Using a Resmed S8 on 12V power

[SoarWestBees]

In preparing for an upcoming canoe/backpacking trip, I wired up a 12v connector for my ResMed Autoset S8. Sadly I found out the hard way that it wanted a negative center pin (very unusual). I fried my unit. [As a note I consider it negligent of ResMed to not provide a safety diode in the system that prevents what appears to be a common plug from frying the unit!] I will be writing the company to explain this in detail.

Meanwhile, the backup unit is on it's way, I would like to repair this unit and keep a backup around. I took it apart and do not see anything apparently wrong with the power circuit. Does anyone know which part needs to be replaced? I have reasonable soldering iron skills. I just need to know which parts to replace, and detailed instructions would make it easier.

If I can't do this on my own, can anyone suggest a reasonable repair facility in the US. I live in Phoenix.

Thanks, Dale

ps: it is unusual here, I have over a dozen devices that all use a similiar plug and none of them have negative centers. Perhaps it's the industry my items are in (computers, automation, radio controls) but it's definately not common to have negative centers in the gear I have, this is the 1 and only item. It should also be pointed out that even these less expensive radio controllers etc are protected from reverse polarity and do not fry if it happens. Yet, this expensive medical device fails with a simple mis-matched plug. Poorly engineered for sure.

[billbolton]

it wanted a negative center pin (very unusual).

Not unusual, over time I've discovered its about 50/50 as to which way around the polarity is across all commercial 12V equipment that uses that sort of barrel connector.

In any case, they no longer use barrel connectors on the current models.

Cheers,

Bill

[ktmken]

My beef with the whole 12 volt convertor topic is - they don't last-
I bought a dc-12 convertor a few years ago and I have used it maybe 6 times. The last time I went to use it on a camping trip, it did not work.
I took it apart looking for an obvious fuse that had blown, but did not find one.
I just bought a new dc 12 today for 150.00 canadian dollars.
I hope it lasts better than the last one.

[SiguiBvB]

I'm on my first trip to Australia soon and I'll use my CPAP in the Outback on remote spots wuthout 230 V AC.

Today after collecting all available information I ordered a 12 VDC adapter with a cigarette lighter jack. Costs 60 EUR.
I red the very useful threads Bill posted over the years and to be shure I'll find out with a continuity tester that the
negative voltage will be on the negative centre pin and not on the outside, before.
To connect directly to the battery it is my idea just to modify the cable with good to distiguish blue (-) and red(+)
alligator cramps, blue (-) to the centre pin and also to minus on the battery.
I can see the battery connectors (+/-) and I make the good connection. On our camper we have two 100 Ah AGM batteries.
The ResMed 12 VDV is expensive (200 EUR) and 600 grams, but it keeps the voltage constant and protects from low voltage
and mismatched poles, but it should work directly connected too.

to Bill: Will this work or should I better invest in inverter/converter Sinus 12 V DC/230 VAC with 300 VA direct in Australia?
ResMed is "Made in Australia".

[billbolton]

to Bill: Will this work.

With 200AH of battery capacity available and there is little risk that you would run down the battery terminal voltage to a state where the S8 went into any into any unpredicatable operating mode.

You will need to make certain that you have disconnected the S8 before you run anything that will recharge the battery.

Also, if you have other devices connected to the 12V battery supply at the same time that you are using the S8, particulary anything with a motor in it like a cooler (etc), there is a possibility that you might have electrical noise on the 12V DC supply that might cause some problems for the S8.

Cheers,

Bill

[bigrak]

My beef with the whole 12 volt convertor topic is - they don't last-
I bought a dc-12 convertor a few years ago and I have used it maybe 6 times. The last time I went to use it on a camping trip, it did not work.
I took it apart looking for an obvious fuse that had blown, but did not find one.
I just bought a new dc 12 today for 150.00 canadian dollars.
I hope it lasts better than the last one.

This statement is why I ask for a generic version that may last longer and be cheaper.

Some one must make a generic dc-12 converter with the same safe guards for the S8 ? No? Thanks.

[billbolton]

This statement is.....

... odd, as no one else has reported any reliability issues with a DC-12.

Cheers,

Bill

[GumbyCT]

I thought I saw this somewhere before just couldn't remember where.

To anyone interested.

I have photos on my web site of me running an S8 Escape off my cars 12v direct.

Works fine.

Issue is that if running direct, the voltage should not drop below 12 (as in a slowly discharging battery) also if the car engine is running & the alternator is charging at say 15 VDC, this I believe may have some effect.

The plus & minus 12 vdc variations are the obvious issues.

