TW201929310A - Segmented charging method and system for battery including a balance power source, a plurality of balance switches, a plurality of voltage management units, and a control unit - Google Patents

Abstract

The present invention provides a segmented charging method and system for battery to improve the disadvantages of the two-stage charging method of the prior art. The battery is first charged to any segment voltage to complete the cell balance, and then continues charging to the next segment voltage in this balanced state such that the cell balance of each segment can be performed with a small voltage difference between the cells until the charging process of the fully charged segment is completed. The segmented charging system includes a balance power source for introducing electricity from an external power source; a plurality of balance switches electrically connected to the balance power source, wherein each of the balance switches is connected to each battery of a battery pack; a plurality of voltage measurement units respectively electrically connected to each of the batteries for measuring voltage of the batteries; and a control unit electrically connected to the balance switches and the voltage measurement units for controlling the balance switches to perform segmented charging according to the voltage information of each battery returned from the voltage measurement units.

Description

Battery segmented charging method and system

The present invention relates to battery charging technology, and particularly relates to a method and system for charging a battery in a segmented manner, which improves the existing two-stage charging method.

Lithium batteries are currently used as energy storage and power batteries in electric vehicles, green energy regeneration systems, and portable electronic devices. Generally speaking, the number and method of charging and discharging are related to the battery life, but the consumer market usually requires charging. The shorter the time, the better. Therefore, high-current fast charging is often used. However, too fast and too strong current charging methods will seriously deplete the battery life and increase the long-term battery purchase cost. Balance is a necessary issue in the field of battery power applications.

Generally, the methods used to charge lithium batteries include the following: (1) Constant voltage charging method (CV): As the name implies, this charging method provides a fixed voltage to charge the battery from the beginning to the end of charging. When this charging method When the battery is initially charged, the charging voltage is greater than the internal voltage of the battery, so a high current will be generated in the battery, which will cause the temperature in the battery to rise sharply; as the battery level increases, the internal voltage of the battery will approach the given value given by the charger. At this time, although the internal current of the battery decreases, the charging time increases, so this method requires the longest charging time. (2) Constant current charging method (CC): The constant current charging method is from charging to junction Beam charging uses a fixed current method to charge the battery with a large constant current. Although the charging time will be greatly shortened, the charged battery will generate a higher temperature, which will lead to a reduction in battery life. The battery is charged at a constant current and the relative temperature is low, but the charging time will be prolonged. (3) Trickle charging method: The trickle charging method is a two-stage charging method. At the beginning of charging, the battery is charged with a large current method. In the later period, the battery is charged with a small current method. This method can protect the battery and extend the battery life. , But it is difficult to determine whether the battery is fully charged and the time required for charging is also long. (4) Pulse charging method: Also known as Pulse charging method, the battery is first charged with a constant current, and then the battery is charged at a constant current after a period of rest. This method can increase the charging efficiency of the battery, as it provides rest during the break Time, so it provides the battery to withstand the maximum current and shorten the charging time, but the purchase and design costs of charging equipment are higher.

In the traditional two-stage charging method, when the first-stage charging is completed, the lowest battery voltage is selected to give priority to the second stage of charging, until the battery is fully charged, and then the next battery is divided. Charging, because the same battery cell is charged for a long time, the temperature will continue to rise. Due to the chemical reaction during charging and the current flowing through the internal resistance of the battery, heat is generated, so the temperature will continue to increase over time.

In order to solve the shortcomings of the prior art, the present invention provides a battery segmented charging method and system, which improves the shortcomings of the conventional two-stage charging method. The battery is first charged to any segment voltage to complete the cell balance state. Again This equilibrium state continues to charge to the next segment voltage, so that the cells (battery cells) are balanced in each segment with a small voltage difference until the charging process of the fully charged segment is completed.

