electronic components on the MSW that may eventually translate into earlier failure.
Since a pure sine invertor can't be bought for anywhere near the price of the Resmed DC convertor I'll probably pick one of those up for convenience as I do a lot of camping where commercial AC simply isn't available.

[DiverCTHunter]

At $85 the ResMed DC convertor is really not that bad- is is very similar to many laptop DC convertors and they are typically in the same price range or more.

Of course, if you can also chain two smaller deep-cycle batteries in serial and get 24VDC that way. Just saying

[123.Shawn T.W.]

I don't have a "M series" but both my S1 550 & 560 owners manual say NOT to use their PR 12v adapter while the engine is running, as the alternator puts out more than 12v (my truck runs at 14vdc)

They also recommend a 350w invertor, and said a MSW was fine. (I spent a LOT of time on the phone with them!)

I'm a long distance over the road truck driver, and use a 400w invertor, 8cm h20 - 10cm h20, humidifier set at 3. I have 4 110ah batteries, I also run my thermo electric cooler all night (which is about the same draw) ... No problems starting engine in the morning.

[BudSky]

At $85 the ResMed DC convertor is really not that bad- is is very similar to many laptop DC convertors and they are typically in the same price range or more.

Of course, if you can also chain two smaller deep-cycle batteries in serial and get 24VDC that way. Just saying

True, but then my camp and my RV is all set up for 12v with deep cycle 12v batteries in place. I figure buying two more batteries just to run the CPAP and then buying either a 24V charger or having to carry a another charger in the RV to individually charge the two smaller 12v batteries, and having to find the somewhat odd connector Resmed uses for DC on the S9 Autoset.....well it just isn't worth it to me.
I have no issues with anyone else doing it that way though

[archangle]

By the way, if you have a Resmed system you will probably want an inverter.

However, if you have a ResMed S8 system, an inverter may damage the humidifier, so be careful. S8 humidifiers can't take a MSW waveform from an inverter.

doesnt the s8 run on 12v

The S8 humidifier runs off of AC only. There's a 12V input, but it doesn't run the humidifier, just the blower. ResMed says you have to buy their DC DC-DC converter that converts 12VDC to 12VDC. I don't know what happens if you try to run it off regular 12V DC instead of "safe ResMed approved" 12V DC.

S9 machines run the blower and humidifier off of DC with their DC-DC inverter.

[archangle]

At $85 the ResMed DC convertor is really not that bad- is is very similar to many laptop DC convertors and they are typically in the same price range or more.

Of course, if you can also chain two smaller deep-cycle batteries in serial and get 24VDC that way. Just saying

There's a third wire in the plug we haven't quite figured out yet. Part of what it apparently does is tell the blower unit which power supply it's connected to so that it can decide if there's enough power to run the humidifier and heated hose. We don't know what is necessary on this third wire to make the blower unit work.

We also haven't found a source for the plug, unless you cut one off of a ResMed power brick or inverter.