Oxygen concentrator on power inverter in car?

Can I run an O2 concentrator on a power inverter in my car? How do I figure it out?

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Jack A Lopez5 months ago

Hey. This post is going to be just sort of a summary of possible solutions to your portable oxygen problem, starting with what is simply a direct answer to your question, "Can I run an O2 concentrator on a power inverter in my car?"

The answer to that question is likely, "Yes." And in a post, yesterday, I kind of summarized how that works. It is an electrical power problem. I suggested putting a power meter on your O2 concentrator, as sort of a first step, to get an accurate estimate of the amount of power your machine wants. Then from there, you can start thinking about how big, in terms of rated power (500 W? 1000 W?) of an inverter is actually needed, and how many amperes this will draw from the car's alternator, and wire sizing (what AWG size) for wire connecting the alternator to the inverter.

Also if the current draw really is like 40 A continuous, you might need a bigger (higher current rating) alternator, but I am hoping you won't. I am hopeful that the time averaged current draw would be something much less, but the only way to find out, is to get some reliable numbers for the real power use, by measuring it, with a power meter.

So I think that is a good answer to, "Can I run an O2 concentrator on a power inverter in my car?"

However the actual underlying problem, as I understand it, is something more along the lines of, "How can I provide myself with medical oxygen, while stuck in my car, for a time duration as long as 20 hours, in a slow moving ((300 miles)/(20 hours)=15 mph average) traffic jam?"

And it is that implied question that kind of maybe points to other, more exotic solutions, of which I have discovered just two, so far.

One is cryogenic liquid oxygen, which I thought was mostly the domain of like rocket ships and rocket scientists, but it turns out the medical industry actually sells, and distributes, this stuff too. It begs the question, well, where's the nearest place to refill a LO2 cryo-container? Is it as easy as, asking Google(r) Maps about "liquid oxygen refill near me"?

https://www.google.com/maps/search/liquid+oxygen+r...

I dunno. Somehow my intuition tells me that if an actual evacuation order was given, that time would be better spent driving out of town, than driving to the place that refills the LO2.

The second possible solution, that is out there, but maybe not well known, are portable chemical oxygen generators.

The advantage of these, is that they can be stored, inert, for years, but when activated there is this kind of exothermic... I mean, hot, smoldering, reaction that makes usable oxygen in large volumes.

https://en.wikipedia.org/wiki/Chemical_oxygen_gene...

I knew they had these things on commercial airplanes, and also space stations,

https://www.instructables.com/answers/How-the-oxyg...

But just for the sake of finding what else is out there, I decided to ask Google about "portable chemical oxygen generator", and one of the results that came up, that was an actual product, and not just a patent,

http://www.o2pak.com/specs/

and it would probably be a good deal for you if they sold them cheap, in a 48-pack, because I am guessing each one would last you about 0.5 hours.

(Of course, state-of-the-art, medtech gizmos like this, are usually NOT sold cheap.)

For some reason, the physical appearance of one of these things is superficially similar to a can of beer. Or that's the way it looks to me.

The procedure for activating one, looks similar too. You should watch some of their Youtube videos, e.g.

Or maybe the resemblance to a can of beer is me thinking that because I am totally out of beer.

I am curious to know if this gizmo reminds anyone else of beer.

Anyway, that's all I have got for now, regarding other car-portable, medical oxygen solutions.

There may be other things out there to discover, if you just search for them.

Jack A Lopez5 months ago

I was kind of wondering: Is the oxygen for peoples in the car? Or is it for to help combustion in the car's engine?

The reason the question is important, is because car engines can use oxidizers besides air, and air plus oxygen. One of the more well-known gases is nitrous oxide (N2O).

https://en.wikipedia.org/wiki/Nitrous_oxide_engine

And I think the advantage bottled N2O has over bottled O2, is that it is possible to liquefy N2O at ordinary temperatures, and as a consequence of this, you can fit a lot more moles of N2O, versus moles of O2, into a steel bottle of a particular volume.

By the way, it is possible to store O2, as liquid O2, but this essentially a cryogenic liquid.

https://en.wikipedia.org/wiki/Cryogenic_fuel

The advantage of cryogenic O2, is you get high density, minus the volume wasted by thermal insulation. The main disadvantage, besides cost, is that O2 must boil off, and be vented, lost at some rate, just to keep itself cold.

Final note: The Wikipedia has articles for both "Oxygen concentrator" and "Portable oxygen concentrator",

https://en.wikipedia.org/wiki/Oxygen_concentrator

https://en.wikipedia.org/wiki/Portable_oxygen_conc...

which makes me wonder, what is the difference between those? Do the portable ones use less power? That's kind of a relevant question, if you are considering trying to power it through your car's cigarette lighter socket.

NotAPot2PN (author)  Jack A Lopez5 months ago
Hi, Jack -- the O2 is for me, preparing for the next hurricane evacuation. I can't use the ;"portables" because they don't provide continuous flow. The tanks, even the largest size, only last maybe 3-4 hours - and in the last evacuation, it took me 19 hours, 20 minutes to travel 289 miles. Good thing I didn't need the O2 back then.

I really appreciate all the good information. Thank you for taking the time.,
iceng NotAPot2PN5 months ago

Didn't know it was that short... How many liters/Hr do you need ?

You could go to LOX a Liquid Oxygen tank but it self cools and needs to be topped off every few days...

Hey. Regarding this question of how long a tank of compressed O2 will last, at a given flow rate, I found some calculators for that, and I will link to two of them here:

http://respondo2.com/calculator/

http://www-users.med.cornell.edu/~spon/picu/calc/o...


