Variable constant-current constant-voltage charging method

Abstract

The invention discloses a variable constant-current constant-voltage charging method which comprises the following steps: when the voltage of a battery is relatively low, trickle charging is carried out according to information fed back after sampling; when the voltage of the battery rises to a large-current charging set threshold, a large-current constant-current charging mode is adopted, wherein the charging current in the process only can fall gradually, but cannot vary reversely; then, the battery is in a constant-voltage charging stage. The variable constant-current constant-voltage charging method is provided based on analysis of the advantages and the disadvantages of common charging strategies and the charging and discharging characteristics of a lithium titanate battery, integrates the advantages of a constant-current constant-voltage charging method, a pulse charging method, a variable-current intermittent charging method and other charging strategies, and overcomes the defects of the common charging strategies.

Description

Technical field [0001] The invention relates to the field of charging, and more specifically, a variable constant current-constant voltage charging method. Background technique [0002] On the whole, the technologies of charging, discharging, maintenance and energy management of power batteries are still relatively backward, and it is still common for improper charging strategies to cause battery damage and shortened life. Many batteries are not worn out but charged. bad. There are two main reasons for this phenomenon. The first is insufficient understanding of battery characteristics. As far as lithium batteries are concerned, its charging and discharging is a very complex chemical reaction process, which is affected by battery manufacturing materials, charging and discharging history, and environmental conditions. The temperature and many other factors are affected; and the battery is nonlinear in nature, and the control difficulty coefficient is relatively large. The second ...

AI Technical Summary

Problems solved by technology

[0002] Generally speaking, the charging, discharging, maintenance and energy management technologies of power batteries are still relatively backward, and the phenomenon of battery damage and shortened life due to inappropriate charging strategies is still relatively common. Many batteries are not used up but recharged. bad

There are two main reasons for this phenomenon. The first is insufficient understanding of battery characteristics. As far as lithium batteries are concerned, their charging and discharging is a very complicated chemical reaction process, which is affected by battery manufacturing materials, charging and discharging history, and environmental conditions. Influenced by many factors such as temperature; and the battery is nonlinear in nature, and the control difficulty coefficient is relatively large

The second is that our research on charging methods and the impact of various charging methods on batteries is not deep enough

[0003] 1. In the initial charging stage of the constant current charging method, the charging current is much lower than the acceptable charging current of the power battery, which results in a longer charging time in the early stage; in the later stage of charging, the charging current is greater than the acceptable charging current of the power battery, resulting in a sharp drop in battery temperature. Elevated, affecting battery life

[0004] 2. The constant voltage charging method also has its shortcomings, mainly in the charging current is too large at the initial stage of charging, which is likely to exceed the maximum acceptable charging current value of the battery, which will adversely affect the life of the battery, and at the same time it is easy to bend the battery plate. Cause the battery to be scrapped; however, at the end of charging, the charging current is very small due to the rise of the battery electromotive force, which may easily cause the battery to be undercharged.

[0005] 3. The constant current and constant voltage charging method avoids the shortcomings of excessive charging current at the initial stage of charging and overcharging at the end of charging, but it does not improve the problem of undercharging, and the charging current value at the initial stage of charging is single, and Safe, fast and efficient charging cannot be achieved

[0006] 4. Three-stage charging method It is difficult to control the transition points of the three charging processes. If you switch from the previous stage to the next stage too early, the charging time will inevitably be extended; but if the transition is too late, it may enter the overcharge state , causing problems such as increased battery temperature rise and shortened service life

[0007] 5. The pulse charging method has the characteristics of high charging efficiency, fast charging speed, and fewer components used than the switching power supply charging method. The disadvantages are that it is extremely difficult to control, high in cost, and the pulse current is large and easy to damage the battery.

[0008] 6. The hardware control of the variable current intermittent charging method is very complicated, and it is difficult to accurately control the output voltage and current value

[0009] The variable constant current-constant voltage charging method improves the disadvantage that constant current charging or constant voltage charging is easy to cause overcharging or undercharging. Secondly, the variable constant current-constant voltage charging method is similar to the three-stage charging method. The control of the battery is linked to the real-time state of the battery, and the charging curve is closer to the ideal charging curve of the battery

The pulse charging method is faster than the variable constant current-constant voltage charging method, but the pulse charging control is more difficult, has a greater impact on battery life, and the corresponding cost is higher

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