The 25 watt fast charge can not charge the 15 watt mobile phone, because the power is different, it may damage the phone. Mobile phone charging is best to use the factory equipped charger, because the same brand of mobile phone, mobile phone models are different, equipped with different chargers, such as a brand of mobile phone, equipped with a charger to support 27w,18w,10w, then all the brand of mobile phone, as long as the factory equipped charger power in 27w,18w,10w, one of the Can be mixed, remember, do not cross brand mix, it will damage the phone.