"A charging method that can make the battery reach or close to the fully charged state within 1 ~ 5h. It is commonly used for the charging of traction battery when it needs to recover to the fully charged state in a short time. The normal charging of battery takes about 10 ~ 20h. How to charge quickly without damaging the performance and service life of battery is a hot research topic.
Circuit characteristics
1. After the output voltage is set (e.g. 36V), if the electrode plate of the charging battery falls off and is disconnected, resulting in a battery failure or short circuit, the battery terminal voltage [1] will be reduced or zero, and the charger will have no output current.
Electric vehicle fast charging station
2. If the voltage of the charged battery deviates from the set voltage, for example, if the set voltage is 36V, connect 24V, 12V, 6V batteries by mistake, and the charger has no output current. If the set voltage is 24V, connect 36V batteries by mistake, because the output voltage of the charger is lower than the battery voltage, the battery cannot be charged. 2. If the two output terminals of the charger are short circuited, the SCR trigger circuit in the charger cannot work, so the thyristor is not conductive and the output current is zero.
3. If the positive and negative poles of the battery are connected reversely during use, the thyristor trigger circuit is cut off reversely, there is no trigger signal, the thyristor is not connected, and the output current is zero.
4. The use of pulse charging is conducive to prolonging the battery life. Since the low-voltage AC is pulsating DC after full wave rectification, the thyristor will be turned on only when its peak voltage is greater than the battery voltage. When the pulsating DC voltage is in the trough area, the thyristor will reverse bias and cut off and stop charging the battery. Therefore, pulsating DC flows through the battery.
5. Fast charging, full stop. Since the voltage at both ends of the battery is low at the beginning of charging, the charging current is large. When the battery is about to be full (36V battery terminal voltage can reach 44V), as the charging voltage is closer and closer to the peak value of pulsating DC output voltage, the charging current will be smaller and smaller, and it will automatically become trickle charging. When the voltage at both ends of the battery is charged to the maximum peak of the rectified output, the charging process stops. After the test, the three electric vehicle batteries are 36V (12V / 12Ah three in series), which can be fully charged in only a few hours.
6. The circuit is simple, easy to manufacture, and almost does not need maintenance and repair.
Principle and application of fast charging technology
Generally speaking, the power of the mobile phone is exhausted, and the time to fully charge is more than 3 hours. In fact, the time is not long, but people in urgent need will feel that this time is quite long. The previous solution was to carry the mobile power supply with you and connect it directly when there is no power; However, fast charging technology has been developed, which can fill more than half of the power in only 30 minutes, greatly reducing the charging time. What is fast charging technology? What are the existing fast charging technologies? This article will analyze the principle and application of fast charging technology one by one.
Recognize mobile phone battery
Before introducing the fast charging technology, let's first understand the "battery" that enables the normal use of mobile phones. Among many battery types, mobile phone batteries are "lithium-ion batteries" that can be recharged and discharged repeatedly, also known as "secondary batteries". Although most people often call lithium-ion batteries "lithium batteries", But in fact, lithium batteries refer to disposable batteries that cannot be recharged and discharged repeatedly, and their properties are completely different.
Lithium battery was invented by Edison with lithium metal or lithium alloy as cathode material and non-aqueous electrolyte solution. Later, people used different materials to make a variety of batteries, which are also widely used in electronic products. Lithium ion battery is charged and discharged by the movement of lithium ions between the positive and negative electrodes. During discharge, lithium ions leave the negative electrode and enter the positive electrode to generate current. During charging, lithium ions move in the opposite direction and enter the negative electrode from the positive electrode to restore to a state that can be discharged again.
Significance of lithium ion battery labeling
Lithium ion batteries that meet safety standards must have clear information signs on the battery, so users must also have a basic understanding of these signs in order to understand the meaning they want to express. The possible signs on the battery are: a (ampere) is the current; V (volts) is the voltage; W (watt) is the electric power, which is derived from the product of voltage and current; Wh (watt hour) is the amount of electricity that the battery can release in an hour. The capacity of the battery is expressed in ah (ampere hour, abbreviated as ampere hour) or MAH (milliampere hour), where h is time and M represents a unit reduced by a thousand times. Since the capacity of the mobile phone battery is very small, MAH is used as the unit, and the calculation formula is Mah = ma (milliampere) x H (time).
