700 or 1000 watt power inverter for Resmed S9?

[OMyMyOHellYes]

Hey, if that's what blows up your britches, knock yourself out. But it is contrary to what ResMed publishes. My personal advice in this regard would be to not ever even use an inverter.

OMMOHY

[Sleep2Snore]

I would use 12vDC if I could, especially if camping or where dampness or water might be around.

[Lanco]

ok thanks.  It's pretty much as I suspected.  An inverter is not a good idea the way it sounds.  Thankfully we missed the storm and didn't need that or the power generator.  I guess I'll sell the inverter.

[archangle]

Re: Car batteries vs. Deep Cycle batteries.

A regular car battery is just fine for emergency usage for most of us, especially if it's only for one or two storms.

In theory, a good regular car battery is good for a dozen or so deep discharges before it starts to show any harm at all.  Even if you run it all the way to the point where your CPAP quits working before recharging it, you'd probably get at least a dozen cycles.

If it's your standby system for occasional outages, and you only run one night before recharging, you'd probably get 100 or so cycles before it starts to weaken due to usage. 

What's more important is to keep in mind that, no matter how little you abuse it, deep cycle or normal batteries lead acid wear out in 5 years or so.

[archangle]

Do NOT sell the inverter.   Your S9 will have no problems at all.   It may even run better on a modified sine wave inverter than on regular power.   The power brick rectifies the incoming voltage before using it, and couldn't care less about the waveform.  

Note that that is for the S9.   The A10 is a more complicated issue.  See the next post.

[archangle]

BTW, if someone is hell bent on running with an inverter, the Battery Guide shows 150 W modified sine wave (stepped, not pure sine wave) is fine with the S-9 (as the minimum).

OMMOHY

Note that this is true for the S9, not necessarily for the A10 machines.  Also, Resmed machines before the S9 should not be used with a MSW (modified sine wave) inverter if the machine has a humidifier.  

Look at (https://www.resmed.com/us/dam/documents/...lo_eng.pdf)

Note that they say a modified sine wave (MSW) inverter is fine for S9, even with an inverter. 

Note that they do NOT say that for the A10/Air10 models.  They actually don't even mention running an A10 machine on a pure sine wave inverter.   They only mention running it on their overpriced DC to DC inverter.  

I don't know if there's a real problem with A10 vs. inverters, if they just never updated that part of the document, or if they just decided to leave that out in order to make more profit selling DC-DC converters.

[archangle]

...And inverters are a terrible way to go because they are so blasted inefficient.  Much better to go direct DC. 

Unfortunately, you can't do direct DC with ResMed S9 or A10.   You have to use their overpriced DC-to-DC converter. 
Even if the inverter is inefficient, CPAP doesn't draw that much power.   If it's compatible to begin with, you will simply get a shorter amount of run time on a battery charge.

[archangle]

CPAPs don't care if it is a sine or stepped wave form.  Either is fine as far as the modern machines go.  (ResMed says exactly that in its Battery Guide)....

Once again, they don't say that for the A10/Air10 machines, only S9.

It used to be true that most modern devices don't care about inverter type.   However, the legislatards in Washington have intervened.   They made a poorly informed decision to require power factor correction on small electronic devices.  As a consequence of this, many switching power supply designs were changed and they can no longer handle MSW waveforms.

Power factor correction (PFC) legislation for small electronic devices is a really stupid idea.   A good power factor makes the electric grid more efficient.   Unfortunately, in small electronic devices, PFC makes the device less efficient, far outweighing the energy conservation in the grid.  It's also considerably less reliable and more expensive.

[archangle]

How it affects your electric components and your health long term.

The Difference Between a Sine Wave Inverter and a Modified Sine Wave Inverter...

The "heath effect" bit is nutjob talk.  Your health is not going to be affected by MSW power in your house. 

There are a lot of things modern science doesn't understand.   The health effects of low level electromagnetic fields is not one of these mysteries.

[Sleep2Snore]

You should use the DC to DC converter, however, if it runs on 12vDc  you don't really need it.
In fact try to get hold of one now, over here anyway, they stopped making them causing a panic.
Turns out that what it does is to protect against someone connecting it round the wrong way (it just will disconnect and nothing will work) and also protect the battery by disconnecting the CPAP/APAP machine should the voltage drop below a certain voltage, this is not so much to protect the machine, but to protect the battery against being discharged to far.
So it is a lot better to use the DC to DC converter for protection, however, in an emergency it can be used without it, but be very careful you connect it round the correct way and that the battery(s) you are connecting it to is 12vDC and not 24v or 36vDC.  24vDC is often found in boats, trucks etc.
36vDC can be found on boats and trucks as well, however, it is usually 24cDC.  It is over here anyway.

Resmed attended a conference over here that I attended, they did not recommend using a modified (square wave) power converter, however, they did say using a good sine wave power converter was acceptable.  This was a good while ago now, but they did say that it would apply to all their machines in the future.  (Keep in mind this is rip off Britain over here).  They did mention their DC to DC converters, but wouldn't go much into them, just that you should use them as they protected against wrong connection and also protected the battery and protect from over voltage.

They did bring some power converters with them for sale, but they said even before they finished their talk that they only had a few for those that were in remoter parts of the country and likely to have power interruptions.  I think they only had around six or eight with them.  They did say where to buy them, but they didn't appear to be very interested in selling them.  I looked at one, but they asked where I stayed and said they wouldn't sell me one on the day as they would only sell them if I stayed in a more remote area.  Instead they gave out a list of suitable power converters and a list of suppliers.
They sold everyone a raffle as we came in and gave one away and some other stuff they raffled, however, I was not lucky and went home empty handed.  There was another company there that was selling power converters, however, they underestimated the demand.  They were selling Nasal Pillows and power converters, but sold out in no time.  Within five minutes of the conference ending they had sold everything.
Opportunity missed for them I think!
However, going by what people are saying here, it sounds as if they are not giving the same advice over there!  

Archangel, what you say makes a lot of sense, thing is, if you do use an alternative supply, keep it as short as possible and if using DC direct, watch how you connect it up, I know it is common sense, but it would just surprise you how often people do it in a hurry or after a drink and do a lot of damage to equipment.  If you do make a mistake connecting it the wrong way round and you blow it, if you are very lucky you will have blown the internal fuse and the idiots diode at the rear of the machine.  However, don't bother opening the machine looking for the fuse as it often does not look like a fuse as we know it, then there is the diode that will have to be replaced, they are often surface mounted and not for anyone that does not know their way around a circuit board and can use a good soldering iron.

Does anyone know a where the DC to DC power supplies can be obtained?  I keep getting asked and I am told they are no longer available?