Saturday, April 30, 2016

CPAP Amp Usage

This post is about conserving DC when using a CPAP while boon-docking.

Any device can be powered from an inverter. But, inverting/converting is not without some loss. Call it a toll fee. Now consider a CPAP that runs on DC voltage, requires a “brick”, that rectangular object on a power cord, to convert AC to DC. In the  RV environment this means inverting the batteries DC power to AC and then the brick converting back to DC. Two toll fees. Both unnecessary, since my CPAP requires DC and the coach batteries have want it needs.

My CPAP unit, a Dreamstation by Respironics, is native 12 volt, that’s why I selected it. It comes with a 120 volt power cord and a brick that converts to 12 volt DC. Normally I would have made up a 12 volt cord for it, but I had to buy a power cord from Respironics, since I could not find a source for the odd size 9mm plug it uses. I now own an $18 length of wire with a cigarette lighter plug on one end and the 9mm plug for the CPAP on the other end.

I did not want to install a female “cigarette plug” over my bed as the Mothership does and have the wire hanging down. So I tapped into the 12 volt house system in the raceway above my bed. [MB] I drilled a hole in the bin floor behind the cornice and dropped the power cord down and then across the bed platform so that it’s totally concealed. The machine lives on a table between the beds.

I went to this trouble to minimize amp usage. Powering it from inverter used 3 amps. Now, usage is 1.7 amps. [That’s without the humidifier which I am yet to use]  That’s about 13.5 amps used during 8 hours. I can live with that. 24 amps was a concern for me.

I suggest that anyone concerned about battery use when boon-docking and that has a CPAP that is 12 volt powered to make or buy a cord to power it direct from the house batteries and save those toll fees.