Solar for outlets

But I was hopeful they would have one solar powered elect outlet by the bed.  Wishful think, I suppose

Why do you need 120vac? Solar is dc so will connect to your 12v battery system via a charge controller.

You wont be able to run the micro, a coffee pot, hair dryer, or the a/c from an inverter, those take too much energy to operate. And all your lights, fan, furnace, water pump, , stereo, fridge are on 12vdc already.

So if the only thing you want to run from 120 vac is the cpap then get a cpap that can run on 12v. Install a 12v power port near the bed area and call it good. More efficient, cheaper, and easier than putting in an inverter and a new receptacle from it (you can't use the existing receptacles both from an inverter and from the grid without having a transfer switch) to select between them.

Get a power port that has a usb outlet and a voltmeter built in and you can charge your electronics from 12v and keep track of your battery charge level too. That leaves the TV, I suggest getting a dual voltage TV as well so you can run it on 12v too. They're not expensive.

As for solar and battery sizing, if you are going to be off shore power for more than overnight get dual 6v golf cart batteries, case size GC2. Start with a portable 100watt of so solar kit and see how that goes. You can always add more solar in future.

Originally posted by Colt http://www.cpaptalk.com/viewtopic.php?t=102179 Actual data. Sizing a solar system is a little more than just plugging in a panel or 2.

That data supports getting a 12v powered cpap, the bestek inverter efficiency was only about 60%.

As for sizing photovoltaic systems, I've been doing that for 40 years now. There are two parts of course, batteries and PV modules. Dual GC2's provide the highest capacity practical on an rpod short of going to a Li battery system. A Li conversion is too complex for the OP to consider at this point, as well as very expensive.

That leaves the PV array itself. Portable is easiest to start with and allows for setting up the trailer in the shade. 100 to 120 watts will provide 25 to 35 amphours per sunny day. That is consistent with the higher loads stated for the cpap in the link (with the humidifier operating), and well above the requirements for the cpap pump itself.

Of course there are other loads too, and the OP does not yet have a good idea what those will be. So, I would start with one solar module and a 20A controller what will handle 2 modules, and add a second one if needed.

All that being said, we are all still limited by battery capacity from boon docking indefinitely on solar. If you want a highly reliable PV system you will need something in the range of 5 to 10 days battery autonomy. That is more than we can carry unless using Li batteries, and very expensive to do with Li. Unless you have many days if battery autonomy the PV array sizing is very inexact because of solar resource variation. That variation only averages out over longer time intervals. There are sophisticated statistical design tools for stand alone solar systems that predict loss of load probability based on available weather data for the location, array shading and orientation, and a well defined load. None if that is appropriate for a travel trailer moving from place to place, with varying loads, and a small battery.

So, if you have critically needed loads and want to boondock for more than a couple of days there needs to be a backup fossil fuel power source for cloudy periods, in effect making our power systems hybrids. That can either be a small generator or the tow vehicle alternator. I carry a Honda 2k gen for that purpose, which also allows use of the microwave and a/c (with an easy start).

With a generator on hand the solar array becomes optional and it's sizing rather arbitrary. The objective is to limit generator use. Personally, as I live in the cloudy East and mostly camp in forests anyway, I don't carry solar. It would be dead weight much of the time I find about an hour of runtime daily from the generator is sufficient. I do this around dinner time when we generally want to use the microwave.

If it's a hot afternoon I will get the battery recharged then while running the a/c. With the 2k I run the WFCO charger first until the charge current drops to a level where the genny can support both it and the a/c. That is usually only a few minutes.

Still, consider running the CPAP directly off DC instead of running through an inverter. That is the best option.

Beth, you don't need to keep your Li battery outside. It doesn't produce hydrogen gas like lead acid batteries do. It's ok to install it somewhere in the trailer, in fact it's better to do so if you ever camp in below freezing conditions. Li batteries dont like being charged when cold.