For example, a battery marked with 2000mAh has a current of 200mA, which means that the service time of the battery is about 10 hours. However, in fact, the battery has the factor of self discharge loss, and the long storage time of the battery will affect the service time. Therefore, it is normal if the battery runs out less than the marked time.
▲ the batteries marked with lithium on the surface are non rechargeable lithium batteries, that is, the so-called disposable batteries.
▲ for the battery shown in the figure, the capacity is 2900mah, the voltage is 3.85v, and 11.2wh can be released in one hour.
▲ for this battery, if you want to know its wh, you can calculate it through the formula wh = V x MAH / 1000, so it is 7.2V x 1200mAh / 1000 = 8.64wh.
Charging principle of mobile phone battery
When the workload of the mobile phone increases, it means that the battery consumption speed will also become faster. The fully charged battery may only have half of the power left after a short trip. Although the current mobile phone battery capacity is getting larger and larger, it is still difficult to resist the speed of consumption, not to mention that the time taken to fully charge the high-capacity battery will also be proportional to the extension, It is also common to rush out and find that the mobile phone battery is not full, so improving the charging speed of the mobile phone is the most direct way. First, let's briefly explain the charging principle of the battery. A battery will consume power under normal use. This process is called "discharge". After discharge to a certain extent, you have to "charge" the mobile phone through the charger to recover power.
The process of battery charging can be divided into three stages: small current charging (TC), constant current charging (CC) and constant voltage charging (CV); Because the output voltage of the charger is higher than that of the battery, the current will flow from the high voltage to the low voltage. When the battery has over discharge, due to the low voltage, it must be charged with a small current to a certain amount of power before entering the constant current charging mode. This will gradually increase the voltage of the battery and change to the constant voltage charging mode after rising to a certain value, At this time, the current will slowly decrease and finally reach the state of full charge.
Non technical fast charging skills
Before the development of fast charging technology, we can actually achieve the effect of fast charging through some small skills. Although it is insignificant compared with the real fast charging technology, it is also of great help to those in need.
1. Power off and charge: the mobile phone can speed up the charging speed of the battery without power loss;
2. Turn off unnecessary functions: turn off 3G, Wi Fi, GPS positioning, Bluetooth and other functions, or prohibit some unnecessary power consuming programs from operating automatically, so as to save charging time;
3. Avoid charging in high temperature environment: since the heat will reduce the efficiency of the battery, it is best to charge at room temperature.
Myth of lithium ion battery charging
Q: The new battery used for the first time needs to be charged 8? 12 hours before use?
A: Early nickel cadmium batteries and nickel metal hydride batteries did need to be recharged 8? It can be used after 12 hours, but the current lithium-ion battery is completely unnecessary. Even if the battery needs to be fully charged, it only takes about 4 hours. The battery has some electricity when it leaves the factory. If you want to use it to a certain extent, you can recharge it.
Q: The battery must be completely dead before it can be charged?
A: The reason for such cognition comes from nickel cadmium battery and nickel hydrogen battery. These two rechargeable batteries will produce "memory effect" when charging before the power is completely used up, which will temporarily reduce the capacity of the battery and shorten the service time. Therefore, these two batteries must be discharged before they can be recharged. However, the lithium-ion battery has no memory effect and can be charged at any time. If it is over discharged, it will damage the battery and shorten the battery life.
Q: Will continued charging after the battery is fully charged cause damage to the battery?
A: When the mobile phone continues to be connected with the charger after charging, the mobile phone is directly powered by the power supply, which reduces the charging times of the battery, but is conducive to prolonging the battery life. However, if the mobile phone is connected with the power supply to play games and talk on the phone, it may cause the mobile phone to overheat and affect the battery.
▲ when the power of iPhone is lower than 20%, it will pop up a window to remind users that it is time to charge, because low power will damage the mobile phone battery.
How to realize fast charging?
The "voltage" and "current" output by the charger are the two keys to determine the charging efficiency. Each mobile phone charger must indicate the data of these two information. The most common combination is "5V / 1A" and "5V / 2A". The value obtained by multiplying the two is the rated output power (the power when the charger can operate normally and continuously). When the battery capacity remains unchanged, The higher the output power is, the faster the charging speed will be. Therefore, there are three ways to realize rapid charging: one is to keep the current unchanged and increase the voltage; the other is to keep the voltage unchanged and increase the current; finally, both the voltage and current are increased.
