(05-15-2014, 01:26 PM)sjssf Wrote: I bought a "multi night" battery. I have a one and a quarter night battery with plans to not shop online with Supplier #1 or buy anything from Transcend.
Regardless of the claims, it's not possible to violate the laws of physics.
The maximum power required by a CPAP machine is stamped on the power supply.
Mine, for example, uses 60 watts, maximum. I measured it and it's closer to 50, depending on pressure and humidity settings, but that's a nice round number. My old machine used quite a bit more.
50 watts @ 12 volts = 4.2 Amps (approx).
4.2 Amps for 8 hours is 33.6 Amp-Hours, which requires a battery the same size as is generally used in golf-carts and which is much bigger than anything you'll find in a portable battery pack (or at least anything you would want to carry around).
The newer lithium-ion batteries have a higher power-to-weight ratio, but there's still no free lunch, and a little battery back is not going to run a CPAP machine and humidifier for a whole night.
When camping, I actually use a deep-cycle 100 amp-hour marine battery which I leave in the car, and run an extension cord to the tent.
Given the current state of battery technology, there is nothing I'm aware of that you would be happy to carry around, that would give you an entire night of usage with a humidifier and a medium or high pressure setting.
Now it is possible to run a CPAP with no humidifier on a relatively small battery, but at least for me, this isn't helpful, since I need the humidifier.