Full time RV with CPAP

[Hosehead4ever]

First off, I know there are threads here about camping with CPAP, and I have read through some of them... But my search on 'RV' came up short. There is very limited info on RV sites about CPAP so I hope someone here can chime in. My husband and I are in the planning stages of moving into an RV and travelling full time some time in the next few months. We are going to have relatively high power needs as he will still be employed full-time as a software engineer. So even with our (planned) solar, we are anticipating not always making it through the night if we don't have power hookup. We'd like to avoid running the generator if possible (gas is bloody expensive!)

I have decided that a dedicated CPAP battery backup would be a wise decision and now I'm trying to choose between them. I see there is a battery made my Resmed specifically for my machine. I like how discreet it is that I could charge it pretty much anywhere there is a publicly available power outlet and it would look like any other electronic item I am using and not draw attention. Other than that it is made for my machine, is there any other reason to spend twice as much on this battery rather than a generic battery?

Resmed:
https://www.cpap.com/productpage/resmed ... curve.html

Vs.

Transcend + Solar Charger

https://www.cpap.com/productpage/Transc ... ttery.html
https://www.cpap.com/productpage/somnet ... arger.html

The Trascend + solar charger is nearly $200 cheaper and also comes with charging ability which would come in handy if we're boondocking in remote areas, like in the desert southwest with lots of sun.

I've never used my machine on battery before. Any tips? Or any specific threads I should read?

Thanks for any help.


EDIT: I guess I missed the fact that the Transcend battery is only for Transcend machines. But there is still a generic battery it seems - the C 100. So the question remains essentially the same - $200+ for the C 100 or $700+ for the Resmed specific battery?

[Randy in Maine]

Why not just plug your cpap machine into the RV's "house battery" by getting a cord for the cigarette lighter.....DC to DC? The RVs engine or solar panel is usually set up to charge up the house battery anyway. I carry a "normal battery charger" and just got a "battery tender" for when I have AC power someplace.

My "house battery" is a "29 series" (pretty big and 66 pounds 845 amp hours) should go 40 hours or so without any re-charging.

[Goofproof]

You could get a XPAP that runs on 12 volt d/c, much more power friendly, using real world power options. You could get more deep cycle batteries, to add to the capacity of your rv power. Jim

[ClayL]

We lived full time in our motor home for 11 years.
Although we did almost no boondocking and almost always had shore power available I did set up for battery use when necessary. ( It was not uncommon to have power outages in some RV parks).
At first I used a 300 watt modified sine wave inverter. My unit would run on 12 vdc but it would have been a real PITA to run the necessary 12 volt wiring to the bedroom slide.
I next installed a 600 watt true sine wave inverter that could power our two CPAP machines (wife got one a few years ago). Most of the time it was used for powering the laptop while traveling, and when stopped the TV, sat receiver, wireless router, laptops and other devices that required relatively low power.

[Hosehead4ever]

Why not just plug your cpap machine into the RV's "house battery" by getting a cord for the cigarette lighter.....DC to DC? The RVs engine or solar panel is usually set up to charge up the house battery anyway. I carry a "normal battery charger" and just got a "battery tender" for when I have AC power someplace.

My "house battery" is a "29 series" (pretty big and 66 pounds 845 amp hours) should go 40 hours or so without any re-charging.

We plan on boondocking as much as possible and relying on solar if we can. I don't know much about solar but I know my mom, who is off grid, has six panels and two batteries and her system produces 1.5 kWh on a bright, not hot, sunny day. She runs almost nothing on her electric but a few LED lights and her laptop and she *has* run out of power after days of dense cloud and her system not fully charging. I have only seen two panels on any of the RVs we've looked at that already have solar and while I'll readily acknowledge that this is about the extent of my current knowledge of solar power systems, I am worried that my husband's power needs during the day of two laptops, a stand alone LED LCD monitor and lighting will be a drag on the system and not fully charge the batteries.

I have run my old PRS1 on a deep discharge marine battery a few years ago, and while that was interesting at the time, I don't think I want to go that route as a permanent setup.

I am going to get a battery backup for my machine. Really, my only question is, is there any particular reason to spend such a large amount on a battery made specifically for my machine or is the C-100 just as acceptable? If anyone on this forum has personal knowledge of that.

[Hosehead4ever]

We lived full time in our motor home for 11 years.
Although we did almost no boondocking and almost always had shore power available I did set up for battery use when necessary. ( It was not uncommon to have power outages in some RV parks).
At first I used a 300 watt modified sine wave inverter. My unit would run on 12 vdc but it would have been a real PITA to run the necessary 12 volt wiring to the bedroom slide.
I next installed a 600 watt true sine wave inverter that could power our two CPAP machines (wife got one a few years ago). Most of the time it was used for powering the laptop while traveling and when stopped, the TV, sat receiver, wireless router, laptops and other devices that required relatively low power.

