Using a Resmed S8 on 12V power

BobMcT wrote:I read all the posts. One question I wanted to be clear on. In an RV that the inverter is modified sine wave, i can run my S8II AutoSet, but I can't use the humidifier. Is it ok to have the humidifier (H3i) connected to the S8, but turned off completely. It would still have some effect as a passive humidifier. Also, I don't like using my S8 without it attached as my nasal pillows get much nosier - something about the air cavity in the humidifier.

Thanks, Bob

I wouldn't risk it unless you can somehow hook the humidifier up to the air path without having it electrically connected. It looks to me like the S8 humidifier plugs into the electrical power when you hook it up to the blower unit.

You could get an external passover humidifier. They probably provide more humidity than an unpowered heated humidifier. https://www.cpap.com/productpage/respir ... -hose.html

I wouldn't risk it unless you can somehow hook the humidifier up to the air path without having it electrically connected. It looks to me like the S8 humidifier plugs into the electrical power when you hook it up to the blower unit.

I appreciate the quick response. The H3i humidifier does connect to the blower unit receiving it's AC power from the unit. But, the H3i has it's own power switch can be switched off completely where it's light is off and there's no heating. I guess I can call ResMed to confirm if it would be ok to run on modified sine wave power as long as the humidifier was turned off. I don't like using the blower unit without the humidifier attached because it makes my nasal pillow mask much louder at my face. I've used it attached with no water and turned off. Before I try it, I definitely need to make sure if would be ok.

Bob

I called and got a tech at ResMed to clarify. The S8 blower units will work on a modified sine wave inverter, but the H3i humidifier can not (must be pure sine wave). BUT, it is ok to leave the units connected running on modified sine wave AC, as long as the humidifier unit is turned OFF. The off position breaks it's AC connection to the unit. I plan to buy a DC-12 converter so I can use my unit on DC. Humidifier can also be connected but receives no power when running on DC. When the RV generator is running and I'm not on shore power, I can plug into an AC outlet on the RV and use the unit with the H3i attached, but the humidifier must be turned off. If left on and the generator shut off, the inverter would then supply modified sine wave power which the humidifier can not run on. Don't want to risk damaging it.

When on shore power all would be normal - just like home. Thought it would be a good idea to post what I found out.

Bob

I have recently taken a look at the power supply card inside the resmed s8 lightweight machine, and the rated output is 12V DC, 3.5 Amp (max). And I found that for cases where AC mains voltage is NOT available, then you can use the 12V DC input socket to supply 12V DC to the power supply card via a 12V DC supply. And if using a 12V DC external voltage supply, then that voltage supply needs to be stable (ie regulated), and that supply also needs to be capable of supplying up to 3.5 Amp of current. But very importantly, if not using the genuine DC supply made for the resmed s8, then I do NOT recommend plugging in just any commercial DC supply unless you're absolutly sure about the polarity for the input voltage - as I recall something about the DC input socket for the resmed having a configuration where the INNER pin is meant to be the negative side, while the outter metal contact surface is meant to be the positive side.

I know I am 10 years late but, I still use an s8 resmed cpap and need a DC-12 Converter which is now discontinued...can i use a standard 12v direct plug with a reverse polarity bit on the front?

The only 3rd party chord I can find is 80 usd

https://www.ebay.com/itm/12V-POWER-CORD ... Sweq5axEFd

but here i see another 3rd party chord sold out that is only 20 usd

https://www.bestcpapprice.com/Owell-12V ... _1397.html

Seems to me the only thing i need to be careful of is the reverse polarity, any advice would be welcomed

My plan is to buy this

https://www.amazon.com/MEROM-5-5x2-1mm- ... 93&sr=8-10

and this

https://www.amazon.com/SoulBay-Reverse- ... 252&sr=8-3




PLEASE HELP

THANKS
-Scasper1010

I do believe the early Resmeds were -12V.

You should be able to reverse polarity w/o the Reverse Polarity Converter Cable.

I've not seen a cable with the replaceable connectors you couldn't reverse the polarity. Just be sure to measure w/a volt meter before connecting.

SleepGeek wrote: ↑

Fri Feb 19, 2021 7:54 am

I do believe the early Resmeds were -12V.

You should be able to reverse polarity w/o the Reverse Polarity Converter Cable.

I've not seen a cable with the replaceable connectors you couldn't reverse the polarity. Just be sure to measure w/a volt meter before connecting.

