Adding an inverter

[mmuratet]

I need 110v in my travel trailer for a CPAP machine, and the cheapest alternative appears to be adding an inverter to the trailer. I was thinking about adding another battery in parallel next to the one already on the trailer tongue. The trailer has a WF-8735/8740 power panel, which can supply 35 amps of charging My truck alternator can supply 100 A, both seems adequate. I plan to put the inverter in the equipment bay in the compartment in the front of the trailer and connect the AC through the existing electrical cable. The GFI plugs are on the same circuit as the microwave and refrigerator. The battery charger (converter) is on a separate circuit, which I would leave off.This seems like a sound plan to me, have I overlooked a problem?
Thanks

[Yooper906]

Originally Posted by mmuratet

I need 110v in my travel trailer for a CPAP machine, and the cheapest alternative appears to be adding an inverter to the trailer. I was thinking about adding another battery in parallel next to the one already on the trailer tongue. The trailer has a WF-8735/8740 power panel, which can supply 35 amps of charging My truck alternator can supply 100 A, both seems adequate. I plan to put the inverter in the equipment bay in the compartment in the front of the trailer and connect the AC through the existing electrical cable. The GFI plugs are on the same circuit as the microwave and refrigerator. The battery charger (converter) is on a separate circuit, which I would leave off.This seems like a sound plan to me, have I overlooked a problem?
Thanks

Your truck alternator will never supply 100 amps through the charge wire in the 7 way socket. Possibly look into a DC to DC charger, not sure. I know there are quite a few CPAP users on here, maybe someone can point you in the right direction, maybe a few tips.

What trailer and truck do you own?

[RogerR]

I would look into a direct 12 volt to whatever your Cpap takes instead of taking 12 volts to AC/120 volts then back to whatever voltage your cpap takes.
Several posts on this in the past that you can search on the search function above.

Please add your make, model and year of RV plus the brand and model of Cpap machine for best advice on wiring and cpap usage.
Based on prior posts I read and seem to remember I would suggest you look into a lithium battery to get the needed amps to run that Cpap for more than one night.
Also, most posts suggest that adding a new battery to an older one is not a good idea and one problem of lead batteries is that the recharge limit will be governed by the older battery and waste some of the capacity of the new one.

[Stavman]

Also look into a Portable power Station

Most will run a CPAP all night if setup correctly. But will need to be charged again prior to use, but, so would a battery with all the powersitic drains

[muckinfuss]

Inspire is a good alternative.
https://www.inspiresleep.com/

[Jagiven]

Converting from 12V DC to 120V AC and back to DC wastes a lot of power. Does your CPAP have the ability to use a 12V DC cord? I have a Dream Station (the one that is recalled). I bought a 12V plug for it. It works good, and is very energy efficient.

I installed a 12V outlet next to the bed. Low cost, easy to use.

[GTS225]

Same here as Jagiven. Got my 12vdc power cord out of Amazon. You will need to wire in a power port/lighter socket, though. As a quick & dirty setup, I wired one in to the water pump supply under the bed, being as we leave it on all night for bathroom trips. Worked fine as a stop-gap measure. I have since installed one on each side of the bad, tapped into the overhead lighting circuit.

If you really have to throw an inverter at it, the Harbor Freight, 2KW, modified sine wave does do the job. My Dreamstation does not complain about it at all.

Roger

[mmuratet]

Originally Posted by Yooper906

Your truck alternator will never supply 100 amps through the charge wire in the 7 way socket. Possibly look into a DC to DC charger, not sure. I know there are quite a few CPAP users on here, maybe someone can point you in the right direction, maybe a few tips.

What trailer and truck do you own?

Trailer is 264BHW JayFlight SLX. Truck is 2011 F-250 with a 6.2L (gas) engine.
Thanks!

[dxrobertson]

Note amp draw of CPAP device and understand basically the 120V amp draw is * 10 for 12V.

A second battery is always a good idea.
Mount the inverter as close to the batteries as possible, and use adequate gauge wire.

Are you just charging this device while driving or plan to use it while dry camping? If you plan on using this CPAP device while dry camping, then theres more calculations involved.

[Jagiven]

On 12V, using a single 105 ah battery. My charge drops 0.2V overnight. This is using the CPAP, frig on propane and maybe a little led lighting.

[mmuratet]

Thanks to everyone for the good advice. I spoke to the provider this morning and they are looking for a 12v cable. They also said there are power supplies available on Amazon. The device is 50W average and 100W peak.There is a 12V cigarette lighter port in the camper that says "TV Power" but I haven't found its power rating yet. There is a solution in here somewhere.
Thanks!