I really know next to nothing at this point about power systems and feeling a little out of my depth. Do you run all those things at the same time on battery?

[Hosehead4ever]

You could get a XPAP that runs on 12 volt d/c, much more power friendly, using real world power options. You could get more deep cycle batteries, to add to the capacity of your rv power. Jim

I bought my current unit out of pocket just last year and I'm very happy with it. I'd prefer to buy a battery backup rather than a more power friendly machine. This may be a really stupid question, but would an inverter to change the draw from AC to DC use less power?

[palerider]

You could get a XPAP that runs on 12 volt d/c, much more power friendly, using real world power options. You could get more deep cycle batteries, to add to the capacity of your rv power. Jim

I bought my current unit out of pocket just last year and I'm very happy with it. I'd prefer to buy a battery backup rather than a more power friendly machine. This may be a really stupid question, but would an inverter to change the draw from AC to DC use less power?

no, every time you convert power, you lose some as heat, 12v directly, great, 12 to 24, nearly as great, 12v to 120 and back, worse.

[Randy in Maine]

I bought this cord to run the cpap off the battery....24 volt machine on a 12 volt battery. IMO it is more efficient to go DC to DC as opposed to DC to AC to DC.

https://www.cpap.com/productpage/resmed ... hines.html

[CapnLoki]

First off, I know there are threads here about camping with CPAP, and I have read through some of them... But my search on 'RV' came up short...

Although my posts usually are in response to questions on camping or backup, my real experience is living on a boat completely off-grid for several months at a time - not unlike living in an RV. (My shore power cable hasn't been used in about 6 years.) You're over thinking this - at least the cpap part of the issue - the load of the cpap (not counting humidity) for the night is lower than running a computer or TV or led screen for an hour. The savings gained by getting a special low power cpap are about the same as an led lamp for an hour, maybe one amp-hour a night. Also, the special "designed for cpap" batteries are a complete waste of money for your application.

Here's my advice:
Use your regular cpap with no humidity if you can get away with it - I never need it on the boat, of course. If you need humidity try to make a low setting work so your total load will be 10 amp-hours or less. And it almost goes without saying, NEVER use an inverter!

Make sure your RV has the largest battery bank that it can fit. Many smaller RVs come with one battery, or about 100 Amp-hours. You should have at least 200 amp-hours. I have 480 amp-hours, but my fridge is battery powered which is a 40-50 AH hit every day (I'm guessing yours will be propane powered). This doesn't count any starting batteries which should never be used for "house power." Calculate your total load for a day and make sure the bank is at least triple that. This will allow you to discharge to 50% then recharge to 85% every day with one hour of the generator. (Going below 50% diminishes lifetime and getting above 85% is tedious.) If you can even double that so much the better so you can handle 2 days of no solar. If you're worried about killing the batteries, get a quality amp-hour meter and learn never to take them below 50% - that way you'll always have enough left in the tank to get through the night. Trust me, you'll start checking the battery status (and water levels) several times a day as a matter of habit.

As for charging, my life got a lot better when I added two 100 Watt solar panels. Instead of charging over an hour every day, I almost break even. However, on rainy days, I fall behind so in practice I run about an hour every third, with the bonus that it heats water for showers. It is inevitable that you will need to supplement the solar, unless you're planning to be in a desert.

Here's the result of my usage tests with various configurations:
viewtopic.php?t=102179

[CapnLoki]

You could get a XPAP that runs on 12 volt d/c, much more power friendly, using real world power options. You could get more deep cycle batteries, to add to the capacity of your rv power. Jim

I bought my current unit out of pocket just last year and I'm very happy with it. I'd prefer to buy a battery backup rather than a more power friendly machine. This may be a really stupid question, but would an inverter to change the draw from AC to DC use less power?

No. Inverters will almost double the load. Although the specs often say 90% efficient that is only at specific loads. In general they are 60% or worse. The big inverter that comes with the rv may cost 10-20 amp hours a day just to be turned on. You should look for computers that runs efficiently on 12v or you'll be running the generator all day.

If you live off grid you will probably run the genset some. Every amp hour wasted is roughly a minute of running the genset.

Sent from my SM-T350 using Tapatalk

[CapnLoki]

...
My "house battery" is a "29 series" (pretty big and 66 pounds 845 amp hours) should go 40 hours or so without any re-charging.

