12 Volt Power to My Outlets

The figures that MEX gives probably vary by machine as well as manufacturer.

A few observations from my experience using CPAP in an RV.

In my own experience, my Respironics machine (REMStar Auto) worked very well on 12 VDC. I boondock a lot in cold weather (spring and fall). I do not know for sure whether my voltage at the machine ever fell below 11.5, but it likely did so. I can’t remember ever disconnecting my CPAP from 12 VDC when charging the batteries using a generator plus the on-board converter (WFCO). I’m sure voltage went above 13.5 when charging, but then I was never using the CPAP at the time. I’ve never had a problem. At 19,000 plus hours it is still going strong.

The new rig has a modified sine-wave inverter and I’ve only used the old CPAP about 10 nights with it, so far. It remains to be seen whether that becomes a problem.

My wife used a ResMed VPAP Adapt ASV in the past and it was no end of problems. First of all, the 12 VDC cord cost over $100, vs. $25 for the Respironics. When we went to use it in the TT, it immediately shut down. The only way to get it started again was to start up the Yamaha Ef1000is and plug it into 120 VAC. Then it would immediately fail again when returned to 12 VDC. Long story short, after speaking to a technician/engineer with ResMed, I found that it was designed to shut down if the voltage went below 12.00 VDC. Camping in the mountains in the early spring with batteries in a box on the tongue, good luck maintaining 12.00 VDC or better, especially if something else using 12 volts (such as the furnace blower) cycles on. The technician/engineer protested that they worked fine for him, in the lab with his 12-volt power supply, and argued that there was something inherently wrong with using 2 T-105s in series and that it was my fault because of that! As I told the technician/engineer, 1) I was using a big 12-volt battery that I could carry around in 2 6-volt packages and 2) their product was designed to fail in the real world, where batteries sometimes get cold and their machine isn’t always the only thing drawing power!

The answer was a small pure sine-wave inverter. I installed a small Samlex (300/400? Watt) pure sine inverter just inside the front wall, using heavy wire (AWG 8) for the short run, and had no further problems. (I wish I had thought to keep that little Samlex when I sold the TT.)

I bought the Samlex after trying another brand of pure sine inverter recommended by a CPAP place failed miserably – sorry, I can’t recall the other brand. (It released the smoke inside when after installing I load tested it using a portable lamp with a 100 Watt bulb!) The Samlex is worth a few extra bucks.

Wayne

"my preference would to be to pull a dedicated wire from the 12v distribution panel and install the outlet near where she plugs in for the 110 volt feed. This way she has either voltage depending on our power situation."

This sounds right to me.

Personally, I limit inverter use as much as possible when boondocking. If I'm at work, sleeping, or away from the camper in general, I do not have the inverter on. Fridge, heat, etc., are all wired direct to bank.

Johno02 wrote:
They are easy to find! Just walk around the campground and ask!

True dat! :B

Getting powerfrom the bedside light circuit would probably work, but installing a dedicated citcuit would be best, if feasible. The wiring for the light circuit may not be adequite for the CPAP, and or the fuses might be too small. In our case, the converter and power panel are under the bed, so it was easy to install a plug with good wiring and a fuse.

Getting powerfrom the bedside light circuit would probably work, but installing a dedicated citcuit would be best, if feasible. The wiring for the light circuit may not be adequite for the CPAP, and or the fuses might be too small. In our case, the converter and power panel are under the bed, so it was easy to install a plug with good wiring and a fuse.

They are easy to find! Just walk around the campground and ask!

They are easy to find! Just walk around the campground and ask!

Johno02 wrote:
...have an electrical engineer experienced with delicate medical equipment to plan and design the structural design, and anexperienced RV technigian to perform the actual installation tasks. Then have an electrical inspector approve the entire job....

That is hilarious;

It is unlikely an electrical engineer had anything to do with designing the electrical system in your RV to start with.

I doubt many RV technicians have much electrical knowledge when it comes to wire gauge and resistance.

Where exactly do you go to find an electrical inspector to check your 12vdc electrical receptacle inspection? Inspectors R Us?

Double post, delted.