Cheers

Doug


http://www.internetage.com/cpapinfo/
Go to 'cpaps & software' menu (left list) & choose item 8 off that menu

Also see Bill Bolton's home built battery pack under the contributed items section.

D

Also I just found out that some laptops have a 24v supply and with some research you can prob find a laptop supply with a cigarette plug on it, for those who need it

[SiguiBvB]

Hello Bill,
I had no chance to use my ResMed S8 on 12 V power!
My campingtrip through the Australien outback (Strezlecki, Birdsville, Oodnadatta, Binn Track) was phantastic.
I used my S8 all over the trip where there was a 230 V connection. I couldn't use it oun our outback campsites:
Innaminka, Clayton Station, Arthur River on the Plenty Highway.
The 12 V looked good, doublechecked +/- and tried. I saw the "Welcome" and it seems to do work.
But it was disappointing: After a few seconds it was dead. I repeated (jack in and out) and it was
just the same, even without the humidifier the same failure on 12 V. It still works and worked on 230 V.
Why my ResMed S8 refused to work on 12 V with fully loaded 2 x 100 AH batteries! Do You have an idea?
Is there a kind of registration on the chipcard necessary? Shall I phone ResMed?

[GumbyCT]

The 12 V looked good, doublechecked +/- and tried. I saw the "Welcome" and it seems to do work.
But it was disappointing: After a few seconds it was dead. I repeated (jack in and out) and it was
just the same, even without the humidifier the same failure on 12 V. It still works and worked on 230 V.
Why my ResMed S8 refused to work on 12 V with fully loaded 2 x 100 AH batteries! Do You have an idea?

If I had to guess, I'd say the DC cable is defective. But then there is this -

This statement is.....

... odd, as no one else has reported any reliability issues with a DC-12.

Cheers,

Bill

So you have to ask yourself - are you odd two?

[billbolton]

I saw the "Welcome" and it seems to do work. But it was disappointing: After a few seconds it was dead.

The fact that it powered up and displayed an initial message indicates that the DC-12 was working. If you are saying that as soon as the the S8 blower started up the whole circuit went dead, then it seems the 12V power source "socket" could not provide adequate power (for whatever setting you run your S8 at), and had some sort of current limiter [/in-line/] between the socket and battery(s).

Did the socket have any indication of the current rating (or power rating) of the outlet?

Cheers,

Bill

[GumbyCT]

had some sort of current limiter [/in-line/] between the socket and battery(s).

You mean like the DC-12? Or are you still of the opinion there is absolutely no way any DC-12 could be defective?

btw- I came to the same conclusion. Whatever is between the 100AH X2 batteries and the load is the problem. If it was just a wire that is too small to carry the load that one thing, but it's NOT just wire. Unless the batteries are not fully charge they should be able to handle the load.

So to me either the DC-12 is doing what it was designed to do or it is defective. Is there another possibility?

[PieterSA]

How long will the DC 12 and machine run before the battery is flat, when using a normal car battery?

[archangle]

Hello Bill,
I had no chance to use my ResMed S8 on 12 V power!
My campingtrip through the Australien outback (Strezlecki, Birdsville, Oodnadatta, Binn Track) was phantastic.
I used my S8 all over the trip where there was a 230 V connection. I couldn't use it oun our outback campsites:
Innaminka, Clayton Station, Arthur River on the Plenty Highway.
The 12 V looked good, doublechecked +/- and tried. I saw the "Welcome" and it seems to do work.
But it was disappointing: After a few seconds it was dead. I repeated (jack in and out) and it was
just the same, even without the humidifier the same failure on 12 V. It still works and worked on 230 V.
Why my ResMed S8 refused to work on 12 V with fully loaded 2 x 100 AH batteries! Do You have an idea?
Is there a kind of registration on the chipcard necessary? Shall I phone ResMed?

If you just plug in and don't start the blower, does it shut off? If there's a bad electrical connection somewhere in your wiring, your setup might be able to supply 12V as long as there isn't much current draw, but voltage drops when the machine starts drawing more current.

Cigarette lighter plug connections like on the DC-12 are often very problematic this way. Fuse holders or fuses are also a common source of problems.

This is also a common way for lead acid batteries to fail. They will show a good voltage with no load, but drop down to nothing when you try to put a load on it. Think of a car battery where the overhead light is bright, but when you try to crank it, the light goes dim and the car won't start. However, if you've got two 100 AH batteries, this doesn't sound that likely, since the load from the S8 should be pretty darn small in terms of those batteries. Try to find some fairly heavy load you can put on the battery and test them.

Of course, if something's wrong with the DC-12 or S8, that would do it, too.

[BobMcT]

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