My battery backup setup

[justMongo]

As Dude said, only one bridge (of 4 diodes) are required.

[sdb7802]

The reason I suggested the 10 amp fuse was because the ResMed converter pdf says it uses a 20 amp fast-blow fuse. In our case, operating at 24 volts requires half the current (10 amps).

Well, for some reason I decided to look at the pdf again and I noticed that the converter will run on 24 volts too. That certainly adds some versatility.

Just something to keep in mind.

[sdb7802]

I will google for a freeware schematic program (if they exist), which would make things far simpler to draw (and better looking).

Check out DipTrace. It's what I use and there's a freeware version.

[verbatim1]

The reason I suggested the 10 amp fuse was because the ResMed converter pdf says it uses a 20 amp fast-blow fuse. In our case, operating at 24 volts requires half the current (10 amps).

Thanks for explaining that we only need to worry about half the current, so, we'll stick with a 10A fuse.

In addition, it would be nice to see if ResMed offers a BATTERY 24V supply, because they'll specify the voltage range.

For example, in this "ResMed Power Station (RPS) II" factsheet PDF, they say their Lithium Ion battery (which has a different range than SLA batteries), is 24 to 26VDC plus or minus 1/2 volt so that's 23.5 to 26.5 volts for that one supply.

http://www.resmed.com/us/dam/documents/p...er_eng.pdf

Well, for some reason I decided to look at the pdf again and I noticed that the converter will run on 24 volts too. That certainly adds some versatility.

I searched for that PDF and I think I found a 16-page user guide for the 12/24VDC DC-to-DC converter for the S9 here:
[link to commercial DME website removed per rules]
(I presume the A10 is the same as the S9?)

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[verbatim1]

Check out DipTrace. It's what I use and there's a freeware version.

Thanks Steve for suggesting Diptrace.
I found the Windows freeware here: http://diptrace.com/download-diptrace/
32-bit http://diptrace.com/downloads/dipfree_en.exe
64-bit http://diptrace.com/downloads/dipfree_en64.exe

[verbatim1]

Steve,
Just to be on the safe side, what do you think about us considering adding a 24VDC voltage regulator?

Googling for 10 amp 24VDC linear IC voltage regulators, I found this, for example:
Linear Technology LT1038 10A Positive Adjustable Voltage Regulator
http://cds.linear.com/docs/en/datasheet/1038fa.pdf

The datasheet says it can handle inputs up to 35 volts and it can output transient amperage of 24 amps for 500μs.


Googling further, I found this Texas Instruments LM138 & LM338 series 5 amp voltage regulators (12 amps max) which can be set to regulate at 24 volts:
http://www.ti.com/lit/ds/symlink/lm338.pdf

I also found the ST L4970A which is a 10Amp switching voltage regulator, but at 15 pins, it was more complicated than the other two 3-pin devices for me to understand whether it fits our needs.
http://www.st.com/content/ccc/resource/t...000080.pdf

[sdb7802]

Well, for some reason I decided to look at the pdf again and I noticed that the converter will run on 24 volts too. That certainly adds some versatility.

(I presume the A10 is the same as the S9?)

The S9 is different from the A10. It has a different input connector and requires a different dc converter.

You can find the A10 dc converter pdf here: google "directhomemedical airsense-cpap-dc-cord-instructions-for-use.pdf"

[OMyMyOHellYes]

Is the discussion past the point, in terms of required effort, of making the expensive resmed power box look attractive?

As a dedicated tinkerer, I can't believe I just said that.

OMMOHY

[sdb7802]

Steve,
Just to be on the safe side, what do you think about us considering adding a 24VDC voltage regulator?

Googling for 10 amp 24VDC linear IC voltage regulators, I found this, for example:
Linear Technology LT1038 10A Positive Adjustable Voltage Regulator

The LT1038/LM338 are linear series pass regulators which means the output voltage is always lower than the input voltage. The L4970A is switching buck (step-down) regulator which has the same limitation.

A buck-boost regulator will output the correct voltage whether the input voltage is lower or higher than the input voltage (within limits). The ResMed converter will do this for either a 12V or 24V battery input.

[sdb7802]

Is the discussion past the point, in terms of required effort, of making the expensive resmed power box look attractive?

As a dedicated tinkerer, I can't believe I just said that.

OMMOHY

Really attractive. I'll run my battery test and if it works; I recommend we post the simple circuit for those who want to tinker.