How is the Android battery health determined?

Question

I am not talking about how to read the value.

Rather, I am interested in how the value of BatteryManager.EXTRA_HEALTH is being set.

Does it come from the fir

Answer 1

To be more specific: The battery health is determined by the driver (in the kernel). Said driver exports information via the sys file system (/sys/class/power_supply, to be exact). The Android daemon healthd (as of KK, 4.4.x) picks up this information, and implements an IBatteryPropertiesRegistrar interface on it. It polls continuously (using epoll_wait to run in a timeout loop for periodic updates, as well as netlink notifications for the POWER subsystem - say, for example, if you connect or disconnect a charger). The system's BatteryStatsService then registers a listener with healthd (via binder) and then gets the data that is published by healthd,

Check out /sys/class/power_supply, and you'll see:

lrwxrwxrwx root     root              1970-02-05 14:20 ac -> ../../devices/f9923000.i2c/i2c-84/84-006b/power_supply/ac
lrwxrwxrwx root     root              1970-02-05 14:20 batt_therm -> ../../devices/battery_tm_ctrl.78/power_supply/batt_therm
lrwxrwxrwx root     root              1970-02-05 14:20 battery -> ../../devices/f9923000.i2c/i2c-84/84-0036/power_supply/battery
lrwxrwxrwx root     root              1970-02-05 14:20 touch -> ../../devices/virtual/power_supply/touch
lrwxrwxrwx root     root              1970-02-05 14:20 usb -> ../../devices/msm_dwc3/power_supply/usb
lrwxrwxrwx root     root              1970-02-05 14:20 wireless -> ../../devices/bq51013b_wlc.77/power_supply/wireless

then check out "battery"

/sys/devices/f9923000.i2c/i2c-84/84-0036/power_supply/battery:
-r--r--r-- root     root         4096 2014-02-26 13:26 capacity
-r--r--r-- root     root         4096 2014-02-26 13:26 charge_full_design
-r--r--r-- root     root         4096 2014-02-26 13:26 current_now
lrwxrwxrwx root     root              2014-02-26 13:26 device -> ../../../84-0036
-r--r--r-- root     root         4096 2014-02-26 13:26 health
drwxr-xr-x root     root              2014-02-26 13:26 power
-r--r--r-- root     root         4096 2014-02-26 13:26 present
-r--r--r-- root     root         4096 2014-02-26 13:26 status
lrwxrwxrwx root     root              2014-02-26 13:26 subsystem -> ../../../../../../class/power_supply
-r--r--r-- root     root         4096 2014-02-26 13:26 technology
-r--r--r-- root     root         4096 2014-02-26 13:26 temp
-r--r--r-- root     root         4096 2014-02-26 13:26 type
-rw-r--r-- root     root         4096 2014-02-26 13:26 uevent
-r--r--r-- root     root         4096 2014-02-26 13:26 voltage_max_design
-r--r--r-- root     root         4096 2014-02-26 13:26 voltage_min_design
-r--r--r-- root     root         4096 2014-02-26 13:26 voltage_now

and by looking at the files, all details will be revealed.

Answer 2

Lithium ion batteries have simple onboard computers that track and report the health; the state indicators are standardized but the conditions that trigger them to be reported by the battery are determined by the battery manufacturer.

Answer 3

By using this code you can get information regarding battery..

private BroadcastReceiver battery_receiver = new BroadcastReceiver()
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        boolean isPresent = intent.getBooleanExtra("present", false);
        String technology = intent.getStringExtra("technology");
        int plugged = intent.getIntExtra("plugged", -1);
        int scale = intent.getIntExtra("scale", -1);
        int health = intent.getIntExtra("health", 0);
        int status = intent.getIntExtra("status", 0);
        int rawlevel = intent.getIntExtra("level", -1);
        int level = 0;
        String temp=null;

        Bundle bundle = intent.getExtras();

        Log.i("BatteryLevel", bundle.toString());

        if(isPresent)
        {
            if (rawlevel >= 0 && scale > 0) {
                level = (rawlevel * 100) / scale;
            }

            String info = "Battery Level: " + level + "%\n";

            info += ("Technology: " + technology + "\n");
            info += ("Plugged: " + getPlugTypeString(plugged) + "\n");
            info += ("Health: " + getHealthString(health) + "\n");
            info += ("Status: " + getStatusString(status) + "\n");
            info += ("Temp: "+getTempStatus(temp,intent)+"\n");

            setBatteryLevelText(info + "\n\n" + bundle.toString());
        }
        else
        {
            setBatteryLevelText("Battery not present!!!");
        }
    }
};
private void registerBatteryLevelReceiver(){
    IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);

    registerReceiver(battery_receiver, filter);
}