solar power for dry camping & cpap machine

[TxGregory]

***Link Removed******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,

[2oldman]

SoundGuy wrote:
And a PITA at 3am in the morning when you suddenly lose campsite power and have to go outside in your jammies to unplug the main service cable from the now dead campsite post and plug it into the inverter.

better than 3pm in the morning.

How would you know if your power went out in the middle of the night?

[TxGregory]

12thgenusa wrote:
You need to ditch the idea of a 3k inverter. There is no way to power its capacity from a single battery. If you really need 3k watts you need a much larger battery bank, many more solar panels and a knowledgeable person to install it all properly for you.

A 600w inverter will power cpaps and computers.

12gen,
I am with you. I would like to go with a smaller inverter, then I could stow it in its own battery box with the controller. But If I did that, I would have to be really careful about what I plugged into my abundance of AC outlets in my trailer. And for that matter if someone turned on the Air conditioner, it would trip the inverter. Oh, and there is the microwave.

Whereas, if I go with something that will put out close to 30 Amp, 120 volt, then I would not have to be so careful. (my controller supports 4X100W panels). I plan to add a couple of more batteries and panels in the future. So I am thinking that making everything capable of supporting 30 Amp 12 Volt will be a better solution long term. I used to design and build IT, and we always had to be careful about bottlenecks. I don't want my inverter to be a bottleneck. Now my assumption has been that if I had the 3000W inverter plugged into a 12v 100amp/hour deep cycle rv battery ... and I ran the Air Conditioner, that it would drain the battery and do no harm. I saw a post from someone with a configuration similar to mine and that is what they said their did. If I am wrong, I would sure like to find out before hand! 🙂

[SoundGuy]

MrWizard wrote:
YES
But he wants this for dry camping, which means no shore power to lose at 3 A.M.

Being inverter, even with shore power is a safety, no problem if shore power drops out
But not the op question

Actually, the OP said in his opening post -"I also dislike rv parks, and I really want to spend my time elsewhere, and preferably not plugged in all the time."

Sorry, but "not plugged in all the time" by definition means he will be plugged in at some times and therefore subject to the vagaries of park power just as we all are. :R

I'm not suggesting "whole house" isn't a solution for some but there is more to it than just plugging the trailer's main service cable into the inverter. 😉

[MrWizard]

And a PITA at 3am in the morning when you suddenly lose campsite power and have to go outside in your jammies to unplug the main service cable from the now dead campsite post and plug it into the inverter. The better solution is to either hardwire the inverter through an automatic transfer switch OR not run the inverter "whole house" at all and instead install a few dedicated receptacles inside the camper that are fed directly by the inverter. I did, and now when I lose power in the middle of the night all I have to do is roll over in bed and hit the inverter's remote switch to activate the duplex receptacles it feeds.

YES
But he wants this for dry camping, which means no shore power to lose at 3 A.M.

Being inverter, even with shore power is a safety, no problem if shore power drops out
But not the op question

edited for clarity

[pianotuna]

There are many ways to accomplish what you wish to do. Pick one, get a mobile rv repair person to implement it to YOUR desires.

In general, kits may tend to come with inadequate charge controllers. The Grape that Mr. Wizard found is a "best buy" and for anything below 40 amps would be my "go to" solution.

[SoundGuy]

TxGregory wrote:
.. the only connection would be through the 30 amp shore power cord, and I can use my existing AC outlets throughout the trailer.

2oldman wrote:
That's what I did. Works great.

And a PITA at 3am in the morning when you suddenly lose campsite power and have to go outside in your jammies to unplug the main service cable from the now dead campsite post and plug it into the inverter. :M The better solution is to either hardwire the inverter through an automatic transfer switch OR not run the inverter "whole house" at all and instead install a few dedicated receptacles inside the camper that are fed directly by the inverter. I did, and now when I lose power in the middle of the night all I have to do is roll over in bed and hit the inverter's remote switch to activate the duplex receptacles it feeds. :B

[westend]

Right now I am planning on a solar panel starter kit that includes a controller, a separate battery, a 3000W true sine wave inverter connected to the separate battery, and an extension cord plugged into the shore power outlet when I am parked. This would all be separate from the trailer, and the only connection would be through the 30 amp shore power cord, and I can use my existing AC outlets throughout the trailer. Yes I will waste lots of power in the inverter and the converter for that matter. But it will be KISS

I'm getting the understanding that the reason you wish to have this new 12V system and inverter is that you fear any rewiring of your RV's current 12V and 120V systems. The solution that you've come up with is wasteful ($$$ spent) and has the potential for not working well.

I'd suggest you take your RV to someone knowledgeable about RV electrical systems and have them install what is a practical system.
A mobile RV technician should be able to handle this.

If it was my situation this is what I'd do to have enough power to handle the Cpaps: First, determine if your Cpap machines can run on 12V. If so wire in 12V receptacles for the machines. If I wanted whole house 120V, I would add in battery capacity and an inverter to fulfill my 120V power needs. I don't use high power 120V devices so a smaller inverter is possible. I would install a transfer switch to connect to the 120V load center. That makes 120V power automatic and no extension cords are needed.

