The difference between Xiaomi car charger 20W and 30W is that the charging power is different. The maximum output power of the 20W car charger is 20W, while the maximum output power of the 30W car charger is 30W, that is, the 30W car charger can charge the phone faster. In addition, the 30W car charger may be a little larger because it requires more power to provide higher power.