What is fast charging?

First of all, we must be clear about the principle of charging and discharging lithium-ion batteries, which have two poles: the positive pole is a lithium compound, and the negative pole is graphite. Charging and discharging are the mutual conversion of electrical and chemical energy, in the lithium ion in the process of movement of the positive and negative electrodes, but also in the process of turning into different compounds.

Fast charging is a relatively general concept, which has three different forms of implementation.

(1) constant voltage and increased current.

(2) Constant current and increased voltage.

(3) Both voltage and current are increased.

But to really achieve fast charging on cell phones, it is not just enough to do a boost in voltage and current. Fast charging technology requires a full set of customized circuits, batteries, interfaces, data cables and supporting fast charging adapters, and you also need to do a set of intelligent power management system to enable the phone to provide safe and intelligent charging protection according to different charging situations.

Analysis of different fast charging solutions

At present, there are broadly three fast charging technologies.

1, OPPO's VOOC flash fast charging.

2, Qualcomm Quick Charge fast charging.

3, MediaTek Pump Express Plus fast charging.

Qualcomm Quick Charge

Qualcomm Quick Charge is a typical solution of high voltage and low current, Qualcomm Quick Charge technology has unknowingly come to the Quick Charge 4 fourth generation, from the initial QC 1.0 only supports the highest 5V/2A charging power, to QC 2.0 can be compatible with 5V/9V/12V/20V four charging voltage, and to achieve a maximum of 3A charging current level. Quick Charge 3.0, on the other hand, is an improvement on QC 2.0, supporting dynamic adjustment of operating voltage from 3.6V to 20V in 200mV increments. This enables cell phone manufacturers to adjust to the optimal voltage according to the needs of their own products to achieve the expected current and improve the charging efficiency of their phones.

The upgraded QC 4.0 enjoys up to a 20% increase in charging speed compared to its predecessor QC 3.0 through Qualcomm Technologies' parallel charging technology Dual Charge. In addition to boosting charging speed, QC 4.0 achieves shorter charging times and higher efficiency, protecting batteries, systems, cables and connectors while more accurately measuring voltage, current and temperature. On the one hand, it improves charging speed, and on the other hand, it protects the battery, charger and other devices.

OPPO Super Flash Charge

Next, take a look at the low-voltage, high-current standard OPPO VOOC flash charging technology, VOOC is chosen to keep the voltage constant, by increasing the current to improve the charging speed. Review OPPO VOOC flash charging these two years, the first born in 2014, followed by the launch of VOOC mini in October of the same year, 15 years of user volume has exceeded ten million, recognized by people inside and outside the industry, early last year, OPPO and launched a super flash charging technology, charging speed but also ahead of the OPPO VOOC flash charging.

Before understanding the super flash charging technology, familiarize yourself with the three stages of cell phone battery charging, which are constant current pre-charging, high current constant current charging and constant voltage charging. When the phone is at a low battery level, the voltage will be reduced accordingly, at which time the charger will use a lower current to charge the battery, and when the battery voltage is higher than the predetermined value, constant-current charging will be used.

And OPPO's latest flash charging technology is the use of such a working principle, strict regulation of the current, the advantage of this is to avoid the way to boost the power, so the line loss will be reduced a lot, and effectively curb the phenomenon of cell phone heating. After the first generation of VOOC fast charging charger huge and charging cable interface will be broken after the hidden danger, now finally presented to us in fast charging, portability and safety of the three aspects of fast charging technology, but this technology is only adapted to OPPO this product, compatibility is not enough.

MTP Pump Express Plus fast charging

In addition to Qualcomm and OPPO, the two more prominent fast charging technology, MediaTek MTP Pump Express Plus fast charging technology and Qualcomm Quick Charge principle is much the same, is to ensure a constant current, by increasing the voltage of the charger to the phone's USB port to achieve greater charging power.

We have found that in the last two years PumpExpress technology has begun to emerge, with a built-in PMIC power management integrated circuit that allows the charger to determine the initial voltage required for charging based on current. A pulse current command is sent from the PMIC to the charger via the USB Vbus, and then the output voltage is adjusted according to this command.

Currently, the latest Pump Express 3.0 claims to be able to fully charge a smartphone up to 70% in 20 minutes, while consuming 50% less power compared to PumpExpress Plus, indirectly reducing heat generation. Compared to QC 3.0's practice of 200mV for one step increments, PumpExpress 3.0 voltage trim is only 10mV, providing a theoretical maximum of 5A charging current.

In addition, such as a plus DASH speed flash charging is also similar to OPPO's VOOC flash charging technology, the original charger can output 5V/4A power; and then Meizu's mCharge 3.0, because it is based on MediaTek platform, so mCharge fast charging technology is basically also dependent on the Pump Express launched by MTK.

What is the dual-protocol fast charging solution?

