12 Volt CPAP power

[Berndad]

Hello all,
We are deep into our 1st year of Escape joy.
All last summer I was able to use a 12 volt outlet and a Resmed purchased 12 V DC to 24 volt DC adapter for my Resmed CPAP. Now ,for no apparent reason, it will no longer provide continuous power. It will power on , run for a few moments, shut down, reboot and start all over.
Runs fine on 110 original power supply (110 AC to 24 volts DC.
Any thoughts?
Thanks for consideration.
Bern

[cpaharley2008]

check you 12v outlet for output and if good then the adapter may have gone kaput...not sure how 12v can be converted to 24v in first place, always thought you had to go down not up.

[Hawkeye Ed]

What is the make and model number of the adapter? Does the adapter plug directly into your trailer’s 12 volt outlet? If not, what do you need to connect it? Are you able to monitor voltage at the 12 volt outlet and/or the battery?

[Berndad]

Originally Posted by cpaharley2008

check you 12v outlet for output and if good then the adapter may have gone kaput...not sure how 12v can be converted to 24v in first place, always thought you had to go down not up.

I will have to wait to get home as I unintentionally left my voltmeter at the house.
Voltage can be stepped up or down, all depends on how you wind the coil!
Think high voltage transmission lines, stepped up to travel long distance without as much loss and then stepped down at point of use.

[Berndad]

Originally Posted by HawkeyeEZ

What is the make and model number of the adapter? Does the adapter plug directly into your trailer’s 12 volt outlet? If not, what do you need to connect it? Are you able to monitor voltage at the 12 volt outlet and/or the battery?

ResMed 90 watt DC converter, R360-792(DA-90824)DC INPUT 12/24 VOLTS -13/6.5 AMPS
DC OUTPUT +24VOLTS - 3.75 AMPS
Plugs straight into the 12 volt socket but does have a switch on the connector (another possible source of loss) and uses the standard 3 prong ResMed plug into my S9 unit (looks identical to the AC transformer units plug).
Battery voltage is great, and this is occuring while plugged into AC power as well, I installed a Victron shunt and battery monitor months ago.
I did use a 12 volt drop near the 12 volt outlet that was factory installed to add some in cabinet lighting, but did not touch the outlets supply.
The unit has a replaceable fuse that is 10 amps, so I may start by replacing it, just odd that it would work for awhile and then act like it is not getting enough power.
as per my post to Jim, I have no voltmeter with me, not even the cheap plug in kind.
Thanks to both you and Jim

[Hawkeye Ed]

Berndad, Thanks for the additional info about your CPAP setup. This particular adapter is for ResMed S9 machines that are fairly old, so maybe this adapter is too. There's a lot of electronic trickery going into that DC voltage converter box.

Without the voltmeter that you say you don't have, you can't be completely sure if the converter box is the culprit or not. The box could be have a bad internal component that overheats and fails, only to work again when it cools down after a few minutes.

Maybe one of the online CPAP stores will sell you a returnable converter box to test. Sorry.

Ed

[Berndad]

Thanks Ed,
I bought it new for my old machine last July, so may still be in warranty.
Good thoughts.
Bern

[Jeff Thoelke]

I plan to duplicate your setup so I'm interested in this thread. My hunch is your 12-volt adapter is bad. That's a guess based on my experience with other power adapters (computers and computer screens). The adapters are cheaply made and could have an internal short.

[Vermilye]

Originally Posted by Berndad

I will have to wait to get home as I unintentionally left my voltmeter at the house.
Voltage can be stepped up or down, all depends on how you wind the coil!
Think high voltage transmission lines, stepped up to travel long distance without as much loss and then stepped down at point of use.

Transformers (coils) to step up & down voltage/current only work on AC; the 12V system in your trailer is DC. That said, they do make DC to DC converters, some of which can step up or down.

If your adapter is bad, depending on the cost of a replacement, it may be cheaper to build your own. An example that is probably larger than you need.

[tdf-texas]

Originally Posted by Vermilye

Transformers (coils) to step up & down voltage/current only work on AC; the 12V system in your trailer is DC. That said, they do make DC to DC converters, some of which can step up or down.

If your adapter is bad, depending on the cost of a replacement, it may be cheaper to build your own. An example that is probably larger than you need.

20 amp output may be a little large but a great idea. Maybe one of the voltage regulators that I have been using for my trailer devices would be OK. A little over $10 ea.
- Input voltage:5～32V
- Output voltage:2～24V
- Output current:0.01-14A

https://www.ebay.com/itm/DC-DC-Conve...-/111580295460

Here is a link to how I have been using them.
https://www.escapeforum.org/forums/f...tor-14667.html

[Hawkeye Ed]

Bern's CPAP story is a good reminder to pick a machine that runs on 12 volts, not 24 volts. Bern's machine requires 24 volts to run so both his AC adapter and the DC adapter output the same voltage:24 volts. The machines that run on 12 volts, like the current Phillips Respironics models, don't need a voltage converter to work in an RV. In fact, Respironics sells a $25 12 volt adapter that is wired straight thru from the cigarette plug on one end to the machine plug on the other: simple, simple.

For those who are interested, here's an adventurous fellow who built his own ResMed adapter when his OEM one died:

http://www.cpaptalk.com/viewtopic/t1...rsense-10.html

[Curious Mike]

Originally Posted by HawkeyeEZ

Bern's CPAP story is a good reminder to pick a machine that runs on 12 volts, not 24 volts.

Good info IF you have a choice. My doctor ordered my Auto-CPAP; a ResMed AirSense 10, also known as an APAP. It's 24-volt. Auto-CPAP machines require a prescription. Years later, I tried buying a spare one at a couple of the larger online CPAP stores. Couldn't do it without a current prescription. I ended up getting a used one off of Craigslist and ordered new replacement hoses.

I might add that I decided to use a 500Wh Portable Power Supply whilst boondocking and forego the adapter altogether. If I turn off the hose heater and humidifier I can get at least 2 nights use before needing to recharge.