CodePen Embed - YNjRaw

<header class="demo-header">
  <p class="not-support" hidden>Your browser doesn't support the Battery Status API :(</p>
</header>

<article class="battery-card">
  <h1 class="battery-title">Battery Status</h1>

  <div class="battery-box">
    <strong class="battery-percentage"></strong>
    <i class="battery"></i>
  </div>

  <dl class="battery-info">
    <dt>Power Source</dt>
    <dd class="battery-status">---</dd>

    <dt>Level percentage</dt>
    <dd class="battery-level">---</dd>

    <dt>Fully charged in</dt>
    <dd class="battery-fully">---</dd>

    <dt>Remaining time</dt>
    <dd class="battery-remaining">---</dd>
  </dl>

</article>

/*! normalize.css v3.0.2 | MIT License | git.io/normalize */html{font-family:sans-serif;-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%}body{margin:0}article,aside,details,figcaption,figure,footer,header,hgroup,main,menu,nav,section,summary{display:block}audio,canvas,progress,video{display:inline-block;vertical-align:baseline}audio:not([controls]){display:none;height:0}[hidden],template{display:none}a{background-color:transparent}a:active,a:hover{outline:0}abbr[title]{border-bottom:1px dotted}b,strong{font-weight:700}dfn{font-style:italic}h1{font-size:2em;margin:.67em 0}mark{background:#ff0;color:#000}small{font-size:80%}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sup{top:-.5em}sub{bottom:-.25em}img{border:0}svg:not(:root){overflow:hidden}figure{margin:1em 40px}hr{-moz-box-sizing:content-box;box-sizing:content-box;height:0}pre{overflow:auto}code,kbd,pre,samp{font-family:monospace,monospace;font-size:1em}button,input,optgroup,select,textarea{color:inherit;font:inherit;margin:0}button{overflow:visible}button,select{text-transform:none}button,html input[type=button],input[type=reset],input[type=submit]{-webkit-appearance:button;cursor:pointer}button[disabled],html input[disabled]{cursor:default}button::-moz-focus-inner,input::-moz-focus-inner{border:0;padding:0}input{line-height:normal}input[type=checkbox],input[type=radio]{box-sizing:border-box;padding:0}input[type=number]::-webkit-inner-spin-button,input[type=number]::-webkit-outer-spin-button{height:auto}input[type=search]{-webkit-appearance:textfield;-moz-box-sizing:content-box;-webkit-box-sizing:content-box;box-sizing:content-box}input[type=search]::-webkit-search-cancel-button,input[type=search]::-webkit-search-decoration{-webkit-appearance:none}fieldset{border:1px solid silver;margin:0 2px;padding:.35em .625em .75em}legend{border:0;padding:0}textarea{overflow:auto}optgroup{font-weight:700}table{border-collapse:collapse;border-spacing:0}td,th{padding:0}
/**
 * Mobile First
 */
body {
    font: 100%/1.4em "Helvetica Neue", "Helvetica", "Arial", sans-serif;
    margin: 0 auto;
    padding: 0 0.625em;
    color: #444;
    -webkit-text-size-adjust: none;
}

/**
 * Small Screens
 */

.demo-header {
  margin-bottom: 80px;
  text-align: center;
}

.demo-title {
  font-size: 4em;
  line-height: 1em;
  text-align: center;
}

.battery-card {
  font-family: "Helvetica", Arial, sans-serif;
  display: block;
  width: 300px;
  overflow: hidden;
  border: 1px solid #D5D5D5;
  border-radius: 6px;
  font-weight: 100;
  margin: 0 auto;
}

.battery-title {
  background: #4c4c4c url('bolt.png') no-repeat 95% 15px;
  color: #fff;
  font-size: .9em;
  line-height: 50px;
  padding: 0 15px;
  font-weight: 100;
  margin: 0;
}

.battery-percentage {
  font-size: 2.5em;
  line-height: 50px;
  display: inline-block;
  vertical-align: middle;
  margin-right: 10px;
}

