Does fast charging reduce battery life?

 After reading this article, you will find out what fast charging does to your smartphone battery.

What is fast charging?

Fast charging is a technique used in smartphones to charge the battery rapidly. It works by boosting the amount of power transferred to the battery, allowing it to charge more quickly than traditional charging methods. Qualcomm Quick Charge, Oppo VOOC (Voltage Open Loop Multi-step Constant-Current Charging), and Samsung Adaptive Fast Charging are a few fast charging technologies.

The effects of Fast Charging

The common effects of Fast charging on a mobile phone are:

• Charge time is reduced.
• Higher battery temperature.
• Decreased battery life over time.
• Reduced battery capacity.
• Higher power consumption.
• Requires specialized charging equipment.

Important Note: From above points, it is clear that fast charging has it's own effects on your smartphone battery. Therefore, it's recommended to always use original charging equipment provided by the phone's manufacturer to reduce the risk of damaging the battery or other components.

Now let’s find out the science behind;

• Charging a completely discharged Li-Ion Battery
• Fast charging and it’s effect on Battery Temperature
• What high temperature can do to the battery internally
• Fast charging and it’s impacts on Battery Capacity
• Safe charging

Charging a completely discharged Li-Ion Battery

A discharged Li-Ion battery initially consumes more power while charging since it must raise its voltage level before the charging process can continue to go more slowly. The constant current phase is called high-power phase.

The battery receives a high current from the charging device during the constant current phase, which quickly raises the voltage level. Up to a certain time, the voltage level keeps rising, and at a point the charging device enters the constant voltage phase. 

In the constant voltage phase, the voltage is kept constant while the current decreases as the battery becomes closer to being fully charged. This phase helps to reduce the risk of overcharging and extend the overall lifespan of the battery. Once the battery is fully charged, a trickle charge is applied to the battery to maintain its voltage level and prevent it from discharging. The trickle charge rate is much lower than the constant current phase, which helps to prevent overcharging and extend the overall lifespan of the battery.

Overall, the initial high-power phase, followed by the constant voltage phase, and finally the trickle charge, helps to ensure that the battery is charged safely and efficiently.

This can be seen in charge curve shown below for a 2000 mAh battery charged by a 4.2V_Max charger. The constant current is shown by red colour which is constant up to 95 minutes and at the same point the voltage in black colour shows it is entering constant voltage phase.

At 120 minutes, the battery is almost fully charged. (not fast charging obviously)

Fast Charging and it's effect on battery temperature

In above charging example, the simple charging mechanism is explained. But when you use a fast charger to charge a discharged battery, for example Oppo 65W SuperVOOC 2.0 which has typical current ratings of 5A to 10A and voltage ratings of 5V to 11V, the peak power of 65W will be absorbed by the battery initially in high-power phase (the actual current and voltage ratings may vary depending on model and device it is used with). 

Therefore, high power means more unnecessary heat is generated due to which the battery becomes warm or hot which directly affects the life and efficiency of the battery.

Also note that the battery temperature is monitored by the temperature sensors, and if it becomes too hot, the phone will slow down or stop charging to prevent harm to the battery or other components. That's why one should avoid charging the phone in direct sunshine or other hot places, since the heat created by the battery and the surrounding environment might cause the battery temperature to rise even more.

High temperature and it's effects on the internal mechanism of the battery

The following are the negative impacts of high heat on the chemistry of a Li-Ion battery:

• Degradation of the electrodes: High temperature can cause the electrodes in the battery to degrade, reducing the overall capacity of the battery. This degradation can also lead to the formation of lithium metal on the anode, which can cause a short circuit and reduce the safety of the battery.

• Reduced battery life: Exposure to high temperatures can reduce the overall lifespan of a lithium-ion battery. This is because the chemical reactions taking place inside the battery are temperature-sensitive, and high temperatures can speed up the rate of these reactions, leading to a faster decline in capacity over time.

• Decreased efficiency: High temperatures can reduce the efficiency of a lithium-ion battery. This is because the voltage of the battery decreases at high temperatures, reducing the amount of energy that can be stored and used.

• Safety concerns: High temperatures can also increase the risk of thermal runaway, a condition where the internal temperature of the battery increases rapidly, leading to a thermal runaway reaction that can cause the battery to explode or catch fire.

Therefore, high temperature can have a significant impact on the chemistry and performance of a lithium-ion battery, so it's important to keep the battery within a safe temperature range during use and charging.

Fast charging and it's effect on Battery Capacity

Fast charging can reduce battery capacity over time due to the increased stress on the battery cells. The high voltage and current delivered during fast charging can cause the battery cells to degrade more quickly, leading to a reduction in battery capacity. 

To help extend the battery's lifespan and maintain its capacity, it's recommended to charge the phone slowly when possible, and to avoid charging it to 100% unless necessary.

Safe charging

A constant-voltage charging method, also known as "constant voltage with current limit," is commonly used to charge lithium-ion batteries. The voltage across the battery is kept constant during this process, and the current is restricted to a specific value that lowers as the battery approaches full charge. 

This technique of charging ensures that the battery is charged securely and effectively. By keeping the voltage constant, the battery may be charged at a steady rate, reducing the danger of overcharging and extending the battery's total lifespan. The current limit prevents the battery from being charged too rapidly, which can cause excessive heat and degrade the battery's total capacity.

Overall, the constant-voltage charging approach is chosen for charging lithium-ion batteries because it balances safety, efficiency, and battery life.

Conclusion

After the above discussion about charging of a Lithium-Ion battery, it is concluded that Fast Chargers are harmful for your smartphone if used for prolonged and repetitive charging. 

Recommendation

It is recommended that one should avoid prolonged and repetitive charging of smartphones using fast chargers unless necessary and use the specific charger provided by the manufacturer of the device. Additionally, even though the cut-off circuit prevents overcharging, it's still recommended to avoid charging the battery to 100% unless necessary. Instead, it's better to charge the battery to around 80% and then unplug it, which can help extend its overall lifespan.