How does charging a phone beyond 80% decrease the battery’s lifespan?

Question

Samsung and Apple both released new phones this year that let you enable a setting where it prevents you from charging your phone’s battery beyond 80% to improve its lifespan. How does this work?

In: 2724

Answer 1

You can charge to 100%, but if you leave it at 100% when stored the capacity will erode.

For very long-term storage, store at 50%, 3.7V per cell

For daily charging, charge to 90% for overnight storage, 4.1V per cell

If you are going to use a lithium-battery powered device right away, charging to 100%, 4.2V per cell, is fine.