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Powering CPAP in MY
- Thread starter Zompopo
- Start date
It seems like most CPAP machines don't draw a lot of power, 30-60w maybe : Can I sleep with a CPAP in my RV?). That amount of power would be okay to feed through the "cigarette lighter" socket using an inverter. You wouldn't need a battery in that case but the car would need to stay awake, for example using camp mode. You should make sure by checking the exact power consumption of your device.
EDIT: I think the socket supports 120w continuous and 150w spikes, but someone else could confirm.
EDIT: I think the socket supports 120w continuous and 150w spikes, but someone else could confirm.
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Travel machines like the ResMed Air Mini can be powered directly with a 12V accessory cable or with a battery. In our camper I use a full size home machine powered by a small inverter plugged into a 12v outlet. The overnight draw on the house battery is pretty much insignificant, at least when running it without the humidifier.
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Check with the manufacturer of the CPAP machine. The current production Tesla Model Y vehicle uses a 15.5V lithium starter battery module (replaces the older 12V lead-acid starter battery.) The Tesla Model Y Owner's Manual states that when using equipment such as a power inverter the inverter must be able to operate using 16V DC.
Note: For vehicles manufactured after approximately November 2021, power inverters plugged into the low voltage power socket must support 16V DC input to function.
Model Y Owner's Manual | Tesla
Note: For vehicles manufactured after approximately November 2021, power inverters plugged into the low voltage power socket must support 16V DC input to function.
Model Y Owner's Manual | Tesla
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I'm still patiently waiting for Tesla to release an adapter to power devices from the pack like a Kia. I thought I read somewhere that the Tesla hardware has the ability to use the pack to power devices like the Chevy truck and Kia do. They just haven't implemented an adapter for it.
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Pricedm
Member
For my dad to be able to do off-grid camping (7 day whitewater river trip) his set-up is a Goal Zero 500 battery, Goal Zero folding solar panel, and Philips 12v DC power supply (links below). The battery would power the CPAP for 2-3 nights with humidifier, before needing solar recharge.
If your Model Y has a legacy-style "cigarette" plug (like my 2018 Model 3), then yes I believe in Camp Model, the accessory port will have continuous power. This Philips 12c DC power supply will likely work.
Yeti 500X
Nomad 50
($10 for shipping if anyone can use this)
www.cpap.com
If your Model Y has a legacy-style "cigarette" plug (like my 2018 Model 3), then yes I believe in Camp Model, the accessory port will have continuous power. This Philips 12c DC power supply will likely work.
Yeti 500X
Nomad 50
($10 for shipping if anyone can use this)
Philips Respironics Shielded DC Cord for DreamStation CPAP Machines | CPAP.com
Used to connect your Philips Respironics DreamStation to a cigarette lighter–style 12v outlet, the Shielded DC Cord for DreamStation CPAP Machines works to power your DreamStation and heated humidifier or heated tubing. Lea
www.cpap.com
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I searched this forum for "CPAP", and I found a few threads about it:
teslamotorsclub.com
teslamotorsclub.com
teslamotorsclub.com
Using DC Power Converter in the Model 3 during Camp Mode
Hello Community! We've been camping a little more often now, and I want to try sleeping in the Model 3 using Camp Mode. However I need to use a CPAP machine when I sleep and wanted to use 12v Power Socket with the ResMed AirMini Travel CPAP 65W DC Converter. By the looks of the specs and...
teslamotorsclub.com
110 outlet in Model 3
I would like to pull into a RV Park and plug into a 14-50 outlet and then be able to plug into 110 outlet inside the car to be able to use a CPAP machine and sleep in the car. It could be part of a camping package.
teslamotorsclub.com
12 Outlet question--car camping
I have some 12v camping gear and I have a 12 volt adapter for a CPAP machine I use at night. I simply would like to know whether the current in the MX 12v outlets comes from the small 12v battery or from the massive traction battery? Makes a huge difference in knowing how much I can use the 12...
teslamotorsclub.com
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It would appear so. The inverter in the link you provided can operate on DC voltage from 10V up to 17V. The maximum stated output of the inverter is 110 VAC, 155W (modified sign wave power.) What does the CPAP manufacturer specify on the CPAP power adapter brick that would normally be plugged into the wall outlet? The inverter price is less than $50. Find out if you can return the inverter within 30 days if it does not meet your needs.