As an example, I fed the first calculator:

"Adult Regulator","1 LPM","Jumbo D/647", "Full Cylinder"

and it returned:

"10 Hour(s), 47 Minute(s)"

It looks to me like the math here, for a full tank, is just dividing the nominal tank capacity, by the flow rate; i.e. (647 L)/(1 L/min) = 647 min = 10hour+47min

I am guessing the physical tank size is smaller than the number of STP (standard temperature and pressure) liters it can hold, by, roughly, a factor of about 100. I mean the ratio of the full tank pressure to atmospheric pressure is about (2000psi)/(14.7 psi) = 136, and the volume ratio will be about the same.

Using this estimate, I am imagining this cylinder called, "Jumbo D/647" has an actual physical volume of about 647/100 = 6.47 ~=6.5 L.

Not sure which size tank OP is thinking of when he writes,

"even the largest size, only last maybe 3-4 hours"

Yeah, I guess you're going to need something so you can breathe, and get out of Dodge,
https://en.wikipedia.org/wiki/Emergency_evacuation

at the same time.

The math in Iceng's reply is accurate; i.e. a {120 VAC * 3.4 A} load will require about 40 amperes of current, at 12 VDC, as the input to the inverter. In terms of power, that's roughly 480 watts in and 408 watts out, and the ratio of those numbers is just that 1.15 estimate for power losses in the inverter.

Although, regarding the numbers you quoted, {120 VAC * 3.4 A} , if you got those just by reading the name plate, then I think it might be worth your time to double check that with an actual power meter, to see if the numbers on the plate are like, truthful.

Or I mean, with the power meter, you'll be able to get a more complete picture of how your thing is drawing power. For example, 3.4 A (408 W) might be a peak value, and the time-averaged current draw is only 1.8 A (216 W), or whatever.

I might be getting ahead of myself. My goal is to try to answer your question, "How do I figure it out?", and I think the short answer to this is that every component in your power chain (i.e. alternator, inverter, cables, connectors, etc.) has to be able to withstand the power flowing through it, in both a peak-power sense, and in a time-averaged-power sense.

In other words, your estimates for power throughput are answering the individual questions of how big of a?, how highly rated?, power converting, handling, component, thing.

As an example, our estimate for power, on the 120 VAC side, of the inverter, was 408 W. That suggests you need a power inverter rated for a quantity of power greater than that, like 500 W, or maybe 1000 W if you want buy a little more capacity and like, err on the side of keeping the inverter cool and comfortable.

This estimate for current from the alternator, 40 amperes, that might be a cause for concern, depending on rating of your existing alternator.
https://en.wikipedia.org/wiki/Alternator_(automoti...

Older automobiles with minimal lighting may have had an alternator
capable of producing only 30 A. Typical passenger car and light truck
alternators are rated around 50–70 A, though higher ratings are becoming
more common, especially as there is more load on the vehicle's
electrical system with air conditioning, electric power steering and
other electrical systems. Very large alternators used on buses, heavy
equipment or emergency vehicles may produce 300 A. Semi-trucks usually
have alternators which output 140 A. Very large alternators may be
water-cooled or oil-cooled.


So, you know, the alternator has to push current through your load, i.e. 40 A, plus all the other electrical loads in the car. E.g. the headlamps are a big draw, when both are on, those can pull about 20 A = 10 A * 2 headlights, typically. Anyway, the alternator has to supply the sum of all those load currents, 40 A + 20 A + 10 A + etc, and if that sum is a number greater than the rating of the alternator, then the alternator gets very hot and uncomfortable, and maybe melts itself.

The wires connecting the inverter to the alternator, or battery... you can probably connect it at the battery... those will have to be some, somewhat beefy, copper conductors.

From the table, in Wikipedia's article for "AWG",

https://en.wikipedia.org/wiki/American_wire_gauge#...

I am guessing that 6 AWG (pronounced, "gage", rhymes with "age"), or 4 AWG, would be appropriate for a current of 40 A, continuous. At that amount of current the I^2*R (pronounced,"eye squared are") losses, in a length of 6 AWG wire, are about (40A)*(40A)*(1.296e-3 ohm/m) = 2.073 W/m, which is about 10 W, over a 5 meter length, 2.5 m from and back, which is small (like 2%) compared to our estimate of 480 W, on the DC input side of the inverter.

Anyway, all this math, depends strongly on that estimate based on the scribbles, {120VAC *3.4 A}, on the name plate of your thing, your O2 concentrator.

That is why I was saying it would be good to get a, like, better estimate of how much power your thing actually uses. The Kill-A-Watt(r) power meter, also known as "P3 International model P4400", is a good one, and also pretty easy to find, to , how do they say: buy, borrow, or steal.

e.g. Buy:
https://www.harborfreight.com/kill-a-watt-electric...

Borrow:
https://en.wikipedia.org/wiki/Tool_library

Steal:
???

I dunno. I just think it would be worth it to get better numbers for what the power is actually doing.

Also be sure to build, and thoroughly test, and get it all working trouble-free, in your ride, before the next evacuation-worthy hurricane arrives, whenever that might be. For stuff like this, it is preferable to get all the bugs worked out, well ahead of time.

steveastrouk5 months ago

How much power does it need ? I seem to remember its quite a bit

NotAPot2PN (author)  steveastrouk5 months ago
120v 60Hz 3.4A
iceng NotAPot2PN5 months ago

So at 12V your inverter will draw 34A and efficiency will cost 15% more.

34 x 1.15 = 39.1 Amperes say 40A out of your car battery..

You will certainly need to keep your car running.

Better yet rent an O2 cylinder from a med supply or welding shop..

If it is to "save on fuel" you will notice that you need much more fuel to run the equippment than what you might expect to save by adding oxygen to the fuel mix.
Not to mention possible legal issues as oxygen is classified and requires proper handling, installing and equippment ;)