Demystified: Will fast charging of mobile phones affect battery life?

by:CTECHi     2021-08-06

Currently, the mainstream fast charging technologies used in mobile phones include Qualcomm Quick Charge 2.0 (the latest Quick Charge 3.0), MediaTek Pump Express, and OPPO VOOC flash charging. Among them, Qualcomm and MediaTek use high voltage charging, while VOOC flash charging uses High current charging.

OPPO mobile phones have always focused on charging speed, and even the slogan is marked 'Charge for 5 hours, talk for 2 minutes'. The latest Meizu PRO 6 is also equipped with fast charging technology. The poster has such a sentence 'Why When they talk about fast charging, they never talk about battery life?'

So will fast charging affect battery life?

Quickly understand lithium-ion batteries

First of all, we must understand the charging and discharging principles of lithium-ion batteries. The battery has two poles: the positive electrode is a lithium compound, and the negative electrode is graphite.

Charging and discharging are the mutual conversion of electrical energy and chemical energy. During the movement of positive and negative electrodes, lithium ions also become different compounds.

We can regard lithium ions as a small car with electric charge: during charging, the electric field makes the car all drive to the negative electrode to store a certain amount of energy (lithium ions are inserted into the graphite carbon layer of the negative electrode. When discharging, these charged lithium-ion trolleys ran to the positive electrode due to a chemical reaction (the deintercalation of lithium ions makes the positive electrode in a lithium-rich state). In this process, a current supply is formed.

In an ideal state, as long as the chemical structure of the positive and negative materials basically does not change, and the reversibility of the battery charge and discharge is very good, the lithium ion battery can guarantee a long-term cycle.

Fast charging is mainly to ensure that lithium ions are quickly inserted from the positive electrode and quickly inserted into the negative electrode, without causing the deposition of lithium ions.

But when the current increases, a layer of semipermeable membrane (SEI membrane) on the surface of the negative electrode (graphite) of the electrode will rupture to a certain extent, causing the electrode material and the electrolyte to react with each other, and the temperature will increase. It will also cause side reactions inside the battery to destroy the chemical substances on the battery, resulting in a decrease in reversibility (that is, the lithium-ion car can no longer drive back and forth) battery capacity will continue to decrease.

It is what we often feel. It is clearly fully charged, why the battery is becoming more and more unsustainable. Take the lithium battery of DJI UAV as an example. A 4480mAh 68Wh lithium battery with a voltage of 15.2V takes only 1.5h to be fully charged (compared to iPhone6s plus with a battery capacity of 2750 mAh and a voltage of 3.8V), but there is no one in DJI. The lithium battery life of the machine is only 200 cycles. The decline in battery life is obvious. According to the latest report from DIGITIMES, Apple is also working on upgrading battery charging technology recently, preparing to use 15V to 20V charging equipment to improve battery efficiency and promote new IC technology. However, the equipment provider of the PWM IC also indicated that this requires a great risk.

Protection mode for fast charging

The three fast charging solutions will all have battery temperature monitoring solutions. When the voltage is increased, the temperature rise is inevitable. If you are using Qualcomm’s QC fast charging technology while playing large-scale games, at this time, due to chip control, the external voltage is limited to ensure that your phone will not seriously heat up, but the charging efficiency will decrease.

For VOOC flash charging, the charging current is controlled in segments, and the charging cable and battery are set in multiple lines. To put it simply, one battery was charged before, and now it is divided into several batteries and charged separately.

In terms of safety, because fast charging has a 'handshake protocol

Lithium battery charging is divided into three parts: constant current pre-charge (CCPre-charge), high current constant current charge (CC Fast Charge) and constant voltage charge (CV).

The voltage drops after the mobile phone is exhausted. When it is lower than a certain value, the charger will use a relatively low current to precharge the lithium battery. After a period of time, after the voltage of the lithium battery is higher than the predetermined value, it enters the second stage of high-current constant-current charging. At this time, appropriately increasing the current can speed up the charging speed.

If you are using a non-fast-charge mobile phone, the fast-charge charging head will not output high voltage and burn your mobile phone. Just like when you use the iPad charging head to charge the iPhone, the iPhone will automatically recognize it and input 1A instead of the original 2A.

From the perspective of numerous protection measures, the charging voltage and current of fast charging are in a safe state. As long as the original mobile phone charging adapter is used, there will be no safety hazards.

Finally, will fast charging affect battery life?

The answer is yes.

Even though the batteries equipped on some fast-charging mobile phones have improved cell material and design, they can realize the rapid insertion and insertion of lithium ions in the battery, but the large voltage and current still make the battery produce loss.

But if you are used to changing a mobile phone in one or two years, or are willing to change a new battery, the impact will be minimal for you.

Currently, most companies that provide fast charging solutions have not given the impact on battery life from the perspective of batteries. However, under the national standard, the battery capacity is more than 80% after the battery is charged and discharged 500 times Qualified, it has little effect on use within one year.

If you want to use your phone for 2-4 years without changing the battery, the following suggestions may help you:

Reduce the number of fast charging and use it only when you need it urgently;

Quick charge when the battery is only about 30% instead of 3%;

When using fast charge, it is best not to run games with large memory.

As smart phones are getting faster and faster, are you more willing to abandon the shortened battery life and enjoy the convenient technology of fast charging when safety is guaranteed?

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