Why two plugs for my machine

Hello all,
I'm brand new to this, I've also searched the wisdom folder.
I have a ResMed S8 and it has a spot to plug in my 110V AC cord, as well as a spot to plug in a 12V DC cord.

I'm currently using the 110 V DC spot , but when I go camping, I'll want to use battery power. I'm confident that I can construct a 12V DC cord, but ResMed sells an inverter for use with this model. What gives? Is the 12V DC spot on the machine REALLY 12V DC, and if so, why would I need the inverter?
I'll be running the machine (if possible) with a couple six volt batteries wired in series.
Thanks for your help.

Read the "In House Comments":

https://www.cpap.com/productpage/DC-12-Inverter.html

Depending on which one you're using....

https://www.cpap.com/productpage/DC-to- ... or-s8.html

ResMed machines need "pure-sine-wave" power.

Den

Wulfman wrote:ResMed machines need "pure-sine-wave" power.

The S8 flow generators work fine from modified sine wave AC power, its only the H3i humidfiers that needs pure sine wave power.

Cheers,

Bill

If you do make up a car power cable for your machine - get the polarity right. It is the reverse of most other brands (center pin opposite voltage).

The S8 will run off a car battery - the preference is to include a regulator in the event the battery starts to go down, without a cut-out regulator the machine will still try to run on low voltage & it will mess up the therapy.

DSM

http://www.internetage.ws/cpapinfo/s8-12vdc-1/

billbolton wrote:

Wulfman wrote:ResMed machines need "pure-sine-wave" power.

The S8 flow generators work fine from modified sine wave AC power, its only the H3i humidfiers that needs pure sine wave power.

Cheers,

Bill

Thanks for the clarification, Bill.

Den

According to this document from the ResMed web site, both HumidAire 2i and HumidAire 3i humidifiers require a pure sine wave inverter with a continuous power rating of 200 watts or higher. It further states, “Other ResMed heated humidifiers must not be used with inverters.” (See page 3.) In other words, it appears that a ResMed flow generator can be used with a modified-sine inverter only if you are not using a ResMed humidifier with it.

So far as I know, the DC-12 converter in Den’s first link works as it should, although I feel it is ridiculously expensive. Be careful if you try to make your own 12-volt adapter as it is critical that you get the polarity correct. If you reverse the polarity, you will probably ruin your flow generator. Note: The humidifier will not heat on 12 VDC, but you will probably find that using it as a passover will be just fine while you’re camping.

A special warning regarding the inverter in Den’s second link: I bought one of these with the intention of using it to power my wife’s VPAP Adapt SV while camping. (The DC-30 volt converter for this machine is engineered by idiots so that it will not work in the real world. But that’s another story.) Lucky for my wife, when we received the AIMS pure-sine inverter, I checked the voltage output with a digital voltmeter. The no-load voltage was 103, which is unacceptably low for a nominal 120-volt load. When I called to request to return it, the operator told me that this inverter must be used with the S8 only, and that they have had many complaints of it causing other flow generators power supplies to burn up! DUH! This is a result that should be expected with such unacceptably low voltage output. The S8 power supply must be especially tolerant of out-of-voltage conditions.

I am very disappointed that CPAP.com has not followed my advice and removed this item from their catalog. There are other good pure-sine inverters available in the same price range.

Wayne