Be sure that the fan voltage is not lower than the voltage from the wall charger; otherwise the fan motor may burn out. If the charger voltage is lower than the fan voltage, the fan will run slower, but that may be okay. If the charger voltage is lots lower than the fan voltage, the fan may not run at all. Also make sure that both charger and fan are either both AC or both DC. Also, if the charger current out is less than the fan requires, the charger may burn out. Bottom line is that you really should match the voltage and current from the wall wart to the fan you are using.