Fast charging: What effect does 120W fast charging have on the battery? Why does it degrade faster?

Nowadays, many smartphone companies claim fast charging of 120W or more, which can charge the phone from 0 to 100% in just a few minutes. But does such high-speed charging shorten your battery's life? Therefore, before purchasing a smartphone with ultra-fast charging, you should understand the advantages and disadvantages of fast charging phones.

Why does it reduce battery life?
120W fast charging puts high heat and voltage stress on the battery. Repeated use of fast charging rapidly reduces battery life. Research suggests that fast charging reduces battery cycles. In fact, ultra-fast charging puts more thermal stress on the battery, which can accelerate its degradation. This is why users begin to notice a decline in battery life after just a few months.

What are the disadvantages of 120W fast charging?
High-wattage chargers like 120W deliver very high current to the battery, which puts a heavy load on the lithium-ion cells inside. This process accelerates the electrochemical reactions in the battery abnormally. Faster reactions mean more heat, more stress, and faster battery degradation. This causes the battery's health to deteriorate rapidly and its charge-holding capacity to decrease.

Increasing heat from fast charging is a battery's biggest enemy.
Heat has the greatest impact on the life of lithium-ion batteries. During 120W charging, the phone's temperature rises much faster than with a normal charger. When the battery heats up, the cells inside it deteriorate faster, and their capacity decreases. Many tests show that batteries used in high heat conditions can deteriorate 20 to 30% faster than normal batteries.

Impact on charging cycles
Every battery has a limited number of charging cycles, after which its capacity begins to decline. Fast charging further shortens this cycle because ultra-fast charging continuously exposes the battery to a high state of charge, which is not good for the battery chemistry. The result is that battery health begins to drop to 90% or below within 8-12 months of use.

What is the correct way to use it?
Do not use fast charging daily. Use a 120W charger only when urgently needed; otherwise, it's better to charge at a regular 10W-30W speed. Avoid charging overnight and avoid gaming or heavy use of the phone while charging. To maximize battery life, it's safest to always keep it between 20% and 80%.

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