Running the CPAP from the inverter is fine, But it is far more efficient to get the 12v transformer for your machine.
Most CPAP machines actually run on 24v. The power supply steps down your 110v to supply 24v. That being said, when you run your inverter you have a power loss when converting 12v to 110v. Then you again have a power loss converting 110v to 24v.
Get the 12v transformer that steps the voltage for your machine and save some amp hrs. in your batteries.
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Steve
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