Question

I am using :

UIDevice *myDevice = [UIDevice currentDevice];
[myDevice setBatteryMonitoringEnabled:YES];
float batLeft = [myDevice batteryLevel];
int i = [myDevice batteryState];    
int batinfo = batLeft * 100;

to find the battery status.
I am looking out to find, how to find the time remaining until the charge is complete.
ex: 1 hour 20 min remaining.
How can I find it programmatically?

Answer 1

I haven’t found any method for this in the official documentation, neither in the class-dumped, private header of the UIDevice class.

So we have to come up with something. The best “solution” I have in mind at the moment is similar to the approach taken when estimating download time: calculating an average speed of download/charging, and dividing the remaining amount (of data or charge) by that speed:

[UIDevice currentDevice].batteryMonitoringEnabled = YES;
float prevBatteryLev = [UIDevice currentDevice].batteryLevel;
NSDate *startDate = [NSDate date];

[[NSNotificationCenter defaultCenter]
    addObserver:self
       selector:@selector(batteryCharged)
           name:UIDeviceBatteryLevelDidChangeNotification
         object:nil
];

- (void)batteryCharged
{
    float currBatteryLev = [UIDevice currentDevice].batteryLevel;
    // calculate speed of chargement
    float avgChgSpeed = (prevBatteryLev - currBatteryLev) / [startDate timeIntervalSinceNow];
    // get how much the battery needs to be charged yet
    float remBatteryLev = 1.0 - currBatteryLev;
    // divide the two to obtain the remaining charge time
    NSTimeInterval remSeconds = remBatteryLev / avgChgSpeed;
    // convert/format `remSeconds' as appropriate
}