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Wiring a cpap machine


Grassy

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We don't normally boondock (at least not now) but when we do, it is usually over nighting in a wally mart parking lot.

 

I have tried not using my machine but with the longer hauls, it really affects my body.

 

I just bought a specific inverter for my machine. In the provided literature, you are supposed to connect it into a 12v plug or have a marine grade 12V batter sitting by your bed.

 

I want to hard wire it directly to my 5th batteries (AF 29-5t). I can deactivate the humidifier and we normally do not disconnect the umbilical from our tv at night and it has 2 big 12v batteries. Less important, we have solar on the roof.

 

Going through the literature today, I read this warning.. "DO NOT connect this cable to a battery that is installed in a vehicle or has any additional equipment attached to it".

 

Will this iverter damage the electrical system in my rig or are they concerned that I will drain the battery prematurely ?

 

Am I missing something ?

 

Thanks..

 

 

 

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First step is to determine if you can support your machine. (And this would apply to any device on the 12 volt side of life).

 

My CPAP is a Resmed Airsense 10 and uses 3.75 amps X 24 volts or 90 watts. 90 + 9 (power supply loss) /12 = 8.3 ah @ 12 volts (machine use).

 

So figure that I use the machine 8 hours per night. OK that 8.3 x 8 = 66 ah @ 12 volt. The normal deep cycle battery has about 110 ah so MY machine would last all night on one battery.

 

My old machine was not as power intensive and used 1/2 the power

 

Now with the humidifier off or turned turned low, this would help the power curve a lot.

 

Now that warning - I have mine connected (and my former machine) to the trailer batteries 24/7. I put a 12 volt socket by the bed and use that rather than modifying the plug. If you have ever had a power loss during the middle of the night and had that space alien sitting on your face and sucking your breathe in the middle of the night....Sorry, I digress, With the trailer battery floating between the charger and the machine, it provides power similar to a UPS even if the main power goes out. Before we hit the road, I had a UPS powering the CPAP even in the S and B.

 

The idea being that the voltage fluctuations from charging, spikes from things turning on and off. basic electrical noise, they are protecting themselves.

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I too have an Airsense 10 and I use the 12 volt power source from Resmed. I just plug it into a 12v outlet within reach each night. I do not use the humidifier when on 12v but I have just gotten some HME (heat moisture exchange) filters to give a try. They retain the humidity from your breath.

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The DW has a Resmed Cpap. I installed a pure sine wave inverter that she has used off and on for three years with no problems.

Would only use pure sine wave and not a modified sine wave though. Some medical equipment and other electronics are sensitive to the incoming power.

The two house batteries that we have hardly notice the draw.

Just my two cents.

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Back to your original question "Will this iverter damage the electrical system in my rig or are they concerned that I will drain the battery prematurely ?"

 

This might be covering themselves in case there is a problem, but I suspect they are worried about a large voltage drop when another load on the battery kicks in.

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Regarding your specific trailer ". . . AF 29-5T . . . "

you may want to also ask over on the Northwood RV Owners Association forum: http://www.nroa2003.com/forum/

 

I used to belong there but I dropped my paid membership so interaction is very limited. Great forum though..

 

I think this is more of a generic issue..I suspect most trailers use the same parts for their electrical system...

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..had that space alien sitting on your face and sucking your breathe in the middle of the night....

 

I suspect we have had a few of the same experiences :) ,,,,until I found a mask I could live with, I was thinking that the cure was worse than the problem..

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More info.

 

My machine is a Respironics system one. The inverter that I bought is made specifically for this machine and sold through respironics.

 

I am old enough to be cynical of some warnings and I think Bill hit the nail on the head...we are leaving on a 5K mile trip this week so i will do a dry run. Nothing is on in our rig when we overnight except the odd light.

 

From what I am reading, I could disconnect the umbilical cord from my TV..

 

Thanks for confirming what I thought..

 

:)

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My Resmed system One lived on the 12 volt power cord for 3 years. Are you sure it is an inverter? Mine was just a power cord with 2 chokes on it. They do make them, and Resumed does sell them but you use an extra amount of power doing it that way.

 

http://www.cpap.com/productpage/respironics-12volt-dc-power-cord.html

 

Just asking cause if you 'take' out the inverter and power supply, you should get 20% longer battery life.

 

 

My Airsense 10 has a true inverter. It works on 24 volt, so I do pay a price, but it inverts from 12 to 24.

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Bill,

 

Great eye. My kit is similar ..I also have a gizmo with alligator clips to attach to a battery.

