Power for CPAP off grid.Whats the best way to go?

[Griffithii]

We've mostly stayed on site with EHU but planning more adventurous travel this year.
CPAP machine via inverter ran the Hab battery flat by 5 a.m. the only time we used it off hook up.
Newish Chausson 638EB Welcome.
We're thinking second hab battery and solar panel.
Advice Please- will that be o.k. for a couple of nights and which battery?

 

[100brian]

We've mostly stayed on site with EHU but planning more adventurous travel this year.
CPAP machine via inverter ran the Hab battery flat by 5 a.m. the only time we used it off hook up.
Newish Chausson 638EB Welcome.
We're thinking second hab battery and solar panel.
Advice Please- will that be o.k. for a couple of nights and which battery?

Yes definitely second battery and 300watts solar

 

[Langtoftlad]

For something that was medically critical, I think I'd be looking at buying the appropriate kit.

 

[hilldweller]

CPAP machine via inverter ran the Hab battery flat by 5 a.m.

Questions: Do you know that state of charger before you turned it on. How many watts is it, it will be written on somewhere.

Trouble is, solar is so weather, place and season dependent. Might be great in a Spanish summer but fail in a German autumn.

I hate to use the G word but a generator, if used and tested regularly is just about the only guaranteed solution.

 

[Basildog]

I’ve been told it’s in your sleep

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[Stacetop]

Our friend has a 12v machine. I believe he had to buy an adapter! He uses his off grid with just a solar panel to charge batteries.
Adapter was through the hospital I believe!

 

[Ivory55]

Generator or b2b charger either is not weather dependable.

 

[138go]

12v DC one would be better. Converting DC to AC using an inverter needs the inverter to match the unit. No point in just buying a BIG inverter because the unit its self uses power. Ideally the inverter should be run at near maximum output to get the best out of it. 12v unit would work better and you can then have spare batteries. Batteries can be charged during the day or when your engine is running. A solar panel is dependent on location. The further North you go the less power you get as the sun is lower in the sky. A panel on a flat roof is not going to give much output this time of year.

 

[TheBig1]

The advice depends on which cpap you have been issued and by which health authority. my wife has one that runs on 19v dc which is the same as most laptops so can use a 12v laptop charger. The NIPPY machine I was first issued had a backup battery installed but the 12v supply was not available. your NHS authority will have a policy about use with no hookup. Some say no, others will issue you the 12v charger on request

either way, you need to increase the leisure battery bank on your van and also the solar to charge it off grid

 

[Griffithii]

We realise solar is sunlight dependent. We're doing Spain and France in June so imagine enough light.
If he doesn't get long enough on the CPAP it just means I'll have to drive and I prefer not to!

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[rb62]

I have a Res Med autoset machine and I bought the appropriate, they call it a 'converter' so it plugs straight into the 12v. Never had a problem yet and I always have at least 7.5 hours sleep,two solar panels and two Varta LFD 90s.
The Res Med machines are DC,so DC to DC is far more efficient than running it through an inverter,they quote max of 1AH. The problems start when you need a humifier or oxygen

 

[Pausim]

At home I use a ResMed Airsense 10 but in the mh I have a ResMed S9 with H5i Humidifier. I power it from a Victron 12-500 Inverter. A 12V adapter would be more efficient but with iPads, iPhones, toothbrushes and shaver there is always something that needs charging overnight so I run the inverter.

My overnight useage together with a bit of lighting and tv comes in regularly at about 30AH, as shown by my Victron BMV-700 battery monitor. I suspect a good chunk of this useage is the humidifier rather than the CPAP.

200W of portable solar replenishes this on good summers days but not in winter. I don’t bother with the panels if I am moving on every day or two because my Votronic 1212-45 BtoB can replace 30AH in less than 1 hour of driving. My sense of energy security comes from the BtoB and 100AH LiFePO4 battery rather more than from the solar because I know it will always be available if needed.

