Project Choose Your Own Adventure

[Evan]

Im guessing the APAP motor runs on DC (24v?),  did you think about a DC to DC converter?  would be smaller and much more efficient.

here's a clip from the user manual (its a ResMed AirSense 10) thats relevant:



i never considered DC to DC...i'm not familiar enough about electrical systems to have ever thought of that.  so you're saying i could bypass the AC power supply completely and somehow hook a DC converter up to it?  i'm definitely intrigued although at this point i'm not sure its worth it to tear the AC inverter back out.

Yes exactly.   Going from 12vDC to 110vAC then down to 24v is very very inefficient.   Going from 12v to 24v is easy cheap and over 90% efficient.
The 2 battery thing like Adam said would work fine,  but then you have to have 2 batteries,  and they would be 24v only and you would have to charge with 24v too.  On the plus side its simple and nothing to break.
Id probably do a regular 12v,  wire 1 fused circuit to a 24v step up converter for the apap, and another fused 12v circuit for phone chargers and misc stuff. your charger can go straight to the terminals.    Get a good quality 5A step up converter and carry a spare.