Sorry, this is the cheaper version of the Tripp-Lite that _doesn't_ have an oxygen adapter.
Seriously, though, this is another good answer to the thread I was wondering about a couple of days ago: http://www.apneaboard.com/forums/Thread-...-Post-Pics
A comment at Am*zon _quoting_Tripp-Lite_ says that on battery it doesn't generate pure sine waves: "The AC output waveform for the SMART1500LCDT in battery mode is a modified, or pulse width modulated (PWM) sine wave" and " It will not be compatible with PCs that have power supplies that require pure sine waves at all times". Ouch.
But in general: why wouldn't it work to attach an outboard 12v lead-acid battery of higher watt-hour capacity in parallel to give a UPS much longer run-time for a CPAP with a peak requirement of 60 - 80 watts? I'm "assuming" that if a particular UPS can handle supplying hundreds of watts for 90 minutes, it could handle 1/10th the workload for 5 times the time. But I'm not a EE. In fact, I'm not most things...
It might be desirable (or mandatory) to disconnect the external battery to recharge it separately, but it still seems like it would provide power regulation and several days' CPAP run-time at comparatively low cost, at least for those living where power almost never goes off for more than a few minutes at a time. (BTW, does anyone have any deeper background on the failure of "voltage suppressors" during the recent Napa earthquake?)