Detailed detailed details of charging lithium battery charging

Detailed detailed details of charging lithium battery charging

The secondary lithium-ion battery has the advantages of high single output voltage, long cycle life, large energy, low-discipline, no memory effect, no pollution, and working temperature range, etc., is widely used in various fields, such as Electronic instrument, digital and home appliances, electric vehicles, etc..

Regarding the lithium-ion battery, the charging method has a large performance, and the reasonable charging method can extend the life of the lithium-ion battery and improve charging efficiency.. This paper analyzes the various charging methods of lithium-ion batteries, compared to their own advantages and disadvantages on charging speed, service life and achievement cost, for everyone’s reference exchange.

I. Theoretical foundation 1972 American scientist J.A.

mas proposed the battery in the charging process in the charging process: i = I0E-αt, in the formula; I0 is the initial charging current of the battery; α is the charging acceptance rate; T is charging time. The value of I0 and α and the type of battery, structure and new and old. At this stage, research on battery charging methods is important based on optimal charging curve.

. As shown in Figure 1, if the charging current exceeds this optimal charge curve, not only the charging rate cannot be increased, but will add the quantity of the battery; if it is less than this best charge curve, although it will not cause damage to the battery, but will Extend charging time, reduce charging efficiency. Figure 1 Characteristics of lithium ion battery charger, charging method, charging method of lithium ion batteries, there are many kinds, according to charging efficiency, can be divided into conventional charging and fast charging.

The conventional charging method includes: constant current charging, constant voltage charging, stage charging and intermittent charging, and fast charging includes pulse charging and reflex charging, and finally analyzed intelligent charging.. 1.

Constant current charging The constant current charging of the charging current can be divided into fast charging, standard charging and trickle charging. During the entire charging process, it is generally adjusted to adjust the power charging voltage or change the resistance value of the battery, and the battery’s charging current is not changed..

This method has the advantage that the control is simple, suitable for charging the battery packs connected in series in multiple batteries.. A disadvantage is that the ability to charge the lithium-ion battery will gradually decrease with charging, and the charging current in the late stage of charging will cause air bubbles inside the battery, causing damage to the battery.

. Therefore, constant current charging is often a link in stage charging..

2. Constant voltage charging constant voltage charging is during the entire charging process, the charging voltage is kept constant, the size of the charging current is automatically adjusted by the battery condition..

As charging, charging current gradually decrease. Compared with constant current charging, its charging process is closer to the best charging curve, simple control, low cost. The disadvantage is that the charging time is longer, and the battery charging current is too large in the charging initial battery, directly affects the life and quality of use of lithium-ion batteries.

. Therefore, the constant voltage charging method is rarely used alone, and only when the charging power supply voltage is low, the current is used..

3. Constant current constant press charging is shown in Figure 2 is a constant current constant pressure charger. Before starting charging, first detect the battery voltage, if the battery voltage is below the threshold voltage (about 2.

5V), the battery is trickle with the small current of C / 10, so that the battery voltage rises slowly; when the battery voltage reaches the threshold voltage When the constant current is charged, the battery is quickly charged at this stage, and the battery is rapidly charged, the battery voltage is rapid, and the battery capacity will reach around 85% of its rated value; rising battery voltage After the upper limit voltage (4.2V), the circuit is switched to the constant voltage charging mode. The battery voltage is substantially maintained at 4.

2V. The charging current is gradually reduced, and the charging speed is slow, this stage is important to ensure that the battery is full, when the charging current drops When 0.1c or 0.

05c, it is determined that the battery is full. Figure 2 constant current constant pressure charging curve constant current constant pressure charge prevention of the problem of excessive charging current at the beginning of constant voltage charging, and overcomes the phenomenon that the constant current charging is easy to overcharge, the structure is simple, the cost is low, currently The charging method of the lithium-ion battery is widely used. But it does not eliminate polarization in battery charging, affect charging effect.

4. Pulse charging is shown in Figure 3, which is a pulsed charge curve, and it is important to include three phases: precharge, constant current charging and pulse charging..

Figure 3 Pulse charging curve charges the battery at a constant current during constant current charging, most energy is transferred to the inside of the battery. When the battery voltage rises to the upper limit voltage (4.2V), enter the pulse charging mode: charging the battery with a pulse current of 1C.

. The battery voltage is continuously increased in a constant charging time Tc, and the voltage will slowly fall when charging is stopped..

When the battery voltage drops to the upper limit voltage (4.2V), charging the battery with the same current value, starting the next charging cycle, so recycled until the battery is full. During the pulse charging process, the speed of the battery voltage will gradually slow, and the stop time T0 will become long.

