cpap machine

when I first got my respironics, remstar plus, I ordered the 12 volt kit for it. seemed rather cheap, $25 or so IIRC. all it was was a standard 12 volt cigarette lighter style plug and a plug that fit the CPAP.
don't remember any instructions to not use it when motor was running however. also have an airline hookup,.
bumpy

ldm468 wrote:
I have just acquired a Phillips CPAP that will operate on 12 volt DC if you purchase (at extra cost) its designated adapter cord. One of the cautions in the manual, is that you should not operate the unit when the motor is running. While the documentation does not explain the reason for this caution, I wonder if the electronics do not like the voltage spikes that occur with rapid battery charging.

Or, perhaps it means that you should not use a CPAP unit while driving.:)

According to the Respironics tech I spoke with the unit is designed to operate on 12 vdc. The battery voltage of 12.6 at full charge is as high as it is designed for. With the engine running an alternator puts out over 14 volts. In my motor home the alternator puts out 14.5 vdc.

Way back when I designed instrumentation for heavy equipment and over the road trucks I designed for a continuous max of at least 16 volts with a lot of additional transient voltage protection as high as 500 volts.

20 years on CPAP and 14 years RVing with CPAP. Whenever I have needed/wanted a new CPAP I have insisted on one with 12 V DC input. The head of our bed is on the other side of the wall from the bathroom. Pulled power off the bathroom light switch and mounted the outlet through the wall.

I don't use a humidifier (they were new when I got my machine, "for women" they said) so the draw going directly from 12VDC is pretty small.

What everyone else said about invverters/converts etc.

I have just acquired a Phillips CPAP that will operate on 12 volt DC if you purchase (at extra cost) its designated adapter cord. One of the cautions in the manual, is that you should not operate the unit when the motor is running. While the documentation does not explain the reason for this caution, I wonder if the electronics do not like the voltage spikes that occur with rapid battery charging.

Or, perhaps it means that you should not use a CPAP unit while driving.:)

Its all about battery management. I installed an additional 12 volt battery for boondocking use. If you are short of house capacity,,turn down the humidifier, eliminate the 12 to 120 to 12 volt conversion, add capacity. If you are not short, life is great.

Flyfishingfool - it would be helpful to know the make and model of your CPAP. My Resmed S9i has a 12v power brick available as an option. I purchased it specifically for use in my fifth wheel when boondocking. If I don't use the humidifier, I can spend ten days in the woods without draining the house batteries.

I have a resmed vpap and per resmed if the water tank is used it must be operated on 120 volts AC or psw inverter. However if the water tank is removed it can be used with a modified sign wave inverter.

Regarding pure sine wave or modified sine wave inverters. It depends on the brand. My first and current Respironics CPAPs are okay with a 300 watt modified sine wave unit.
The last time I checked, the Resmed web site said a pure sine inverter was required for their CPAPs.
I don't know about other brands. Their customer service could probably tell you.

In my motor home when shore power was not available I used a 300 watt MSW inverter because it was difficult to run the dc to the bedroom slide and very easy to plug the inverter in by the bed. If I had a need to run the machine often without shore power I would have installed the dc wiring. We very rarely were without power so I didn't bother.

Thanks everybody for your input

Mine just does 120 VAC...and works fine