How to power a cpap

[CactusBob]

My last question was not posed correctly especially on a DIY forum and my apologies. Hopefully this will be much better
I am trying to power a CPAP machine while away from utility power. This system is going to run the CPAP and possibly charge a cell phone once in awhile so if it grows I may double the batteries to increase the run time but that's it.
I plan on solar charging this most of the time but would like to use a wall outlet when available
One thing I am looking at is building a battery pack using Panasonic NCR18650B cells 3400mah in a 7S 5P configuration which I estimate about 430 Wh at 24V, a 60A 1400W BMS, 12V dc output and a 5V 2.4A or 3A USB output

The CPAP is rated on the wall adapter at 12V 5A and although I don't currently have a Kill-A-Watt I found someone online who has the same unit and measured his at 8A starting current and about .4 amp the rest of the night and used 40Wh. I will be getting a dc plug for this so the draw should go down.

Would this be better to just build as a 12V system and not worry about the converter, since cables will be in inches I wouldn't think there would be much loss either way.


My biggest concern for this is reliability
The cost is estimated at @ $250 to $300

Bob

 

[snoobler]

Best to feed the CPAP directly with 12V. Best to get your own kill-a-watt and measure your own usage. CPAP pressure also influences usage as does heat.

Is the goal to have a project or get a working system?

 

[CactusBob]

Best to feed the CPAP directly with 12V. Best to get your own kill-a-watt and measure your own usage. CPAP pressure also influences usage as does heat.

Is the goal to have a project or get a working system?

The goal is a working system, once I show the wife it works then I will buid a second for hers and redundancy so if one breaks we can use the other until I can fix it. Trying to find the best parts for the money with the best reliability thrown in. I'm not looking at cheaping it out but I also don't want to go broke doing it

Bob

 

[DThames]

My last question was not posed correctly especially on a DIY forum and my apologies. Hopefully this will be much better
I am trying to power a CPAP machine while away from utility power. This system is going to run the CPAP and possibly charge a cell phone once in awhile so if it grows I may double the batteries to increase the run time but that's it.
I plan on solar charging this most of the time but would like to use a wall outlet when available
One thing I am looking at is building a battery pack using Panasonic NCR18650B cells 3400mah in a 7S 5P configuration which I estimate about 430 Wh at 24V, a 60A 1400W BMS, 12V dc output and a 5V 2.4A or 3A USB output

The CPAP is rated on the wall adapter at 12V 5A and although I don't currently have a Kill-A-Watt I found someone online who has the same unit and measured his at 8A starting current and about .4 amp the rest of the night and used 40Wh. I will be getting a dc plug for this so the draw should go down.

Would this be better to just build as a 12V system and not worry about the converter, since cables will be in inches I wouldn't think there would be much loss either way.


My biggest concern for this is reliability
The cost is estimated at @ $250 to $300

Bob

My wife has a CPAP. It has a heater that heats water to keep the air moist. The heater cycles on and off. So the watts vary a lot. As CactusBob said, measure yourself is best. We bought a cord that will plug into a car lighter. I plan to just build a 12v pack that it can run off of directly.

Put your 3400 mah cells in boxes like this for a neat package. I am not sure if one of these would all night, but you can put 20ah in one of them.

 

[snoobler]

https://www.costco.com/interstate-27dc-marine--rv-battery.product.100476408.html and an 8-10A charger. Done. Hard to get more reliable than 100+ year old technology.

That has a reserve capacity of 160 minutes meaning it can deliver 25A for 160 minutes above 10.5V. That translates to about 80Ah at a 20hr rate. That could run 2X 30W CPAP for 8 hours each and stay above 50% SoC. Charge up with an 8-10A AC charger or a single 100-150W panel w/cheap PWM controller.

Get a 12V to 5V converter for USB charging.

Done.

 

[DThames]

I tested my wife's CPAP last night. Kill-o-watt meter says 0.15, so about 150 watt hours, about 8.5 hours of use.

 

[snoobler]

I tested my wife's CPAP last night. Kill-o-watt meter says 0.15, so about 150 watt hours, about 8.5 hours of use.

Nice. That's pretty low power use.

The battery in that setup I describe above should power that CPAP for 27 hours and stay above 50% charge. The single CPAP usage you describe will not take the battery below 84%, which would further extend its life.