.battery-box {
  margin: 0 auto;
  padding: 50px 0;
  text-align: center;
  border-bottom: 1px solid #D5D5D5;
}

.battery {
  display: inline-block;
  position: relative;
  border: 4px solid #000;
  width: 85px;
  height: 40px;
  border-radius: 4px;
  vertical-align: middle;
}

.battery:before {
  content: '';
  display: block;
  box-sizing: border-box;
  background: #000;
  height: 40px;
  position: absolute;
  border: 1px solid #fff;
}

.battery:after {
  content: '';
  display: block;
  background: #000;
  width: 6px;
  height: 16px;
  position: absolute;
  top: 50%;
  right: -11px;
  margin-top: -8px;
  border-radius: 0 4px 4px 0;
}

.battery-info {
  font-size: 12px;
  margin: 0 auto;
  padding: 15px 45px;
  overflow: hidden;
}

.battery-info dd {
  float: right;
  margin-top: -22px;
  text-align: left;
  width: 35%;
}

footer {
  margin: 70px auto 0;
  text-align: center;
}

.heart {
  font-style: normal;
  font-weight: 500;
  color: #c0392b;
  text-decoration: none;
}

#github-button {
  display: block;
  margin: 30px auto 0;
  position: relative;
  left: 40px;
}

#github-ribbon {
  display: inline-block;
  position: fixed;
  top: 0;
  right: 0;
  z-index: 100;
  border: 0;
  width: 149px;
  height: 149px;
}

.github-buttons {
  text-align: center;
  margin: 1em 0;
}



/**
 * Medium Screens
 */
@media all and (min-width:40em) {}

/**
 * Large Screens
 */
@media all and (min-width: 54em) {}

(function() {
  'use strict';

  var battery;

  function toTime(sec) {
    sec = parseInt(sec, 10);

    var hours = Math.floor(sec / 3600),
        minutes = Math.floor((sec - (hours * 3600)) / 60),
        seconds = sec - (hours * 3600) - (minutes * 60);

    if (hours < 10) { hours   = '0' + hours; }
    if (minutes < 10) { minutes = '0' + minutes; }
    if (seconds < 10) { seconds = '0' + seconds; }

    return hours + ':' + minutes;
  }

  function readBattery(battery) {
    var percentage = parseFloat((battery.level * 100).toFixed(2)) + '%',
        fully,
        remaining;

    if (battery.charging && battery.chargingTime === Infinity) {
      fully = 'Calculating...';
    } else if (battery.chargingTime !== Infinity) {
      fully = toTime(battery.chargingTime);
    } else {
      fully = '---';
    }

    if (!battery.charging && battery.dischargingTime === Infinity) {
      remaining = 'Calculating...';
    } else if (battery.dischargingTime !== Infinity) {
      remaining = toTime(battery.dischargingTime);
    } else {
      remaining = '---';
    }

    document.styleSheets[0].insertRule('.battery:before{width:' + percentage + '}', 0);
    document.querySelector('.battery-percentage').innerHTML = percentage;
    document.querySelector('.battery-status').innerHTML = battery.charging ? 'Adapter' : 'Battery';
    document.querySelector('.battery-level').innerHTML = percentage;
    document.querySelector('.battery-fully').innerHTML = fully;
    document.querySelector('.battery-remaining').innerHTML = remaining;
    if (battery.charging) {
      document.querySelector('.battery-title').style.backgroundColor = '#57ad4f';
    } else {
      document.querySelector('.battery-title').style.backgroundColor = '#f41a1a';
    }
  }

  if (navigator.getBattery) {
    navigator.getBattery().then(function(battery) {
      battery.addEventListener('chargingchange', function() {
        readBattery(battery);
      });

      battery.addEventListener('levelchange', function() {
        readBattery(battery);
      });
      readBattery(battery);
    });
  } else {
    document.querySelector('.not-support').removeAttribute('hidden');
  }
}());

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