Although some players have questioned whether the Battery Saver mode worked or made any difference at all in the initial version of Pokémon Go for iPhone, what's certain is the current version of the game destroys your battery. Take, for example, this anecdote from a Thrillist employee per our earlier story about the loss of the feature this week:
"In 11 minutes, his phone drained 5% of its battery. In 19 minutes, it drained 8%. Again, if you care about the math: that's 0.45% per minute, or 3 hours 42 minutes of life; and 0.42% per minute, or 3 hours 58 minutes of life. Not nearly as egregious, but consider he simply had the app open and wasn't playing."