Choosing a Power Inverter for ResMed S9 CPAP

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I have been working with Randy Thinnes from ResMed. Just last week Randy, gave me a call and asked me to test the new ResMed S9 CPAP System. I did some testing here in our facility. Along with the machine we also received the Heated Climate Line 2, which is an exclusive technology for ResMed.

The first round of testing was done using the new ResMed S9 Elite-Autoset CPAP system. For the intial part of the testing we used the standard air hose, with pressure set to “20” and humidity set on “6.” With these settings the maximum usage was 1.11 AC Amps. Which is very low usage. The unit actually runs around .86 AC amps, its difficult to know exactly what the run amps are because the machine cycles up and down every second or so. You only see the spike when it is heating up the water.

The next test that we did was with the ResMed S9 Elite-Autoset CPAP system, with the Heated Climate Line 2. This is a great addition and the best part is that it uses very little extra power. During the test the pressure was set to “20” and the climate temp was set to “86 degrees.” When you hook up the Heated Climate Line the setting on humidity changes to climate temp. The maximum use with these setting was 1.13 AC amps. Then the usage leveled out to 0.95 AC amps, its difficult to know exactly what the run amps are because the machine cycles up and down every second or so.

I am going to use the data from both test, our maximum usage was 1.13 AC amps. Lets do some math.

ResMed S9 Elite CPAP system with Standard line:
We recorded 1.11 AC amps maximum usage with the heater set to “on” at level 6 and pressure set 20 cmH2O (maximum pressure) which is 133 watts max usage.

ResMed S9 Elite CPAP system with Heated Climate Line 2:
We recorded 1.13 AC amps maximum usage with the climate control set to “86” and pressure set 20 cmH2O (maximum pressure) which is 136 watts max usage.

I found in both test that there is very little power usage difference between the system with and without the heated climate line. I would like to point out that in an environment where the temperature changes often, the climate control setting could use more power. This setting relies upon the ambient temperature in a room, then adjusts the machine settings automatically to keep the air at a an optimum moisture and heat. This additional features could use more power in certain conditions, for example in a tent where the ambient temperature can vary through out the night. For more information about this new system please visit the ResMed website.

We used an AIMS 400 Watt Modified sine power inverter for all of these test. I direct connected to a battery for the test. I do not recommend that you use a cigarette plug for this equipment. Even though the watts are low enough for the plug to handle the load, most cables for cigarette plugs are not thick enough to handle the load. The cables for cigarette plugs are only rated at 80 watts per UL requirements. So to prevent damage to your vehicle, inverter or CPAP, direct connect to the battery. You will get more efficiency this way also.

I did one more test on this machine, I wanted to see how long this CPAP would actually run on our test battery bank. Let me tell you a little bit about our test battery bank. Our test bank is built with two 6 volt 220 amp/hr AGM batteries. We use this bank daily, it has been charged and discharged at least once a day for the last 2.5 years. The point is that this is a real world test. These batteries are not brand new, I conducted a test to find the approximate amount of amp hours on the batteries. We connected 550 watt bulb on the bank and it ran for just over 3 hours. Indicating that the bank has about 143 amp hours.

I used the all the maximum settings 86 degrees, CPAP pressure set to 20, and the Heated climate line was also used. I did refill the water once during the test, this was to simulate the heating of water at the beginning of a night’s rest. During this test we ran the ResMED S9 Elite for 23.7 hrs continuous. I used the internal timer in the ResMED unit to measure the run time. Above you will find my bench testing information shows that the machine runs at around 114 watts continuous. This is an approximation, because the machine actually cycles up and down every second of operation. It is very difficult to measure the exact usage, but we do know the peak continuous usage which is the number that we reported in our bench test.

In summary our test showed a lot of promise for this new machine. It uses very little battery power. Keep in mind that there are many variables involved in usage on this machine. First, it keeps up with ambient temperature, working constantly to maintain water temperature equal to ambient temperature in the room of use. Second, My test facility is located at above 4500 ft in elevation, water boils or heats up faster at higher elevations. Lastly, if you are not using the climate line or have your pressure and heat set lower than our test. All these factors could increase or decrease your actual power consumption, or battery life. What we were trying to do with this test is a worst case scenario. The night of the test was over a weekend, where the heater is off in the lab warehouse and it was just above freezing outside that night. I think we accomplished our goal. With all this said, you may ask how much battery do I need? Well you can safely say that this machine uses about 6-7 DC amps/hr. This means for an 8 hr sleep you will need about 48-56 DC amps. I would recommend that you use an 80 amp/hr battery, this will be sufficient enough for a full nights sleep, while still maintaining optimum battery health. It is not a good idea to run a battery down to zero, you will increase battery lifespan, by running it down no more than 60-80%.

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3 thoughts on “Choosing a Power Inverter for ResMed S9 CPAP

  1. A contradiction for the RESMED S9 …. the video said 180 watts for the cigareete plug … you say, the cables for cigarette plugs are only rated at 80 watts per UL requirements.

    Which is correct?

    Thanks, Fred

  2. I read some sales info for the “trip” brand inverter that it is not recomended to use the heating portion of the S9CPAP humidifier with a inverter.
    Also, Resmed now sells a DC/DC converter for the S9. I use the S9 and am looking for the best way to run it at home during rare blackouts as well as mabey a camping trip.
    Please advise.

    I have read your blog on the S9

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