Solar power and a CPAP

[Netter]

Hi everyone!

I have a question about solar power.

How long does the energy in a battery bank last/or how much solar would I need to run a cpap machine for 6-8 hours each day? Does anyone use a cpap with their solar?

 

[Netter]

It says in manual, 53 watts typical, 104 watts maximum power consumtion

 

[tripper]

Short answer, if you do not use the humidifier, you should have two 100AH deep cycle batteries (two 6v Trojan golf cart batteries ideal) and 300 watts of solar. If you use the humidifier you will need 4 x 100 AH batteries and 400 watts of solar. This is solely for CPAP use, you will need more if you are using the batteries and solar for other items too.

The minimum you can get away with if you are very careful with power use is one 100 AH 12v battery and a 100 watt panel. Your battery will make 3-4 days before you need an external power source to recharge it fully (such as having it hooked into the autos charging system and driving for a couple of hours) and the battery will probably completely die within a year due to chronic undercharging with this setup.

I have a CPAP and have experimented with it for years. I found the best setup was losing weight and improving my cardio to the point where I no longer need it.

 

[Netter]

Thank you very much! I am making a list needed now!

 

[DLTooley]

You need to look at your specific machine. Mine is a newer Phillips Respironics which uses flexible pressure. This reduces the actual power consumed greatly from the rated maximum. Most people do NOT use their humidifiers as that is a big power draw.

I've had zero issues with a 50 watt panel and a cheaper walmart battery. I didn't do much else with it, save charging smaller batteries. The above configurations are very good options for a basic solar set up. You can reduce your battery use by timing your heaviest loads during the middle afternoon when your battery bank is getting full and the sun is still strong.

 

[Netter]

Hi, I think we may have the same one, mine is set to auto sense from 5 to 15. But it does have the humidifier, also set to auto, but I can adjust all settings if i want to. I just got it a week or so ago.

Thanks!

 

[mpruet]

My wife uses a ResMed S9 CPAP system. 

A year ago we decided to take an Alaska RV trip.  I knew that there would be plenty of times that we might have to go several days with no hookups so I researched as to how I could fill the requirements of my wife's CPAP system.  As others have pointed out, the battery attachment for a CPAP doesn't really support using the water attachment, so I knew that would not be a good solution.   After doing a bit of research, I found out about a ResMed converter which only managed the 12 to 24 volt conversion that was needed to run the ResMed.  (http://www.thecpapshop.com/resmed-s9-series-cpap-dc-power-converter).  Since it was a converter and not an inverter, the draw on the DC battery was much lower and variable based on the settings of the CPAP.   I found that using my wife's settings that I could supply power for two nights on only a 35 AH deep cycle battery.  Since I didn't need a huge battery for the CPAP, I was able to purchase four 35 AM batteries which more than covered the amount of off-grid time between where we had hookups. 

For anyone needing to power a CPAP when off-grid, I would strongly urge to check out using a converter rather than going through an inverter.  It's best to try to keep all your stuff in the DC world when off grid because inverting requires a tremendous loss of energy. Also with something like a CPAP since the needed draw of the CPAP is actually variable based on your CPAP levels, then you only draw what you actually need from the battery system.

 

[John61CT]

Yes, many CPAP mfg offer 12V power adapters, definitely more efficient and reliable than going through an inverter.

100W panel should be fine for "average" conditions, but best to get a handle on what you're actually drawing out and putting in with a Watts Up meter.

Ultimately you need to put more energy back into the battery bank than what you take out, and the bank will last **much** longer if you rarely go below 50% SoC and usually get it back to 100% Full charge.

Besides solar, if you drive a lot alt charging can help. Even better, get on mains power overnight a couple times per week.

Some find it helpful to carry a small genny, all depends on your unique situation.

The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, less than $180 per 200+AH pair from BatteriesPlus or Sam's Club.

Perhaps "too many" AH for you, but long as you keep getting them back to 100% as above, they will last for many many years.

 

[bonvanroulez]

The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, less than $180 per 200+AH pair from BatteriesPlus or Sam's Club.

You post this statement a lot and it has a grain of truth, if you assume that vandwellers are all Sams Club members, and if you ignore taxes and core charges.

Those batteries are actually $100 each from Batteries Plus. with taxes and core charges they come out to $256 for a pair.
If you factor in members fees for Sams Club, their price is similar if not more.


Not sure why you need to exaggerate their value, but it is misleading.

 

[GotSmart]

The serious systems are now using the UB121000....

About $170 Amazon Delivered.

Unless you want to experiment.

 

[VanKitten]

John...

What CPAP system do you use? Where does your experience with them come from?

 

[RVTravel]

Also, if you go with two golf cart batteries for 200+ AH capacity, you are then forced to get at least 200-400 watts of solar to keep them charged (some keep saying we must have 2 to 1 panel to AH). That won't fit on many cars. That is very expensive. And the batteries will be ruined if you don't charge them fully.

 

[Spaceman Spiff]

You post this statement a lot and it has a grain of truth, if you assume that vandwellers are all Sams Club members, and if you ignore taxes and core charges . . .
Not sure why you need to exaggerate their value, but it is misleading.

It took me 10 minutes to find an acquaintance that has a Sam's Club membership willing to escort me in to buy my batteries.
Taxes and core charges vary by location, so are not usually included when quoting prices; not misleading.

Also, if you go with two golf cart batteries for 200+ AH capacity, you are then forced to get at least 200-400 watts of solar to keep them charged (some keep saying we must have 2 to 1 panel to AH). That won't fit on many cars. That is very expensive. And the batteries will be ruined if you don't charge them fully.