The present invention is a battery segmented charging method for charging a battery pack having a plurality of battery cells. The steps of the battery segmented charging method include: (a) performing charging on the battery pack until the When the voltage of any battery cell in the battery pack reaches the full voltage, stop charging; (b) Sort all the battery cells of the battery pack according to the current voltage level, starting from the lowest voltage battery cell, and sort all the batteries according to the order The cores are charged to the first segment voltage separately; (c) all the battery cells are charged to the second segment voltage according to the order; (d) all the battery cells are charged to the third segment voltage according to the order, and the Segmented charging of the battery pack.

In one embodiment of the present invention, the battery is a lithium iron battery or a lithium ternary battery.

In one embodiment of the present invention, the third segment voltage is a full-charge voltage of the battery cell.

In an embodiment of the present invention, the step (a) further comprises: detecting the voltages of all battery cells simultaneously while charging the battery pack, and when the voltage difference between one battery cell and the other battery cells exceeds a first balance setting When the value is equal to the value, the battery cell is supplemented with balanced power, so that the voltage difference between the battery cell and other battery cells is less than the second balance set value, and then the charging is stopped. The first balance setting value is 50 mV, and the second balance setting value is 30 mV.

The present invention also provides a battery segmented charging system. The system includes: a balanced power source that imports power from an external power source; a plurality of balanced switches that are electrically connected to the balanced power source, and each balanced switch is separately connected to Each battery cell of the battery pack; a plurality of voltage measurement units electrically connected to each of the battery cells for measuring the voltage of the battery cells; and a control unit electrically connected the balance switches and the For some voltage measurement units, the control unit controls the balance switches to perform the battery segmented charging as described in the battery segmented charging method according to the battery cell voltage information returned by the voltage measurement unit.

In one embodiment of the present invention, the balanced power supply has a DC-DC Forward Converter.

In one embodiment of the present invention, the external power source is a commercial power source, an energy storage battery, a solar power generation system, a wind power generation system, or other types of green power generation systems.

The above summary and the following detailed description and drawings are all for further explaining the methods, means and effects adopted by the present invention to achieve the intended purpose. Other objects and advantages of the present invention will be described in the following description and drawings.

A‧‧‧battery pack

1‧‧‧ Battery Segmented Charging System

10‧‧‧External Power

11‧‧‧ balanced power supply

12‧‧‧Balance switch

13‧‧‧Voltage measurement unit

14‧‧‧Control unit

S01 ~ S04‧‧‧Battery charging procedure

FIG. 1 is a structural diagram of an embodiment of a battery segmented charging system according to the present invention.

FIG. 2 is a flowchart of an embodiment of a battery charging method according to the present invention.

FIG. 3 is a voltage-time curve diagram of an example of a two-stage charging method and a charging test of the conventional technology.

FIG. 4 is a schematic diagram of a large voltage gap between cells when the second-stage charging method of the conventional technology is not completed.

FIG. 5 is a voltage-time curve diagram of an embodiment of a battery charging method according to the present invention.

The following is a description of specific embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

The battery segmented charging method and system of the present invention improve the split charging stage of the traditional two-stage charging method. In order to improve the defects of long-term split charging of the same battery cell and excessively increasing the temperature of the battery cell, the present invention The invention divides the battery cell voltage into sections and charges them in a voltage-balanced manner, so that each battery cell is fully charged and not overcharged. Because the traditional two-stage charging method requires a complete charging process before the cell balance can be reached, the charging time is prolonged, and the present invention is to charge each cell to the cell balance state of any segment voltage first. Based on the balanced state, the partial charging of each segment is continued to be completed, so that the battery cells are balanced with a smaller voltage gap each time until the charging process of the fully charged segment is completed. Therefore, the present invention can reduce the The balance time can avoid the shortcoming that the single battery cell receives too much power at one time and causes the temperature to increase excessively, resulting in a shortened battery life.

