Advice on Cheap Solar Setup for camping with CPAP

Submitted: Wednesday, Apr 24, 2013 at 11:42
ThreadID: 101849 Views:4310 Replies:4 FollowUps:14
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Hi All,

I am looking for a cheap solution for camping with a CPAP machine. I have a Resmed S9 Austoset with humidifier. I have only had the CPAP for 6 months but a recent weekend away without the CPAP proved to me it is now an essential part of my life.

I only go camping 2-3 times a year max at most at the moment, although I'd like to go more. I don't have a camper, just tents & a 4wd. The 4wd is a leased vehicle so I am not interested in installing a permanent 2nd battery and would prefer a separate system that can be used on the next vehicle or in a mates if we take his.

I've had a read of the Solar Blog and done a search on CPAP and solar. In particular I have found some of the prices through searches to be way different to whats on ebay now, but at least in a good way.

What is limited at the moment though is my budget. So what are the bare essentials I would need to power the CPAP, some Lighting (12m strip lights on a gazebo say), and recharge Iphones/Ipads (keep the missus happy) and a 7amp SLA battery (for my kayak's fishfinder).

From looking so far on Ebay and a few online stores it looks like I could get away with something like:

120w Ebay Solar Panel for around $175
100amp AGM Battery for around $175 (from Batteryvalue)
1500/3000w Inverter for around the $120 (ebay)

Do I need to add in a MPPT regulator for a simple system and relatively low load since I won’t be hooking up a fridge (I have a 3 way)?

Would I be able to get away with an 80w panel and smaller battery? Is the inverter big enough for those needs?

If I could keep everything below $500 the missus may not castrate me when it gets delivered.

Anyone with any tips before I go ahead with making some purchases on the above would be appreciated. As mentioned budget is limited. Most of my camping will be one place for 3 days to a week.


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Reply By: Allan B (Member, SunCoast) - Wednesday, Apr 24, 2013 at 12:21

Wednesday, Apr 24, 2013 at 12:21
Hi Lazybugger,


Before anyone can give you advice on this application it will be necessary to know the power consumption of your CPAP plus the humidifier.
1) A search revealed either 90w or 30w for the CPAP. Which is your model?
2) There was no power rating given for the humidifier but as it heats water it may be considerable. Do you have its power consumption?


You referenced a 1500w inverter. If loaded to 1200w it would be drawing 100Amp from your battery. The 100ah AGM battery would be flat in 30 minutes!
Why a 1500w inverter? Did you perhaps mean 150w? For $120 it would seem so.

If you can provide these answers people will be able to help you.
Cheers
Allan

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Follow Up By: Lazybugger - Wednesday, Apr 24, 2013 at 12:46

Wednesday, Apr 24, 2013 at 12:46
Hi Allan,

From memory the power supply would be the 90w since I have the Humidifier, and the one supply powers both. The 30w is for units without the Humidifer but i don't have that one. However I did have a weekend at a powered site in Feb and didn't bother with connecting the humidifer, I think its something I can easily do without for a camping trip.

I was mainly looking at the larger inverters because they have the convenience of 2 plugs. I would most likely be charging at least a phone/ipad or the sounder battery while I slept. The price I got on the 1500w was from ebay. I can see some are more expensive.

http://www.ebay.com.au/itm/Modified-Sine-Wave-Power-Inverter-DC-12V-to-AC-220V-1500W-Max-3000W-/181057241030?pt=AU_Boat_Parts_Accessories&hash=item2a27da3fc6

I am guessing from your comments these must be the really really low end of the range and should be avoided and may be more than I need anyway?
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Follow Up By: Member - Boobook - Wednesday, Apr 24, 2013 at 12:54

Wednesday, Apr 24, 2013 at 12:54
You would also need to state the hours of use per day to calculate the right battery / solar set up. But with say 100W of CPAP I would get a 200 to 300W SINEWAVE inverter. Modified sinewave is hit or moss with many appliances.

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Follow Up By: Lazybugger - Wednesday, Apr 24, 2013 at 13:03

Wednesday, Apr 24, 2013 at 13:03
6-8 hours sleep would be standard for me.
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Follow Up By: Jarse - Wednesday, Apr 24, 2013 at 13:13

Wednesday, Apr 24, 2013 at 13:13
You can use either inverter with the S9. I bought the power converter from Resmed, so don't need an inverter.

