Confused about run times for CPAP battery banks

[BeerMeister]

I will be using Lifepo4, not lead acid. The AC adapter uses some power, but measuring AC usage would get pretty close. I am planning on a direct DC connection to the Dreamstation.

Can't go wrong with this one!
Runs my CPAP for 3 nights with heated hose and humidification when camping, and could likely go for 4-5 nights...
With no charging even, depending on ambient temperature.
My setup:
Battery: SOK 12V 100Ah
Charger: Victron Blue Smart 12V/15A
CPAP: ResMed Airsense 10 Autoset + ResMed 12V adapter (90 Watts/7.5 Amps max)
I also use this setup as a UPS for CPAP at home by leaving charger connected.

[remstarcpap]

I will be using Lifepo4, not lead acid. The AC adapter uses some power, but measuring AC usage would get pretty close. I am planning on a direct DC connection to the Dreamstation.

Can't go wrong with this one!
Runs my CPAP for 3 nights with heated hose and humidification when camping, and could likely go for 4-5 nights...
With no charging even, depending on ambient temperature.
My setup:
Battery: SOK 12V 100Ah
Charger: Victron Blue Smart 12V/15A
CPAP: ResMed Airsense 10 Autoset + ResMed 12V adapter (90 Watts/7.5 Amps max)
I also use this setup as a UPS for CPAP at home by leaving charger connected.

That's a lot of power for 27lbs, but man, $571! I'd rather just turn off humidity and heated hose.

[remstarcpap]

See my thread here:

viewtopic/t186673/Great-deal-on-battery ... -8lbs.html

4 days runtime for Resmed S9.

[Lane101]

I have a Dreamstation 1 CPAP that says it uses 6.67 amps at 12 volts, or about about 80 watts of power. It appears this must include the humidifier.

How does a CPAP battery with 160 watt hours of power manage to power a Dreamstation 1 for 8 hours? Does the CPAP really not take 80 watts? My minimum pressure is 15 so my power usage would be on the higher end. At 80 watts I would need 640 watt hours minimum to power my CPAP for 8 hours. I am thinking about getting a Kill-A-Watt meter to see what it really uses.

The 6.67 amps is the maximum power draw with the humidifier on the max setting. Without the humidifier the unit will draw a small fraction of that. Exact draw will vary with your pressure setting. In my case, at 10cm pressure my DS1s draw around .6 to .7 amps per hour from a 12 volt battery when connected directly via the proprietary Philips DC cable. That's around 8 watts per hour or 64 watts over 8 hours.

I use 20 amp hour sealed agm lead-acid batteries that can be drained to 80% of capacity: 16 amp hours or 192 watts. These batteries easily deliver two nights (128 watts) of use with plenty left over for charging cell phones, etc. I have two of these in DIY battery packs that can deliver up to 4 nights off grid and up to a full week when combined with my solar panel.

Again this will vary with your pressure so best to test it out. Note if you have lithium ion chemistry you should be able to use most of the 80 watts available versus the 64 watts from an agm battery.

[remstarcpap]

My little 8lb Li-Ion battery (23 aH)runs my Resmed S9 thru a 12 v adapter for 4, and even 5 days if it's 7 or less hours per night. You just have to turn off humidification and heated hose, which is usually fine for a few days, and even if dry, I can use saline spray up the nose to fix the issue.