I place more importance on being able to replace the AHs used than on having a massive battery bank because sooner or later the energy used has to be replaced. If you stay put in one place for a week or more and then drive on then a bigger battery bank and solar might make better sense. If you make frequent short hops BtoB could be your answer. If needed I could draw 90AH over 3 days from my lithium battery but generally prefer to top it up more often.

With hindsight I think perhaps an Efoy Fuel Cell might have been easier but at first sight it looked expensive and low powered. However, running silently in the background even the lowest powered one could have comfortably kept up with my demands.

Budget available obviously comes into any decision. From your original post I get the impression that you will probably move on every couple of days and if it were me I would be looking at perhaps increasing my battery capacity a bit and leaning towards a BtoB.

I was surprised that you were out of battery by 5am, I have never managed less than 1 full night even before I modified anything so perhaps the size and condition of your leisure battery should be the first thing to check.

 

[Sundowners]

We bought the 12 volt adaptor for mine, a Resmed with humidifier. Ran flat first night out even though we had enough battery. Ran it without humidifier, no problems after that. Thankfully don’t need it anymore, however son came to Portugal over Christmas, no humidifier, using it on 12 volt adaptor, not Resmed, can’t remember the make, had no problems.

 

[Dilwyn]

I use a Phillips Respironics CPAP which will run on mains or, with an adaptor lead, on 12 volts. However, rather than use the habitation battery to supply 12 volts in the motorhome, I use a Tracer 12V Ultra CPAP 22Ah Lithium Polymer Battery Pack which will power the CPAP for about 4 nights if used without humidifier and heated hose. It's quite compact being about 2/3 of the size of a house brick. It is expensive at about £300 but is also useful in hotels, ferries and as back-up for mains power cuts. The battery pack comes with a mains charger and a lead to charge from 12 volts while travelling.

 

[ChrisL]

I also have a Resmed autoset, i can get a whole weekend out of a 110 AH battery used exclusively for the autoset running from a 300 watt inverter. I now have the 12 volt adaptor but haven't used it yet.

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[Pausim]

W

I also have a Resmed autoset, i can get a whole weekend out of a 110 AH battery used exclusively for the autoset running from a 300 watt inverter. I now have the 12 volt adaptor but haven't used it yet.

With or without humidifier?

 

[rb62]

Usefull document here regarding batteries and power usage for those with Res Med machines.

https://www.resmed.com/us/dam/documents/articles/198103_battery-guide_glo_eng.pdf

 

[Pausim]

Usefull document here regarding batteries and power usage for those with Res Med machines.

https://www.resmed.com/us/dam/documents/articles/198103_battery-guide_glo_eng.pdf

Very helpful, I had forgotten about this document. For my machine the humidifier and what level it is set at make a very big difference.

 

[ChrisL]

W

With or without humidifier?

Without the humidifier.

 

[Pausim]

Without the humidifier.

Thanks, it seems to make a big difference.

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[scotzsue]

John's is also a resmed, supplied by NHS, he explained he would be using it in a motorhome and they took away his other machine and gave him this one. We have managed 5 days in winter with an 80W solar panel and 2 batteries, which i think were 80amp. this was the last van, solar generated enough energy despite it being so foggy, wet and winter, we couldn't see the next field and we were next to the fence.Seem to be doing ok with this van too but think longest we have done without hook up or a decent drive is 4 nights. We take a gennie to motorbike meets, as the noise wouldn't be noticed, but have yet to use it in earnest.

 

[Griffithii]

Thanks for these useful replies.
Our dealer quotes £850 for a solar panel fitted, Road Pro is £300 cheaper, but will that be a problem for the damp warranty?

 

[trophychap]

Question - we might need to get a nebuliser - have Googled them and you can buy them with mains and 12v leads - but if you need one - do the NHS happily supply such things?

 

[Puddleduck]

I have a Res Med autoset machine and I bought the appropriate, they call it a 'converter' so it plugs straight into the 12v.

