The Apple AirPods Max, somewhat strangely, do not have a power button, so you can’t turn them off if you’re looking to save battery.

That makes conserving the life a little trickier, and Apple’s explanations have bred a little confusion thus far. Now the company has sought to clarify things with a new support document detailing the £549 noise-cancelling headphones’ various low power modes.
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https://www.trustedreviews.com/news/airpods-max-low-power-modes-explained-how-to-preserve-battery-life-4115195