It’s happened to all of us: Right in the middle of composing an email, updating social media, or video-calling friends, a low-battery notification pops up, sending you scrambling for the nearest charger. Smartphones have quickly become one of the most indispensable tools in our everyday lives, making it critical to keep your battery up and ready to go. However, how often you actually need to charge your phone is highly debated. Should you wait until your battery is almost dead to charge your phone? Should it always be charged to 100%? Is it bad to leave your phone plugged in overnight? Here’s a quick guide to understanding how your phone battery works, and how to keep it charged and in tip-top shape.