Current Draw

[TxBobS]

Has anyone found or done a dc current draw comparison of different machines?

I have an S9 VPAP right now that in order to use it from 12v I have to run their DC to DC converter. According to their doc, it only uses about 1 amp. That seems pretty low when compared to some of the "travel" machines that are in the 2a range.

I want to get a new machine but current draw is a key factor in deciding which one since this will be for off-grid camping.

[HoseCrusher]

You may find this thread informative...

viewtopic/t114012/Choosing-a-Battery.html

[TxBobS]

Thanks. I had read that but it seems to deal with a specific machine and how much power one might need in their system. My system is pretty much done at this point. I am just looking to minimize the load so I can camp longer.

If I looked at the no heat option correctly in that example, that is a .5a machine. What bothers me is I see some that would be in the 2-3a range according to their specs. (all for non-heated/no-moisture)

If you're curious I have 235ah lead acid cells so ~115ah usable. I have 180 watts of solar but I will probably be adding another 180 watts. The goal is to run the generator as little as possible.

[DreamDiver]

This is a video showing current less than one amp on average.

https://youtu.be/c5TSe7o5m_8

At the beginning, it's pretty low, around .2 amp. Clearly, the amperage varies with inhale, exhale, hose heating and tank heating. I had this set for normal humidifier settings. The highest is amperage seen in this short test was .7 amps. Watts range similarly from 20 to 90. I used an AC outlet. I suspect 1 amp is a good upper limit for what this machine will draw. However, the Resmed 90W DC converter for the S9 has identical output, so these measurements should hold true for the machine under battery usage as well.

I hope this helps!

Chris

[TxBobS]

This is a video showing current less than one amp on average.

Thanks. That seems to agree with what they published. When I look at things like the IntelliPap2 and the Z1 Auto for example, they appear to draw significantly more than that. Maybe I should just keep my S9.

[CapnLoki]

Thanks. I had read that but it seems to deal with a specific machine and how much power one might need in their system. My system is pretty much done at this point. I am just looking to minimize the load so I can camp longer.

If I looked at the no heat option correctly in that example, that is a .5a machine. What bothers me is I see some that would be in the 2-3a range according to their specs. (all for non-heated/no-moisture)

If you're curious I have 235ah lead acid cells so ~115ah usable. I have 180 watts of solar but I will probably be adding another 180 watts. The goal is to run the generator as little as possible.

This is the ResMed guide that covers your machine:
https://www.resmed.com/us/dam/documents ... lo_eng.pdf

You didn't mention a pressure but the range for a S9 is roughly 0.5 to 1.0 Amps, slightly higher than the machine I tested in the big thread. A 200+ AH battery should run this for several weeks, but a 180 watts of solar, if well positioned, could generate 20 to 40 AH a day, much more than the pump uses. By comparison, I have about twice the battery and solar on my boat, and I'm able to run refrigeration full time, on top of lights, TV, and computers. The pump is a small part of the load. Your large battery should carry you through several rainy days and a genset allows you to weather worst case situations, so I'm not sure what your concern is.

EDIT: many published specs only show the worst case AC load, not the true DC load. I don't know about the Intelipap, but the true load of a Z1 is rather low, maybe 0.3 amps. As far as new machines go, the Airsense 10 that replaces the S9 seems to use somewhat more power. I haven't tested the new Dreamstation that replaced my 560 but pretty sure it will be similar to the 560. These are all less than your VPAP which will be dependent on the model and settings, but even that should be easily covered by your battery/solar.

[DreamDiver]

Follow up on the killawatt ez meter readings:

After a full 24 hours plugged in, the kwez meter reads 0.26 killowatt hours.
With the machine plugged in and ready for therapy, it draws 0.1 amp at 5 watts. So if you leave your machine plugged in all day, it is drawing some power. 0.26 kwh is about what you can expect for someone with an S9 autoset with pressures at 10.4 to 12 cm h2o. This test is on AC, but hopefully, it will be enough of a gauge to suggest what to expect on battery.

Below are suggestions for battery-operated use based on previous understandings of the S9 firmware and hardware. If others have better suggestions, I'll edit them here.

Best practice 1
Wait at least 2 minutes after your therapy is complete after you tap the power button off and before completely unplug the power from your machine. This is because some data are stored at two-minute intervals, including some ahi data. You may lose some data if you wake up, tap the power button off and then unplug your S9 immediately.

