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Old 07-29-2014, 07:17 PM   #15
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Quote:

I discovered that 12v cables are available for my CPAP and have ordered one, but also saw on the CPAP that it draws 1 amp on 110V and 3 amps on 12V.
So my question is whether it is more efficient to use the 300w inverter to run the CPAP on 110, or to plug directly into 12v.
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Originally Posted by Reed Cundiff View Post

How much power does a CPAP use?

Reed and Elaine
The answer to your question was in his very first post.

Dr4Film ----- Richard
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Old 07-30-2014, 07:26 AM   #16
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Originally Posted by SkiSmuggs View Post
I was disappointed that my battery charge was the same after a night of direct 12v running of my CPAP vs an inverter. Then I checked the status before going to bed and found that after a day on 110v to the house, the charge was about 12.6, but after a few hours playing with the new Renogy 100w portable solar, the charge was 12.68 before plugging in the inverter. So the starting charge was the difference in outcomes.
It seems my morning battery status is 12.54 volts either way, but direct 12v eliminates the inverter fan noise.
My Bestek 300w inverter plugs into the 12v outlet in the BR TV cubby. I could probably mount a pretty nice one like the Samlex PST-30S-12A with a direct battery connection in the BR closet which is right over the battery compartment. What are the advantages to that other than being able to turn down the fan noise by shutting the closet doors?
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Old 07-30-2014, 07:50 AM   #17
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Sorry, I did not realize that you were using a small portable inverter versus a larger hardwired one that normally comes with some RV's.

I have no idea how much power loss and usage loss the small portable units create versus the larger on-board hardwired inverters.

Either way, you are far better off running your CPAP plugged directly into you 12 VDC outlet providing that the wiring is large enough to handle the amps/watts.

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Old 07-30-2014, 07:57 AM   #18
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Sorry, I did not realize that you were using a small portable inverter versus a larger hardwired one that normally comes with some RV's.

I have no idea how much power loss and usage loss the small portable units create versus the larger on-board hardwired inverters.

Either way, you are far better off running your CPAP plugged directly into you 12 VDC outlet providing that the wiring is large enough to handle the amps/watts.

Dr4Film ----- Richard
Thanks, I may add a 12v receptacle to the BR closet where the CPAP sits on the shelf so I don't have to run the 12v extension cord to the TV nook. That way I can be sure of the wiring being heavy enough and it will be more convenient as well. My fiver didn't come with a house inverter that I am aware of, probably because of the Grp 24 battery it came with. This will be an ongoing project as the list keeps getting longer. Part of the fun though.
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Old 07-30-2014, 10:35 AM   #19
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Richard - yep, should read all the posts, particularly the first one.

12 V receptacles are extremely hand. We have four in the living room, two in the bedroom and a couple in the large storage bay. We use them to charge camera and Iphone batteries, lights in the bay, and for the 12 V fans on hot days. The fans make life livable and nights sleepable on warm nights boondocking.
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Old 07-30-2014, 01:50 PM   #20
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12 V receptacles are extremely hand. We have four in the living room, two in the bedroom and a couple in the large storage bay. We use them to charge camera and Iphone batteries, lights in the bay, and for the 12 V fans on hot days. The fans make life livable and nights sleepable on warm nights boondocking.
Reed and Elaine
Other than the BR closet which is right over the battery compartment, I need to figure out how to run wire to the living room as I don't have any 12v there and only the one in the BR and one in the basement. There really isn't any good crawl space past the basement storage.
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Old 07-30-2014, 08:05 PM   #21
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Most of the lights are 12 V, so just attach through one of them. T think the 12V lights are 10 amp circuits.
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Old 07-31-2014, 09:04 AM   #22
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Most of the lights are 12 V, so just attach through one of them. T think the 12V lights are 10 amp circuits.
Reed
Thanks! I hadn't thought of that but am buying receptacles today and will give it a shot. I really like the idea as it makes adding receptacles to the slide outs easy and that is where the need for them is in my fiver and my lights all have LED so I don't have to worry about excessive draw.
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Old 07-31-2014, 05:38 PM   #23
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Make sure of the amperage to the light. Our light circuits are all 10 amps. As you, all our lights are now LED so there are plenty of amps/watts to be used. 12 volt supply is a nice PC alternative up "cigarette lighter"
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Old 07-31-2014, 06:59 PM   #24
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Turning on our 4.0 kW PSW inverter uses around 50 to 60 watts. Then there is definite efficiency loss through the inverter.We agree with Dr4Film at post #4 that AC would use less energy since it is direct from battery.

We have 1420 W of solar, so we are close to what Pasdad1 calls "serious" boondocking.

How much power does a CPAP use?
Reed and Elaine
It says it draws 3 amps DC and 1 amp AC. Using a Bestek 300w converter plugged into the DC outlet seems to result in similar battery status readings in the morning, typically somewhere between 12.51 and 12.56 but there is no real consistency as I have slept up to 9 hours on weekends and 6-7 on weekdays.
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Old 07-31-2014, 10:59 PM   #25
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Take another read on your inverter's manual. Most suggest that the DC plug-in be limited to 100w. That's all the plug-in can handle. You'll be right on the edge if not over with the CPAP.

The Samlex PST-30S-12A hardwired is a great idea. Its what I did for other items. However, I still run my CPAP from a DC plug-in I installed from a DC light circuit next to the bed. 3 amps, ~ 36 watts will be fine.
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Old 08-01-2014, 01:25 PM   #26
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This doesn't make sense either. If the CPAP takes 1 amp on 120 VAC, it should take close to 10 amps on 12 VDC. There could be a little lost with the 120 VAC conversion, but not much.
I think the mfg round things off. I bet it takes way less than 1 amp when on 120VAC.

Either way running the CPAP on 12VDC is going to be the most efficient.
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Old 08-01-2014, 06:40 PM   #27
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As others have noted, just turning on the inverter takes power and there are further power losses in inversion. Our 4 kW takes 50 W just to run and loses one heck of a lot when running the a/c (a 15000 btu) off the battery suite.i guess guess we are all in agreement that DC is the best way to go.
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Old 08-01-2014, 06:52 PM   #28
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Best way to determine actual power consumption of a 120vac device is with a Kill-a-Watt gizmo. Will also tell you usage over time , not just instantaneous consumption. Handy to have to know for sure what's reality is.
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