Community Forums

Ifster · 06-10-2021, 08:04 AM

Hi,

I'd like to setup solar power, just enough to power a CPAP.

I'm thinking two 12V batteries, 750W inverter, charge controller and a 100W panel.
I realize that the amount of sun will play a major role in the batteries charging during the day, but given a condition of full sun all day long, is this enough power for a CPAP?

Thanks again.

carybosse · 06-10-2021, 08:17 AM

Good question. I have an older CPAP machine, probably uses more power than a newer model, and of course, the humidifier setting is probably a big part of the current draw. I sometimes find when camping the humidity is so high, I can turn my humidifier down.

They make CPAP machines with a battery backup, fairly small battery. I would think the solar power would not have an issue handling the CPAP machine, it is everything else electrical that will be the issue.

I will be interested in hearing the feedback. Actually, now you really have me interested in looking at the power draw. I have a setup for my 18 volt Ryobi system with an inverter to 120 volts. I wonder if that could power my CPAP in a power outage, for instance. Maybe without the humidifier (mine is a separate unit that can be disconnected.) Hmmm....

twinboat · 06-10-2021, 08:55 AM

A 100 watt solar panel will produce approx. 7 amps for about 6 hours on a good sun day.
7 amps per hour is 7 AH × 6 hours = 42 AH or 530 Watt hours.

Look at your cpap and see how many watts it consumes.

If it uses 100 watts, it will use up the days charging in 5 hours. E wry day your batteries will get weaker and weaker if you run the Cpap 7 or 8 hours.

ttavasc · 06-10-2021, 09:19 AM

You might check to see if your CPAP will run directly off the 12v system. Mine does so I use a 12v accessory cord to run the CPAP when traveling which avoids having to use the less efficient inverter method. The 12v rating is 5 amps but since I don't use the humidifier when traveling it uses a bit less than that. My average nightly power consumption for the CPAP is around 15-20ah for ~6 hours use.

astrocamper · 06-10-2021, 09:26 AM

My Philips Respironics Dreamstation Bipap Auto SV runs on 13.8 volts from the 120 adapter when at home. I plug it into my trailers 12 volt power when camping so I don't have to run the inverter/charger overnight.

You may want to see if you device actually runs on 12 volts and get the appropriate cable to plug it in. If you want to use less power run it with the humidifier function turned down or off.

Another couple of 100 watt panels will probably do wonders keeping your batteries in good shape for the overnight load of the CPAP and other stuff. Since you live in the southwest you solar input should be very good.

Ifster · 06-10-2021, 11:08 AM

Just took a look at it. It is a DC machine, but needs 24V at 3.75A, 90W.

I could still wire the batteries to provide 24V, but the inverter I have is rated for 12V. Not a problem to get another inverter.

Or, I have two 100W panels for the house batteries already. I bought another 100W panel just for the CPAP, stand alone setup. I can just wire in the new panel to the existing two, for a total of 300W for two house batteries, but then these batteries will be used for other things besides just the CPAP.

Thanks

Ifster · 06-10-2021, 11:29 AM

Just did some looking around and found a DC adopter for my machine. There is already a DC plug in the bedroom from the old TV, so this is by far the easiest way to go.
So now the question is, how will my two batteries, plus three 300W panels do with the CPAP?

Thanks again.

Marine359 · 06-10-2021, 11:43 AM

The cpap with humidifier uses 5amp. That’s more than anything else uses in your RV. I use the humidifier at home, but when boondocking, I bypass it and use a dc/dc adapter. Cuts consumption to about 1.5 amps. You don’t need much solar to replace that overnight usage. A single panel will suffice. Then look at other loads and add up daily consumption. If you have a big enough battery bank, you can go for days with no incoming ac power.

astrocamper · 06-10-2021, 11:49 AM

At 900 watts of solar you probably won't have any issues. If you want a better idea of tracking your battery state of charge buy a Victron Energy SmartShunt for $131 on Amazon.

https://www.amazon.com/Victron-Smart.../dp/B0856PHNLX

Ifster · 06-10-2021, 12:09 PM

I'll have three, 100W panels for a total of 300 watts, plus the two house batteries.
I'm going with the DC adopter and use the old TV plug in the bedroom. We'll see how it work out for this trip and go from there. If it works, great, if not then who needs sleep anyway.

I'll likely go full solar by next year. Seems to be the way to go for ease of travel, finding non-hookup sites and boondocking.

Thanks all for the help.

Alpine36 · 06-10-2021, 01:06 PM

My ResMed is also a 24vdc model. The ResMed 12vdc adaptor is crazy expensive, so I opted for a little 300w PSW inverter. No issue running off the house batteries for a weekend, without solar. One thing that really helps on limited battery power is to turn the heated hose and humidifier off. At fish camp I can run two or three nights off a single grp31 deep cycle battery this way. My fishing partners are quite pleased.

Ifster · 06-10-2021, 01:26 PM

Mine is also the ResMed. The adopter is about $80. I was thinking to make my own with a couple of plug ends and a step-up converter, but I think it's not worth the hassle.

I live where there's 10-25% humidity, turning off the humidifier is not an option. I'll see how low I can go on that and have it bearable.

Ifster · 07-26-2021, 10:52 PM

Thought I'd write a follow up on how things worked out.
I found a much cheaper adopter on Amazon and bought that. I used the CPAP every night for 20 days straight with the humidifier going and there were no issues. There were a couple of full cloudy days and still no issues with the battery power. Here's a link to the cheaper adopter.
Thanks again.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

rffowler55 · 07-27-2021, 07:11 AM

We have solar power off grid backup at our home to power the CPAP and oxygen concentrator so a couple of recommendations from having this system for nearly 10 years:

1) If you need to purchase an inverter the pure sine wave provides energy that is safer for the CPAP machine and other sensitive electronics.

2) The batteries become a very critical part of the buying decision. A Trojan T105 battery has a storage capacity of 225 amp hours so with 2 batteries in a string you would have a better chance of having sufficient power to run the CPAP when the sun has set or during a cloudy day. The batteries are at play whether you use the inverter or the 12v non-inverter component so their capacity should be given 1st consideration.