Sorry if this question is not programmatic enough, but it has significant implications to my future development efforts for the iPod.
I'm running the same app on a ~3 month old iPhone4 (16Gb) and on a 3 weeks old iPod touch (8Gb). The app uses CMMotionManager to sample accelerometer/gyroscope data at a rate of 20 times per second. The data is then processed repeatedly over the course of several hours.
In the airplane mode with the screen brightness disabled: the iPhone4 can survive for 8 hours with 40% battery left. iPod touch 4g dies after ~6.5 hours with 0% battery left That's about 50% battery life difference between iPhone4 and iPod touch 4
I'm using:
UIDevice *myDevice = [UIDevice currentDevice];
[myDevice setBatteryMonitoringEnabled:YES];
int batteryPercentage=([myDevice batteryLevel]*100);
NSLog(@"battery percentage: %i",batteryPercentage);
[myDevice setBatteryMonitoringEnabled:NO];
I've noticed that over 1 hour and 10 minutes, the iPod has lost over 25% of battery charge, and it appears to accelerate as the battery level decreases. (this is for a regular brightness, airplane mode off test).
Is my device defective, or did you notice a significant difference in battery life between your iPod and iPhone devices? Should I try to exchange my development iPod? If it helps, I noticed that my iPod touch has a blush screen, so it never displays true black, like iPhone does. Maybe this is the culprit?
The answer to this question means a simple trip to an apple store or some significant work for the iPod devices.
This is indeed OT, but, like calories, there are basically two different factors that can be culprit:
Of course energy drain is not quite so straight forward ... processor profile, screen profile, firmware updates/energy-saving states/settings, etc. However, holding all other things equal, the iPhone4s does have a larger capacity battery -- about 50% larger ;-)
Happy coding.