Battery Status API

The Battery Status API, more often referred to as the Battery API, provides information about the system's battery charge level and lets you be notified by events that are sent when the battery level or charging status change. This can be used to adjust your app's resource usage to reduce battery drain when the battery is low, or to save changes before the battery runs out in order to prevent data loss.

The Battery Status API extends window.navigator with a navigator.getBattery() method returning a battery promise, which is resolved in a BatteryManager object providing also some new events you can handle to monitor the battery status.

Example

In this example, we watch for changes both to the charging status (whether or not we're plugged in and charging) and for changes to the battery level and timing. This is done by listening for the chargingchange, levelchange, chargingtimechange, dischargingtimechange events.

navigator.getBattery().then(function(battery) {
  function updateAllBatteryInfo(){
    updateChargeInfo();
    updateLevelInfo();
    updateChargingInfo();
    updateDischargingInfo();
  }
  updateAllBatteryInfo();

  battery.addEventListener('chargingchange', function(){
    updateChargeInfo();
  });
  function updateChargeInfo(){
    console.log("Battery charging? "
                + (battery.charging ? "Yes" : "No"));
  }

  battery.addEventListener('levelchange', function(){
    updateLevelInfo();
  });
  function updateLevelInfo(){
    console.log("Battery level: "
                + battery.level * 100 + "%");
  }

  battery.addEventListener('chargingtimechange', function(){
    updateChargingInfo();
  });
  function updateChargingInfo(){
    console.log("Battery charging time: "
                 + battery.chargingTime + " seconds");
  }

  battery.addEventListener('dischargingtimechange', function(){
    updateDischargingInfo();
  });
  function updateDischargingInfo(){
    console.log("Battery discharging time: "
                 + battery.dischargingTime + " seconds");
  }

});

See also the example in the specification.

Specifications

Browser compatibility

See also

• Retrieving battery status information - demo & article
• Hacks blog post - Using the Battery API