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My battery backup setup
Yes that is the exact unit.

Oops, no its not the exact one. I searched for "24V 12V converter" The one I bought was $12.90 US shipped direct from China. I think it has the word "Fulree" on it.

Dave
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I found one that says kree on it. It is in a black case.
More and more, thinking about the scope pattern I saw. I believe the 3.3v to the pin, may be power for the communication circuit.
no one seems to have checked data on the sd card when using alternative voltages on the pin, only that the unit provides some kind of air pressure coming out of the device. I found a couple of converters tonight with the following specs,

Product Description Parameters:
Input voltage: 4.5-40V
Output voltage: 1.25-37V(consistently adjustable and recommend you adjust when in empty load)
Output current: 2A rated current and 3A Max(please add heatsink)
Load adjust ratio: +/-0.5%
Voltage adjust ratio: +/-2.5%
Transferring efficiency: 92% Max(the higher output voltage, the higher efficiency)
ON/OFF frequency: 150KHz
Output ripple: 200mV
Power consumption when in static state: only about 3A
Working temperature: -40 Celsius to 85 Celsius
Module feature: buck and non-isolated
Rectification method: non-synchronous rectification
Adjust method: please use a mini screwdriver to adjust output voltage by adjusting the potentiometer

Note:
1.Please add heatsink when the output power is larger than 15W
2.Please make sure the voltage difference between input voltage and output voltage is at least 1.5V to ensure stable output
3.Please note there is no reversed connection protection, so check the polarity of input voltage before power on to avoid burning due to reversed connection.
4.It has over-temperature and short-circuit protection.

Package includes:
1pcs LM2596 bare board

I will use this to check things out. I am a little concerned that it says 3 amp steady rate consumption. Hope that is a misprint. Will find out. Also hope that on supply can feed two units through separate resistors to separate 7.4mm connector pins. I will have to verify when parts arrive.
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(06-07-2016, 04:18 AM)sdb7802 Wrote: from ResMed doc linked by Mongo:

Not sure if the battery size vs Cpap setting chart got quoted or not. It was in this post of this thread. (Yeah, I see it didn't get quoted.)

Assuming a cpap setting of 10, so 12 amp-hours needed for 8 hours of sleep (per chart) --- how many nights (or hours) will my teeny trailer's battery give me? I don't know how to interpret the numbers on it. It's a "Harris" deep cycle battery, 24D140 Professional Plus.

I'm figuring if I have a household power outage, I'll just sleep in my teeny trailer in the garage. But I'd like to know how many hours that'll cover. And whether I can afford to run the fan & light when I'm actually on a trip, and yet want Cpap time on the battery. The trailer already has a battery tender built in for charging, so all I have to buy is ResMed's "DC POWER CONVERTER WITH CORD FOR AIRSENSE™ 10 CPAP & AIRCURVE™ BILEVEL MACHINES" which includes the cigarette lighter plug too.
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You'll have to call their HQ in Ohio to get the Amp-Hour capacity.
Their PDF on the battery does not state. 24D is the Battery Group Physical size.

It's a flooded cell battery.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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Thanks. No wonder I couldn't find the number either!
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(02-04-2016, 12:08 PM)rhodesengr Wrote: I was discussing this elsewhere. I am deeply involved with radio controlled airplanes and helicopters. No not drones. We use some pretty good size LiPo batteries. They are lighter than the AGM equivelent. There are also LiFe batteries but they tend to be more expensive. A 3S 5Ah (12V) LiPo is about $27 dollars on HobbyKing. I was trying to mimic the 15 Ah battery pack sold by PR for my machine. So that would take three in parallel.

You can also get 6S 5Ah (24 Volts) but they cost about $100 each.

You also need a special charger. But i already have several high power chargers. So I may put something like this together. I understand that using those types of batteries might be a little DIY for many here but for those comfortable with some electrical stuff, it is an option.


