solar power for dry camping & cpap machine

Examine the plug in brick carefully. By law the brick must display the power voltage range admitted from the AC plug in inlet to the brick (this cord is usually disconnectable just like a laptop power brick cord)

And then the brick's info with continue on and then list the output voltage and amperage potential of the brick. Aha! This is what you are after. Write down the voltage (12 volts)? and write down the amperage (5 amps)?

Does the brick say 12 volts and 5 amps (very common)?

If yes, you can purchase a power cord that plugs into a cigarette lighter socket, then purchase a long extension (I have encountered ads for 12 feet) cigarette light plus an socket extension cords.

This is a far more practical way than using a PURE SINE WAVE inverter that wastes power converting 10 volts to 120 volts AC then back to 12 volts. The power waste going to inverter is expensive and is sort of nuts...if tour CPAP is indeed 12 volts.

But with a battery conversion the CPAP must be unplugged from the cigarette lighter before starting the engine.

TxGregory wrote:
***Link Removed***Hello, I recently purchased a 2006 Thor Wanderer 30' travel trailer. I was disappointed that I could only run my cpap machine when the trailer is plugged in. I also dislike rv parks, and I really want to spend my time elsewhere, and preferably not plugged in all the time. I am going to put two 100 W solar panels on top. They come with a mounting kit and a charge controller. I thought about just hooking them up to charge the battery, but that doesn't do much for me, because I still can't run my cpap when I am not plugged in. So I was thinking of connecting them to a second deep cycle battery (I have a place for it up front), then using the second deep cycle battery to power an inverter that I would plug into the 30 amp plug that would normally go to external power. My wife also has a cpap, and we like to spend time on our laptops. I put together a picture of what I was thinking. I need some help from someone proficient in electronics to advise me on this. I don't have a lot of money, and I am not physically able to do crawl around the insides of the trailer reconfiguring things. So I came up with this, hoping that it would not all blow up! I am unsure of the size of inverter I need. I would like to just put a 3000W one on, but they are expensive. The 1000W inverter was much cheaper. Also, I am wondering if I need three panels. I am guessing that 3 panels and a 3000W inverter, on a sunny day, would allow me to run everything just as if I was plugged into power. But I don't want to spend that kind of money if I can avoid it.


Thank you in advance,

Can you make this work? Well yes,but you need to understand better what you are doing. May I suggest a little homework? The 12 volt side of life part 1 (Please read part 2 to.
You lack info that is needed to assist in achieving your goal. If you read this you will understand.

I don't know what brand cpap you have mine is a resmed. I found resmed makes a power supply for it that plugs into a 12 volt power outlet. It works great. If you have the heated humidifier it will use a lot more power. I turned off the heated function. Good luck

TxGregory wrote:
But I don't want to spend that kind of money if I can avoid it.

Not sure about the cost of this but I think you would be better off in the long run to get CPAP machines that run directly off 12 V and then just increase your battery capacity if needed.

Or check the wattage of your present machines and get a small inverter to power just IT from an existing 12 V outlet.

Feeding an inverter into the whole RV is probably not a good idea; too easy to overload it.

TxGregory wrote:
I am guessing that 3 panels and a 3000W inverter, on a sunny day, would allow me to run everything just as if I was plugged into power.

"Everything"? ... hardly. :R Assuming your trailer is wired with 30 amp 120 vac service that's 3,600 watts so although you could simply plug your trailer's main service cable into an inverter output and thereby apply power to every 120 vac circuit in the trailer (referred to as "whole house") you'd obviously be limited to the capacity of the inverter and battery bank supplying it. You'd also have to turn off the converter when doing this so as to not create a closed loop, along with making sure that other devices such as the fridge and water heater electric heating option (if it has one) are turned off so as to not place an unnecessary load on the battery & inverter. From your description it sounds like you have limited understanding of what is involved so I'd suggest you find someone else who does have the knowledge to help sort out the best solution for your particular situation. I've done "whole house" myself, some will go another step further and wire in an automatic transfer switch, but I'd suggest the better solution if all you're wanting to do is power a few select devices is to wire in a couple of dedicated duplex receptacles inside the camper that are fed directly by the inverter, just as I've done (10 pics). Leave the inverter off when it's not being used and you won't unnecessarily draw down the batteries, turn it on only as needed ... simple, but you do have to know what you're doing. :)

A typical 100WATT Solar panel only will produce around 5-6AMPS DC current. This is not a whole lot of DC current especially if you are thinking about using the panels onlys only. You have to still upgrade your battery bank to run all the things you want to run and use the Solar panels to give your batteries a good top off charge during the high sun part of the day...

