Emergency power for CPAP machines!

So, with the hurricane, I have two questions about generating emergency power for CPAP machines.

I looked at the batteries for the PR System One on CPAPauction.com, but it said the Respironics batteries are $570! Unless I misunderstood.

So, I'm looking at inverters. There are two kinds of inverters to convert 12 or 24 volts DC from car and truck batteries to 110 volts.

The first kind is modified sine, and it is cheaper, but does not make the same kind of power as you get normally from the electric company,

The second kind is pure sine, and they make 110 volts equal to or better than the power company, but more expensive.

So does anyone know if you can run a CPAP machine on a modified sine inverter, and if it will run without damaging it in any way?

I know it will run on a pure sine inverter.

I'm going to test the CPAP machine right now with a meter and see how many amps and watts it's actually drawing, I'll post it.

The PR System One, set to 12 auto-pap, tested:

75 Watts
1 Amp

So, why are the batteries for it so expensive?
What is so special about them?
Maybe just because they are for a medical device?

You can buy a huge deep cycle marine battery for $200.

Lee

I run mine on a modified sine wave inverter and a 12 volt deep cycle marine battery...whole thing cost me $170 canadian..so should be cheaper in the US.

Lee, for your PRS1 machine, get the Respironics DC cable, don't mess with an inverter. https://www.cpap.com/productpage/respir ... -cord.html

Note: this plug fits some ResMed machines, but the polarity is wrong, and will cause damage.

You'll lose a significant amount of power converting DC with the inverter, then converting it back to DC with the power supply.

If you're using a 12V battery, driving a PRS1 CPAP machine, there's no advantage to using an inverter. The same is true for Respironics CPAP machines that run the humidifier off of 12V. Some M series machines use DC, some use AC.

By the way, according to my solar power guru, a lot of the "pure sine wave" inverters are unreliable and produce rather "ugly" waveforms anyway.

ResMed claims a modified sine wave inverter will damage the humidifier for most of their machines except the S9 series.

ResMed also claims you need their DC power converters for most of their machines. i.e. an electronic gadget, not just a cable with connectors.

Check this previous post.
viewtopic/t67699/CPAP-Battery-Review.html

archangle wrote:Lee, for your PRS1 machine, get the Respironics DC cable, don't mess with an inverter. https://www.cpap.com/productpage/respir ... -cord.html

Note: this plug fits some ResMed machines, but the polarity is wrong, and will cause damage.

You'll lose a significant amount of power converting DC with the inverter, then converting it back to DC with the power supply.

If you're using a 12V battery, driving a PRS1 CPAP machine, there's no advantage to using an inverter. The same is true for Respironics CPAP machines that run the humidifier off of 12V. Some M series machines use DC, some use AC.

By the way, according to my solar power guru, a lot of the "pure sine wave" inverters are unreliable and produce rather "ugly" waveforms anyway.

ResMed claims a modified sine wave inverter will damage the humidifier for most of their machines except the S9 series.

ResMed also claims you need their DC power converters for most of their machines. i.e. an electronic gadget, not just a cable with connectors.

Arch
I can get four 8 hour nights, not using my humidifier, with my set up. I might even get more, but I haven't tried. I can use this set up for both my M series and my F&P 604. So why do you say I don't need the inverter?

What nanwilson said. If it takes 12V it would be silly not to have that cable ready to go along with whatever extension it takes to your bedroom.

For more battery back up ideas than anyone could possibly want to dig through ... (but maybe something there will help someone )...

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

nanwilson wrote:
Arch
I can get four 8 hour nights, not using my humidifier, with my set up. I might even get more, but I haven't tried. I can use this set up for both my M series and my F&P 604. So why do you say I don't need the inverter?

That was actually advice for Lee with his PRS1 machine. I would consider it to be valid for your M series machine if you have the version that runs exclusively off of 12V. (Some M series machines run the humidifier off the 12V power brick, some use an external 120V power supply.) If you don't use the humidifier, it's still better to run your M series CPAP off of the DC supply.

I do not know about the DC power adapter status of the F&P machines.

(Once again, the Respironics DC plug or Respironics power brick will damage ResMed machines even though the plug fits ResMed. Resmed adapters will probably eat Respironics machines, too.)


Why not to use an inverter if you don't have to:

I'd recommend running any CPAP that will work off of 12VDC with the manufacturer's recommended DC adapter instead of an AC inverter if everything (for instance the humidifier) works off of that.

The inverter converts 12VDC to 120VAC. The Respironics power supply brick converts 120V back to 12V.

The inverter is an unnecessary cost if you haven't already bought it.

The inverter and power brick each waste some of your power. Maybe it doesn't matter to you, but it would to someone with a smaller battery. Or to you if you get a longer outage.

The inverter is an extra part to keep around. More connectors, more cables.

