AA's updated policy is very clear. Batteries are recommended, but not required and you may need a DC adaptor depending on the aircraft. The key here is a decision you must make. Passenger power outlets do not always function and may not supply sufficient power. If that is the case and you do not have batteries, will you suffer any health consequences beyond a lousy night's sleep? If yes, then do not take the risk. If no, then it's purely a risk vs. cost of battery issue.
We recommend you bring any necessary, fully-charged batteries to power your medical devices throughout your flight. Don’t depend on the availability of a power outlet to support your device.- If available, power outlets may be used for medical devices
- The use of onboard power might require a DC power adaptor