Using my car battery for CPAP

[mindxing]

I am planning a camping trip for later this summer. My biggest problem is figuring out how to get power for my CPAP. I have a device that plugs into the cigarette lighter in my truck and provides AC power. It is a "Belkin AC Anywhere Power Converter 140 Watt" (http://www.cdw.com/shop/products/Belkin ... entifier=3). I have a ResMed S9 unit.

Will I be able to run my S9 unit using that AC power converter from my truck battery (using an extension cord to get from my truck to the tent)?
Assuming that I can use the converter, how long will it last? With the humidifier on vs. humidifier off.

Thanks for any info.

[Pugsy]

Do a forum search for "battery" and "camping" and start reading.
Hundreds of threads.

Assuming that I can use the converter, how long will it last? With the humidifier on vs. humidifier off.

How long it lasts depends on pressure used first of all ...and humidifier use will greatly deplete any battery source. Most of the time people who use some sort of battery set up don't even use the humidifier and that's with a deep cycle battery which would hold up better than a regular car battery.

[CapnLoki]

Will I be able to run my S9 unit using that AC power converter from my truck battery (using an extension cord to get from my truck to the tent)?
Assuming that I can use the converter, how long will it last? With the humidifier on vs. humidifier off.

The setup will work - the question is how much will it stress a starting battery that is not designed for deep cycle. One night without humidity isn't too bad, especially if you run the engine the next day to recharge. The humidifier however could drain it to the 50% level which is not good for a starting battery. Several nights might well kill the battery, leaving you need of a jump plus a battery that will no longer be a 100%. Consider getting a "Deep Cycle," starting at about $80 at Walmart. It can handle several nights, and up to a week if you don't use humidity. It could also charge phones, etc, and even run a small TV and jump your truck.

[ALF]

Resmed sells a DC Converter that will run your S9 off a car battery without running it through a DC-to-AC inverter like that Belkin unit. The Belkin inverter will work, but it is very inefficient for this purpose; it is taking 12v DC from your battery, changing it to 110v AC, and sending that to your S9, which changes the current BACK to 12v DC. In the process, you are going to lose 20%-25% of the power out of your battery. The Resmed DC converter takes 12v out of your car battery and delivers that same 12v to your S9. In addition the converter will shut off power to your S9 if the input current starts to drop. This will prevent your car battery from being completely discharged by your S9. It costs about $85, but I think that it would be worthwhile for you. I don't know how far your tent will be from your truck, but you can buy a cigarette lighter plug extension cord. Also, the DC converter comes with clips to attach directly to a battery, as opposed to having to go through the cigarette lighter plug in your dash:

https://www.cpap.com/productpage/DC-Con ... sJgDHw_wcB

[archangle]

Resmed sells a DC Converter that will run your S9 off a car battery without running it through a DC-to-AC inverter like that Belkin unit. The Belkin inverter will work, but it is very inefficient for this purpose; it is taking 12v DC from your battery, changing it to 110v AC, and sending that to your S9, which changes the current BACK to 12v DC. In the process, you are going to lose 20%-25% of the power out of your battery. The Resmed DC converter takes 12v out of your car battery and delivers that same 12v to your S9. In addition the converter will shut off power to your S9 if the input current starts to drop. This will prevent your car battery from being completely discharged by your S9. It costs about $85, but I think that it would be worthwhile for you. I don't know how far your tent will be from your truck, but you can buy a cigarette lighter plug extension cord. Also, the DC converter comes with clips to attach directly to a battery, as opposed to having to go through the cigarette lighter plug in your dash:

https://www.cpap.com/productpage/DC-Con ... sJgDHw_wcB

The ResMed S9 series actually runs off of 24V, but the net effect is the same. The ResMed DC converter changes 12V to 24V and does the other mystical requirements that the S9 machine wants. It also shuts off before the input 12V drops too far and keeps you from draining the battery too far and delivering too low voltage to the S9 unit. The DC converter is probably more efficient than an inverter.

[wm_hess]

Hi

What's your average pressure? I have a S9 and my 95% pressure is 11. I measured my electrical usage using a Kill-A-Watt meter and it tells me I use .05 kwH (kilowatt Hours) without my humidifier and .08 kwH with my humidifier (set at 3).

To determine how long a battery should last, take the amp hours of a battery and multiply by the volts of the battery. Divide the result by a 1000 to get kwH.

Example: A Walmart Everstart Group Size 27 Deep cycle battery is rated at 109 amp hours & is 12 volt

109 (amps) * 12 (Volts) = 1308

1308/1000 = 1.308 kwH

1.308/.05 (kwH for no humidifier used) = 26.16 days of usage

1.308/.08 (kwH for use with humidifier) =16.35 days of usage

You wouldn't want to use the for more than 50% of the rated number of days so the actual usage should be around 13 days with no humidifier, and 8 days with a humidifer. The 50% rule is a limitation of the batteries themselves. I believe this is to avoid permanently damaging the battery due to excessive depletion.

I also have the converter which as others have noted is more efficient at powering your device. If you read the pdf located here http://www.resmed.com/assets/documents/ ... lo_eng.pdf they show differing amp hour required for different pressures. An important note though is they recommend 12 Amp Hours to use an inverter versus 7 Amp Hours to use a converter for a S9 using a pressure of 10.

Last but not least is the differences between a starting battery (your truck battery) and a deep cycle battery. The starting battery has more short term oomph (pardon the technical language) to get the engine started, but doesn't have the lasting power of a deep cycle battery.

-Bill

[Guest]

I am planning a camping trip for later this summer. My biggest problem is figuring out how to get power for my CPAP. I have a device that plugs into the cigarette lighter in my truck and provides AC power. It is a "Belkin AC Anywhere Power Converter 140 Watt" I have a ResMed S9 unit.

Will I be able to run my S9 unit using that AC power converter from my truck battery (using an extension cord to get from my truck to the tent)?
Assuming that I can use the converter, how long will it last? With the humidifier on vs. humidifier off.

Thanks for any info.

You may be able to use a battery jump starter and charge it by running your car with it connected as if you will be jumping it; tho I would start the engine first before connecting.

Search the forum for a post using the quotes and "Another Battery Option". He used a Sears 1150 which also has an AC inverter tho he never used the inverter part so that would be up to you to test BEFORE the camp trip. Or use the Resmed dc-dc converter.

You may already have a jump starter at home.

[Guest]

The S9 is 12 volt capable and you can buy a 12 volt power supply for it. Then all you need is a good deep cell battery. I wouldn't trust using your vehicles battery as you might drain it. Deep Cell (Marine) batteries are designed to be discharged.

The power supply and the battery will cost you a few bucks, but it's worth it. Especially if your power goes out during a storm.

[raftergirl]

Here's a recent thread with lots of good info.
viewtopic/t97350/Battery-power-packs-for-camping.html

I just ran my cpap for 8 nights in the backcountry using a 12V20A Deep Cycle AGM battery with no problems. I didn't use the humidifier.

[WindyCityEsq]

Are you camping out in the remote wilderness or are you camping at a campground or state park? Bc if it's the later, the vast majority have power surges at the campsites. I went camping over Labor Day weekend and Potato Creek State Park. All I needed to bring (along w/my machine) was a long extension cord. CPAP'ed through the night in our tent.

[PlinkerCraig]

Where raftergirl went for ten days is total wilderness as far as anyone would label it. Being self-dependent for such a long trip is liberating if you can overcome irrational fears. Try wilderness sometime