Calling electronics/electrical experts - Need Quick responses please!

An overseas visitor to my house uses a CPAP machine.

I found that it the laptop power brick I use has trhe same tip as the one used by the machine. This is great news because I don’t have to worry about finding adapter plugs, but there is one small doubt in my mind.

The laptop adapter outputs 19.5V - 4.62 A or 15V - 6A (it has 2 modes, I can use either). The machine requires 12V-6.67 A.

My question is - would I fry a $1200 machine if I use the laptop adapter?


YES. Don’t even think about it.

The voltages must match, and your DC power supply (aka brick) must supply sufficient current to run the machine!

Too much voltage, all manner of bad things can and will happen.

Now, on the positive side, you have a piece of cord that has the right kind of tip to connect to this machine. If you need to rig up an alternate power supply, all you need to do is find a power supply lying around that is 12 volts with sufficient amperage. Desktop computers have such a supply in them, electronics parts stores have them, etc.

You could then chop off the tip from your laptop cord and solder it on to the alternate power supply. Don’t forget heatshrink.

I can’t say for certain without knowing the design of the CPAP machine, but with that large of a voltage difference, frying it is a definite possibility. The 15 volt setting might be close enough that the CPAP machine’s internal voltage regulators (if it has any) could handle it just fine. Or it could make the CPAP machine go up in smoke.

The adapter is also a bit shy on current (6A on the 15 volt mode, where the CPAP machine needs 6.67 or greater). You could end up overheating and frying the adapter as well.

You also don’t mention the polarity of the plug. If the polarity is different between the adapter and the CPAP machine that could easily fry it as well.

Match the voltage exactly, match the plug and the polarity exactly, and the current (amps) needs to be greater than or equal to the current required by the device.

Thank you! As an old doper, I knew you guys would come through. Not the answer I was hoping for, but saved me from serious trouble (the visitor is my mother-in-law).

i agree with the above reasons not to try it.

good that 12V supplies are common, though at 6.67 A will take some looking.

Didn’t the machine come with a supply? Yeah, it’s one more thing to toss in the suitcase, but it’d have to be easier to do that than to find a compatible one at a store, or to solder up one oneself.

Agreed with the others. 15 V is borderline but far enough away that I wouldn’t risk it. If it were 13 V I’d say no problem.

Fortunately, power supplies are cheap. For instance, here’s a 12 V @ 8 A supply for $15. Whatever you choose, make sure the current rating is on the high side–8 A or so is good if you need 6.67 A. If the plug doesn’t fit, you can chop the plug off the old one and solder it in (make sure you get the polarity right).

Have you confirmed the CPAP power supply is not an international type? Mine will run on 100-250 and deliver 12 volts. Just need the appropriate AC plug - mine uses the semi-universal “figure eight” type.

Other wild options… Cut the cable off the laptop power supply and connect it to a car battery. The 12 volt battery in a UPS would only be able to run the machine for around an hour, maybe two if she can sleep without the humidifier function.

Last-ditch option for the desperate would be to run out to the hardware store for a US-style plug, cut the plug of her power supply and put the new plug on it, assuming the power supply can run on 120. Then, the dilemma will be to replace the power cord with whatever she’ll need back at home. On second thought, a good travel store or maybe Radio Shack, Target or Best Buy may have an adaptor. The challenge will be that they probably have adapters to plug US things into overseas outlets, but you need something for an overseas plug to fit a US outlet.

I did end up running out to Walmart and getting an adapter plug so that the machine could be plugged in. The machine does accept 110-250V, it was just a matter of finding the right adapter plug. I was just being cheap and trying to save $20.

I saw the laptop cord sitting nearby and was excited about the possibility and the fact that it was late night and I wasn’t too excited about having to make a run to the store.

Thanks a bunch for all the replies!!

Good - most people think they need a power adapter - and almost all electronics today will do 120-240 - so all you need is the plug adapter.

Be warned - that some plugs don’t fit well into all outlets. But it will be obvious if that is the case.