It is normal that the charger of Xiaomi mobile phone is slow to charge other mobile phones, and each brand's mobile phone charging protocol is different.
Each brand of mobile phone has its own matching charger, and the use of matching chargers is generally faster when charging. Millet mobile phone has a special situation, the phone charger is not configured with the phone, but needs to be purchased separately, but many people for budget considerations, did not buy a special millet charging head, but use other charger head to mention, because it is not the original configuration, resulting in extended charging time.