Why Does a Smartphone Battery Still Degrade Even When Turned Off?

Smartphones continue to drain battery life even when fully powered off. While turning off the device significantly slows battery consumption, it does not halt degradation entirely. This phenomenon persists due to battery chemistry, and while powering down remains an effective short-term strategy for conserving energy—especially during travel or extended periods without charging—long-term storage can lead to unexpected capacity loss. Recent advancements in battery capacity and efficiency do not eliminate the risk of sudden power depletion, emphasizing the need for users to consider battery degradation over time, particularly for devices stored for extended periods.