battery consumption check for my app in iOS

Question

I need to get battery consumption details for my app.
I have used instruments for tracking and i am getting energy usage level as 1/20.
What is this 1/20?

Answer 1

1. Shortly :

   UIDevice *Device = [UIDevice currentDevice];
   [Device setBatteryMonitoringEnabled:YES];
   
    int state = [Device batteryState];
   NSLog(@"Now the status: %d",state);
    double batLeft = (float)[Device batteryLevel] * 100;
     NSLog(@"Charge left: %ld", batLeft);
   

2. The API allows you to register to receive notifications for changes to the battery level. It only reports a change at 5% increments up or down, but you can use a timer and measure the time between two changes (or initial battery level and first change). Here's how you register for the notifications:

      // Use this call to get the current battery level as a float
     // [[UIDevice currentDevice] batteryLevel]
   
      [[UIDevice currentDevice] setBatteryMonitoringEnabled:YES];
   
     [[NSNotificationCenter defaultCenter] addObserver:self
                                       selector:@selector(batteryStateDidChange:)
                                        name:UIDeviceBatteryStateDidChangeNotification
                                      object:nil];
   
      [[NSNotificationCenter defaultCenter] addObserver:self
                                    selector:@selector(batteryLevelDidChange:)
                                        name:UIDeviceBatteryLevelDidChangeNotification
                                      object:nil];
   

The first notification tells you the current state, e.g. unplugged, charging, or full. The second will get triggered whenever a 5% increment is reached.

Seems to me that if all you're given is change notifications at 5% changes up or down, accuracy is not something you can calculate very well or quickly. A 5% change could take a very long time if the device isn't doing anything.

Maybe you can monitor [[UIDevice currentDevice] batteryLevel] with a timer, however, while I haven't tried it I think it only gets updated at this same 5% increment.

From: iphone: Calculating battery life

3. Here is a good example : http://blog.coriolis.ch/2009/02/14/reading-the-battery-level-programmatically/