Best Practice 2
Wait until your hose drying sequence has finished (about 20 minutes after your therapy has ended). This will ensure that your hose remains dry for the 10+ hours before your next night's therapy, reducing the likelihood of stuff growing inside your tube. Yes, it's twenty minutes longer, but if you have the power, why not let the machine do it's normal thing?

Best Practice 3
Yes, you could long-press the power button after two minutes to power the device down, but the power draw still remains 0.1 amp at 5 watts. If your battery life is precious and you're not sure when you will next have a chance to charge your battery, it's worth considering unplugging your machine rather than long-pressing to power down.

I'm going to leave it on for a week or so to get a better average for the kwh.

I hope this helps!

Chris

[CapnLoki]

Follow up on the killawatt ez meter readings:

After a full 24 hours plugged in, the kwez meter reads 0.26 killowatt hours.
With the machine plugged in and ready for therapy, it draws 0.1 amp at 5 watts. So if you leave your machine plugged in all day, it is drawing some power. 0.26 kwh is about what you can expect for someone with an S9 autoset with pressures at 10.4 to 12 cm h2o. This test is on AC, but hopefully, it will be enough of a gauge to suggest what to expect on battery.

I don't think this can be right - 260 WattHours for a day means about 90wh for a night, or 7.5 amp-hours for a night at 12 volts. Since this is more that a S9 uses at pressure 10 (without humidity) it would mean that the load goes up when the pump is turned off! I've never measured a S9 but the load of a Respironics is quite low when the pump is not on. That said, there would be no value of leaving it plugged into a battery when not used.

Below are suggestions for battery-operated use based on previous understandings of the S9 firmware and hardware. If others have better suggestions, I'll edit them here.

Best practice 1
Wait at least 2 minutes after your therapy is complete after you tap the power button off and before completely unplug the power from your machine. This is because some data are stored at two-minute intervals, including some ahi data. You may lose some data if you wake up, tap the power button off and then unplug your S9 immediately.

Probably wise to wait a bit, but 10 to 15 seconds is probably enough - that's all a Respironics machine needs to save.

Best Practice 2
Wait until your hose drying sequence has finished (about 20 minutes after your therapy has ended). This will ensure that your hose remains dry for the 10+ hours before your next night's therapy, reducing the likelihood of stuff growing inside your tube. Yes, it's twenty minutes longer, but if you have the power, why not let the machine do it's normal thing?

The value of drying the hose is debatable, but running the pump flat out on a battery wastes a lot of power. I think when I measured my Respironics running free it was about 5 times the normal usage. So drying the hose is like running pump almost an extra 2 hours!

And - if you're running on battery you probably don't use a humidifier and the hose should not be moist.

Best Practice 3
Yes, you could long-press the power button after two minutes to power the device down, but the power draw still remains 0.1 amp at 5 watts. If your battery life is precious and you're not sure when you will next have a chance to charge your battery, it's worth considering unplugging your machine rather than long-pressing to power down.

I don't know the meaning of "0.1 amp at 5 watts" but I agree, unplugging is the best way to make sure you don't waste power. Each situation is different, but I unplug and stash the pump every day when on battery power, mostly to to protect the gear when roughing it.

[DreamDiver]

I don't think this can be right - 260 WattHours for a day means about 90wh for a night, or 7.5 amp-hours for a night at 12 volts. Since this is more that a S9 uses at pressure 10 (without humidity) it would mean that the load goes up when the pump is turned off! I've never measured a S9 but the load of a Respironics is quite low when the pump is not on. That said, there would be no value of leaving it plugged into a battery when not used.

This is over a 24 hour period with the machine plugged in continually with humidity. I could reset the meter each night and try to capture just the time in service. Allow me to get a week's worth of data while continually connected first, and then I'll give that a try.

Probably wise to wait a bit, but 10 to 15 seconds is probably enough - that's all a Respironics machine needs to save.

It's at least 2 minutes. When the S9 first came out, several of us on Cpaptalk helped troubleshoot a firmware problem with Resmed. Our troubleshooting helped Resmed with their second version of the firmware. Our resultant experimentation with the logs confirmed that several logs lose data if you don't wait at least that long after tapping the power button off at the end of therapy.