You mean 845 cranking amps. A Group 29 has about 120 amp hours.

[Hosehead4ever]

First off, I know there are threads here about camping with CPAP, and I have read through some of them... But my search on 'RV' came up short...

Although my posts usually are in response to questions on camping or backup, my real experience is living on a boat completely off-grid for several months at a time - not unlike living in an RV. (My shore power cable hasn't been used in about 6 years.) You're over thinking this - at least the cpap part of the issue - the load of the cpap (not counting humidity) for the night is lower than running a computer or TV or led screen for an hour. The savings gained by getting a special low power cpap are about the same as an led lamp for an hour, maybe one amp-hour a night. Also, the special "designed for cpap" batteries are a complete waste of money for your application.

Here's my advice:
Use your regular cpap with no humidity if you can get away with it - I never need it on the boat, of course. If you need humidity try to make a low setting work so your total load will be 10 amp-hours or less. And it almost goes without saying, NEVER use an inverter!

Make sure your RV has the largest battery bank that it can fit. Many smaller RVs come with one battery, or about 100 Amp-hours. You should have at least 200 amp-hours. I have 480 amp-hours, but my fridge is battery powered which is a 40-50 AH hit every day (I'm guessing yours will be propane powered). This doesn't count any starting batteries which should never be used for "house power." Calculate your total load for a day and make sure the bank is at least triple that. This will allow you to discharge to 50% then recharge to 85% every day with one hour of the generator. (Going below 50% diminishes lifetime and getting above 85% is tedious.) If you can even double that so much the better so you can handle 2 days of no solar. If you're worried about killing the batteries, get a quality amp-hour meter and learn never to take them below 50% - that way you'll always have enough left in the tank to get through the night. Trust me, you'll start checking the battery status (and water levels) several times a day as a matter of habit.

As for charging, my life got a lot better when I added two 100 Watt solar panels. Instead of charging over an hour every day, I almost break even. However, on rainy days, I fall behind so in practice I run about an hour every third, with the bonus that it heats water for showers. It is inevitable that you will need to supplement the solar, unless you're planning to be in a desert.

Here's the result of my usage tests with various configurations:
viewtopic.php?t=102179

Thank you so much!!! That was very thorough and in terms I understand. If I heard you right, kill the humidity, add solar battery capacity not a backup for the cpap, and get an AH meter.

We did use the kill-a-watt last night on the things that we would hope to be using and they draw a lot less power than I had feared. Even the 50" TV he is convinced we should take only draws 30 watts. Where we'll put a 50" TV is another matter but I'm saving that argument for another day.

[Hosehead4ever]

You could get a XPAP that runs on 12 volt d/c, much more power friendly, using real world power options. You could get more deep cycle batteries, to add to the capacity of your rv power. Jim

I bought my current unit out of pocket just last year and I'm very happy with it. I'd prefer to buy a battery backup rather than a more power friendly machine. This may be a really stupid question, but would an inverter to change the draw from AC to DC use less power?

No. Inverters will almost double the load. Although the specs often say 90% efficient that is only at specific loads. In general they are 60% or worse. The big inverter that comes with the rv may cost 10-20 amp hours a day just to be turned on. You should look for computers that runs efficiently on 12v or you'll be running the generator all day.

If you live off grid you will probably run the genset some. Every amp hour wasted is roughly a minute of running the genset.

Sent from my SM-T350 using Tapatalk

More great specifics! Thank you. We don't have any choice about his work equipment that belongs to his company, but I will definitely look into the possibility of replacing our personal laptops with ones that are more power efficient. We'll be towing our car so I'll have access to run into towns and charge at the local coffee house (or McDonalds). My previous travels inform me that there are many places to charge personal devices if you buy a coffee or something to eat. I only truly anticipate it being a problem if we're far from civilization - national forest, BLM land, etc.

I guess what I'm really going to have to look at is the cost of adding battery capacity to the solar vs the cost of replacing devices to use less electricity. There may be a combination of those that we end up doing. Thanks again!

[CapnLoki]

EDIT: I guess I missed the fact that the Transcend battery is only for Transcend machines. But there is still a generic battery it seems - the C 100. So the question remains essentially the same - $200+ for the C 100 or $700+ for the Resmed specific battery?

Just to be clear, the ONLY reason to buy either of these batteries is the light weight. They are only 8 amp hours to meet airline requirements, enough for one or two nights without humidity. By contrast my 480 amp hour house bank, with quality batteries, was under $700.
If you have need of this, either is fine. I probably wouldn't spend $200, since there are even less expensive alternatives; the $700 option is ridiculous. If you can afford it, more power to you.