No need for a 40 watt fast charge. Bracelet charging head can use 40W fast charging head, charging head can output 5V power supply, the bracelet does not need 1W is enough, do not need fast charging.Bracelet battery is small, charging fast is not good. The battery life of the bracelet is 14 days, and the charging time is 2 hours, which is not necessary faster.Ordinary usb port charger can be used.125mAh polymer lithium battery.