12v DC current draw for REMStar Auto

derek · Post by **derek** » Mon Sep 12, 2005 2:21 pm

This is for all of the people interested in running a REMStar from a 12v battery source. I measured the current drain this afternoon, and here are my conclusions.

First, for any fan the current drain is opposite to what most people think: it is a minimum when the flow is blocked, and a maximum when the flow is wide open (the fan is doing no real "work" when the flow is blocked.)

On my REMSDtar Auto at 10 cm H20
1) Flow blocked: approx 0.5 amp
2) Flow wide open (through humidifier - no hose): 2.8 amps.
Therefore Respironics rating of 3 amps is not unreasonable - it represents a worst-case situation - but does not represent normal operating conditions.

Now with the mask on, the situation is difficult to monitor because the flow is varying during the breathing cycle and hence the current is varying and is hard to read on a digital voltmeter. I estimated the following average values:
1) On inhalation: 0.7 amp
2) On exhalation: 0.5 amp
There seemed to be a brief rise to about 0.9 amp at the transition from exhale to inhale, and similarly a dip to about 0.3 amp during the transition from inhale to exhale.

The current did not seem to be affected significantly by the C-Flex setting.

The bottom line: The REMStar Auto seems to draw an average of approx. 0.6 amp under normal operating conditions. In terms of battery usage this translates to about 5 amp-hours (0.6 x 8 ) for an 8 hour night. That's good news!

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, humidifier, hose, C-FLEX, news, auto

lynn · Post by **lynn** » Mon Sep 12, 2005 2:46 pm

Thanks, Mister Science! I just sent a copy of that to our electrician just for grins. He was aboard last Thursday switching our nightstand elec outlets to the inverter system after we happened to discover they weren't on that. Would have been sad when at anchor. Would have turned off the generator to turn in at night and no cpaps! All fixed now!

lynn

derek · Post by **derek** » Mon Sep 12, 2005 4:06 pm

Lynn,
Just in case you misinterpreted me - I was not talking about running a cpap from an inverter running off a battery, I was talking about a direct connection to the battery using the dc connection.
BTW - I've heard that the humidifier should not be run from an inverter unless it is the "pure sine wave" (read that as "expensive") type.

john5757 · Post by **john5757** » Mon Sep 12, 2005 4:35 pm

I noticed that on the RemStar plus manual you should not run pressures more that 10cm of water when using the DC input. What problems could this run into at higher pressures?

lynn · Post by **lynn** » Mon Sep 12, 2005 5:06 pm

Well, who knew, Derek! I'll get back to you on that. Not on the boat until tonight. I think it's a Trace inverter system, and it runs the fridge, freezer, microwave, coffeemaker, TV's and sound system, and now cpaps, among other things I'm probably forgetting. I don't know about the pure sine wave spec but will let you know!

lynn

Guest · Post by **Guest** » Mon Sep 12, 2005 6:19 pm

Someone had to use the dreaded 'I' word . Inverter. Just go straight DC.

Ms Piggy · Post by **Ms Piggy** » Mon Sep 12, 2005 9:58 pm

thanks Derek, that's better than we thought. I won't be so unpopular now

derek · Post by **derek** » Tue Sep 13, 2005 6:04 am

John5757,
I took a look through the user manuals for the Plus and the Auto, and couldn't find any reference to the 10 cm limit for DC use. Am I missing something?

john5757 · Post by **john5757** » Tue Sep 13, 2005 7:24 am

Shielded DC Cord

The Respironics DC Cord can be used to operate Respironics’ CPAP Systems where AC is not available. It plugs into a standard cigarette lighter socket found in automotive vehicles.

If you frequently operate your Respironics System using DC power, have your home care provider set your prescribed pressure while the unit is operating on DC power. There may be a slight (less than 0.5 cm H2O) drop in pressure when the unit is switched from AC power operation to DC power operation.

WARNING: When the DC Cord is used with REMstar Systems, it can only be used for prescription pressures of 11 cm H2O
or less. Any attempts to use the DC Cord with the REMstar for pressures greater than 11 cm H2O will result in inadequate
pressures being delivered.

The 1/2 cm drop on DC and 11cm is the max occurring to the DC cord manual. I will check on my RemStar materials shortly to verfity this. I was under the inpression that I read the limit was 10cm before I ordered the DC cord otherwise I am off by 1.

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derek · Post by **derek** » Tue Sep 13, 2005 8:05 am

John,
Here's what my DC cord manual (dated 6/2/03) says near the top:

"WARNING: This cord will allow all of the Respironics CPAP systems to function throughout their entire pressure ranges except for the REMstar Chioce systems. This DC power cord can only be used with the REMStar Choice systems for pressures of 11cm or lower."

then lower down (under Power Consumption) it repeats the warning for REMStar Choice systems only.

So I think we are OK. I don't know what a "Choice" model is - an older model?

Do you perhaps have an older cord?

lynn · Post by **lynn** » Tue Sep 13, 2005 12:33 pm

Derek, I know now that you are talking about DC connection. We don't have that option in the staterooms, only elec outlets that are fed AC when on shore power or generator, then on inverter when power is cut. Trace inverter is about 2400 watts. I didn't get an answer about the "pure sine wave" spec. Haven't had a problem... Thanks for sharing your knowledge!

lynn

derek · Post by **derek** » Tue Sep 13, 2005 2:31 pm

Lynn,
I think the point is that the current drain of the cpap is so small that on your boat with a generator and 2400 watt inverter it is insignificant!
On my boat, a Pearson 422 sailboat with 450 A-h in the house bank, it is also insignificant compared to the daily load of lighting, refrigeration etc. My inverter is 1750 watts, but I have wired the state-rooms with 12v dc outlets so I decided to use them, and I decided to use a pass-over humidifier to conserve power.
I don't know where I read that the "modified-sine-wave" inverters might destroy the humidifier, but I have a definite recollection of reading it somewhere. Maybe you have disproved it.

Guest · Post by **Guest** » Tue Sep 13, 2005 3:41 pm

Derek, Thanks, I gathered that it would be ok (load wise I had a quick conversation with bro sparky, but I didn't understand too much from his dissertation re pure sine wave ... better this, better that, blablabla I started to go crosseyed. who knew. He thinks all will be ok. Anyway, I appreciate your input!

lynn

P. S. We are a full-displacement wood hull trawler,,, 7 knots, maybe 8 depending on the currents here, to which we pay close scrutiny, and have sailboat friends as we travel about the same speed! Happy sailing!

john5757 · Post by **john5757** » Tue Sep 13, 2005 6:16 pm

derek,

Found out the "manual" that I printed came from the Respironics Web site Product library that is and still is dated 11/27/01. Respironics did not have the word "choice" in the docs listed.

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guy · Post by **guy** » Sun Sep 03, 2006 10:41 pm

can I used an adapter that allow direct connection to the power outlet on an airplane? it says the voltage available is 12-15 vdc

Mask	Humidifier

Additional Comments: i love resmed stuff!

Machine	Mask

Mask	Humidifier

Additional Comments: i love resmed stuff!

Machine	Mask

12v DC current draw for REMStar Auto

12v DC current draw for REMStar Auto

using the dc outlet on an airplane