Trying to use small inverter through cig. lighter adapter

[djbroughton]

I am trying to run my CPAP machine from a light fixture above the bed instead of through the main inverter. I wired a 12 v cigarette lighter outlet into the fixture. The voltage reads 12.5 v and I can run other AC appliances through the portable inverter at the new connection. This inverter, which says 175 w peak and 100 w continuous also works when I plug it into the cig lighter on the dash with the CPAP but not at the new connection. The CPAP adapter says it requires 90 w.

Why will my CPAP machine not run at the new connection?

[msmith1_wa]

I have had similar problems with my cpap using a small inverter or using the plugging in directly using the cpap manufacturer's 12v cord. What I had to do is use the ramp feature to get it to start.

I also think that part of my problem was my batteries were approaching the end of their life, because it worked fine during the day when the solar was charging.

[markchengr]

Hi, I had the same problem. I have a 400 watt inverter. When running it with the supplied ciggy lighter type 12 volt receptacle it would either alarm on low voltage or shut down if it even ran anything at all. Problem was wires to the 12 volt receptacle were much too small. Solution was to mount the inverter inside a cabinet and hardwire it directly to the battery with 10 gage wire (fused of course). Now we can run 2 CPAPs with humidifiers all night. It takes about 20 ampere-hours for 8 hours of use. -Mark.

[time2roll]

resmed lists a dc/dc adapter

http://www.resmed.com/us/en/consumer/products/accessories.html

Otherwise I recommend a 300 watt sine wave inverter and transfer switch so that you can just plug into the closest 120v outlet with the standard power cord.

[landyacht318]

Way back when with my first inverter, it would power my laptop from the dashboard ciggy receptacle but not a rear ciggy plug, unless the engine was running or had been very recently.

Now I don't use ciggy plugs on anything passing more than 3 amps as they are such a problem prone connection, however convenient and ubiquitous they might be.

[pianotuna]

Hi,

There are DC to DC converters for 12 to 24 volts. That would be more efficient than a pure sine wave inverter going into a 120 volt to 24 volt power brick.

djbroughton wrote:
but my machine is a Resmed S9 (Australian manufacturer) and the 90 W adapter says DC output is 24 V. Regardless, for the 2 prong DC cord that goes into the adapter I would still need a matching 2 prong female connector. Where would that come from?

[djbroughton]

BTPO1 wrote:
It may be possible for you to use a 12 volt cord to run your CPAP machine. Mine runs on 12 VDC. When plugging in on 120 VAC it transforms to 12 VDC. If yours is 12 VDC then you would not need an inverter to run it. JMO

See that sounds good but my machine is a Resmed S9 (Australian manufacturer) and the 90 W adapter says DC output is 24 V. Regardless, for the 2 prong DC cord that goes into the adapter I would still need a matching 2 prong female connector. Where would that come from?

[SkiSmuggs]

I ran into the same problem when I tried a cheap 12v extension cord to a 300w inverter, then to my CPAP via 120v adapter. The inverter itself shut down. A quality 12v extension by NOCO solved the problem, but I realized that my CPAP was designed to run of 12V. I ordered the 12V cord for it, installed a 12v outlet from my headboard reading light and everything was good. No inverter, no extension cord and no 120v adapter.

[accsys]

Most 12V lights only pull an amp or two at most so the wire for that light is much too small to carry the 8 to 10 amps or more required for your inverter to feed the CPAP. Get an extension cord (at least 14 gauge), cut the A/C plug/sockets off and run it from the batteries to the cig light. Just use the white and black wires and you will not need the ground (green) wire in the ext. cord but do put a 15 amp fuse in the line for protection.

[fitznj]

Most AC/DC inverters have circuitry built in that switches them off when they detect a low battery voltage. Which means that you can't run the inverter too long without having to recharge the battery again (kind of defeats the object....).

I've never been successful in running an inverter for longer periods of time (even a low wattage TV). They work well in a car/van/truck which has the engine running and charging the battery - again, sort of defeats the object.

f

[time2roll]

Any chance the CPAP will run on 12v direct?

[BTPO1]

It may be possible for you to use a 12 volt cord to run your CPAP machine. Mine runs on 12 VDC. When plugging in on 120 VAC it transforms to 12 VDC. If yours is 12 VDC then you would not need an inverter to run it. JMO

[Fubeca]

Are there any 12V outlets nearer the power distribution center? If not, you may need to pull new wire to a location close to the bed.

[time2roll]

put 'CPAP' in the search box or even google, I dare you. 😉
Otherwise it is a machine to help with breathing issues while sleeping.
Fairly common actually.

[groundhogy]

I am a Genius and could totally solve ur problem...
Oh.. and im a rocket scientist..

What the hell is a CPAP MACHINE !!!!!!!
You may want to specify that up front if you want help.

Sounds like a medical device. Something that shocks you when your heart stops.
Or something related to going to the bathroom.