When a correctly calibrated battery cannot keep the smartphone running between 30% and 40% remaining charge, it means that it has no more amperage and cannot meet the demand.
Under Android you have to put it into perspective, the % indicated is based on statistics, not on a load as a battery tester can do and Android uses this % to turn off the phone. This stat is viable after a battery recalibration.
In this case, turn on the phone and drain the battery until the phone turns off. repeat the operation several times until the on button is unable to turn on the phone.
Connect the charger, exclusively to the "Side" port (possible bug on the bottom port)
Wait for the green light to come on and wait another 1/4 hour without turning on the phone.
(do not panic if the red charging light does not come on right away, it can take 5 min from a 0% battery)
The battery is calibrated, disconnect the charger, you should be able to evaluate according to the time of use, around 5 hours while playing, if it is good