FIG. 1 is a structural diagram of an embodiment of a battery segmented charging system according to the present invention. As shown in the figure, the battery segmented charging system 1 includes: a balanced power source 11 for introducing power from an external power source 10; a balance switch 12, is electrically connected to the balanced power source 11, the number of the balance switches should be at least the same as the number of battery cells of battery group A, each balance switch 12 is connected to each battery cell of battery group A; voltage measurement Unit 13 is electrically connected to the battery cells of the battery pack for measuring the voltage of the battery cells; and a control unit (MCU) 14 is electrically connected to the balance switch 12 and the voltage measurement unit 13. The control unit 14 controls the balancing switches 12 to perform the segmented charging of the battery according to the present invention based on the battery cell voltage information returned by the voltage measurement unit 13. The detailed operation flow is described later.

FIG. 2 is a flowchart of an embodiment of a battery segmented charging method according to the present invention. The flow of this embodiment includes: a charging operation starts (S00); the battery segmented system of the present invention performs string charging on the battery pack, meaning that Charge the entire battery pack, and at the same time, these voltage measurement units continuously measure the voltage of each battery cell (cell) in the battery pack, and return it to the control unit. The control unit calculates the maximum and minimum voltage difference between the battery cells. (S01); When any battery cell voltage reaches the rated full voltage, stop charging in series and prepare for balanced charging between the battery cells (S02); because the electrochemical state of each battery cell is different, when one of them When the battery cell reaches the fully charged state first, other battery cells may not reach the fully charged voltage. If there is no balancing action, continue Charging the entire battery pack will cause the already fully charged battery cell to overcharge, overheat, or even damage the battery cell. The earliest two-stage charging method of the conventional technology is to charge the battery pack to a certain voltage value lower than the full-charge voltage, and stay for a period of time to charge the battery pack to the full-charge voltage. However, the two-phase string charge alone still cannot Ensure that the voltage between the battery cells in different states reaches a balance. Therefore, the two-stage charging method improved by the conventional technology is first charged in series until one of the battery cells in the battery pack reaches a fully charged voltage, and then the other unsatisfied batteries are fully charged. The battery cell with electric voltage is balanced and charged. The main disadvantage of this method is that the balancing action on the battery does not start until the charging time is over, which means that additional balancing time will be added. If the battery is temporarily used during the charging process, for example, the electric vehicle will continue to drive before it is fully charged. In this case, the battery in use at this time is still in a state where the voltage of each battery cell is unbalanced, which adversely affects energy management and battery life. Therefore, the present invention proposes a subsequent segmented charging and balancing mechanism in order to improve the lack of the prior art. During the string charging process, the voltage of each battery cell is continuously measured and the voltage difference between the battery cells is calculated to determine whether there is a battery cell that needs to be charged. The maximum and minimum voltage difference between the battery cells exceeds the first balance set value (for example, 50mV). When the balance switch corresponding to the low voltage battery cell is turned on, and the battery cell is supplemented with electricity, until the voltage difference between the battery cell and the highest voltage battery cell is less than the second balance setting value (for example, 30mV), the balance switch is turned off 5. Stop recharging the battery cell, and continue to detect the voltage status of all battery cells in the string charging process (step (S02)) (S03); continue to step (S02), when the voltage of any battery cell reaches the rated full At electrical voltage, Stop charging the whole battery pack. The control unit sorts all the battery cells according to the current voltage level of all battery cells reported by the voltage measurement unit. Then the control unit starts from the battery cell with the lowest voltage according to the setting, and sorts them as described above. Charge all battery cells to the first segment voltage (if the voltage is higher than the first segment voltage, the battery will not be charged). After all battery cells reach (or exceed) the first segment voltage, The foregoing sequence separately charges all the battery cells to the second segmented voltage, and finally sorts all the battery cells to the third segmented voltage (that is, the fully-charged voltage of the battery cells) to complete the segmented charging operation. (S04).

In one embodiment of the present invention, the purpose of designing the first balance setting value and the second balance setting value is to ensure that the voltage of each battery cell can maintain a certain degree of balance during the string charging process. The first balance setting value and the The actual value of the second balance setting value may be determined according to the type of battery and user needs, and is not limited to the aspect disclosed in the embodiments of the present invention.

