Power needed for a CPAP with Heater/Humidifier

They take a lot more power when the Heater/Humidifier is turned on!

Everyone,

Here’s the first field data I’ve received on how many watt-hours (Wh) of battery power would be required to run a CPAP machine overnight with the heater and humidifier turned on.

Dear Mike,

I have a ResMed Airsense 10 CPAP which has a 120VAC to 24VDC power brick.

I run the heated humidification and heated air tube. Last night over 8 hours it used 1.170 KWh with a maximum draw of 1473 W at 119.6 VAC. I will set it up again with heat and humidification turned off and see what I get. - Bill M.

Dear Bill,

Thanks for the field data. That’s exactly what’s we need to calculate how much battery storage is needed to power a CPAP machine overnight.

Here’s the AGM/FLA numbers

Note that a 12-volt 100Ah Lithium battery will have somewhere around 1.2kWh (1,200 Watt-Hrs) of total energy available. And an FLA (Flooded Lead Acid) or AGM battery should only be discharged down to 50% SoC (State of Charge) for best lifespan. Read my article about battery Deposits and Withdrawals HERE.

So a 100Ah (Amp-Hour) AGM or Flooded Lead Acid (FLA) battery really only has 600 Watt-hrs (0.6 KWh) of usable storage. Yes, you can discharge them down to 0% SoC (State of Charge), but battery life will suffer and you might be replacing your AGM or FLA batteries every season.

That suggests that one 100Ah of AGM or FLA battery can power this CPAP machine for around 4 hours while discharging it to 50% SoC.

What about Lithium batteries?

Since a Lithium battery can be discharged down to 0% SoC without damage, you get twice the running hours. So a 100Ah Lithium battery could power this CPAP Machine with the heater/humidifier on for up to 8 hours while being discharged down to 0% SoC. But you won’t have any battery left for other devices in you RV.

So how many batteries do you need?

My recommendation is at least 200Ah of Lithium batteries if you need to power a single CPAP machine with heater/humidifier overnight, and 400Ah of Lithium batteries if you need to run a second CPAP machine at the same time for your significant other.

Let’s play (and breath) safely out there - Mike