40 watts will charge faster than 18 watts
18W is now only the basic fast charge, charging at 4000 MA 1 1\/2 to 2 hours, 40W is very fast, basically an hour can be filled with 4000 MA!
The 40w charger will not slow down the charging of the 18w mobile phone, on the contrary, the charging time will be full quickly, but it can only charge the mobile phone for a short time, and cannot charge the 18w mobile phone for a long time with the 40w charger, because the voltage and current of the 4Ow charger is higher than the voltage and current of the 18w mobile phone.
With the fast charge protocol, a 40-watt fast charge can be fully charged in 50 minutes, while an 18-watt fast charge can be fully charged in 1 hour and a half. So, to sum up, 40 watts is faster than 18 watts.