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First things first.
- Go to the label on the CPAP machine. Figure out the current and voltage, multiply, and that's the power. Look at the brick/wall-wart, confirm the numbers. Likely that the brick's max output power will be greater than the max input power of the CPAP. While you're at it on the brick, look at the maximum input power, which will be 120 VAC * AC_Current. Get the loss ratio, which will be max_output_power_of_brick/max_input_power_of_brick. Divide that ratio into the max input power of the CPAP, and you'll now the max power draw of the whole shooting match.
- I happen to have a CPAP upstairs. One sec. CPAP says: 24V, 3.75A. Brick says 24V, 3.75A on output, 115VAC at 1.5A on input. So, 90W on the CPAP, 172W on the brick input. (Um. That's a lot of losses in the brick). 90/172 = 0.512. So, 90W/0.512 = 175W... Well, dunno, the numbers don't quite make sense. But figure ~120W. Your CPAP numbers may vary.
- Next question: How many amps out of the 12V socket? Your picture looks like a Model Y. Doing a quick look-up.. On TMC, a lead-acid (12V) socket can do 12A max, 17A peak, but the data is in the user manual. You know, the one on the touch screen in your car. That's 144W or so.
- Checking your link: 10V to 17V input, 155W output. Looks good.
If you get really picky, you can contact the manufacturer of the CPAP machine, tell them what you have in mind, and ask, politely, what the steady-state draw looks like. It's just possible that the manufacturer's web site might have more detailed data, but wouldn't bet on it. Believe you me, they have that data, but they tend to put stuff on the sticker that's legally required. If you have the manual for your CPAP, you might look through there, but that's another place where, unfortunately, manufacturers tend to dumb things down.
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Good information. So, in general, on the input side: These things use switching power converters that, roughly, have the same power draw, no matter what the input voltage. So, if you got 100V @ 1A (low voltage => high current) and 240V @ 0.5A, that's pretty much 100W to 120W input power max. (Not unusual to have a little variation in the efficiency as the voltage on the input varies.)
Output voltage at 17V @ 1.67A => 28.4W. So.. Most DC->DC switching power supplies I run into are around 80% efficient or better; 95% isn't unheard of. Generally, these bricks rectify the AC voltage into a DC voltage, then use (relatively) high-frequency transistors to switch the DC voltage back and forth across the input of a transformer. The output side of the transformer (the transformer, by the by, is what makes the brick heavy, it's likely a ferrite) has either diodes or another set of switching transistors to rectify the output, giving you your 17V. There's a control loop, usually done with an opto isolator, that pulse-width modulates the front-end switching transistors to give one a more-or-less steady DC voltage at variable current.
So, don't know why the label has that 100V-240V, 1A-0.5A input rating: The power numbers on input seem 'way too high. Unless there's an instantaneous surge of current when the thing gets plugged in, which is possible.
So, yeah, the CPAP you've got (you're right, no heating chamber!) could work with the 155W unit that @tm3lrawd found. Lessee, his CPAP is 12V at 6.67A; that's 80W; throw in 80% efficiency on the brick, and that'd be 100W; which should be fine with the 155W unit.
Finally, say that @tm3lrawd uses this thing for 8 hours at 100W; that'd be 8 kW-hr, pretty much a drop in the bucket for a 78 kW-hr battery in his car. Ha. With the car, "on", bet the car itself would be drawing more than 100W, for a total guess (complete with hand-waving) of around 16 kW-hr used up overnight. That's roughly 16/78 = 20% of the charge in the car, so it'd be a Good Idea to have the car at, say, 50% charge before going nighty-nite.
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tm3lrawd
Member
Thank you for such a detailed and quick response! I had a hard time with the calculations.
My MY manual says the power outlet supplies up to 12A continuous and 16A peak. My charging brick input is 100-240V ~ 2.0-1.0A. Output 12.0V 6.67A. My CPAP is also rated 12.0V. 6.67A.
Can you crunch the numbers for me?
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Easy enough. Pay attention, there'll be an exam! (Well, not really..
)Start with the CPAP. That's the load. 12V, 6.67A. Power (in Watts) = Voltage * Current, so you have 12V * 6.67A = 80W. So, your CPAP uses as much power as an 80W light bulb.
Assume that the brick is about 80% efficient: That is, of the power going in, 80% comes out. So, 80W/(0.8) = 100W input to the brick.