The value of drying the hose is debatable, but running the pump flat out on a battery wastes a lot of power. I think when I measured my Respironics running free it was about 5 times the normal usage. So drying the hose is like running pump almost an extra 2 hours!

And - if you're running on battery you probably don't use a humidifier and the hose should not be moist.

I use the humidifier with my battery. I'd be curious to know if others do too. Without humidity, when I wake up my nasal passages are like cracked leather. It feels like I've been kicked in the nose with a soccer ball all the next day if I don't use it. Even with humidity, I wake up with a dry throat. I'm pretty much a humidier user.

I don't know the meaning of "0.1 amp at 5 watts" but I agree, unplugging is the best way to make sure you don't waste power. Each situation is different, but I unplug and stash the pump every day when on battery power, mostly to to protect the gear when roughing it.

Apologies, I'm not an electrician, so I'm probably presenting the information incorrectly.
When the machine is plugged in but not delivering therapy, these are the readings on the meter:
amps: 0.1
watts: 5
volts: 121.1
power factor: 0.39
Hertz: 59.9
VoltAmps: 12

I used the machine for therapy overnight.
When the meter hit 24 hours I took a reading:
killowatt hours: 0.26

The video above shows the amps measured while the machine is on and the mask is in place so that we can acknowledge how it varies with time.

[CapnLoki]

I don't think this can be right - 260 WattHours for a day means about 90wh for a night, or 7.5 amp-hours for a night at 12 volts. Since this is more that a S9 uses at pressure 10 (without humidity) it would mean that the load goes up when the pump is turned off! I've never measured a S9 but the load of a Respironics is quite low when the pump is not on. That said, there would be no value of leaving it plugged into a battery when not used.

This is over a 24 hour period with the machine plugged in continually with humidity. I could reset the meter each night and try to capture just the time in service. Allow me to get a week's worth of data while continually connected first, and then I'll give that a try.

This is confusing - are you saying that you used the pump, with humidity for a night and then letting it stay on for another 16 hours and the 260 watt-hours represents the total? I'm not sure I see the value there - perhaps if you noted the power when you turned off the pump then you could show the idle usage.

And are you saying that it runs the humidifier all day when the pump isn't running? That would seem to be a design flaw!

Probably wise to wait a bit, but 10 to 15 seconds is probably enough - that's all a Respironics machine needs to save.

It's at least 2 minutes. When the S9 first came out, several of us on Cpaptalk helped troubleshoot a firmware problem with Resmed. Our troubleshooting helped Resmed with their second version of the firmware. Our resultant experimentation with the logs confirmed that several logs lose data if you don't wait at least that long after tapping the power button off at the end of therapy.

so this is a bug in the ResMed software? Seems odd but I can believe it.

The value of drying the hose is debatable, but running the pump flat out on a battery wastes a lot of power. I think when I measured my Respironics running free it was about 5 times the normal usage. So drying the hose is like running pump almost an extra 2 hours!

And - if you're running on battery you probably don't use a humidifier and the hose should not be moist.

I use the humidifier with my battery. I'd be curious to know if others do too. Without humidity, when I wake up my nasal passages are like cracked leather. It feels like I've been kicked in the nose with a soccer ball all the next day if I don't use it. Even with humidity, I wake up with a dry throat. I'm pretty much a humidier user.

I certainly use the humidifier at home but I never use it when "off grid" and I think that the vast majority of campers and boaters forego the humidifier. In many locations the ambient humidity is sufficiently high that added moisture is not needed. Certainly not needed on the water, and in many locations the dew point stays high so when the temp drops at night the relative humidity is high. Nothing wrong with using humidity if you have the battery power but I don't think I would call it "Best Practice" unless you're camping in the desert.

I don't know the meaning of "0.1 amp at 5 watts" but I agree, unplugging is the best way to make sure you don't waste power. Each situation is different, but I unplug and stash the pump every day when on battery power, mostly to to protect the gear when roughing it.

Apologies, I'm not an electrician, so I'm probably presenting the information incorrectly.
When the machine is plugged in but not delivering therapy, these are the readings on the meter:
amps: 0.1
watts: 5
volts: 121.1
power factor: 0.39
Hertz: 59.9
VoltAmps: 12

I used the machine for therapy overnight.
When the meter hit 24 hours I took a reading:
killowatt hours: 0.26

The video above shows the amps measured while the machine is on and the mask is in place so that we can acknowledge how it varies with time.

