PR System One DC cable question

[jeremiahchub]

I'm going to try to go back to driving a truck, but i don't want to have to have a power inverter for my cpap if possible. does anyone know if you can use the DC cable for the PR System One to power the machine while the engine is running? I know the alternator will put out up to 14v but it only needs 12v to run the machine. I don't want it to feed it too much if that will damage it. Any advice or answers to this question please?

Jeremiah.

[chrisp]

Jeremiah.
You will not have any problems connecting to your trucks accessory outlets as long as you arent using a heated humidifier. Just purchase the accessory outlet connector from cpap.com or go to radioshack (bring your cpap to get the correct plug) and get the connector.

I had a 1500 watt inverter ij my truck and connected the humidifier to it and the cpap to 12v. You can also get a passover humidifier if you dont want to use the inverter. Try to put it on a 12 warmerto increase its capacity. You may also want to purchase a smaller inverter (150w) to run the humidifier only.

Chris

[JDS74]

Jeremiah:

In the user manual, Respironics states:

Supplying DC Power to the Device
The Respironics DC Power Cord can be used to operate this device in a stationary recreational vehicle, boat, or motor home. The Respironics DC Battery Adapter Cable, when used with the DC Power Cord, enables the device to be operated from a 12 VDC free-standing battery.
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CAUTION : When DC power is obtained from a vehicle battery, the device should not be used while the vehicle’s engine is running. Damage to the device may occur.
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CAUTION : Only use a Respironics DC Power Cord and Battery Adapter Cable. Use of any other system may cause damage to the device.
Refer to the instructions supplied with the DC Power Cord and adapter cable for information on how to operate the device using DC power.

So ... probably not safe while engine is running.

[chrisp]

A fully charged 12v battery actually produces 13.2 volts. A running vehicle produces 14-16 volts. 14.4 is optimal. 12 Volts is the nominal voltage. But if you want to be safe connect it to a jump starter. It should run a few nights and can be charged thru the truck accessory outlet. I run mine solely from batteries. Or run it on the truck inverter. Humidifier and cpap. If you have a APU run from AC power. 115V.

If you want to run 12V from a running truck go to radio shack and ask what resistor is needed to reduce from 14 v to 12V. I believe it is a 50 OHM resistior. Don't forget . You wil now need 2 DC cables. 1 for when the truck is running (with 50 ohm rsistor) and 1 for when it is off.

Another way would be to get a coil of wire (24ga) and measure the voltage from end to end. There will be a voltage drop due to the length. Insert this coil into your circuit to act as a resistor lowering the voltage to 12 v.

[The Texan]

My PR System 1 runs exclusively off the battery, without any problems. I have used nothing but 12v DC for close to 2 years now, with my M series and now the PR 1, without a hiccup. My vehicle system has an automatic battery charger built in, so the applied voltage will increase to 14.4v when ever the batteries call for it and again, no problems. The one thing you need to make sure of is that your DC outlet is wired as a 25A system directly from the battery, not the small amperage output through the ignition many of the built in power points are set for. I use the Respironics DC power cord, which already has 2 filters built in and again, have had no problems.