67W fast charge head can be compatible with 30W.
As long as the charging protocol supports, the 67W fast charger can be downward compatible with 30W, but whether the charging power can reach 30W depends on whether the phone supports it. Use the right charging cable and charging head together to achieve the best charging effect. It should be noted that if you choose a cheap charging cable that does not meet the specifications, it may cause damage to the mobile phone battery, so it is recommended to use the original factory or regular channels to buy the charging cable.
Compatible, but the nominal voltage of the charger must be equal to the rated voltage of the phone.
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If the output voltage of the charger is not the same as the voltage of the phone, the 67-watt charger can not be charged with a 30-watt phone.
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To charge the mobile phone and any electrical appliance (battery), the nominal output voltage of the charger must be consistent with the nominal voltage of the electrical appliance (battery), for this reason, the power of the two can be considered.