You can according to PR tech in Murray Pa , and I just did in the last 24 hrs run a Pr 560 with humidifier etc directly off an ordinary generator.
Actually I ran two at once, a550 and a 560 off a Champion 1400 watt non inverted generator, plus a box fan. I did put a run of the mill surge protector inline.
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Parts starting to come in now. within the next week I should have everything.
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(08-22-2016, 02:47 PM)BadGoodDeb Wrote: Not sure if the battery size vs Cpap setting chart got quoted or not. It was in this post of this thread. (Yeah, I see it didn't get quoted.)

Assuming a cpap setting of 10, so 12 amp-hours needed for 8 hours of sleep (per chart) --- how many nights (or hours) will my teeny trailer's battery give me? I don't know how to interpret the numbers on it. It's a "Harris" deep cycle battery, 24D140 Professional Plus.

I'm figuring if I have a household power outage, I'll just sleep in my teeny trailer in the garage. But I'd like to know how many hours that'll cover. And whether I can afford to run the fan & light when I'm actually on a trip, and yet want Cpap time on the battery. The trailer already has a battery tender built in for charging, so all I have to buy is ResMed's "DC POWER CONVERTER WITH CORD FOR AIRSENSE™ 10 CPAP & AIRCURVE™ BILEVEL MACHINES" which includes the cigarette lighter plug too.

I couldn't find a direct figure for that battery, but it shows "Craniking Amps" so it is a little tiny bit suspect in my mind, but Batteries+Bulbs shows a replacement for that unit on their website (Duracell Ultra Battery Harris 24D140 Replacement SLI24MDC) that shows it with a deep cycle capacity of 75 AH. Not saying it is what you got, but it may be close/comparable for your planning purposes.

OMMOHY
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I have only seen reports of power usage vs a constant pressure. What happens when pressure relief is used. The constant pressure change may raise power requirements with the constant pressure changes. Does anyone know?

Block diagram for power supply.
24vdc is required either by converter or batteries. Since I have a number of mobility chairs/scooter all whom use 24vdc, I plan on that power source. Efficiency=100%.

It has been reported that a 47K ohm resistor can be used to power up the machine, but the scope image has me vary concerned about this as Data line was over 12vdc. I read where as much as 3.6vdc can damage sd cards. Also Every supply resmed sells uses a 3.3vdc regulator through a reported 2.7k ohm resistor. Since Resmed does this, I decided the same was needed.
I decided to drop the voltage in two steps. 1. Drop 24vdc to 5vdc with a usb power converter, as this will allow for charging usb devices, since ac power will not be available. 2. Convert 5vdc to 3.3vdc through ready made available converters. The output of which goes through the 2.7K ohm resistor to Center Pin. Negative 24vdc goes to outer sieve and Positive to inner sieve. The connector is available online and is used on multiple brands of laptops. 7.4mm x 5.0mm x 0.6mm center pin.

Since both my spouse and I need use of our machines, I plan on two of the 7.4mm connectors in my setup. From my 3.3vdc converter there will be twp 2.7k ohm resistors. One to each machine. Therefore, one setup will power both machines.
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The data being sent on the sense pin will not be connected directly to the SD card. I imagine that the ResMed dealers have some sort of device they can plug into the power line and read the data from the machine live.

Putting voltage on that line will not hurt anything - it is strictly an output from what I can tell, and the value of the resistor I am using is high enough that no significant current can flow through the pin.

So I did the testing with my unit.
- Input voltage can be anything from 8.5 to 15V DC, with a steady output of 24V sinking up to 5 amps into a load bank. I would not recommend running it lower than 9V because it seems a bit squirrely. The output voltage jumps around when the voltage is below 9V. If using with a battery, I would suggest some type of low voltage disconnect that trips the system if the battery is dead.

- The resistor I have in my setup is a 49K. I was out of 47K's at the time, and have not put the 47K back in.

- The sense pin floats at 24V when not connected to the machine, then drops to 0.56V when plugged in, then up to about 1.3V, then the data starts right away. I dont have a scope to monitor it. The data seems to stop if the machine is just idle. The data voltage jumps between 3.5 and 4V, and appears to be a TTL serial stream of some type.

Here are some pictures of my setup:
[Image: IMG_20160824_211927.jpg]

Other pics at:
CPAP Pics - IRLP.net

Dave
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