Merge Dragons! has a lot of game elements simulating, so the processor needs to do a lot of work. On some devices, this may use the battery faster than you'd like.

You can try opening the Battery Life option in the settings panel.

Start here, from the world map screen:

Then tap the "Battery Life..." button:



The game gives you 2 choices:
  • Faster, smoother frame rate, but with more battery usage.
  • Lower frame rate, but while saving more of your battery.

Note that if your framerate is already below 60 FPS, then changing the setting to "Battery Saver" may not have any effect.