Does fast charging affect battery life?
Before I start answering this you might need to understand "what is Fast Charging, and how does it Works for Mobile Phone". In simple words, a combination of high voltage and high current battery chargers charge the mobile phone's battery quicker than usual (500 mA through USB). This technology is a huge convenience to the users. However, people have different concepts and different opinions. I have tried to dig down those concepts and surprisingly the answer is not straightforward YESor NO.
Fast charging is sometimes known as Quick Charging or Warp Charging or VOOC charging. Concepts are the same only manufactured and developed y different companies.
Can Quick Charge hurt my smartphone's battery?
Both fast and slow charging use the same CC/CV charge regimes in lithium-ion batteries. The initial CC stage (constant current) stage is where the charge controller applies a constant current charge until the terminal voltage reaches 4.2V (for common lithium-ion batteries). In this stage, the heat of the devices (both charger and mobile phone) will increase. The “fast” in “fast charging” relates to this constant current. A fast charge in a phone may apply a 3A constant, while a “slow” charge may do 5.0–1.0A.
In simple words, the current is not an issue, but the issue is with heat that degrades the battery. It is the heat that may build up due to high wattage/power. If the temperature of the chemistry is less (around 35 degree C to 40 degree C) then degradation is very minor and negligible. Charging and discharging themselves degrades the battery life, no matter slow or fast. However, switching between fast and slow charging nothing to do with the charger. This is a feature of the battery itself. When the battery voltage is low, a high rate of current the battery can consume as the voltage is 4.2V (for common lithium-ion batteries). When the actual battery voltage reached 4.2V automatically the current will reduce. The beauty of fast charge technology is to communicate with the battery charger and the phone processor. The phone processor sending the battery-related information (voltage, current, temperature, etc) to the charger, and the changer can decide the current flow to control the temperature. Basically, during the fast charge process, there are a few pauses to control the temperature rise.
For example, if you use the original 18Watt charger of the iPhone, with recent technology, the fast charge will continue till 80% and then the charging rate will reduce snd to get 100% it took the almost the same time it took from 0% to 80%. But if you connect the iPhone with some other power bank or other uncontrolled charging sources, then it charges faster during 80% to 100%. This implies that the charger plays a good role in battery health.
However, traditional battery charging technology does not come close to the full power requirements of today's large batteries. Fast / Quick Charge is designed to allow device manufacturers to achieve the full rated capability of the batteries they choose while still meeting the performance and safety standards set by the battery manufacturer.
Fast Charge operates within the design parameters of lithium-ion batteries found in most smartphones. It is just charging the battery the way it is designed to be charged. Device manufacturers build smartphones with a specific battery that can accept a specific level of charge. The battery size and maximum current of each battery are design decisions made by the manufacturer and can vary from mobile phone to mobile phone.
However, Oppo has recently released 125-watt SuperVOOC technology which is the fastest wired charging technology in the mobile phone market. And they announced that this will work only works if the battery temperature is below the 40 degree C mark. Oppo also assures that the battery only loses 20 percent of its capacity after 800 charging cycles. This means a 5000mAh battery would have 4000 mAh left after about 2.2 years of use (considering 1 charging cycle per day).
So, the answer is 'NO, the fast charge doesn't affect the battery life if you use, the correct charger, cable recommended by the manufacturer.