Cell phone batteries can be easily fooled. If you always charge it when it is 1/2 way down, then it will think that it is needs to be recharged when it is near 1/2 way down. This will cause added electrical use because it will be charged more frequently. It may also give you the false impression that your battery doesn’t hold a charge.
To “reset” the battery, when it shows you need to recharge your battery, turn yourphone off for a few seconds and turn back on. See if it changes the battery charge indicator position. Also, when you are home and can easily plug in your phone, use the phone until your battery is nearly dead. Having a second battery that is available and fully charged will prevent charging when it’s not needed “just to be safe”
Reminder-unplug the charger when not in use! Anything that is plugged in will draw some electricity. Individual items may not draw much alone, but combine it with all the items in your home, it can add up.