Also I found this

https://www.amazon.com/gp/product/B00EL ... _qh_dp_hza

think it will work?

scasper1010 wrote: ↑

Sat Feb 20, 2021 5:45 pm

think it will work?

While one of the adapter tips may fit, it is rated for only 2.1A. I think that S8 will draw more than that.

Ya know, if you already had this I would say change the fuse and give it a smoke check but don't think I would be willing to spend $20 to try it, but hey that's me.

I don't have a resmed S8 is the power supply built-in and you need an AC cord?

What happened to the power supply you had for this?

Have you checked cpap.com?

SleepGeek wrote: ↑

Sat Feb 20, 2021 6:23 pm

scasper1010 wrote: ↑

Sat Feb 20, 2021 5:45 pm

think it will work?

While one of the adapter tips may fit, it is rated for only 2.1A. I think that S8 will draw more than that.

Ya know, if you already had this I would say change the fuse and give it a smoke check but don't think I would be willing to spend $20 to try it, but hey that's me.

I don't have a resmed S8 is the power supply built-in and you need an AC cord?

What happened to the power supply you had for this?

Have you checked cpap.com?

so I have the AC chord it is a simple standard chord, but i want to go camping and it is most efficient to run it off DC in that instance. The thing is, they stopped producing the true DC adaptor so there are ppl making 3rd party adaptors that are 80$!, i think for 20 if the fuse blows ill replace with a 5a and should be ok in my estimation. (Bottom of the
S8 says it pulls max 2.5A)

Ok got it.

scasper1010 wrote: ↑

Sat Feb 20, 2021 7:05 pm

i think for 20 if the fuse blows ill replace with a 5a and should be ok in my estimation. (Bottom of the
S8 says it pulls max 2.5A)

On the positive side that should get you a connector that will fit.
IF you are handy with a soldering iron or know a friend who is you should be able to make it work.

If you go with the setup as is I would change the fuse first.

What worries me is those switches can be moved w/o you knowing it and IF the polarity reverses you could have smoke.

IF I remember correctly the S8 model the DC cord goes straight in so IF you could find or already have a straight cord then use the connectors that come with the adapter you mentioned above.
Something like this ...
https://www.amazon.com/dp/B07TT1R9Q6/re ... ljaz10cnVl
You can make that work too.
In any case you haven't mentioned IF you have a volt-ohm meter to check the final polarity?

Back in the day you could go into a Radio Shack store and buy all the right stuff you need for this.

I have been looking on the internet for 3 days and I feel like i can make these

https://www.cpap.com/productpage/s8-mac ... er-reviews

Im no engineer but i can twist a few wires together and crimp them, this looks like its a regulator and a fuse to the proper dc male plug (the mm size of the plug is also no where on the internet)

as far as i can tell a negative polarity just means i need to cut and switch the red and black mid cable so at the end they are reversed.

why is this such a hassle i just want to realize my camping dreams.

SleepGeek wrote: ↑

Sat Feb 20, 2021 6:23 pm

While one of the adapter tips may fit, it is rated for only 2.1A. I think that S8 will draw more than that.

First thing, I forgot to mention that 2.5A is at 115V not 12V which will be more.

But let's move on.

scasper1010 wrote: ↑

Sun Feb 21, 2021 12:15 am

why is this such a hassle i just want to realize my camping dreams.

The reason is because this model has been discontinued, many years ago, that's all.

Don't know how long you've been on cpap but sounds as if you do NOT have a backup, correct?

This is a dangerous position to be in. Suppose while twisting these wires you make a minor mistake and smoke this S8. Yea?

This may be the time to get you a backup cpap.
afaik - all of the other cpap mfgs are 12V and have 12V DC cords avail.
For some reason, prob money, resmed decided to make this S8 DC adapter so it can convert 24V to the 12V the S8 uses and this is what makes this adapter cost more than other brands.

Are you agreeable to this?

IF so check Craiglist in your area for an older model in your price range using the money you would spend on this S8 adapter towards the purchase.
Look under Beauty + Hlth search for cpap.

I know the respironics use 12V and I believe Intellipap are also 12V, in fact that Intellipap cord may also fit your S8 but don't forget the polarity is reverse - another resmed idea

I would look for an auto and be sure to try it on battery before camping to work out any defects.

Whacha think?