Can charge a plus, the millet 55W charger can charge a plus mobile phone, because the one plus mobile phone supports PD fast charge, and the millet 55W charger also supports PD fast charge. However, if you are using a OnePlus 9 Pro or OnePlus 9 Pro Pro, you will need to use the official 65W charger from OnePlus to achieve the fastest charging speed.
At present, the 55w charger can be charged with one plus, but it should be noted that if the rated power and the transmission power do not match, it will reduce the use of power supply, extend the charging time and lead to battery damage
You can charge it, but it's not as fast.