When the constant current charge duty cycle is as low as 5% ~ 10%, it is considered that the battery is full and end charging.. Compared with conventional charging methods, the pulse charge can charge with a large current, and the concentration of the battery in the stopper battery and the ohmic polarization will be eliminated, so that the next round of charging is more smoothly, the charging speed is fast, The temperature is small, affecting battery life, and is currently widely used.

However, its disadvantages are obvious: a power supply to a limited stream function, which added the cost of the pulse charging method.. C.

K.Leong et al. Pulse, each charging period lasts about 1s, first charge the battery, then stop and reverse discharge 20 ~ 30 ms.

The forward pulse current is charged to the battery, and the negative pulse current reduces gas from the electrode, and the battery can be used to achieve rapid charging.. 5.

Intermittent charging method, lithium-ion battery, intermittent electricity, intermittent, intermittent charge, and variable voltage intermittent charge. The change in electricity-changing electric change in change is proposed by the Professor Xiamen University Chen Gong, it is characterized by changing constant current charging to a restricted current..

As shown in FIG. 4 (a), the first phase (also important stage) of the change in the change of the change in the change is first, and the battery is charged with a large current value. When the battery voltage reaches the cutoff voltage V0, it stops charging, at which time the battery voltage is sharp.

decline. Figure 4 After the intermittent charging curve keeps a stop time, reduce the reduced charging current continues charging. When the battery voltage is raised to the cutoff voltage V0, the charging is stopped, so that the recovery time (generally approximately 3 to 4 times) charging current will reduce the set cutoff current value.

. Then enter the constant voltage charging stage, charge the battery to the battery until the charging current is reduced to the lower limit, the charging ends. The main conference of the change in electricity-changing charge is increased by the intermittent manner that has gradually decreasing the current, that is, the charging process is accelerated, and the charging time is shortened.

. However, this charging mode circuit is more complicated, high cost, usually only considering when high-power fast charge. Based on the changing charge of the change in electricity, it studies the change of the change in electricity and interval.

. The difference between the two is the first stage charging process, and the intermittent flow is changed to intermittently..

Comparison Figures 4 (a) and Figure 4 (b), see the constant pressure intermittent charge more in line with the best charging charging curve. In each constant voltage charging phase, due to the constant voltage, the charging current is naturally decreased according to the index law, and the battery current acceptance rate is gradually declined with charging..

6. REFLEX Fast Charging method Reflex fast charging method, also known as reflection charging method or “snoring” charging method. Each of the work cycles of this method includes forward charging, reverse instant discharge and three stages.

It solves the battery polarization in a large extent and speeds up the charging speed.. But reverse discharge will shorten lithium ion battery life.

SHENG-YUANOU and JEN-Hungtian have studied the REFLEX fast charging method. As shown in FIG. In each charging period, the charging period is first used in each charging period of 10s Tc, and then the stop time is 0.

5 s. TR1, the reverse discharge time is 1 s TD, the stopper time is 0.5 s TR2, each charging cycle time is 12s.

As charging, charging current will gradually become small. Experiments have shown that such a charging method can increase the charging time of the monomer lithium ion battery to 40 min, the battery temperature is only 1.1 ° C, and the charging efficiency reaches 87.

51%.. Figure 5Reflex charging curve 7.

Intelligent charging method intelligent charging is currently more advanced charging methods, as shown in Figure 6 (a), its important principle is to apply DU / DT and DI / DT control technology, by checking battery voltage and current Increment to determine the battery charging state, dynamically track the acceptable charging current, so that the charging current is from the highest charge curve acceptable in the battery.. This battery can quickly charge the electricity in a very small state of the gas.

. Figure 6 Intelligent charging is shown in Figure 6 (b), combining the neural network and blurring, researching the fuzzy neural network controller, neural network model, and designing intelligent charging control system. It has the characteristics of a fuzzy controller’s related experience in expressing humans, a strong sense of reasoning, and has the characteristics of learning knowledge and learning skills in the control data of neural network controllers.

. Experimental verification, the intelligent charging method is stable during the charging process, the charging time is short, so it is one of the fuzzy adaptive control methods, and the future will be increasingly valued..

Third, the end language is analyzed by various charging methods of lithium-ion batteries. According to JAMAS, there is an optimal charge curve, and when this curve is close to this curve, the speed is the fastest, the highest efficiency, exceeding this curve, battery It will be damaged. Related to constant current and constant voltage charging, smart charging and pulse charging better use J.

a.mas theory, gather the advantages of various methods, and extensive applications. The battery polarization problem during the charging process has always influenced the charging effect.

If the battery polarization can be eliminated in the future, the battery charging speed will last a new step.. Reference: “Summary of Lithium Ion Battery Charging Technology”.

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