CPAP: Adding wiring for 12 volt power

[Kirk E]

Hello everyone.
I’m getting my 2020 Flagstaff T12RBST ready for the start of the season.
I want to add a cigarette lighter socket to power my CPAP while dry camping.
I’m measuring the power it uses nightly at home with a watt meter. Roughly 20-25 ah per night.
Ive purchased the 12 volt cable for the CPAP.
I’m upgrading my battery to a bank of Two Trojan 6 volt golf cart batteries.
Now I want to add a cigarette socket to the camper for the 12 volt cable. I have some questions.
On startup the unit pulls 6.7 A. Then it drops back to about half of that. I’m thinking the wire gage and inline fuse should support 15 amp. Overkill? Should I go 10 amp?
What gage wire should I use for either case?

Has anyone done this? Where did you tie into the existing wiring?
I’m thinking I should make a home run back to the converter and splice into the positive coming right from the battery bank. It’s more work but I don’t want to disrupt any existing circuits.
What is the best way to connect to ground? I traced the black wire from the house battery. It’s connected directly to the frame of the camper.

Many thanks.

[jimmarako]

If your going to run all the way back to the convertor grab some lamp cord. There may be a spot or two left in the DC distribution block that you an just plug a fuse into and attach the new wire. There should be a negative bus bar in the area that all the negatives (12V ground if you call it that) are attached to. This bus bar will be wired to the frame.

Jim M.

[Falcon900Guy]

Originally Posted by Kirk E

Hello everyone.
I’m getting my 2020 Flagstaff T12RBST ready for the start of the season.
I want to add a cigarette lighter socket to power my CPAP while dry camping.
I’m measuring the power it uses nightly at home with a watt meter. Roughly 20-25 ah per night.
Ive purchased the 12 volt cable for the CPAP.
I’m upgrading my battery to a bank of Two Trojan 6 volt golf cart batteries.
Now I want to add a cigarette socket to the camper for the 12 volt cable. I have some questions.
On startup the unit pulls 6.7 A. Then it drops back to about half of that. I’m thinking the wire gage and inline fuse should support 15 amp. Overkill? Should I go 10 amp?
What gage wire should I use for either case?

Has anyone done this? Where did you tie into the existing wiring?
I’m thinking I should make a home run back to the converter and splice into the positive coming right from the battery bank. It’s more work but I don’t want to disrupt any existing circuits.
What is the best way to connect to ground? I traced the black wire from the house battery. It’s connected directly to the frame of the camper.

Many thanks.

Oh those PIA movements with the ol' CPAP.
I would highly encourage you to take a look and investigate the "Inspire" device.
I have one and it is awesome! No more machine. Just a little remote that turns it on when you go to bed and it turns off automatically after a length of time of you choice. Insurance does pay for the procedure.
Try it, you will LOVE it!!

[chriscowles]

My present arrangement is complicated but, the first time I set up 2 CPAPs on 12V, I ran SOOW wire (available by the foot) directly from the 12V outlet I installed near the front of the (front bed) trailer, to the battery outside. I used a cheap 12V outlet splitter but would have used a double outlet if I knew better.

I don't remember what gauge wire I used. Use the calculator at wirebarn.com to determine that. Keep it short. I had an inline fuse of appropriate size on the positive side, close to the battery. I ran the negative directly to the battery, not frame ground. If you do, and if you have a shunt battery monitor, don't connect the CPAP wire to the battery side.

The outlet you choose may be a parasitic drain if it also has a USB charger. Newer versions have an on/off switch but you have to remember to use it.

[chriscowles]

Originally Posted by Falcon900Guy

... Insurance does pay for the procedure. ...

... if you qualify, clinically. But I'm guessing it's hard for them to disprove "I struggle with CPAP.", to deny the prior authorization. I'm one of those lucky people for whom it works well and is easy.

I'm skeptical about elective surgery using new implantable devices, and I have a clinical background. I sincerely hope it benefits you as well as the ads describe. That means I can get it in a few years after you've tested it for us. I appreciate your efforts on behalf of the rest of us.

[NavyLCDR]

I had USB charging ports in my bedroom. I replaced it with a combination USB charging/cigarette lighter socket. It was just tied into the 12v wiring for the lights. It is on the factory installed 15 amp circuit for the lights. Resmed Airsense 10 CPAP. The lights are all about a total of 20 watts.

[chriscowles]

Originally Posted by NavyLCDR

... The lights are all about a total of 20 watts.

... and draw ~0 when using CPAP at night.

[NavyLCDR]

Originally Posted by chriscowles

... and draw ~0 when using CPAP at night.

+1!

[jimmarako]

Originally Posted by NavyLCDR

I had USB charging ports in my bedroom. I replaced it with a combination USB charging/cigarette lighter socket. It was just tied into the 12v wiring for the lights. It is on the factory installed 15 amp circuit for the lights. Resmed Airsense 10 CPAP. The lights are all about a total of 20 watts.

I was going to suggest something like this is probably the much easier approach. Everything is in place already.

Jim M.

[nvs4602]

I would use 14awg automotive wire especially if running where it will be exposed to the outside. Lamp wire as stated earlier is just that lamp wire.

You can use either a 10 or 15 amp fuse. I have found you can slide 1/4" female spade connectors right onto the larger blade type fuses. No need for a fuse holder.

