Power Consumption

[sailberg]

I want to buy a backup power source for my Luna II CPAP.
The cpap consumes 150 watts.
We winter in Mexico and power can go out for hours at a time.
Question is how much power does my CPAP consume in an 8 hour period?
I want to buy a power source that will work the entire night.
The features describe a power source of 300-400 hours. So how long will the CPAP operate.
Thank you.

[Pugsy]

Impossible to answer with limited information provided.

Pressures used directly affect power consumption along with hours of use.
If you use 6 cm pressure all night you are going to use less power than if your pressure was 12 cm.

[sailberg]

My CPAP is set at 10cm.
Not sure what other info I can provide.
Thanks.

[Pugsy]

What mode of operation???? Fixed cpap or auto adjusting?
Does it stay at 10 cm all night or does it vary?

[sailberg]

Auto adjusting, although I think it’s at 10 most of the night.
Sorry for not being knowledgeable on this subject

[Grumpy48]

The biggest power consumer on a CPAP is the humidifier and heated hose. If you can do without those the CPAP will draw much less power and a lesser of a backup power source would be needed.

For my DreamStation 2 I bought a 'power station' similar to the one linked below. It can run the DS2 overnight easily if I don't use humidity with the heated hose. If I wanted to run humidity with the heated hose I would need something substantially bigger and more $$$. People use these types of power stations for camping with a CPAP.
https://www.amazon.com/Jackery-Portable ... =8-17&th=1

It's difficult to know what your Luna II draws for wattage without measuring its use with the humidifier on as well as off. It would be a guess to say the power station linked above would work OK for your Luna II with the humidity off, but I suspect it would run through the night OK. If you really wanted to know the Luna II power consumption, a meter like linked below could be used. I happen to have a 'P3 International P4460 Kill A Watt' which I've had for a bunch of years. Something of less cost would work OK as well that I bought to check power draw of appliances.
https://www.amazon.com/s?k=killa+watt&c ... _sb_noss_2

[zonker]

Sorry for not being knowledgeable on this subject

please don't apologize! if everyone was knowledgeable about cpap, there would be no reason for this forum to exist.

[Dog Slobber]

Here is the Battery Guide for ResMed. I know it won't the same as your Lunar, but it's not going to be wildly different either.

https://document.resmed.com/en-us/docum ... lo_eng.pdf

Plus you aren't buying to match closely what your Luna is drawing. You want capacity well beyond what your Luna draws.

I use the Ecoflow Delta 2. It's expensive, but has a ton of capacity and other features that make it ideal for CPAP. Here's a recent topic:
viewtopic/t189452/If-you-can-afford-one ... s-hit.html

[McSleepy]

Whatever battery-powered source you end up buying would cost you hundreds of dollars. Given that, I understand your desire to try and get the cheapest solution that would satisfy your needs. Calculating it, or even accurately estimating it may be quite difficult, as evidenced by some posts here. Thus, it may be worth it spending $30 on an instrument that would empirically determine that value. Using that tool, you will be able to measure the instantaneous power usage and experiment in different scenarios and calculate your desired result, but also - directly what you really want in the end - the total energy consumption over a period of time (a night's sleep). You want to take many measurements (as sleeping habits vary) over many nights (ideally over different seasons) and record the average and the maximum. Once you have that, get a backup power solution (portable power station or UPS, just make sure it generates a pure-sine wave or close to it to avoid damaging your machine) that fits your needs: if you want to be frugal, get one for the average energy rating you established; if you want to be safe - for the maximum; if you want to be paranoid - even higher. At least you'll know what to expect.

And to honor palerider's legacy (whatever happened to him? I hope he's alright), I will be snarky and correct you all ( ): don't confuse power (watts, W) with energy (joule, J, in SI, but for the purpose here - watt-hours, Wh). Energy is the amount of work that a system has stored or somehow capable of producing, and power is the rate of doing that work, or the amount of energy transferred or converted per unit time. I know, it's confusing - they seem to be defined by one another, but it is important to make the distinction when you are trying to make a decision on something that can cost a lot of money. Thus, the power rating determines whether your power source would be able to handle the maximum demand of your machine without faulting, and the energy rating will determine for how long you can keep doing that.

I hope this helps.

McSleepy

P.S. Full disclosure: I have never used the Kill A Watt device, only heard of if from friends and read about it online, so I can't vouch for its functionality and accuracy from personal experience. What I have experience with is professional devices of that kind (Precision Powers Analyzers) that cost tens of thousands of dollars. I know what those can do, but I've been told the Kill A Watt has similar capabilities, just much cheaper.
McS.

[zonker]

And to honor palerider's legacy (whatever happened to him? I hope he's alright)

haven't seen him now for YEARS. I hope he's okay too. miss have the little imp around.

[McSleepy]

Just to provide some idea of a sample energy consumption of a CPAP machine over a full night of sleep: last night I used my power analyzer to measure the power draw and overall energy consumption, and here are the results.

Machine: ResMed VPAP Auto in spontaneous mode (bilevel CPAP), pressures of 16-21 cm H2O, humidifier set to level 2 (out of 10), heated Slimline hose set to auto-temp, length of sleep - 11 hours (long story).
Maximum power draw: 67W, power factor - nearly 1.0 (meaning, it was mostly the purely-resistive humidifier load), total energy consumption: 470Wh.

This is kind of a worst-case scenario because of the length of the machine usage, my variable high pressures, and the use of a humidifier in an arid climate at altitude (very low absolute humidity), but it could be worse with even higher humidification levels in winter. At the current settings, my humidifier tank is almost empty after a night of use.

If looking for an energy-storing power source, the power draw will not be an issue, as anything that would be able to provide nearly half a kilowatt of energy should be able to handle <100W power load. Now, if you want to avoid the energy losses from the inverter, just get the proper DC battery power source suitable for your machine (whose electronics are using low-voltage DC anyway).

I hope this is useful to those looking to use their CPAP on batteries.

McSleepy

P.S. If you must get an inverter-based source, this seems to be a good baseline (performance/price - 960Wh/$290) for what you'd need.
P.P.S. By the way, the standby power draw with airplane mode ON is around 5W - not huge, but not insignificant, either.

[spitintheocean]

Your CPAP uses 150 W. For 8 hours, you need about 1,200 Wh.
A power source rated 300–400 Wh won’t last the full night—only 2 to 2.5 hours max.
Get a battery with at least 1,200 Wh capacity to run your CPAP all night. Check watt-hours, not just “hours” on the label.

[McSleepy]

Your CPAP uses 150 W. For 8 hours, you need about 1,200 Wh.
A power source rated 300–400 Wh won’t last the full night—only 2 to 2.5 hours max.
Get a battery with at least 1,200 Wh capacity to run your CPAP all night. Check watt-hours, not just “hours” on the label.

I am reporting actual measurements, taken with an accurate device, so it is ridiculous to question it with some speculative, generic label-based-spec calculations. As I said, the maximum power draw, which takes into account the load's power factor, meaning the true reactive power draw, was 67W, and the average - around 45W. The total energy use was 470Wh, thus, a ~500Wh power source will run it all night just fine.

McSleepy

[amenite]

The total energy use was 470Wh, thus, a ~500Wh power source will run it all night just fine.

If we're talking battery power it's good idea to avoid discharging to that depth. Using 50% of available, OK. 80% less OK. In the example above - using 94% - no bueno for some batteries, lead acid ones in particular.

[Dog Slobber]

Your CPAP uses 150 W.

Although the OP said it uses 150 W., it doesn't.

The power supply it comes with is a 65W power supply.