 

[RCinFLA]

I tested my wife's CPAP last night. Kill-o-watt meter says 0.15, so about 150 watt hours, about 8.5 hours of use.

Only potential missing piece of necessary info is any short term peak power that may occur when a heater cycles on. Your power source also has to be capable of supplying the peak load, not just the average. During cold weather it may cycle heater on more often raising the average consumption.

 

[snoobler]

I would be surprised to hear that CPAP used the heater at all.

 

[UncleTodo]

This too is a primary reason for me having a house battery system for my CPAP machine but will use a 12v power supply cable.
110v test lower than expected but i will have to test again using the humidifier.
I'm guessing that's what you mean by heater?
Mine I can turn it on and to a specific level from 0 - 8.

 

[RCinFLA]

I would be surprised to hear that CPAP used the heater at all.

If they are equipped with a humidifier.

 

[DThames]

This too is a primary reason for me having a house battery system for my CPAP machine but will use a 12v power supply cable.
110v test lower than expected but i will have to test again using the humidifier.
I'm guessing that's what you mean by heater?
Mine I can turn it on and to a specific level from 0 - 8.

Yes, the humidifier heater is that metal disk under the water tank.

 

[DThames]

If they are equipped with a humidifier.

My wife says humidifier is critical unless you love pain.

 

[snoobler]

Impressive. I've ordered a kill-a-watt (knock off) for myself to check my own unit. I've seen run consumption of 30W w/o heater and 60W w/heater. Mine's an older Resmed unit - about 7 years. It's huge compared to today's smaller units, so my perception may be skewed.

 

[DThames]

Impressive. I've ordered a kill-a-watt (knock off) for myself to check my own unit. I've seen run consumption of 30W w/o heater and 60W w/heater. Mine's an older Resmed unit - about 7 years. It's huge compared to today's smaller units, so my perception may be skewed.

When she first turned it on, it was about 70w, then down to 50, then back up to 70. I could only watch so long. Not sure what it might have been down to at the lowest point. We have a Sense home monitor. I can get up early and while she is sleeping the Sense has a balloon for the device, that pulses larger and smaller for the watts. I can see her breathing as the load changes with inhale, exhale. The balloon part of the unnamed load of the house so total power needs to be low before I can see her breathing on the Sense.

 

[MrNatural22]

My wife says humidifier is critical unless you love pain.

This is something I have noticed also when not using the humidifier also it tends to dry out your nasal passage and this can produce a very uncomfortable stinging from the dryness. I can always tell when the H2O is depleted by the uncomfortable dryness in my nose. My dream station BiPap has an adjustment also to control the heat, and even with the heating disc turned down it will still provide some level of moistness in the supplied air because the air still passes through the water chamber.
I usually have the heat down to a very low setting year round (1) and have to add H2O nightly.
I haven't run it on 12v yet but watching this thread to see what others come up with.

 

[snoobler]

This is something I have noticed also when not using the humidifier also it tends to dry out your nasal passage and this can produce a very uncomfortable stinging from the dryness. I can always tell when the H2O is depleted by the uncomfortable dryness in my nose. My dream station BiPap has an adjustment also to control the heat, and even with the heating disc turned down it will still provide some level of moistness in the supplied air because the air still passes through the water chamber.
I usually have the heat down to a very low setting year round (1) and have to add H2O nightly.
I haven't run it on 12v yet but watching this thread to see what others come up with.

My particular unit (S9) has a separate chamber with a removable water container. It typically holds 2 nights worth, but I don't sleep a lot.

It has a temperature setting for the humidifier. Max is 86°F, and I keep it pegged there. If the water container is full, I can run it without the humidifier heat active because I do get some humidification from the air passing through the chamber, but I do notice the difference in the morning.

This particular unit is 24V. Power brick is 90W with a 24VDC 3.75A output. There are 3 pins. It's too tight for me to comfortably verify the 3rd smaller pin, but the two big ones are 24V between them, and none have voltage to the "barrel" of the plug. Rather than try to hack it, I'd just suck it up and buy the 12V converter.

 

[DThames]

We are planning a battery run test tonight. I am charging the battery, starting fully charged. 3s Li-ion, 16ah. I have a DC meter that will show watt hours.

 

[snoobler]

whew... 178Wh... good luck!...

 

[DThames]

whew... 178Wh... good luck!...

Living on the edge.