Battery of Apple Watch 4

My battery seems weird.

yesterday night(0000) I see my battery is 82%

and I set an alarm for 830.When I woke up I realize now is 930. I checked my Apple Watch and realize my Apple Watch ruin out battery.This has happened 2~3 times.

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I charge my Apple Watch

realized it charges 7 minutes from 0~24%

30minutes from 0~92%

i instantly feel weird,any solution to check Apple Watch battery life ?

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Im in Apple care (just bought this watch last year August?i think)If there is something wrong with Apple Watch watch. Do I get replacement or repair for free?