CPAP support system

[cwegga]

Recently it has been made obvious to me that I need an electrical system for my small trailer. Or, rather, it's become obvious that I would enjoy camping more if I actually rested and to do that I need to use a CPAP so I breathe all night. My trailer isn't a traditional teardrop, but is similar enough with amenities that the electrical systems should be similar. Here's a picture of a setup boondocking in the mountains.





I was looking at the "Solar Panel without the Technical Stuff" thread and that's the sort of simple setup I'm looking to build, but I am hoping for some specific recommendations for models to buy and places to buy. So I'll lay out my goals, my tentative plans, and solicit advice.

--Goals--
1. Run my CPAP for 3-5 nights of ~8 hours each. (I expect to turn off the humidifier and heating function to lower power draw along with getting a DC to DC power supply)
2. Be able to charge cellphones and tablets also.
3. Charge from Solar to increase runtime during sunny weather.
4. Charge from vehicle when towing.
5. Charge from shore power during rare camping at powered sites, or more likely to top off the battery when at home.

--Plans--
1. 100Ah Lithium battery. (Do I need two? Should I go AGM instead? This is mostly just a very rough guess, since what I'm reading is that 100Ah should be considerably more nights of runtime compared to the $500ish range all in one deals like a Jackery or Bluetti that people say they get 3 nights out of).
2. 1 Solar panel. (Maybe add another later. Initially I'm thinking just mounting to top of my tongue box for convenience. I know the angles will be bad, but always there ready to work some will be better for me than needing to set up ground panels.)
3. Solar controller thing. (Do I just get the one or do I need a separate device to control shore and vehicle charging?)
4. 12v cigarette lighter style sockets x2 at the head of the bed (tailgate end of the trailer) with switches to turn them off and kill parasitic draw from phone chargers. I feel like 12v sockets will give the most future proofing for phone chargers or powering various devices.
*5. Optional, if it is possible to get the battery and shore power charging in a removable box that would allow me to go more mobile for a few days if I'm tent camping or even have a power outage at home to run my CPAP and then lug the battery to a power outlet to charge up.
6. I can install the battery and controllers in the tongue box, or there's lots of room around the frame under the bed that I could mount weather resistant things to.

I feel confident in my abilities to do the mechanical physical parts of the install and hookup of a system like this, but I would value input on specific sizes, capacties, models, and sources to get this setup going. The weather is getting nice and it's time to start camping!

[GTS225]

First things first; Take a peek at the bottom of your machine, or the power block that you plug into the wall. You're looking for "output" on the power block, and input power on the bottom of the machine. I have two machines, one that uses 24VDC, and one that uses 12VDC. The power block is what does that work. If yours uses 24 volts, this is going to be a bit more involved and expensive. You'll end up needing two 12 volt batteries, so that you can run them in series to get the 24 volts. You'll also need a way to charge your bank at 24+ volts, which will mean two solar panels in series, feeding a single charge controller.

Let's find out what you have first, then go from there.

Roger

[cwegga]

It's 24v, but I'm not going to build a 24v battery system. I am going to get the commercial DC to DC 12v to 24v power supply that is available for it and be able to use other normal 12v equipment with my power system. It will be less efficient than staying at 24v and not converting, but will still be better than running an inverter.

[reaver]

My machine runs off 12v, but my wife's requires 24v. I just bought a small 150W inverter that we use to power hers. Is it less efficient? Sure, but it's simple, and it doesn't draw that much more with the heat and humidifier turned off than mine does. Maybe 3-4A over the course of a night. Something to consider.

[nevadatear]

This doesn't have to be complicated. I have run my CPAP machine for 5 years (resmed airsense 9) off a computer power supply with a 12 V converter. I use a Renogy 72000 from Amazon. Cost is $159 and will last 5 nights without humidity or heat. D/C converter cost @80$. If I plan to stay out longer than 5 nights, then I recharge with 100 watt solar daily to keep it topped off, it only takes a few hours if I don't let it get down too low.

[GTS225]

It's 24v, but I'm not going to build a 24v battery system. I am going to get the commercial DC to DC 12v to 24v power supply that is available for it and be able to use other normal 12v equipment with my power system. It will be less efficient than staying at 24v and not converting, but will still be better than running an inverter.

