DC Converter 24V/90W For S9 Machines

A bit of a kludge, but it works well

Lee M, CA – May 11, 2012

"I bought this to interface between my Resmed S9 CPAP and the recommended Resperonics sealed lead-acid battery pack. You need both to run the CPAP off the battery. See my brief review of the battery under "Respironics Battery Pack (No DC Cable)."

Charging the battery to full charge took between five and eight hours. The indicator light on the battery charger changes from red to green when the battery is fully charged. The CPAP.com help desk recommends NOT leaving the battery on the charger much longer than is required to charge it.

The battery has a receptacle on the end or a cord into which you could plug a cigarette-lighter-type plug. To charge the battery, you plug the charger into that socket, and plug the charger's AC cord into your wall outlet. (Do not try to charge the battery from your car's cigarette lighter, unless you purchase a DC inverter, which converts your car's 12 volt system to 110 volts. Then you can plug in your battery charger, or a shaver, or a desktop computer, or whatever.

After charging the battery, unplug the charger's cigarette-lighter-type plug from the battery's inline cigarette-lighter socket. To use the battery to power your CPAP, plug the DC converter's cigarette-lighter-type plug into that inline socket. The black "brick" is similar in appearance to the power supply of your S9 CPAP machine. Other cord coming out of the "brick" has the proper multi-prong plug to plug in the back of your CPAP. So you use this "brick" and hook it to your CPAP in place of your regular "brick" that you plug into the wall.

For my first test, I ran the CPAP AND the humidifier, set to its highest setting. I didn't expect the battery to power the unit an entire night, and it did not. The battery stopped powering the unit after about 5-1/2 hours. Too bad it won't run all night. Perhaps a deep-charge marine battery would run all night. (The converter contains an extra cord with alligator clips, if you want to use a car battery or a marine battery.)

After fully recharging the battery, my second test was to run the S9 with the humidifier turned down to the "off" position, so the humidifier, filled with water, was a "passive" humidifier - no heat.

The battery ran the system for 8-1/2 hours the first night. It might have run a second night as well, but I discontinued the test after 4 hours the second night, because I can't tolerate the dry air; I cough.

If you want to use the CPAP in an automobile (presumably someone ELSE will be driving!), you can plug the converter's cigarette-lighter-type plug into your car's cigarette lighter or power socket. No need to use a separate battery.

Maybe, with a cigarette-lighter extension cord (I presume someone sells one), the car battery could power the CPAP and humidifier all night. This might work if you're camping, say, close to your car. But I don't know if you'd have enough power in the battery to start the car in the morning.

In any case, using the battery, plugging this converter into it, and then plugging the converter into the CPAP machine is a bit complicated, but it works well.

AND, everything -- this converter and the battery and the charger -- (but perhaps not the alligator clip cord) fits into the Resperonics battery carrying case, so it can be carried. But at that point, you're about 15 pounds, so don't plan on carrying it far."

Rick D, OK – May 01, 2012

"Provides power for my cpap from a deep cycle battery and lasts longer than using an inverter to go to my regular power supply."

D.C. Converter

Robert H, CA – April 27, 2012

"Worked just fine on a 10-day sailboat stay. Was able to use a 12-volt jack to power the CPAP. I used only the main body and not the humidifier, as the humidifier draws a great deal more power. Never a hitch..."

Got this in case of power outage or for camping if I decide

Jack Q, LA – March 01, 2012

"Cpap.com delivered this very quickly and the product does work as advertised. Hope I never have to use it, unless I'm camping or on a fishing trip!"

Very bulky, but good performance

Louis P, CT – November 08, 2011

"Having been without power for 8 days as a result of Storm Alfred, I ordered one of these with rush delivery. It arrived super fast, and worked as advertised. Resmed publishes a very useful battery guide (http://www.resmed.com/us/assets/documents/service_support/battery_guide/19825_battery-guide_glo_eng.pdf). The guide is a bit dated and does not cover this particular device, However I followed the battery sizing guidance for my S9 machine and with an inverter, which recommended a 12 amp hour rated battery for my flow rate, without the humidifier. I think the power converter is actually more efficient than an inverter, since the 12 amp hour battery carried me for two nights, when I forgot to recharge the battery one day. I was charging the battery off the generator, which we did not run at night. It was a good at home back up for me. Highly recommend it. Only gave it 4 stars because it is a relatively large unit, as large as or larger than the regular power brick that came with the S9. So not a good item for lightweight travel. But other than that, it operates as advertised. Also, be forewarned that this device is large because it is capable of running the humidifier as well. HOWEVER, the battery requirements jump up 5-6X when using the humidifier (up to 70+ amp hour battery vs the 12 amp hour battery). The 12 amp hour battery is smaller than a lawn mower battery. The larger ones are nearing or at the size of a regular car battery. Definitely not a portable solution. Do not expect to run this off of vehicle power without the engine running. It will kill the battery."