If you want to save power, don't use the humidifier or Climateline.

I remember talking with a tech at Resmed, and he said I would need a minimum of 56AH to rum my setup for 8 hours using a 300w inverter. There are a stack of variables to consider, including:

Humidity setting;
Glimateline Temp;
EPR setting;
Pressure Setting, etc

Running mine off the converter, it uses between 0.3 to 5A, depending on what phase it's in.
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Follow Up By: Lazybugger - Wednesday, Apr 24, 2013 at 13:24

Wednesday, Apr 24, 2013 at 13:24
Hi jarse,

Thanks for the info. I did think about getting the resmed converter but figure that in the end the inverter would be used for the other items mentioned as well, so it seems silly not to get one item that can do all of them.
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Follow Up By: Member - Boobook - Wednesday, Apr 24, 2013 at 13:38

Wednesday, Apr 24, 2013 at 13:38
Assuming your 90W for the CPAP inc humidifier, that will round up to about 100w inc inverter inefficiencies for calculation purposes. That is 800 Watt hours per day ( or about 62AH per day) of energy use.

Again assuming 5 hours of sun a day that means you would need about 800 divided by 5, or 160W of Solar Panels as a minimum if you get a MPPT regulator or about 220W of solar if you get a PWM regulator.

If you need 62 Amp hours per day then you should have a minimum of about 130AH battery capacity.

Add a little to everything if you use other power or are in a less sunny environment.

This would pretty much keep you going indefinitely even if you don't charge the batteries with the car / 240V.


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Follow Up By: Member - Frank P (NSW) - Wednesday, Apr 24, 2013 at 18:34

Wednesday, Apr 24, 2013 at 18:34
Lazybugger,
If you can use a spreadsheet here's one that tells you how long you batteries will last after you input your loads, battery size, solar panel watts and solar radiation. It was prepared by an electrical engineer from an original posted on this site years ago.

It's generic, but I have entered Boobook's calculated loads (62Ah per day) which seem reasonable. You can change anything in the yellow cells to suit your setup.

So with a load of 62Ah a day, a 130Ah battery that you're prepared to discharge to 30%, 160 watts of solar and Sydney solar radiation you can see from the columns below how long you can stay camped before running the genny or starting the car.

Try changing the % discharge, the battery size and the total wattage of panels - it's interesting.

Hope this helps.
FrankP

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Reply By: Lazybugger - Wednesday, Apr 24, 2013 at 14:27

Wednesday, Apr 24, 2013 at 14:27
Jarses comment on the Resmed converter got me to search for a bit more info on it. I came across this great article while looking up a price. Figured it may be of use to anyone else looking at this question in the future so here it is, hopefully it stays there to help others in future.

http://www.cpapaustralia.com.au/resources/file/19825_battery-guide_glo_eng.pdf

I saw the converter for $90, I may go to this + a smaller inverter if its possible to run both off the battery at once.
AnswerID: 509668

Follow Up By: Member - DereelGirl - Wednesday, Apr 24, 2013 at 14:58

Wednesday, Apr 24, 2013 at 14:58
Why not ditch the inverter and charge your phones etc from the 12v battery source? Will save you converting to 240v then back to 12v or less with phones & iPad. Just use your car chargers and make up an outlet connected (via fuses) to your battery.
Cheers
Dereelgirl
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Follow Up By: Motherhen - Wednesday, Apr 24, 2013 at 15:43

Wednesday, Apr 24, 2013 at 15:43
Thanks for posting the link Lazy

I note from the link given

"Products with humidifier (HumidAire 2i™, HumidAire 3i™, H4i™,
C-Series heated humidifier)
Note: HumidAire™ must not be used with inverters!"

I have no experience of CPAP use, but many do use them from 12 v with or without an inverter, but I know some say they do not use the humidifier when on battery power.

