I am on my 2nd day using the 38mm sport and I am not impressed with the battery. Yesterday I managed 13 hours and it went completely flat - it did not even enter power saver mode. Today I have tried to play with the watch less and feel I have barely used it and after 9 hours I'm only on 52% - There are still 7 hours until bed time! I don't understand these people going to bed after 14-16 hours and still having 50% or so... I have noticed a lot of fake activations with wrist detection - maybe this is the cause?