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The p40 charger can charge the mate40Pro, but the charging speed is slower.
Huawei P40 Pro battery capacity: 4200mAh (typical value), the standard charger supports 10V\/4A or 9V\/2A or 5V\/2A output, and the phone supports a maximum 10V\/4A super fast charge.
The charger of the mobile phone is compatible, as long as the interface of the charging line can match.