 

I was told that the actual machine when plugged into 12V with the cord you linked to acts as an inverter.

 

I think I have 2 more years before I can replace this machine ...I was a noob when I bought this one.. the next one I shall research.

 

If I understand you correctly, using my set up will suck an extra 20% out of my batteries so it would be wise to leave my TV connected overnight ?

 

Thanks..

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If you have the item that I linked to, it is the same one that I have and is the most efficient. No voltage changes, no losses, good to go.

 

They sell another one, http://www.cpap.com/productpage/respironics-dc-ac-power-inverter.html and when you kept saying inverter, this one IS an inverter and uses the extra power.

 

Another point, depending how the Freightshaker is wired, most of them 'should' disconnect the batteries from the truck to trailer. Otherwise, you could deplete the truck battery with your trailer use. I would check it out just so you know.

 

Keep a close eye on your trailer battery state of charge. Using 30% to 50% of a battery, with the poor Bargman connector and wiring, you may not fully charge by the end of day.

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I have a Philips Respironics System One that I found a generic 12V power cord for that allows me to plug it into the standard 12V outlet in the bunk of my truck camper. You should be able to do something similar and eliminate the power brick that they use to convert the 120VAC to 12VDC. If for some reason your unit uses a different DC voltage it wont be quite as easy and you will need a small inverter. As for the current draw, the heater does draw about 4-5 amps at 12V upon startup to heat the water in the humidifier. Once the water is up to temperature the current drops to less than one amp.

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Thanks.

 

Should have it wired in soon if it would stop pouring. We leave on Saturday so I will do a trial run with the rig disconnected. I am quite curious now..

 

The only way to disconnect the batteries in my truck is to disconnect the leads..I should probably put a battery disconnect on it..

 

I shall report how it goes :) ..no cpap during a couple days of hard hauling (plus 10 hour runs) is no fun.. but when the dw retires, we won't be dealing with these time constraints..

 

Thanks all...i fell better now installing the wiring..

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Sorry grassy - it would be a relay built into the truck. Properly done, power to the trailer would only be on with the engine on, no engine, no power. This would NOT be something that you would have to do, like disconnect the batteries.

 

I was suggesting that you check it so that you don't have a surprise.

 

Make sure the new installation has a fuse for protection close to the battery.

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I am running a Tekonsha brake controller.

 

I plugged in my umbilical cord (while the tv was off) and hit the lights..the trailer lit up so can I assume power is going to the battery ? I do know years ago, my tt batteries would die and the alarm would go off..I would quickly run out and plug the trailer into my truck and all was ok..

 

Was trying to find a route for the wire today .... and someone mentioned that i could tap into a fixture that works while not plugged into shore power..specifically, the headboard lights.

 

I can test tomorrow, but does any power go to the wall outlets when on battery or only when the trailer is powered up ?

 

Thanks..

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Two separate systems. 12 volt system for lighting, fridge, etc. 120 volt system for plugs and big power stuff.

 

Usually only 2 common points, the converter that charges the battery (120 volt to 12 volt). The other is the fridge. If there is 120 volts there, it powers a heating element otherwise the propane side of life (flame) cools.

 

No power to wall sockets unless you have an inverter.

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Well darn.

 

I am going to explore tapping into the lighting.. I think my body may be a tad too large to crawl into some if the places I think the wire may have to go :)

 

This has to be completed soon..nothing like a deadline to spur you on..

 

Will update when finished.

 

Thanks

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  • 3 months later...

Finished and tested.

I did look into taping into the lights above my bed ...but the wires I found were aluminum..so not a good combo.

Instead, I ran a 12 v plug to the side of my vanity..which is an easy reach for my power plug for the CPAP ..so now I can just plug and unplug when required. I did tap into wiring (not aluminum) in my storage bay and feed it up through.

Before we left, I did disconnect all power sources from the rig ...after I ran the cpap all night there was essentially *zero* effect on my battery.. I have a battery readout in my trailer. I can see no reason not to use the humidifier while on battery...I didn't bother testing because humidity was plus 80 when we were on the road..

 

So total cost... the gizmo I bought from Phillips, a 12 volt socket.. and a bit of wire and time to install....well worth it..

 

Bill,

 

"power to the trailer would only be on with the engine on".

 

Years ago, when we were boondocking a lot..and my battery was getting week...the alarm used to go off in the middle of the night. I would just run out ..I had an extension (oddly enough, it came with the rig when I bought it) ..and I would plug into the truck..the battery would come up and alarm would shut off. Haven't checked this with the present TV and rig..

 

 

 

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