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Maxoak K2 battery question
I  recently purchased a maxoak k2 battery and a 12v to 24v converter to power my cpap when I go camping this summer. When I plug into the 12v port on the battery my cpap won't turn on but when I plug into the 20v port the cpap turns on and run fine. Is it ok to use the 20v port? Shouldn't the cpap work when I plug into the 12v port? Dont-know
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You are using the ResMed Airsence 10 AutoSet correct?

The converter you use should be the proprietary one made for your machine by ResMed. This machine is a 24 VDC machine; plus has a 3rd wire that must carry a correct V and series R to handshake with the machine. The machine has a triaxial power socket.

Question: Whose converter are you using?

Input to their converter can be 12 to 24 Volt DC.

Most people are using 12 VDC SLA/AGM batteries.
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Your post indicates you're using the Resmed 12/24 converter. The MaxOak has two output ports
1 DC OUT (12V/2.5A Round Port)
1 DC OUT (20V/3A Round Port)

These are marginal in amps output to start the CPAP. We were using a Poweradd Pilot Pro 320000 mAh that had 4.7 amp 12 volt output and it did pretty good, but is apparently discontinued. I'm surprised you are able to run on the 20V 3A output port. This one makes me a bit nervous for warranty purposes.
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Sleeprider is correct. As you need over twice the current from a 12V supply to run the 24V ResMed. (Over twice because of conversion loss.)

We could also look at this from a power point of view:
DC OUT (12V/2.5A Round Port) = 30 Watts
DC OUT (20V/3A Round Port) = 60 Watts

The regular AC line powered brick is a 90 Watt supply.
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I got the BPS 24v power converter for Resmed air 10 & s9 series devices. Specs say input:12v dc output: 24v/3.75a max.
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That's not a genuine ResMed converter.

Most often used is ResMed part number 37297:
[Image: Accessories_Air-10-DCNADC_converter_heroimage.jpg]
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The resmed batterie$$$ are 3.75 amp power sources. So any Li-ion power bank that can match that should work. Most of them are intended to power portable devices and have a maximum 2.5 amp output. 12 volts at 3.75+ is what is needed when used with the 12/24 converter, or directly with any 12-volt Philips CPAP. The actual demand of the CPAP is usually less than 1-amp when operating, but startup is generally higher.
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