One is not forced to get anything.  The rule for LA batteries is to bring them back to 100% as often as possible, every day is ideal (method not important).  With a larger battery you will be able to go more days before you MUST recharge; multiple cloudy days happen.

Best advice has already been given:

• Figure out how much power is used by the C-Pap per night.  Kill-A-Watt is the easy way.
• Size your battery bank to meet this need plus any margin you want to include (how many nights before you must recharge).
• Size your battery charging system to fill your battery (solar, wind, alternator, generator, shore power, or a combination).
• Best to have multiple sources of charging for emergencies.

 

[tripper]

You need to look at your specific machine.  Mine is a newer Phillips Respironics which uses flexible pressure.  This reduces the actual power consumed greatly from the rated maximum.  Most people do NOT use their humidifiers as that is a big power draw.

I've had zero issues with a 50 watt panel and a cheaper walmart battery.  I didn't do much else with it, save charging smaller batteries.   The above configurations are very good options for a basic solar set up.  You can reduce your battery use by timing your heaviest loads during the middle afternoon when your battery bank is getting full and the sun is still strong.

CPAP 12V power cords
Yes I left this info out, I have the same CPAP (Phillips Respironics) and ordered the 12V power cord which helped reduce power used, the Phillips can run on 12v. I started with a 100 AH battery and a 100 watt Renogy panel, the CPAP would drain it about 60% every night, and the battery wouldn't get enough charge to make it more than 4 days. That's why I say it is doable on one battery and one 100 watt panel if that's all that can be accommodated. You would really just need to hook battery jumper cables from your vehicle to the CPAP battery about every 3 days and run the car for 1/2 an hour to get a decent charge back into the battery, the solar can make up the rest. The larger battery/solar recommondations I made will cover nightly CPAP use over years with no real damage to the batteries. CPAPs in general draw too much power for a single battery setup so one battery will generally die in about a year.

I see you had no issues with a 50 watt panel and a Walmart battery, that might work in strong AZ sunlight in the summer, but I found in partially cloudy year round or short winter sunlight  conditions that wont last long.

 

[bonvanroulez]

It took me 10 minutes to find an acquaintance that has a Sam's Club membership willing to escort me in to buy my batteries.

So you figured out how to circumvent paying the Sam’s Club member’s fee. I assume people would buy them legitimately as a paid member or pay the requisite surcharge. You would probably not be able to get warranty on them.

Taxes and core charges vary by location, so are not usually included when quoting prices; not misleading.

The merchandisers always disclose those fees in their listings, that is not misleading. John61ct giving people the impression that they can own a pair of gc2s for under $180 is misleading.

 

[BigT]

Here's a huge thread on the topic I started a while ago. https://vanlivingforum.com/showthread.php?tid=11661

It got some really good replies from members like SternWake, who knows what he's talking about when it comes to anything battery or electrical.

 

[mkitchen]

This would be a good topic for a RTR seminar.  Many people are tied to a CPAP and there is so much information out there and quite a bit of it is mis-leading.  
I have been using a cpap for many years and found that I can run my cpap from my trailer, my truck and even my motorcycle.  So lots of options and few restrctions if you are using a cpap.  
Mikey

 

[DLTooley]

CPAP 12V power cords
Yes I left this info out, I have the same CPAP (Phillips Respironics) and ordered the 12V power cord which helped reduce power used, the Phillips can run on 12v. I started with a 100 AH battery and a 100 watt Renogy panel, the CPAP would drain it about 60% every night, and the battery wouldn't get enough charge to make it more than 4 days. That's why I say it is doable on one battery and one 100 watt panel if that's all that can be accommodated. You would really just need to hook battery jumper cables from your vehicle to the CPAP battery about every 3 days and run the car for 1/2 an hour to get a decent charge back into the battery, the solar can make up the rest. The larger battery/solar recommondations I made will cover nightly CPAP use over years with no real damage to the batteries. CPAPs in general draw too much power for a single battery setup so one battery will generally die in about a year.

I see you had no issues with a 50 watt panel and a Walmart battery, that might work in strong AZ sunlight in the summer, but I found in partially cloudy year round or short winter sunlight  conditions that wont last long.

You don't say whether you are using the humidifier or not.  My settings are a bit higher than the original poster and draw much less.  You may have issues with your setup, I've used mine in all conditions but never in AZ in the summer.

 

[DLTooley]

So you figured out how to circumvent paying the Sam’s Club member’s fee. I assume people would buy them legitimately as a paid member or pay the requisite surcharge. You would probably not be able to get warranty on them.



The merchandisers always disclose those fees in their listings, that is not misleading. John61ct giving people the impression that they can own a pair of gc2s for under $180 is misleading.

Batteries Plus prices did go up $10, but they are now back down - likely a seasonal variation.  They've had a 10% online coupon since I've been watching them, which puts them at 179.88 for the pair.  Core fees are standard in this market.  In SW Colorado Batteries Plus is in the same not so nearby Cities as Sam's Club. 

There may be vendors at Quartzsite that could provide a competitive price.

https://www.batteriesplus.com/productdetails/sligc110

 

[DLTooley]

Hi, I think we may have the same one, mine is set to auto sense from 5 to 15. But it does have the humidifier, also set to auto, but I can adjust all settings if i want to. I just got it a week or so ago.

Thanks!

There are a number of different models, on mine the humidifier is removable.  I never bring it on the road, as water leakage would also be an issue in transit. If yours is not removable, there should be a setting of zero.  My auto flex settings are higher.  The 12v cable was $30ish.