Here is what I do have and what works for me: I use a 1000W inverter and off that I run a 120V fridge and all my entertainment devices. I have 300 AH of battery capacity. The inverter's 120V output is dedicated to a couple of 120V receptacles and is not connected through a transfer switch. Additional to this, I have 235W of solar charging and the controller that handles the solar. I bought all the pieces for this system online and not in a kit. Kits have a markup to the total and are sold mostly to those that don't know what they need. You can do better without a kit.

[ktmrfs]

MEXICOWANDERER wrote:
ANY ANY ANY 12 volt light fixture can be tapped to run a duplex wire to feed a CPAP 12 volt machine. Running an inverter is not quite up to minimum intelligence specifications.

on the light fixture, In theory, yes, in practicality, given trailer wiring, not always. Trailer wiring is often 14ga, sometimes 16 ga wiring, and sometimes long runs. plug in a cpap and in some cases and the voltage at the cpap drops below the cpap input threshold and oopps.

Or, it runs, you think your home free, then discover in the middle of the night, cpap off because battery voltage dropped just enough to cut it off, or your battery was fully charged at home, and your at 90 percent when camping and oopps, drops out.


Seen that happen on several trailers I've helped wire for cpap's. often the cpap may not need that many amps to run, but inrush is high enough that it can't get going.

Best to check first

And cpap with humidifier can really wreck havoc with marginal wiring.

Best solution is if in doubt, run a dedicated short line with 12ga wire to the cpap.

I agree, using an inverter is not a good idea unless you have either a very old cpap or a odball new one that won't run on either 12V dc or 24V dc. The 24V dc ones have 12-24 dc to dc converters readily available.

[2oldman]

TxGregory wrote:
.. the only connection would be through the 30 amp shore power cord, and I can use my existing AC outlets throughout the trailer.

That's what I did. Works great.

[SoundGuy]

TxGregory wrote:
Right now I am planning on a solar panel starter kit that includes a controller, a separate battery, a 3000W true sine wave inverter connected to the separate battery, and an extension cord plugged into the shore power outlet when I am parked.

WHY such a large inverter when just one battery won't be anywhere near enough to power it to it's full capacity? :h Keep in mind also that while powering the trailer "whole house" can work it does mean you have to be careful to always first turn off the converter and ensure anything that may otherwise be set to run on 120 vac is either switched off or switched to run on gas mode only. Also, whenever running on battery power alone make sure the fridge climate control is turned off, otherwise you'll be wasting valuable battery reserve. Unfortunately, some fridges don't offer this option, in which case it would be wise to add your own switch just as I did.

[12thgenusa]

You need to ditch the idea of a 3k inverter. There is no way to power its capacity from a single battery. If you really need 3k watts you need a much larger battery bank, many more solar panels and a knowledgeable person to install it all properly for you.

A 600w inverter will power cpaps and computers.

[TxGregory]

MEXICOWANDERER wrote:
ANY ANY ANY 12 volt light fixture can be tapped to run a duplex wire to feed a CPAP 12 volt machine. Running an inverter is not quite up to minimum intelligence specifications.

So you are suggesting I cannibalize the light fixture over my bed to run two 5A 12V CPAP machines? I just peeked at my dc fuses, and it is 15 amp for lights. So maybe that would work. But then I would either have to try to install two DC outlets, or have the wires hanging over my head when I sleep. I really hate to mess with my trailer, as I have very limited electrical skills, and I don't want to do damage do it.


Right now I am planning on a solar panel starter kit that includes a controller, a separate battery, a 3000W true sine wave inverter connected to the separate battery, and an extension cord plugged into the shore power outlet when I am parked. This would all be separate from the trailer, and the only connection would be through the 30 amp shore power cord, and I can use my existing AC outlets throughout the trailer. Yes I will waste lots of power in the inverter and the converter for that matter. But it will be KISS

What I am trying to figure out now is where to put the 24 inch long inverter!

[MEXICOWANDERER]

ANY ANY ANY 12 volt light fixture can be tapped to run a duplex wire to feed a CPAP 12 volt machine. Running an inverter is not quite up to minimum intelligence specifications.

[MrWizard]

haven't we gone off topic
this is supposed to be about cpap
not our battery charge routines

[BFL13]

pnichols wrote:

MrWizard wrote:
The answer.. Not full because it never got to the proper voltage
It is/was near full , but not full until topped charged at the correct voltage

I've proved over and over again (to myself) that when my AGM battery bank reaches zero current acceptance using only 13.6 - 13.7 volts from my 7345 converter - then hitting them right afterwards with 14.XX volts from the alternator changes nothing - the ammeter remains at zero.

Does anyone know why?

(I always use AGM batteries with a specified float voltage of 13.5 - 13.8 volts. Maybe this has something to do with it.)

Phil, whatever you are doing works for you, so keep doing it.

Meanwhile, the rest of us have to figure out what works for us.