Here's my Camp battery set up

[Dive Apnea]

Hi all,

This is what I put together, I found connections that make it easy to attach to battery and my 400W inverter. I got an attwood battery box, drilled small hole for the wires to go through. I have two deep cycle marine batteries, and two boxes.

Any of you electronics experts know if I should leave the fuse housing with 7.5 amp fuses in them? These wires were extra for float chargers I bought, they trickle charged 6v and 12v batteries.

I suppose I can take my batteries out of my boat to see if they will work or not, but not sure if there will be some benefit to having fuses inline like this. My RESMED AUTOSET says it has 1.25 (FG) 3.75AMP (SYS). Not sure what is FG is, and how much extra amp per hour draw using the humidifier does.

What do your setup look like?

I am SOCAL, so luckily we rarely have power outages, so I only need this for camping. Weather does fluctuate 1-2º from 70º once in a while though.

[avi123]

Check if you see anything here:

viewtopic.php?f=1&t=83669&st=0&sk=t&sd= ... tery+power

[archangle]

You need a fuse in the cable right at the battery post. If the lengths and connectors are right, just swap ends of the cable and use the fuse holder you have.

There's a large gap between the top and bottom case to the right and left of the strap. This provides ventillation, but it's also a good place to run the wires. That way, you can take the top off of the case without having problems with the wires.

[bosstow]

JohnBFisher has a great design - this is the most current version.

viewtopic.php?t=89123#p817936

I will be assembling one of these myself soon.

[CapnLoki]

Hi all,

This is what I put together, I found connections that make it easy to attach to battery and my 400W inverter. I got an attwood battery box, drilled small hole for the wires to go through. I have two deep cycle marine batteries, and two boxes.

Any of you electronics experts know if I should leave the fuse housing with 7.5 amp fuses in them? These wires were extra for float chargers I bought, they trickle charged 6v and 12v batteries.

I suppose I can take my batteries out of my boat to see if they will work or not, but not sure if there will be some benefit to having fuses inline like this. My RESMED AUTOSET says it has 1.25 (FG) 3.75AMP (SYS). Not sure what is FG is, and how much extra amp per hour draw using the humidifier does.

What do your setup look like?

This looks good; as someone mentioned the fuse should be close to the battery. The wires look like they can handle 7.5 Amps, if they came with the fuse it should work. What you're protecting is an accidental short of the system - worst case is something like a wrench falling on the battery terminals, so its good you have it protected by a battery box.
It would be informative if you mentioned the battery type and size, also the charger. Here's a link to the ResMed battery guide; make sure you're within the 7.5 Amps or you have revisit the wires/fuse
http://www.resmed.com/assets/documents/ ... lo_eng.pdf

Remember, the load almost doubles when using the "inverter - AC supply" setup; its worth considering the DC-DC converter from ResMed, about $100. And if the inverter gets used for a TV and/or computer, you could go over the 7.5 Amp level.

My setup is on a cruising sailboat, so its based on a 450 AH battery bank; the CPAP load (direct DC and no humidifier) is small compared to the fridge, computer, TV, lights, etc.

[Dive Apnea]

I have two 105amp deep cycle marine battery's. (used in my boat).

Both ends have a fuse, as these wires were extra from battery float chargers, I used alligator clips it came with for different batteries. I think the fuses may be unnecessay all together. This setup is only for camping, and only for my CPAP, nothing else will be used on it.

That set up on that link is nice, if I had regular weather power outtage issues, I'd definately put something together on a float charger like that.

[JohnBFisher]

... Remember, the load almost doubles when using the "inverter - AC supply" setup ...

That is only true if you have a VERY old inverter or a pure sine wave inverter. If you have a "Modified" sine wave inverter the loss is MUCH less (around 5 to 10% at the most).

I agree with Dive Apnea, since he just uses it for camping having lots of extra connectors and such is not needed.

[CapnLoki]

... Remember, the load almost doubles when using the "inverter - AC supply" setup ...

That is only true if you have a VERY old inverter or a pure sine wave inverter. If you have a "Modified" sine wave inverter the loss is MUCH less (around 5 to 10% at the most).

So this comment has haunted me for a while. I've always taken it as axiomatic that a direct 12V supply was much better than an inverter and power brick. Since I live on a boat several months of the year every Amp-hour used to power a TV, computer or CPAP is paid for with annoying engine or generator running, so I take efficiency very seriously. What if John is right? Could I save 5 or 10 minutes charging time a day?