[1911Garand]

Speaking with experience on this one - I use a Jackery Explorer portable power station for a cpap and love it. Many options and ratings available, very high quality. Also, it has 10,000 uses and is excellent for emergency back up. No doubt that this will work and you will love it. Good luck!

[GTS225]

Just looked at the bottom of my Dreamstation II, and read 12vdc, 6.67 amps. I'm thinking most, if not all, modern CPAP's use a power block between the unit and the 120VAC outlet, dropping the power to 12vdc. There's a LOT of retired folks hitting the roads, and the industry saw that, thus going to 12VDC for the operating voltages.

Roger

[mmuratet]

The manufacturer of my device makes a cigarette lighter adapter and I have ordered one. Really expensive for what it is, but I know it will work. The TV power plug in the trailer is 15A as near as I can tell, which should be adequate. The short pole in the tent right now is the house battery, which is a 24MD-DL at 85 amp-hours. The device is 100W (8.3A at 12v), so the battery should run the device for eight hours with some margin. I am looking for a higher capacity battery that will fit in the battery box. I will let you all know how it turns out, and thanks for all the help.

[RogerR]

QUOTE The short pole in the tent right now is the house battery, which is a 24MD-DL at 85 amp-hours. The device is 100W (8.3A at 12v), so the battery should run the device for eight hours with some margin. "


Please watch a couple of youtubes on lead batteries. As I understand it, running a battery below half rated capacity will cut into it's lifetime. The lower you go the more it cuts lifetime and capacity.


Again, as I understand it a 24 with "85" amps will only be good for 45 or so amps actual use before it damages the battery. Run it dead for a few nights and it is toast!


If you are going to invest in something to run your Cpap, consider lithium. In a lithium rated 100 amps you actually have something like 95 amps before it shuts down with no damage.

More money in the beginning but saves in the long run. Plus if you recharge with a generator it can be charged up to 50 amps per hour if you house system works with lithium or you but a charger.

[Jagiven]

To improve the battery time, turn off the heated hose (major power hog), and humidification.

I still put water in the tank, it just does not evaporate as quickly.

[Bendmac]

SWMBO and I both use a CPAP. Initially, we'd take our "home" units camping with us, doing the cigarette lighter adapter thing off 12v. Even with solar, I'd always be sweating drawing the batteries down overnight and then crossing fingers for a recharge during daylight hours. I'd often let her run of the trailer and I'd run off a separate 12v battery that I'd use a portable panel on for daytime recharge.

Our solution was the Resmed AirMini. We added an inverter, a power monitor, bumped the solar up a bit and are running (2) 6v deep cycle batteries. The AirMini draws something like half to two-thirds LESS load than a big machine. Think of them as the "LED replacement" for the old(er) filament light bulbs. (I think I read somewhere you can run ~10 LED bulbs on the same power draw it takes for a filament bulb).

No heated hose (power hog, anyway) but they do have both standard and "humidified" cartridges for the Minis.

We can easily do quite a few days off the grid with this system.

[jimmoore13]

I have a 500 watt inverter that will easily run a CPAP. But we also have 400 watts of solar and 2 x 6-volt golf cart batteries good for 115 USABLE amp hours.

In sunny Colorado, our batteries are topped off by solar by about 1 or 2 PM. In less ideal conditions, your generator is your friend.

A standard CPAP uses 40 to 80 watts. At 80 watts and 12 volts, your CPAP may consume 7 amp per hour x 8 hours = 56 AMP HOURS (AH). That's pretty much the full capacity of two basic group 24 cheezo marine batteries that dealers like to install on RV tongues (about 35 AH usable each). So, you need more battery than that, but if you don't have solar, you can recharge your batteries with the generator and about 5 to 6 hours of run time.

There's no magic with power consumption vs. battery capacity and charging source(s). Run the numbers on what you have and what you need to consume (furnace anybody?) and plan accordingly, or get your hands on a far more efficient CPAP.

I've run the CPAP without any problems many times with my configuration.

[dchillman]

You can find them on the internet or at your cpap provider. The cpap units are 12v, i used an inverter for years, but now i am going buy the dc adapter. I am presently using a battery pac that i have to recharge every 3 to 5 days

[mmuratet]

It's taken awhile, but I put a cigarette lighter jack with two USB charger ports near the queen bed for the CPAP machine. I swapped out the lead acid battery for a lithium battery and then I replaced the charger with the model compatible for lithium. I just replaced the DC part and left the AC connections alone. Everything seems to be working OK. Can't wait to go camping.
Thanks for the help
Mike