About fast charging technology many consumers have a misconception, always think MediaTek SoC equipped with MTK fast charging technology, Qualcomm Snapdragon SoC equipped with QC fast charging technology. In fact, not necessarily, fast charging technology chip and circuit can also be purchased separately, the most classic example is the Meizu PRO 5 although the use of Exynos platform, but the integration of MTK PEP fast charging solution, rather than Samsung AFC standard. Similarly, many of Vivo's MTK platform models still support dual-engine flash charging technology based on the QC 2.0 standard.

On the other hand, Samsung flagships are equipped with its own AFC fast charging standard, which is also compatible with QC 2.0, while the Samsung C5 and Samsung C7 do not support QC fast charging technology and must use Samsung's own fast charging head for fast charging. Samsung Galaxy Note7 more simultaneously support QC, PD and AFC three major standards.

Based on this principle, it is not difficult to understand the dual-protocol fast charging solution, cell phone manufacturers as long as they are willing to pay, you will be able to get solutions from different fast charging suppliers, not to mention the integration of two fast charging solutions, and then more theoretically possible.

Is fast charging safe?

For now, each of the fast charging or have technical security. Because the power management module in a set of fast charging solutions has long been preset to the highest voltage, current, temperature and other safety mechanisms for cell phone batteries, including temperature protection, short-circuit protection, over-discharge protection, over-current protection, over-voltage protection and many other protective technologies, to be exact, fast charging technology is safe.

Will fast charging affect the battery life?

In principle, the damage to the battery basically comes from two sources.

On the one hand, when the battery is charged and discharged, the cathode and anode of the battery will shrink and expand with the release and absorption of ions, and prolonged fast charging will damage the chemicals on the battery, resulting in a shorter battery life.

On the other hand, in the fast charging, due to the relatively high current, the thermal effect of the current will intensify, resulting in high temperature battery, high temperature will also make the capacity plummet and the phenomenon of permanent damage to the battery cell.

As we all know, one of the advantages of lithium batteries is that you can charge the lithium-ion battery at any time at a convenient moment, without having to think about charging after the electricity is used up. So, what do you mean by a charging cycle?

A charge cycle means that all the power of the battery from full to empty, and then from empty to full process, which is not the same as charging a single charge. To put it simply, 600 mA lithium battery, you first charged from 0 mA to 400 mA, with ah with ah with N mA; then you charged 150 mA, then with N mA; finally charged 100 mA, when the last charge to 50 mA, this battery a charging cycle is up. (400+150+50=600)

A lithium battery in the first day only half of the power, and then fully charged for it. If it is still so on the second day, i.e., it is charged when half is used, the total of two charges down, this can only be counted as one charge cycle, not two. Therefore, it may usually take several charges to complete a cycle. Each time a charge cycle is completed, the power will decrease a little. This is why many people who use Li-ion phones often say, "This stupid phone, which could last 4 days when I first bought it, can now only last 3.5 days on a single charge. However, this power reduction is very small, high-quality batteries will still retain 80% of the original power after multiple cycles of charging, many lithium-powered products after two or three years still use as usual. Of course, lithium battery life to the end or need to be replaced.

The life of a lithium battery is generally 300-500 charge cycles. Assuming that a complete discharge provides 1Q of power, if we do not consider the reduction of power after each charge cycle, the lithium battery can provide or replenish a total of 300Q-500Q of power during its life. From this we know that if it is charged with 1/2 at a time, it can be charged 600-1000 times; if it is charged with 1/3 at a time, it can be charged 900-1500 times. And so on, if random charging, the number of times is variable. In short, no matter how to charge, the total replenishment into 300Q-500Q of power this is constant. Therefore, we can also understand that: the life of lithium batteries and the total charge power of the battery, and the number of times to charge has nothing to do with. Deep discharge deep charge and shallow discharge shallow charge for lithium battery life is not very different.

In fact, shallow discharge shallow charge is more beneficial for lithium battery, only when the power module of the product is calibrated for lithium battery, there is a need for deep discharge deep charge. Therefore, the use of lithium-powered products do not have to be bound to the process, all the convenience first, charge at any time, do not have to worry about the impact on life.

So ordinary charging state lithium battery also has the problem of life, each charge will also cause a little damage to the battery, only this damage is minimal, it takes up to a year or more to show up on the phone. So whether it is fast charging or ordinary charging will actually produce irreversible damage to the battery, but the damage of fast charging will be slightly stronger than the ordinary charging state. But from the current fast-charging technology under a variety of safeguards, this battery damage is still in a safe and reasonable state.

At present, the vast majority of companies providing fast-charging solutions are not given from the battery point of view of its impact on battery life, but the national standard for battery charging and discharging 500 times after the battery capacity of more than 80% are qualified, within a year on the use of the impact is not significant.

If you are used to changing a phone in one to two years, or are willing to replace a new battery, the impact of fast charging is minimal.