I have had the battery drain problem for a while now. It would randomly drop quickly and sometimes just switch off. Using any fitness tracking apps caused the battery to last max 1 hour. Mine was out of warranty, so I had nothing to lose. I order a new battery and the tools to replaced it. The old battery was very swollen and look damaged. It might be a bad batch of batteries or a software update changed the way the it charges and damaged it. The new battery is now showing 16% after 4 days off charge. Hopefully that's it sorted.
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