To resolve this I brought home all of my small inverters and put together a simple Amp Meter to test the load of my PRS1 560 APAP, which can run off of direct 12V. I immediately discovered that in normal use the load jumps from 0 to about 0.6 Amps on every breath. With an inverter it went from about .1 to 0.9 or 1.0, but it was clearly impossible to measure. Worse, I could vary the load by changing my breathing, so I needed a different approach.

I did this: I pulled the hose off the pump and let it run free. The load stabilized at 1.5 Amps on the DC supply. I then tried my three inverters (all 150 Watt modified sine wave) with the power brick. First was my 10 y/o Xantrex which I've used for TV, computers, etc. - it used 2.6 Amps. Next was a newer, small West marine unit that I use sparingly because I decided it was too cheap and had a noisy fan - it was 2.7 Amps. Last was a new Bestek that claimed in it's specs 90% efficiency - it was slightly better at 2.5 Amps. Running the numbers, I get the following results:
DC Load 1.5 Amps 100%
Xantrex 2.6 Amps 57%
West 2.7 Amps 55%
Bestek 2.5 Amps 60%

This is consistent with the report from Philips. I also tested a few other devices and got similar results. So where is the loss? The power brick is class "V" which means 85% according to some averaging formula, but it could easily be less than that at certain power levels. Similarly, inverters will list the max efficiency, usually at around 80-90% of full power, but can easily be much less at lower power.

So I stand by my claim that an inverter with power brick can use almost twice the power of a direct DC feed. What this means, of course, is that a battery will last almost twice as long with an direct DC cable. (I don't know the efficiency of the Resmed 12-24V converter, but I could believe its fairly high, enough to justify it $90 price if used frequently.) I would love to hear about any inverter that really has 90% efficiency over a wide ranges of loads.

[billbolton]

I immediately discovered that in normal use the load jumps from 0 to about 0.6 Amps on every breath.

That strongly suggests that there is something amiss with your measurement method, as the current should never be zero. The blower motor may adjust it's rate depending on breathing (and any exhale reduction settings) but it will ALWAYS be running when in treatment mode.

So I stand by my claim that an inverter with power brick can use almost twice the power of a direct DC feed.

It seems to me that the only thing demonstrated with your "open hose" test with a ~150W inverter, is that using an inverter which of much higher capacity than needed for the purpose is not a great idea

According to your maximum DC current draw measurement, a ~20W inverter would be fine to run your blower.

Cheers,

Bill

[squid13]

I followed John Fishers design for building a battery backup and use this to power my S9 https://www.cpap.com/productpage/DC-Con ... hines.html

[Tech Guy]

This is a rather silly question, and sorry skimmed the post and not sure what equipment you are running. Why not go directly to the battery and omit the inverter all together? My PR system one uses a 60 watt 12 volt supply rated at 5 amps. The amperage isn't the issue, but guessing you are trying to use the factory power supply into the inverter, then into the 12 volt battery. As long as the battery isn't charging, 12 volts is 12 volts. You could put a $10 voltage regulator set at 12 volts instead of maybe the 13 or 14 volt output from the battery to guaranty no voltage fluctuations. Mine uses a 3.5 mm jack that can be purchased at radio shack for a few dollars. Haven't tested the polarity or power output from the supply, but make sure if you go this route the polarity is correct for positve and ground. As long as the factory input voltage is within spec, should work fine. Seems a bit redundant to attach an inverter then your unit's power supply unless you are concerned about stabilized dc input voltage. These additional accessories just pull more juice from the battery and probably not necessary.

[JohnBFisher]

This is a rather silly question, and sorry skimmed the post and not sure what equipment you are running. Why not go directly to the battery and omit the inverter all together? My PR system one uses a 60 watt 12 volt supply rated at 5 amps. The amperage isn't the issue, but guessing you are trying to use the factory power supply into the inverter, then into the 12 volt battery. As long as the battery isn't charging, 12 volts is 12 volts. You could put a $10 voltage regulator set at 12 volts instead of maybe the 13 or 14 volt output from the battery to guaranty no voltage fluctuations. Mine uses a 3.5 mm jack that can be purchased at radio shack for a few dollars. Haven't tested the polarity or power output from the supply, but make sure if you go this route the polarity is correct for positve and ground. As long as the factory input voltage is within spec, should work fine. Seems a bit redundant to attach an inverter then your unit's power supply unless you are concerned about stabilized dc input voltage. These additional accessories just pull more juice from the battery and probably not necessary.