That seems quite reasonable and practical. My suggestion would then be two, roof-mounted rigid solar panels, parallel-feeding a single charge controller for a single, 12-volt, AGM battery. If you want to save a few bucks right now, go with a standard flooded lead-acid RV battery, and get an AGM at a later date. The AGM is mostly as a safety measure, should things get crazy and it gets tossed around (or worse) off-road.
Two panels for the added raw power, just in case you have to rely on the solar system for a few cloudy days.

Start watching your local marketplace listings for a pair of used solar panels. You might be lucky enough to have a (relatively) local outfit that sells them. (They buy in bulk from some corporation that's swapping theirs out for better efficiency.)

Roger

[cwegga]

Ok, here's what I'm thinking now. I've really struggled to find any specific recommendations. It seems most of the basic DIY solar info out there I can find is for small setups without much application to my life. Stuff with no alternator power, no shore power, and only big enough to run a small cabin.

Anyway, other than that Renogy battery bank which looks tempting I'm not finding much. Right now I'm thinking this battery and DC-DC charger+MPPT charger, https://www.amazon.com/Battery-Lead-Aci ... 143&sr=8-1, this battery, https://www.amazon.com/Litime-LiFePO4-P ... r=8-3&th=1, and then source some solar panels.

Shout out if those are horrible, my plan won't work, or even if you just think I'm ugly.

[GTS225]

If you're going the Li-Po route, or lithium in any form, I'm not your advisor. I've been dead set against lithium power sources since they grounded airplanes with cabins full of smoke. Seems "we" should wait awhile before embracing the technology.

Maybe someone with more lithium experience can chime in.

Roger

[tony.latham]

Maybe someone with more lithium experience can chime in.

I've had a lithium battery on my belt and often in my shirt pocket for–-who knows how long? I'm talking about my iPhone, of course. I just wrapped up a 21 day camping trip through Southern Utah. Driving through the Salt Lake basin, the most commonly seen car is the Tesla. None were on fire.

When I built my last teardrop five years ago, I chose an AGM. It was generally a financial consideration. $200 vs $500 or much more. When I needed a trolling motor last year, I went with a 50 amp Weize lithium ($200). It's a much better battery for the cost. 50 Useable amps vs. 35.

Times have changed. When the AGM in my teardrop dies, I'll put that same lithium in it and recycle that chunk of lead.

Tony

[reaver]

Maybe someone with more lithium experience can chime in.

I've had a lithium battery on my belt and often in my shirt pocket for–-who knows how long? I'm talking about my iPhone, of course. I just wrapped up a 21 day camping trip through Southern Utah. Driving through the Salt Lake basin, the most commonly seen car is the Tesla. None were on fire.

When I built my last teardrop five years ago, I chose an AGM. It was generally a financial consideration. $200 vs $500 or much more. When I needed a trolling motor last year, I went with a 50 amp Weize lithium ($200). It's a much better battery for the cost. 50 Useable amps vs. 35.

Times have changed. When the AGM in my teardrop dies, I'll put that same lithium in it and recycle that chunk of lead.

Tony

If you're going the Li-Po route, or lithium in any form, I'm not your advisor. I've been dead set against lithium power sources since they grounded airplanes with cabins full of smoke. Seems "we" should wait awhile before embracing the technology.

Maybe someone with more lithium experience can chime in.

Roger

I'm going to agree with Tony here. Lithium has come a long ways in the last few years. I have two different LiFePO4 batteries. One for the trailer, and another that stays in my Xterra full time. Both are from different manufacturers, and both are flawless.

I went camping on black friday. Temps got down to about 18* overnight. I was running my diesel heater all night, battery heater, and water tank anti freezing pad, in addition to my cpap. My 100Ah LiTime Mini still had 15% battery when I climbed down from the rooftop tent.

LiTime also has a 50Ah battery you may want to consider. Keep in mind that the mini, and the 50Ah don't have low temp cutoff, so unless you have a way to keep it warm, don't charge it if the temps are below freezing, or you can kill the battery.

[featherliteCT1]

Lithium Ion a/k/a Lithium and Lifepo4 are two different chemistries.

Lithium is not safe (especially if not charged properly).

Lifepo4 is safe (much safer than lead acid).

The LiTime battery OP linked to is Lifepo4.

By "safe" i am referring to fire and chemical hazard.

[GTS225]

Didn't say it hasn't gotten better. I also understand the differences in battery chemistry. It's just that I won't jump feet-first into the "system", (if you will), but rather let you all be the field research team. When I do go the lithium route, I'll thank you folks for taking the risk in my stead.

Roger