Battery goes down from 100% to like 80-75% so fast Why does my LG L90 battery goes down from 100% to like 80-75% so fast (about 30 mins) and then the battery lasts quite a while? Is it because the battery has been charged only a few times? Because I bought the phone week ago.
From the question comments, you have not calibrated your battery (in a long time or ever).

You need to do a proper calibration:


Do a full charge of the device's battery.
Use the device until it turns off on its own. Do a full discharge of the battery. One neat trick is to get some game that has wakelock (does not let the screen turns off) and leave it running with the device on a well-ventilated place.
After the device dies of low battery, wait for it to cool down and turn it on and use it a bit more. When it refuses to turn on at all, its fully discharged.
Plug it in and let it charge to max.


This will set the flags for FULL and EMPTY battery, and the meters should be accurate.

If the problem persists, your battery may be damaged. If the device's battery is still under warranty, take it to the service center.