That's what we have as well - not the machine model but the 12v connector. Buy direct form the machine manufacturer and if you have certain conditions it is exempt from VAT. Ours was about £60

We have a single 135 Amp Hour battery and a solar panel (not sure how big but not massive) and it works well - we can have 3 nights off grid with no solar gain and still have more than 50% battery but we don't have a tv and are frugal with other power use. We do have a spare battery and charger that we will take with us if we think we might need it but it doesn't connect up to anything except the machine.

If you have humidifier / heater or anything else apart form the basic machine you will use more power.

 

[Puddleduck]

Question - we might need to get a nebuliser - have Googled them and you can buy them with mains and 12v leads - but if you need one - do the NHS happily supply such things?

NHS Scotland do not supply the 12v lead or the battery pack. They are extras / add ons / luxury items so you have to get them yourself.

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[trophychap]

Very helpful to people in Scotland Puddle! We're smack in the centre of England though!

 

[autorouter]

We're thinking second hab battery and solar panel.
Advice Please- will that be o.k. for a couple of nights and which battery?

You need to know:
1. how much charge your batteries hold when fully charged
2. How much charge your CPAP machine uses per 24 hours/overnight.
3. how much charge is in your batteries at any time.
Then you can tell how long you can stay in one place without EHU or driving to charge the batteries.
So:
1. On the battery label will be a number of amp-hours (Ah). Don't confuse it with the 'cold cranking amps' (CCA) number which is not relevant to this question. I expect it to be between 75 and 120 Ah for each battery. You should aim to use only about 50% of the charge capacity, to ensure good battery life and give yourself a bit of reserve for emergencies.

2. On the label of your CPAP machine should be the power (Watts). Divide this number by 12 (volts) to get the Amps. Multiply by the number of hours the CPAP is running to get the charge used in Amp-hours.
Example: 100 watts is 100/12 = 8.3 amps. For 8 hours this uses 8.3 x 8 = 66 Ah.

3. You need a proper battery monitor, not just a meter that reads volts. For most people it's a nice-to-have, but for you it's a must-have. It will tell you at any time how much charge you have left. You will soon work out what percentage of the charge you use in one night, so you'll always know whether there's enough charge for the night or not. There's a number of brands, but these two are good:
Amazon product ASIN B0088YDHS2https://www.es-store.co.uk/product_...MIv5CCrf3w3wIVCkPTCh0SGgA7EAAYASAAEgIc4fD_BwE

 

[autorouter]

2. How much charge your CPAP machine uses per 24 hours/overnight.

Alternative method for (2) How much charge your CPAP machine uses per 24 hours/overnight. Use the numbers from @rb62's link in post #17.

For each different machine, for each setting, it gives the amps used and the recommended battery size for 8 hours of use.

I know nothing about these machines, I'm just reading from the tables:
Example: S9 AutoSet with H5l set @ 6: For Treatment Pressure 12, recommended battery is 63 AH , uses 5.17 amps. How do they work this out?

5.17 amps for 8 hours is 41.36 amp-hours (AH). If you want to discharge a battery down to 34%, you need this 41.36 AH to be 100 - 34 = 66% of the battery capacity. The battery size you need is 41.36/66 x 100 = 63AH.

Discharging a battery to 34% is a bit low for my liking, I'd prefer something nearer 50%. Easier to do the sums as well: 41.36 x 2 = 82.72 AH.

That's just for one night of 8 hours use. Obviously that's 82 x 2 = 164 AH for two nights. And don't forget that's just for the CPAP machine. You'll need at least 40 to 50 AH for the rest of the habitation devices, but that depends greatly on what you use the power for.

 

[rb62]

Question - we might need to get a nebuliser - have Googled them and you can buy them with mains and 12v leads - but if you need one - do the NHS happily supply such things?

It'll be a postcode lottery,you won't know until you ask! I had to buy my converter,well two actually as I went from a S8 to a S9 and they are machine specific

 

[Pausim]

When I first had a cpap none of the kit was NHS supplied in my area. I now get a home cpap but would not expect the NHS to supply my adapters etc. so that I can go off grid in my motorhome. They probably have other priorities. We choose an expensive pastime and have to accept that there are costs involved.

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