Not all xPAP devices can go directly from battery to xPAP device. Resmed units require 24vdc - not the standard 12vdc. So, you need a converter of some sort. For about $90 or so you can get a converter to convert from 12vdc to 24vdc. While that will be more efficient, the $90 for the converter is a bit of a sticker shock. Phillips Respironics went with 12vdc power input a LONG time ago for the very reason you suggest. It's easier for everyone.

[CapnLoki]

I immediately discovered that in normal use the load jumps from 0 to about 0.6 Amps on every breath.

That strongly suggests that there is something amiss with your measurement method, as the current should never be zero. The blower motor may adjust it's rate depending on breathing (and any exhale reduction settings) but it will ALWAYS be running when in treatment mode.

Well, it's true I did not calibrate the Ampmeter against a full range of loads - maybe its time to pull out the box of resisters. But I have no trouble believing that the pump essentially turns off; that's certainly how it feels. And the purpose was not to measure the pump, it was to measure the inverters.

So I stand by my claim that an inverter with power brick can use almost twice the power of a direct DC feed.

It seems to me that the only thing demonstrated with your "open hose" test with a ~150W inverter, is that using an inverter which of much higher capacity than needed for the purpose is not a great idea

According to your maximum DC current draw measurement, a ~20W inverter would be fine to run your blower.

There are several problems with this. FIrst, you want an inverter capacity substantially higher capacity than the expected load to handle startups and unexpected events. Although I expect my pump to use no more than an Amp, as I showed if you scatched your nose and triggered a major leak the load would jump way up. I frequently "pop" the breaker on the inverters using load that don't seem anywhere near the limit - you certainly don't want that to happen in the middle of the night. Second, its almost impossible to find an inverter under 150 Watts, and when you do, they invariably are so cheaply made that you wouldn't want them in your "life support" system. And finally, a number of posters talked about a 400 Watt inverter - a reasonable general choice since it could also handle power tools, etc. Since I have a 2K inverter for short term, higher power use, I try to use the smallest possible inverters for small, long term uses. I would expect the 400 Watt unit to be even less efficient at low power, though.

[CapnLoki]

This is a rather silly question, and sorry skimmed the post and not sure what equipment you are running. Why not go directly to the battery and omit the inverter all together?

Actually, that's exactly what I do. I also have a PRS1, and run it directly off of 12V.

My PR system one uses a 60 watt 12 volt supply rated at 5 amps. The amperage isn't the issue, but guessing you are trying to use the factory power supply into the inverter, then into the 12 volt battery. As long as the battery isn't charging, 12 volts is 12 volts. You could put a $10 voltage regulator set at 12 volts instead of maybe the 13 or 14 volt output from the battery to guaranty no voltage fluctuations. Mine uses a 3.5 mm jack that can be purchased at radio shack for a few dollars. Haven't tested the polarity or power output from the supply, but make sure if you go this route the polarity is correct for positve and ground. As long as the factory input voltage is within spec, should work fine.

Most of the readers here would not need anything beyond the basic 12V PR cable, or the ResMed 12-24V converter since they would not be using a charge source while sleeping. And I would guess that the pump could handle and input from a charger regulated at 14.4 Volts or less. That is sort of implied when a vender supplies a "cigarette lighter" plug since the common usage is in an environment that has a charger.

Seems a bit redundant to attach an inverter then your unit's power supply unless you are concerned about stabilized dc input voltage. These additional accessories just pull more juice from the battery and probably not necessary.

As John points out, a Resmed user must either buy the converter ($90) or an inverter, which can be as cheap as $20 and serve multiple purposes. My point is mainly that the inverter path means that the battery has to be twice as big. (Now, if someone can test the efficiency of the ResMed converter ...)

[billbolton]

FIrst, you want an inverter capacity substantially higher capacity than the expected load to handle startups and unexpected events.

You don't need a 150W inverter to do that!

I frequently "pop" the breaker on the inverters using load that don't seem anywhere near the limit

This discussion here is about powering xPAP kit from inverters, not your personal general use of DC power for a variety of maritime purposes.

The bottom line is that inverters run most efficently when the inverter capacity is reasonably well matched to the load. If you run an current technology inverter a with load which is very significantly under its capacity (for example a ~20W peak load on a 150W capacity inverter), the inverter will not be operating in it most efficent zone which is pretty much the only thing you demostrated with your inverter measurements

Making sweeping claims about the efficency of current inverter technology based on a flawed testing and analysis process is just plain silly