An MSW (Modified Sine Wave) inverter doesn't supply the sine wave the power supply is designed for. Depending on how the power supply is designed, this may or may not matter. ResMed says MSW inverters are OK for most of their CPAPs and S9 humidifiers, but will damage S8 humidifiers. I haven't heard an official statement from Respironics about MSW inverters. Even "pure" sine wave inverters produce an "ugly" waveform with lots of harmonics.

I do not know F&P's position on MSW or pure sine wave inverters.

The inverter is an extra part to fail. Lots of inverters are poorly designed and built. A failed or malfunctioning inverter might damage your power supply.

That doesn't mean the inverter is "wrong." It's mostly the "KISS" principle. Keep it as simple as possible. If the inverter solution works for you and you are willing to accept the extra risks of an inverter, go ahead.

Generally, if your CPAP takes 12v, the most efficient way to run it is off a 12v battery (some jump start battery packs work well). If, as with my older Respironics Bipap Auto SV Advanced, the CPAP takes 24v, you have the option of a 24v battery (or two 12v batteries in series), or the Respironics DC-DC adapter from a 12v battery. DC-DC converters are quite efficient these days, more so than inverters. Inverters can be reasonably efficient, especially if matched properly to the expected load, but are the least efficient of these three solutions.

Heated humidifiers are the real pain when it comes to camping. Not only do they take a lot of juice, they are particularly about the taste. As others have suggested, the best solution is to do without one if you can, or to use passive humidification (either just turn off your heated humidifier or get a more efficient "cold" humidifier if that isn't enough). You'd think someone would make a 12v heated humidifier for camping--would be easy enough--but I don't know of any.

Archangle wrote
I do not know F&P's position on MSW or pure sine wave inverters.


Arch
I called F&P prior to my purchase of the MSW and battery for my 604. They replied to me the next day via email exactly what I needed...........
a modified sine wave inverter and a 12 volt deep cycle marine battery.
The inverter cost me $40 canadian and the battery was $130 canadian. It should cost less in the states.
Nan

Here's an older post I put together to help with creating a backup battery for my ASV unit. You might not need as large a battery as I did, but if you are moderately handy you can easily make a usable backup battery that can last a few nights.

viewtopic.php?t=49115

[ edited to make the link a hyperlink ]

Hi All:

You guys are AWESOME. I never expected to get so much great info.

archangle, in my case, the adapter you linked to will end up being just what I need. I was not sure if the machine would accept 12 volts dc direct from a battery. No real reason it shouldn't, just being careful.

If anyone happens to know, I've been researching for days the best way to power 5 or 6 low voltage dc electronics, like a wireless router and cable modem, during an outage. The one thing I haven't found info on yet is how much more efficient it is to power them directly with 12 volts DC instead of using an inverter to go into their stock plug-into-outlet transformers. It seems to me that is a very inefficient way to go, but I need to read more on it.

So if my CPAP draws 75 watts running on the AC adapter, I wonder how much less it draws running directly on DC? That figure that was mentioned, I think 4 8-hour days of sleep off a battery sounded too good to be true!

Nan, do you know the part number or brand of the battery you're using? I wondered how many amp-hours, and amps it was.

Thanks Everyone! It's been a fear of mine needing a night's sleep and having no power, so this will be good when I have this worked out!

Lee B.

Hi Lee
Had to go out to my motorhome to write all this down..
Battery
Motomaster Nautilus Marine Crank 730A
Reserve capacity/amp hour 160 min/100ah
Inverter
Motomaster Eliminator
300 watt with two household outlets.

I have used this set up for the past year and a half and I consistantly get 4 eight hour nights with my humidifier running in passover mode. I haven't been out for more than 4 nights at a stretch, so don't know if it would go longer.
Motomaster is the brand name of Canadian Tire, I'm sure there would be an equivalent type store in the states.

lee_leses wrote:archangle, in my case, the adapter you linked to will end up being just what I need. I was not sure if the machine would accept 12 volts dc direct from a battery. No real reason it shouldn't, just being careful.

The Respironics cable is just connectors, fuses, toroids, and wires. No electronic stuff, no voltage regulation, etc.

It does have "toroids" that keep the machine from radiating or receiving radio frequency noise on the power line. These are just donuts of magnetic material in the bulges on the cable. This is probably mostly for regulatory reasons, but it might occasionally protect the machine from radio interference in some rare circumstances. It's a sign of quality construction, but it would probably work just fine without them.

I would have no qualms about building my own cable from parts you can buy at Radio Shack. The only way to do damage to the machine would be to get the polarity backwards.

ResMed makes a big deal about needing their "electronic" DC adapter, even on the machines that use 12V.

(I'll comment again that ResMed and Respironics connectors may plug together, but the voltage is reversed and BAD things will happen.)