For AC circuits the Watts is what counts - the amperage is a bit of an illusion, especially when the power factor is so low. The 5 watts means the actual current load is closer to .04 amps, but even that is way too high for the machine at idle - its essentially the load of the pump at low pressure. Measuring the AC power to determine the DC load is problematical, especially the low load of idle. The DC power brick is probably inefficient at low power, and the KillAWatt meter has rather mixed reviews for accuracy. The only thing that makes sense is to measure the DC load from a battery.

But again, it only makes common sense to unplug the battery when its not being used.

[chunkyfrog]

The Kill-a-Watt (trademark) meter is an excellent tool.
We have used one to determine how much it actually costs to use the water distiller.

[Jas_williams]

Where is this meter located ? Is it the mains side of the powerbrick if so your including losses due to heat of running the 110v to 24v power conversion which is separate to machine usage.

[DreamDiver]

This is confusing - are you saying that you used the pump, with humidity for a night and then letting it stay on for another 16 hours and the 260 watt-hours represents the total? I'm not sure I see the value there - perhaps if you noted the power when you turned off the pump then you could show the idle usage.

And are you saying that it runs the humidifier all day when the pump isn't running? That would seem to be a design flaw!

Yikes. Maybe I shouldn't reply late at night. Apologies for confusion.
I use a humidifier. It stays connected and ready to use whenever I use the machine. I use the S9 for usually about 7.5 hours each night. Sometimes it's split into a nap and less time at night. The S9 remains plugged in and drawing power regardless of whether it's on and delivering therapy or sitting dormant. Over the 24 hour period, including the time in therapy and machine dormancy, it used 0.26 kwh.

There is a period of time after the S9 is turned off when the blower runs at extremely low pressure to dry out the tube. The S9 is dormant (idle) when the blower isn't drying out the tube and no therapy is being delivered. It still draws current when idle.

so this is a bug in the ResMed software? Seems odd but I can believe it.

The Resmed bug was resolved in the 2nd iteration of its firmware. It involved increasing distance between apnea/hypopnea indices and where they were actually located on the graphs. It had nothing to do with the 2-minute logging closure time that is still required by the S9. They are separate issues.

I certainly use the humidifier at home but I never use it when "off grid" and I think that the vast majority of campers and boaters forego the humidifier. In many locations the ambient humidity is sufficiently high that added moisture is not needed. Certainly not needed on the water, and in many locations the dew point stays high so when the temp drops at night the relative humidity is high. Nothing wrong with using humidity if you have the battery power but I don't think I would call it "Best Practice" unless you're camping in the desert.

This is like full face or nasal. Perhaps debating the point is about as fruitful.

For AC circuits the Watts is what counts - the amperage is a bit of an illusion, especially when the power factor is so low. The 5 watts means the actual current load is closer to .04 amps, but even that is way too high for the machine at idle - its essentially the load of the pump at low pressure. Measuring the AC power to determine the DC load is problematical, especially the low load of idle. The DC power brick is probably inefficient at low power, and the KillAWatt meter has rather mixed reviews for accuracy. The only thing that makes sense is to measure the DC load from a battery.

But again, it only makes common sense to unplug the battery when its not being used.

The pump was not running at idle (dormant). You may be right about accuracy. It's really better for measuring long-term usage. Hence my wanting to look at it over a week.

[DreamDiver]

Where is this meter located ? Is it the mains side of the powerbrick if so your including losses due to heat of running the 110v to 24v power conversion which is separate to machine usage.

It's between the power brick and the wall outlet (mains). Consider: the S9's DC power brick goes from 12v to 24v and will still require the S9 to draw power if plugged in right? Given that a power brick is required under both circumstances, but that the cost in heat is likely lower in the 12 to 24 DC conversion, do you suspect the kwh drawn from a fully charged DC power source will differ greatly from the kwh drawn from the AC power source?

[Jas_williams]

I would expect the conversion from 12v DC to 24v DC to be more efficient than the conversation from 110v/240v AC(I am in the UK) to 24v DC as more heat will be produced in the Rectifier/Step Down transformer than a DC-DC Step up transformer. As we are considering 12V use as that is where power is limited.