How do you properly charge lithium ion batteries?

[AC Question]

How do you charge properly lithium ion batteries?

To keep cell phone batteries properly charged to last as long as possible.

 

[B. Diddy]

Welcome to Android Central! This is a great resource: Basic to Advanced Battery Information from Battery University

In general, follow these guidelines:

1. Don't let your battery drain to zero on a regular basis (this can decrease the overall lifespan of the battery). Try to start charging when you reach 30-40%.
2. Li batteries don't have "memory," so there's no harm in a partial charge.
3. Li batteries can't be "overcharged," so don't worry about leaving it plugged in overnight.
4. If you're not going to use your device for an extended period of time, store it at about 50% charge (not 100%).
5. Extreme temperatures aren't good for the battery, so avoid leaving it in a hot car in the middle of summer, or in subfreezing temperatures in your unheated ski cabin.