[chriscowles]

Originally Posted by jimmarako

I was going to suggest something like this is probably the much easier approach. Everything is in place already.



Jim M.

In the trailer I had at the time described earlier, the outlet was not located conveniently and it was a LONG distance to the power center. I had to add one but it's not a hard project if you aim for simple.

[chriscowles]

Originally Posted by nvs4602

I would use 14awg automotive wire especially if running where it will be exposed to the outside. Lamp wire as stated earlier is just that lamp wire.



You can use either a 10 or 15 amp fuse. I have found you can slide 1/4" female spade connectors right onto the larger blade type fuses. No need for a fuse holder.

SOOW is indoor/outdoor. I'd use a protective cover for the parts exposed to road hazards (rocks, etc.) and where it passes through a tight spot, to protect it from abrasion.

[Kirk E]

Thanks everyone.
I’d like to avoid snaking wires back to the area of the converter but I a bit gun shy. Other ideas are welcome.
My first attempt I power this up failed and I’m glad I didn’t damage anything. If you are familiar with this camper there is a storage cabinet to the left of the refrigerator. It also houses the water pump and the filter. I installed a 150 watt rated cigarette socket into the cabinet frame above the door. I tapped into the wiring for the water pump at the pump on off switch.
The cpap touchscreen powers up. When I start the blower the cpap dies. This is accompanied by a click sound that sounds like it is emanating from within the cabinet. Whatever clicked reset and you can repeat the sequence. I’m speculating the the negative is traveling to ground through the water pump and is unwelcome. The water pump still works. I’m going to restore the wiring at the water pump switch back to its original condition.

Again any suggestions how to get to power to the cigarette socket closer to where it is now located are welcome.

[chriscowles]

Where is the converter in this layout?

[CedarCreekWoody]

Be sure you use properly sized wire guage. 1 amp at 120 volt is 10 amps at 12 volts. 150 watts is 12.5 amps at 12 volts.

[Kirk E]

Originally Posted by chriscowles

Where is the converter in this layout?

Hello, The converter is located below the cushion to the right of the stove top. the cigarette jack is in front of the right lower corner of the sink.

[pgandw]

Originally Posted by Kirk E

Again any suggestions how to get to power to the cigarette socket closer to where it is now located are welcome.

Yes. Run the cigarette socket wires (both) to the converter compartment, and tie to the fridge DC circuit (and fuse). You will likely never be using the fridge on DC at the same time as the CPAP. And the fridge has a 15A? fuse, and is the only device on that circuit/fuse. On my 2014, pulling off the front panel of the converter gave a readout of which circuit is which, and what color wire was used for the fridge DC circuit.

If you can see the 12V power for the fridge, you could tie there instead of going back to the converter.

Use 14 gauge wire (rated for 15 amps).

On the negative side, neither of my A-frames had a bus bar. The negative wires, generally white, were tied together in a chain of wire nuts. I put in a negative bus bar when I changed out the converter, but there is only one negative wire going into the converter/fuse panel. The negative bus is a nice-to-have, but not essential.

hope this helps
Fred W
now 2019 Flagstaff T21TBHW A-frame
then 2014 Rockwood A122 A-frame
2022 Hyundai Palisade

[Kirk E]

Originally Posted by pgandw

Yes. Run the cigarette socket wires (both) to the converter compartment, and tie to the fridge DC circuit (and fuse). You will likely never be using the fridge on DC at the same time as the CPAP. And the fridge has a 15A? fuse, and is the only device on that circuit/fuse. On my 2014, pulling off the front panel of the converter gave a readout of which circuit is which, and what color wire was used for the fridge DC circuit.

If you can see the 12V power for the fridge, you could tie there instead of going back to the converter.

Use 14 gauge wire (rated for 15 amps).

On the negative side, neither of my A-frames had a bus bar. The negative wires, generally white, were tied together in a chain of wire nuts. I put in a negative bus bar when I changed out the converter, but there is only one negative wire going into the converter/fuse panel. The negative bus is a nice-to-have, but not essential.

hope this helps
Fred W
now 2019 Flagstaff T21TBHW A-frame
then 2014 Rockwood A122 A-frame
2022 Hyundai Palisade

Thanks Fred.
The 12 volt refrigerator circuit is a great idea. Better than the water pump, which might get run in the middle of the night. I didn’t see a negative bus bar either but I was going to double check. The wiring in the space behind the converter is a real rats nest. How much more time would it have taken to keep it at least a little neater.

[chriscowles]

Originally Posted by Kirk E

Hello, The converter is located below the cushion to the right of the stove top. the cigarette jack is in front of the right lower corner of the sink.

That's very close. Connect the new outlet directly to the power center by running a wire to it. Is there a spare fuse circuit?

[chriscowles]

Originally Posted by Kirk E

Thanks Fred.
The 12 volt refrigerator circuit is a great idea. Better than the water pump, which might get run in the middle of the night. I didn’t see a negative bus bar either but I was going to double check. The wiring in the space behind the converter is a real rats nest. How much more time would it have taken to keep it at least a little neater.

Using the refrigerator circuit is a good idea from someone with experience with your trailer. But, if there is an unused fuse circuit (not likely), I suggest using it instead. The reason is that we always use our CPAP on 12V. That way our sleep is not interrupted in the middle of the night if there's a 120V power failure, because the 12V is always on. It has happened, which is why I do that.