Question

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.

Answer 1

This is indeed OT, but, like calories, there are basically two different factors that can be culprit:

1. Total Capacity; and,
2. Energy Drain

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 😉

• The iPod touch (2st Gen) has a 930mAh battery
• The iPhone4s has a 1420mAh battery

Happy coding.