system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Is it better to charge a cell phone every night or only when it's low, and why?
gpt
Every night; or before it reaches 20%, whichever is earlier.

Recharging every night is most convenient, and lithium-polymer cells are not affected by the 'memory effect' that happened to early designs of nickle-cadmium cells.

The only things that do stress the chemistry of cells is deep discharges, or storing them fully charged. Keeping them above 20% is a good idea.