aerothemeplasma/plasma/plasmoids/org.kde.plasma.battery/contents/config/main.xml

<?xml version="1.0" encoding="UTF-8"?>
<kcfg xmlns="http://www.kde.org/standards/kcfg/1.0"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.kde.org/standards/kcfg/1.0
      http://www.kde.org/standards/kcfg/1.0/kcfg.xsd" >
  <kcfgfile name=""/>

  <group name="General">
    <entry name="showPercentage" type="bool">
      <label>If true, the battery will display a little charge percentage label inside.</label>
      <default>false</default>
    </entry>
  </group>

</kcfg>