To be sure if its not the battery thats bad, connect it to the charger and charge for a while. Monitor the light indicator at the top right of the phone.It should start from red to green after its fully charged. then try to restart it by turning on the power button also at the top right of the phone.
If after these procedures the phone does not start up or it shows some temporal 3 seconds flash of power, you may need to get another battery. If a new battery does not start your phone,then its a power fault.It needs to be rapaired.
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