It may be that too many apps are opened, you can shut down and restart it, and then charge it again.
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If there are no special circumstances, you can also shut down first, and charge it in the shutdown state.
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Shut down also can not charge into the electricity, it should be the battery is broken, you can consider changing the battery. You can also try it with a more powerful charger.
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Display charging, do not use the phone, can charge slowly, use the phone while charging power off, most of which is the data cable\/tail plug damage,
The controller is damaged and the main control board needs to be replaced. After the ISO 16 upgrade, the iPhone cannot be charged with 20 watts fast charge, indicating that the control board cannot be configured with voltage. Therefore, you need to replace the main control board in time