Does this mean that as long as you use a non original charger with high output power to charge, you can achieve the effect of fast charging? In fact, this statement is true, but doing so may lead to excessive battery load due to high power, damage the mobile phone battery, or even burn out the mobile phone due to overheating; However, if the charger with higher rated power is replaced within the safe load range, it is indeed a way to realize fast charging.
Fast charging will charge most of the power in the first few minutes or tens of minutes, and then the charging efficiency will decrease significantly, but it can save a lot of time compared with the standard charging method.
Effect of fast charging
The three stages of battery charging have been mentioned earlier, but in fact, the small current charging mode only exists when the battery has over discharge, so the normal charging process is mainly the constant current and constant voltage mode, while the fast charging is to shorten the constant current charging time, and the constant voltage charging time remains the same, that is, the first 70% of the battery capacity? 80% can increase the charging speed, but the rest can only be charged through a slowly decreasing current.
This is why fast charging technology often emphasizes charging most of the power by increasing the current or voltage in the first few minutes or tens of minutes, because the later charging effect is not much different from the general standard charger, so we can draw a conclusion: the advantages of fast charging can be fully demonstrated when the power of mobile phone battery is very low, If the battery itself has at least 50% of the power, the effect of using fast charging will be similar to that of general charging.
▲ the data of voltage and current will be clearly marked on the charger. The figure shows the charger with voltage of 5V and current of 1.5A.
▲ if you want to know the actual voltage and current value of the battery, you can buy the USB test tool on the market for testing.
Qualcomm quick charge technology
Qualcomm released the quick charge 1.0 charging technology several years ago, which can increase the charging power to 10W. Through the 5V / 2A charger, the charging speed can be increased by 40% compared with the traditional 5V / 1A charging speed, and the charging time can be reduced by one hour. This can be said to be the ancestor of the fast charging technology. Almost all mobile phones using snapdragon 400 chip have built-in quick charge 1.0 technology.
The charging power of the new generation quick charge 2.0 technology is increased to 36W, and supports three voltages of 5V, 9V and 12V and a maximum current of 3a, which not only improves the charging speed by 75%, but also means that it can be applied to a variety of devices; However, to make fast charging work, the device must not only support quick charge 2.0 technology, but also be equipped with special high-voltage chargers (9V and 12V), otherwise the charging effect will be the same as that of general charging.
▲ both mobile phones and chargers must support fast charging technology to give full play to the effect of fast charging.
In addition to USB, quickcharge 2.0 can also be used on micro USB and usbtype-c, and has the ability of downward compatibility. Its built-in IC will judge whether the charging device supports quickcharge 2.0. If it does not support, it will automatically reduce to general 5V charging. Therefore, there is no need to worry about the risk of battery damage or mobile phone overheating. At present, more and more mobile phones support quick charge 2.0 fast charging technology, and some manufacturers have launched charger, mobile power supply and other products. In addition, it can be found that quick charge 2.0 shadow exists in Samsung's fast charge and asus's bootmaster fast charging technology, which is widely used.
▲ Qualcomm released the latest quick charge 3.0 technology, which greatly improved the charging efficiency.
The latest third generation fast charging technology quickcharge 3.0 adopts the "optimal voltage intelligent negotiation (inov)" algorithm, which can select the appropriate voltage from 0.6V to 20V according to the device to charge, maximize the energy conversion efficiency, improve the charging efficiency by 38% compared with the previous generation, and provide additional mechanisms to protect the battery life cycle. It only takes 35 minutes to charge, The battery can be charged from 0% to 80%, greatly reducing the charging time. At the same time, it is also downward compatible with previous versions of quick charge and usbtype-c, providing more devices with ultra fast charging experience. Details are as follows:
According to Qualcomm, a traditional mobile phone can be charged from 0% to 80% in about 35 minutes.
Here are two points that Qualcomm must say when promoting quick charge 3.0. First, compared with quick charge 2.0, the fast charging speed is up to 27% and the power loss is reduced by up to 45%; Second, it is better than quick charge
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