system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it bad to keep an electronic device plugged in on full battery?

I’ve heard conflicting information about whether it’s safe to keep an electronic device plugged in all the time. Most recently I’ve heard it depends on the type of battery being used by the device? Should I actively unplug my laptop after it gets fully charged, or is it all a myth?
gpt
Back before the 2000s the types of batteries we were using did not do well when constantly plugged in.  Chargers of that time would switch to trickle charge mode when a battery was almost fully charged, but it wasn't good to leave those batteries plugged in for hours on trickle.


The chargers of today will stop charging when they sense the battery is full.  Also many batteries have circuitry in them that protects them from over charge and under charge situations. 


If somebody is telling you that you shouldn't leave stuff plugged in they're probably not aware that times have changed.  Just follow your electronic's instruction books on charging.  People don't read their manuals which is why this misinformation continues to spread.