Motherhen
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Follow Up By: Motherhen - Wednesday, Apr 24, 2013 at 15:44

Wednesday, Apr 24, 2013 at 15:44
Also

"Warning
Other ResMed heated humidifiers must
not be used with inverters. Damage to the
unit or serious injury to the user may
result. If you are using another brand of
heated humidifier, check with the
manufacturer for their recommendation."
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Follow Up By: Lazybugger - Wednesday, Apr 24, 2013 at 15:50

Wednesday, Apr 24, 2013 at 15:50
Thanks for pointing that out Motherhen. Although i do note that the table listing power usage via inverters does include the S9's with Humidifiers. I believe the ones you've highlighted may be older models.

In any case I am happy enough to leave the humidifer at home when camping. Any sore/dry throats etc usually disappear after 10mins or a drink.
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Follow Up By: Motherhen - Wednesday, Apr 24, 2013 at 15:54

Wednesday, Apr 24, 2013 at 15:54
Then if you can, run it direct from 12 v as it is more efficient use of power, and as others have pointed out, the noise of the fan in an inverter can disturb sleep. I know this doesn't help you with size of solar panel and battery.

Mh
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Follow Up By: LIFE MEMBER-snailbait - Wednesday, Apr 24, 2013 at 16:34

Wednesday, Apr 24, 2013 at 16:34
Hi all
I have been using CPAP FOR THE LAST 10 YEARS and I could not use the humidifiers on previous machines.
But now with the S9 I can use the humidifier and it does not up set the converter
The Converter converts the 12 volt to 24 volts dc.
To use the S9 I would suggest you have at least a 105 AH Deep cycle battery for 1 night sleep for the weekend camping for a long weekend 2 or 3 night plus camping you will need to recharge the battery.
This can be done if you are travelling ie 4wheel driving the vehicle will charge the battery if you are staying in one place you will need other ways to charge the battery for the time that you are there.
Solar panels are one way but worse case means dull days raining and no sun another way is a genie. the 12 volt charger on most genn will not charge up a batter so you must have a 240 volt 12 volt smart battery charger .
There is however a company that makes 12 volt battery charger for under $800-00
Sleep apnoea is a life thearting condition in more ways than one
Lazybugger I hope you have advised your power suppler with a letter from you Dr and you get a rebate from you power suppler for the power that the S9 RESMED uses
Also the buying of the equipment is Tax Deductible ie Charger Battery and cable even setting up your vehicle to sustain the CPAP MACHINE is tax deductible talk to your tax agent also get letters from you Dr
Hope this helps
Terry
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Follow Up By: Member - Leigh (Vic) - Wednesday, Apr 24, 2013 at 20:27

Wednesday, Apr 24, 2013 at 20:27
Always a bit of a challenge, trying to get a good setup. I have a S9 but also one of the old machines that runs directly off 12v. That one stays permanently in the 4wd. Given it draws such low current a portable battery pack will power it. Charge up the next day whilst on the move. If you base camp a small solar panel will assist but they re a pain to cart around. Think about one of the old units second hand, leave the good stuff at home! You could probably run it off your starter battery without compromising a cold morning start. Cheers
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Reply By: Member - Craig F (WA) - Thursday, Apr 25, 2013 at 13:20

Thursday, Apr 25, 2013 at 13:20
Just come back from Tuff truck. Myself and 6 others flew to Sydney then hired a 12 seater Toyota van. We slept in swags for three nights and didnt use the car for the duration of the stay. We charged 7 phones and a HD hero off the 12 v system and ran my brothers CPAC for 7 to 8 hrs a night. We idled the car for 30min a day. At the end started the car and back to Sydney. No second battery or solar.
Before you do anything go into a repratable 12v shop and sit with them and discuss your needs then get a quote of your options. For examble a 2nd battery like the ARK may be the better option. As for running big inverters this will never be efficent or cheap.
AnswerID: 509745

Reply By: Member - Laurie K (WA) - Thursday, Apr 25, 2013 at 14:52

Thursday, Apr 25, 2013 at 14:52
I use a Resmed without the humidifier, and have the Resmed inverter (90 w). I run it from the 12v plug via a heavy 12v extension cord. Inverters used with a Resmed must be pure sine wave (PSW). For all other electric stuff, I use a Projecta 150w PSW inverter (has 12 volt plug - higher voltages need to be wired in I believe) and chatge stuff while driving.

I have been using this system on all of our camping trips for 7 years now.

cheers
Laurie
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