Regulated 24V power needed for CPAP machines S18V20F24

I’m looking to make a backup power source for my Resmed Airsense 10 Cpap machine and have a question about regulators. The power specifications on the AC adapter are as follows:

Adapter: ResMed 90W DA-90D24
DC Output: 24Vdc
DC Output: Amperage: 3.75A

  1. My plan was to use two 12v batteries hooked in series to equal 24v.
  2. A smart charger would be connected to the batteries to maintain the charge.
  3. A power cable with voltage regulator would connect the battery to the CPAP for continuous uninterruptible power.

When I found out about the S18V20F24 regulator I believed this would be super simple but the specs fell short of meeting the required amperage. Originally I was thinking just put two or three regulators together in parallel to raise the maximum total amperage to compensate for the loss as voltage decreased. After reading on the forum some it appears that this will not work.

Can you recommend another product or suggest another route? Would I be better off looking at stepping-up to 24V from a 12V battery setup instead? If so, do you have a step-up regulator that would meet the voltage requirements?


Hello, Bob.

Unfortunately we do not have a more powerful step-up/step-down regulator, and as it already sounds like you found from other posts, we do not recommend connecting regulator outputs in parallel. In case you have not seen it already, I suggest reading this thread which has a more detailed discussion about why if you are interested.

We also do not have a powerful enough step-up regulator for your requirements. (The approach to use a step-up instead of a step-up/step-down is okay, but it would probably be less efficient than using a step-up/step-down.)

- Patrick