30w charging efficiency of the cell phone with 10w charger will be no harm to the battery or cell phone, only the charging speed is slower. It is better to use the original charging cable of the cell phone, 10 watt cell phone will automatically reduce the power to 10W to charge, the speed will be a little bit faster than 10W, may be on 12-15W power to charge.

Mobile phone chargers are made to have a fixed nominal voltage of about 5V, this voltage is normal for the lithium battery charge management circuitry, 10W or even 18W charging head currently on the market, charging will not have a lifespan impact on the battery. Generally speaking, the battery will slowly decay in the process of use, this is a normal phenomenon.

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Higher power will not accelerate battery depletion unless you use a very high power, but then the battery IC chip will also be current limiting. 10W charging head costs more than 5W. The cost of a 10W charging head is higher than a 5W charging head, but sometimes the battery is depleted faster than a 5W charging head, which often happens when you play with your cell phone while charging, or when the battery is exposed to high temperatures for a long period of time.

The cable connector is definitely the first thing to consider, and the charger's parameters can't be ignored. If we use a 5V/1A charger to charge the phone, the charger will always be overloaded, and the charger is hot, and prolonged use will shorten the life of the charger, and the main thing is that the charging speed is also very slow.