Next: You'll have a box that delivers 120 VAC at 100W (That's about 0.833A. If P = V*I, I = P/V. Whee.)
Assume that the box that converts from DC to AC that you're going to plug into the car is also 80% efficient. (If the manual says otherwise, my apologies). So, Power_From_Car = 100W/0.8 = 125W.
So, this is where it gets a little fun. Power into the inverter (the box that takes in DC and converts it to AC) will be, roughly, constant, no matter what voltage is coming out of the car's power outlet. So, suppose that your car has 12V present? Then, I = P/V = 125W/12V = 10.4A. Well, that's less than the 12A the car can do, max, so that's good.
Suppose your car is 15V? Well, I = P/V = 125/15 = 8.33A. Which is also good and less than the 12A the car can supply.
Finally: Say you've got the CPAP hooked up and running and the car's in Camp Mode. How much of your Model Y battery is going to be discharged?
Power is a rate, like gallons per minute in a hose. Energy is like water in a bucket, like, say, a 5 Gallon bucket. Energy is (in SI units) measured in Joules; a Watt is a rate of one Joule per Second.
For various historical and idiosyncratic reasons, we tend to measure battery capacity in Watt-hours. One Watt Hour is 3600 Joules. (That's because there's 3600 seconds in an hour...) A typical Model Y battery has a capacity, I think, of 81 kW-hr.
So, how much energy does the CPAP use in 8 hours? 125W * 8 hours = 1 kW-hr. (or 3.6 Million Joules). Percent of charge reduction for just the CPAP running is 1 kW-hr/81 kW-hr = 1.23%. That's not much of a reduction. Funny bit: I think that the car, itself, runs more than that when it's in camp mode.
Best bet: Put the car in Camp Mode and leave it in the garage (or wherever you keep it) overnight, checking the State of Charge before and after. The difference will be the amount of energy used by the car's camp mode, in State of Charge percentage. Add to that the 1.23% we came up with, and you'll have the State of Charge reduction.
How many miles of range is that? The energy graph in the car will tell you the "rated" W-hr/mile; it's probably around 270 W-hr/mile. So, say you figure out that, between the car being on and you running your CPAP, the car loses 5% of charge overnight. 5% of 81 kW-hr = 4.05 kW-hr. 4050 W-hr/(270 W-hr/mile) = 15 miles of range.
Not a lot
.
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Thing is, none of the above requires a EE degree. Or even a EET. Or even an electrician's license. We all got exposed to Ohm's Law in High School or earlier. This is just the first time in NN number of years that people have had to start thinking about it.
Base equations:
V = I*R
P = V*I
Energy = P * Time
Most complicated: 3600J of energy is the same as 1 Watt-hour.
Oh, yeah: Cost is in $ per kW-hr. (Like.. 43 cents per kW-hr). Used by electrical utilities and people with electrical energy to sell everywhere
.
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I would suggest an EcoFlow , Bluetti or the like. But make sure it’s one with a Pure Sine or UPS feature.
They’re useful for camping on their own and should provide a better source of power.
The computers in some CPAP can be a little picky. Besides these are medical devices and at least for some are life support systems so don’t mess with subpar power.
Prices on these things are so cheap anyways. Certainly far cheaper than pitching most CPAP machines.
They’re useful for camping on their own and should provide a better source of power.
The computers in some CPAP can be a little picky. Besides these are medical devices and at least for some are life support systems so don’t mess with subpar power.
Prices on these things are so cheap anyways. Certainly far cheaper than pitching most CPAP machines.
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Um. That kind of depends. The alternator output, back in ye olde days, would be AC, get rectified, go through a regulator, which would then charge a lead-acid battery. Max voltage on a lead-acid is around 13.6 VDC, if memory serves. Put more than that into the battery and it can be damaged, which is why battery chargers definitely don’t do that.
The regulator sets the max current into the battery at a particular battery voltage, reducing the current as one approaches the max battery V.
So, on a car with a lead-acid battery connected to all the hardware, 13.6 is the max one’ll see, no matter what the alternator (not present on a Tesla) voltage might be. Min voltage for an ICE might be around 9V when one is cranking the engine on a cold day.
Finally, the charger/regulator voltage and current is very definitely marched to the battery chemistry. There might be an exception for some kind of auto-figuring-it out charger that can recognize the battery type out there, but that’s it.
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