Measuring current draw on CPAP for battery calcuilations

[WomblingFree]

I have a clamp for measuring amperage.  I have large electric dc motors that draw in excess of 100 amps, and my multi meter will not accommodate those loads.  I would not be without a multi meter.  It is the best diagnostic tool period.  Everyone should have one and know how to use it.

Agree except for the last bit.
And everyone should have a go at brain surgery or dabble with other stuff they know nothing about. Hey what could go wrong...

[OMyMyOHellYes]

I have a clamp for measuring amperage.  I have large electric dc motors that draw in excess of 100 amps, and my multi meter will not accommodate those loads.  I would not be without a multi meter.  It is the best diagnostic tool period.  Everyone should have one and know how to use it. [emphasis added]

Agree except for the last bit.
And everyone should have a go at brain surgery or dabble with other stuff they know nothing about. Hey what could go wrong...

There's a bit of difference in testing that stray AA battery you find in a drawer to see if it has juice or if it's dead - and doing brain surgery.  Testing batteries ain't no where near rocket science or brain surgery.

Battery stuff like that gets done a few times a year or month or so around my house.  Brain surgery, pretty much never have a need.  Besides, you have to have a license to cut up living brains.  There is no such requirement for using a voltmeter/ohmmeter/ ammeter.  

And no, dropping batteries on a hard surface to see which ones bounce or stand up or whatever is not a valid means to test battery charge.

OMMOHY

[Walla Walla]

I know how to change a battery that's about it. But I saw your name and reminded me of Tom Petty. I love that song!

[OMyMyOHellYes]

Fun fact - Reset the currnt meter average when I got up today to see what current is pulled when off. It's not zero - my PR SysOne 560 draws 67 milliamps when turned off. Board, clock, memory I guess.....

OMMMOHY

[silversnore]

I have a clamp for measuring amperage.  I have large electric dc motors that draw in excess of 100 amps, and my multi meter will not accommodate those loads.  I would not be without a multi meter.  It is the best diagnostic tool period.  Everyone should have one and know how to use it.

Agree except for the last bit.
And everyone should have a go at brain surgery or dabble with other stuff they know nothing about. Hey what could go wrong...

I agree that a neophyte should not probe around dangerous electrical loads nor should he try to fly a plane without proper instruction.  Everything we encounter these days relies on some sort of electrical controller or powered by electricity.  Being prepared to try to trouble shoot a car that want start or a light that will not turn on is certainly a plus when there is not mechanic anywhere around.  Understanding electricity is not a difficult task should one choose to explore the principals.  Brain surgery on the other hand........ not something that I want to do unless I spend the night in a Holiday Inn Express!!

[justMongo]

I think we need to apply the Laplace Transform.

[silversnore]

the only thing that i can derive is a car

[OMyMyOHellYes]

RESULTS
From my 35 AH battery, I should get 24 hours or 3 nights use with the humogrificator set at *2*; I should get almost 58 hours or 8 nights use with the humogrificator set at *0*;

From my 39 AH battery, I should get 27 hours or almost 4 nights use with the humogirficator set at *2*; I should get more than 64 hours  or 9 nights with the humogrificator set at *0*.

Oh, and just to see, I tried a swampy humogrificator setting of 4 and that REALLY sucked juice.  it cut run time for that relatively sizable 35 AH batter to a miserable one and a half nights.

Notes:
Calculation based on nominal AH Rating of the battery divided by 150% of measured current draw or Hours = AH / i*1.5)
In the calculations I use 1.5 or 150% to include that pesky 50% safety margin for sub-optimal battery condition or Mr Murphey's take.....
Current (i) measured using Agilent (nee HP Test & Measurement Division) U1233A multimeter
Phillips Respironics System ONE 560 Auto PAP, with humogrificator but NO HEATED HOSE
Sleepyhead data for hours, pressures, ahi for corresponding nights