Without the larger battery bank you not be happy with what you have.

Also keep in mind a 3000WATT PSW Power Inverter will want to demand 250 DC Amps PLUS whenever you have it it loaded down with appliances. This is alot of DC Current and two 100WATT Solar Panel will not be much help keepinig up...

I'm sure you can imagine how long a couple of 12V batteries is going tolast providing 250AMPS of DC Current... Only a few minutes at best when loaded down with appliances...

ALot of folks camp all the camp with the CPAP units and having one with DC Mode is best. Most of them have that capability...

We camp all the time off road with around 255AHs of Battery capacity and are able to run just about everything we do at regualr Electric sites with the exception of the Air Conditioner and Highwattage Microwave units. Everything else is pretty much usable. Having LED lights is must do thing. Each 12V incandescent automotive bulb will draw around 1 AMP of DC current. Add all of your up and you see the advantage of having LED lights installed.

We draw around 20-AMPS of demand from out batteries from the 6PM to 11PM time frame and our setup has about 1-2AMPS of parastic drian on the battery all the the time. In our situation we use a 2KW Generator connected to the Trailer at 8AMP each morning to charge up our Battery bank which has dropped back ot its 50% charge state by this time and this will take three hours of generator run run time to bring them back to their 90% charge state. Having two 100 Solar Panels to top off the batteries during the high sun day will decrease the use of the generator in our case probably down to one hour of generator run time.

This is what works for us and been doing this since 2009...

You will have to have a high solar panel farm to do what you are wanting to do. The best back up plan for you IMO is to have a 2KW Generator around along with at least 220AHs of battery capacity to run your needs including the CPAP unit. You know this is going to work. Solar panels only work when in high sun... Got to have the batteries to run when the Sun goes down...

Just sending all this along for your information on how we deal with camping off-grid...


Camping OFF-GRID at Doris Camp in Wichita Mtns Wildlife Refuge at Medicine park, OKLA

Roy Ken

The least amount of expense will be running Cpap's on 12V from the two batteries. The most efficient use of the batteries will be to connect both of them together. You will get more power from two connected than separately. An easy way to do this is to connect an inverter to the batteries and locate it very close, run an extension cord to the inverter, and plug your Cpaps into the extension cord.

IF you wish to not use an extension cord, you can use the shore power cord but this involves access to the inverter, turning off the onboard converter and any other largish 120V power devices.

Two 100W panels, a decent charge controller, and adequate batteries should offer enough power to maintain the inverted power and the Cpap's. You state that you are using other devices like laptops and you will have the typical 12V hotel loads. You should use a calculator and pencil to add up all the power usage before embarking on this project. There are online calculators to help with this. It's important that you choose the right amount and type of batteries, the correct amount of solar to charge them, and the size of any inverter.

Since the Cpap's are medical devices and health is a concern, I'd suggest you carry a generator for those times that solar charging isn't available.

BTW, solar charging "kits" are the most expensive route to getting solar charging. Do your homework and ask questions here. It will save you hundreds of $$.

first thing I'd do, and I do use a cpap is double and tripple check that it is NOT 12v compatible. virtually ALL the recent cpap machines will run off either 12V or 24V DC. 12V dc is a simple solution, plug it into a cig lighter adapter. 24 V is also very very simple, battery power solutions as well as the mfg of most of the 24 V machines make a 12V to 24 V DC to DC converter.

Turn off the humidifier and you can run a cpap for easily 4-5 nights off a good battery.

Or lithium ion rechargeable battery packs are available as well that will run the cpap for at least one night without the humidifier.

that solves the cpap problem.

Next, most every laptop can be run off 12V as well, no need for an inverter. check on amazon or the mfg of the laptop and you will likely find a 12V power source available.

Really need six+ batteries to properly drive a 3000 watt inverter anywhere near the max.

I think 300 watts would be fine for what you describe as your camping needs. Maybe 200 to 400 watts solar.

If you want microwave, electric coffee, toaster, hair dryer etc you are looking at 2000 watt inverter, four+ batteries and 500+ watts solar. Or just add a Honda 2000 to the above.

If you want air conditioning and the rest you need 4000 watt inverter, 3000 watts solar, and a large lithium battery. All running at 24 or 48 volts. Or add a second Honda 2000 to the above.

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