My battery backup setup

[verbatim1]

the load in question will not receive the proper voltage and will either not operate at all or will exhibit strange behavior.

My mistake for not being clear.

I guess what's most important is how much power is required when the machine is in camping mode, which, for me, would be stripped down to use the least amount of power to conserve on battery juice:

• Connected to a 12VDC car battery (up converted & send resistored)
  
• The normal apap settings for me
  
• No humidifier
  
• No heater, no heated hose
  

If the power consumed under those minimum-use circumstances was, say, under 30Watts, then there's nothing useful a 90W power supply could supply over what the 30 Watt power supply supplies.

Right?

So, I guess the question can't be answered unless we know how much current is required at 24 VDC for the machine in the typical "camp" mode, which is just the cpap and nothing else.

QUESTION:
Q2: Does anyone know what current an A10 consumes under typical camp mode (e.g., we can assume apap 10 to 20 cm water if that matters)?

[justMongo]

You're pretty much stuck using the ResMed 12VDC to 24 VDC up-converter.
So, the question should be, what current is drawn from the battery in that configuration.
It will draw about 1 Ampere. check this document: http://www.resmed.com/us/dam/documents/a...lo_eng.pdf
See page 20.

Seems you have access to a PR machine... Someone like Sleeprider will be able to translate your setting from A10 to PR machine. Then you can use 12 VDC directly.

[Sleeprider]

Anyone have a handle on how many 12-volt amp hours a Resmed A10 needs to operate through the night? Assume 24 v up-converter, no humidity or heated hose.

[Sleepster]

Anyone have a handle on how many 12-volt amp hours a Resmed A10 needs to operate through the night? Assume 24 v up-converter, no humidity or heated hose.

I don't know the answer, but I do know the answer depends on the pressure. The higher the pressure the shorter the battery life.

[sdb7802]

from ResMed doc linked by Mongo:
   

[Sleeprider]

Thanks sdb7802 (and JM). That is the approximation I was looking for.

[verbatim1]

You're pretty much stuck using the ResMed 12VDC to 24 VDC up-converter.

If I stick with the ResMed device when camping, the up-converter seems to be the way to go, for finesse.

Of course, putting two 12VDC 35Amp-Hour gel cells in series gives us 24VDC, so then all we need to handle is the 3.3VDC voltage regulator with 2.7KOhm sense resistor circuitry...

So, the question should be, what current is drawn from the battery in that configuration.
It will draw about 1 Ampere. check this document: http://www.resmed.com/us/dam/documents/a...lo_eng.pdf
See page 20.

Thanks for locating that information that we can nominally assume about 1 amp for standard cpap settings. For an 8-hour night, that's 8amp hours, so, it seems like two nights would do with, at a minimum, a 16-amp-hour battery, so, the often stated 35 Amp Hour battery should be fine for a weekend, right?

Seems you have access to a PR machine... Then you can use 12 VDC directly.

Yes. You are correct.

My good friend and I both abhor non-standard power supplies and cables (we met at an Apple conference, where we lamented their "walled garden" approach).

When I told him about the hugely non-standard ResMed AirSense 10 Audoset power supply requirements, he immediately gave me access to his standard-power-supply-fed Philips Respironics Bi-PAP Auto Bi-Flex 750P pictured below, so that I wouldn't have to deal with the purposefully-non-standard ResMed power supply issues.

He said I only need to give it back if his current machine breaks down.


This 12VDC device "says" it sinks 5 Amps maximum, but, just like with the ResMed, I suspect it's less than half that on average. Given 2.5 Amps, and 7 hours a night, a two-night campout should consume 2.5 amps over 14 hours, which would dictate a 35 Amp Hour battery.

Someone like Sleeprider will be able to translate your setting from A10 to PR machine.

As you noted, Sleeprider is advising me for the task of matching the settings of the non-standard-power A10 to the standard-power 750P for camping purposes:
http://www.apneaboard.com/forums/Thread-...amping-use

Given that the non-standard-power ResMed is set to automatic of 10 to 20 cm of water with a pressure relief of about 2 cm of water, so far I've set my friend's standard-power Respironics 750P to the following settings, which I am testing as we speak:
- Mode = Auto
- Max IPAP = 20.0
- Min EPAP = 7.0
- Max PS = 3.0
- Flex Type = None
- Rise Time = 0 <---------- this appeared when I set flex type to none!
- Bi-Flex = 3 <---------- this disappeared when I set flex type to none!
- SYSTEM = X2
- LOCK SYS = off
- Ramp Time = 0:10
- Ramp Start = 7.0 <---------- this dropped from 7.5 to 7.0 when I set flex type to none!
- Auto on = on
- Auto off = on
- Mask alert = on
- Humidifier = off
- Show AHI = on
- Split night = off

I think the 750P has a default minimum pressure support of 2cm of water, so, tonight I will probably change the Minimum EPAP to 8 (from the 7 that Sleepster recommended above) so as to better match the 10cm to 20cm APAP settings of the non-standard-power ResMed machine.

I'll test these settings again tonight, so that I have a ready-made 12 volt standard-power-supply cpap machine available to me, so that I don't have to deal with the issues that ResMed put on the table just to make the power supply non standard.

[verbatim1]

from ResMed doc linked by Mongo:

You know what's strange about that chart?

Notice the voltage on the current-draw column?

That voltage doesn't make sense, for an A10 (which is 24VDC, not 12VDC).

Or am I misreading the chart?

[sdb7802]

You know what's strange about that chart?

Notice the voltage on the current-draw column?

That voltage doesn't make sense, for an A10 (which is 24VDC, not 12VDC).

Or am I misreading the chart?

When I copied the relevant part of the chart, I left out the page heading (on a preceding page where they introduce the 24 volt machines):

ResMed devices powered with converter

So they mean the 12 volt battery current drawn by the 24 volt converter and 24 volt cpap.

Sorry for the omission.

[verbatim1]

I've found that the A10 will run from a +24 volt power supply (non-ResMed) when the center pin is connected to +3.3 volts thru a 2.7k ohm resistor. I use a +3.3 volt three-terminal voltage regulator fed from the +24 volt power supply. The resistor functions as a pull-up resistor to +3.3 volts and tells the cpap the power rating of the supply. I've tested this on two units.

Steve

Hi Steve,
I'm not an electrical engineer, so, can you kindly vet this diagram of what I think you are suggesting for the ResMed non-standard battery-based power supply circuitry?

Would you please let me know if/where I made mistakes?