The battery segmented charging method of the present invention is an improvement of the two-stage charging method of the prior art. When charging is started, the first stage of string charging is performed first. If any battery cell has a voltage difference greater than 50mV during the string charging, This cell is balanced and pulled up to less than 30mV, and the first stage of the series charging is ended until any cell reaches a fully charged voltage, and then the sequence of the voltage is performed and the second stage of equalization and charging is performed. The battery segmented charging method of the present invention divides the cell voltage into three segments in the second stage. First, the battery cells are charged one by one to the voltage value set in the first segment to reach the battery cell. Balance, and complete the balancing conditions of each segment in sequence until the set value of the full-charge voltage in the third segment is completed, that is, Complete the two-stage charging process, so that each battery cell is fully charged and not overcharged. Compared with the prior art two-stage charging method, the present invention has the advantage that the balancing action is performed in stages and multiple times during the charging process. Even if the battery pack is put into use before being fully charged, it can ensure that all battery cells are roughly in The voltage is balanced, and the current charged by the battery cell in each segment is small and short. The battery cell is less likely to accumulate heat and the temperature rise is lower. It also helps the battery life and performance. beneficial.

3 to 5 are comparison diagrams of battery cell voltage trends of the battery segmented charging method and system of the present invention and the two-stage charging method of the conventional technology. Taking a battery pack with 8 battery cells as an example, in general, The time required for the first stage of the two-stage charging method is much shorter than the second stage of subcharging, because the control logic such as detecting the voltage of each cell and calculating the balance charge parameters will be more complicated than simply charging the entire battery pack. In practical applications, transportation vehicles such as electric vehicles and electric buses often require charging as fast as possible, and can be driven on the road without being fully charged. Therefore, the battery pack is often put into use without completing the second-stage charging procedure. Most of the cells are in an unbalanced state. The two-stage charging method in FIG. 3 is a series charging of the entire battery pack, and then separate charging of individual battery cells. In theory, if the full charging operation in FIG. 3 can be completed, the battery pack can reach a balanced state. However, in practical applications, the battery may be put into use without being fully charged. When the full charging operation in FIG. 3 cannot be completed, there may be a large difference in voltage between the completed sub-charge core and the uncompleted sub-charge core. The battery cell voltage trend chart of the battery pack is more turbulent as shown in Figure 4. Chaos means that the voltage of each cell in the battery pack cannot reach equilibrium. The battery cell voltage trend graph using the battery segmented charging method of the present invention is shown in FIG. 5. A total of three segmented balances were made in the longer period of the second stage of charging, and it can be seen that the present invention can significantly reduce the partial charging. The problem that the voltage gap between the series cells is too large when the battery must be interrupted. Because the cell voltage gap in the segmented area is smaller than the two-stage charge method before the improvement, it will reduce the divided charge cell and the uncharged cell when incomplete charging occurs. Battery cell voltage difference between sub-charging cells.

In an embodiment of the present invention, the number of voltage segments and the voltage value of each segment in the second stage can be changed according to the type of battery and user needs, and are not limited to the aspects disclosed in the embodiments of the present invention. . Taking a lithium iron battery as an example, the voltage value divided into three sections can be set to 3.4V, 3.5V, 3.6V, and the lithium ternary battery as an example, it is 4.0V, 4.1V, 4.2V.

Therefore, the present invention provides a battery segmented charging method and system, which improves the shortcomings of the conventional two-stage charging method. The battery is first charged to any segmented voltage to complete the cell balance state, and then balanced. The state continues to charge to the next segment voltage, so that the battery cells (battery cells) balance the cells in each segment with a small voltage difference until the charging process of the fully charged segment is completed. According to the present invention, the balanced charging of each segment can enable the battery cells to reach the cell balance at a faster speed. The conventional charging mechanism of the technology is that the cells charge each single cell one by one to full capacity. It is necessary to wait for the completion of the second-stage process to achieve the equilibrium state of each battery cell. The improved charging mechanism of the present invention does not directly target the full-charge voltage as a balancing target, but performs voltage segmentation and uses the lowest segmented voltage value. Cell first Balance, and then charge the cells to full capacity one by one in a balanced state, so the balanced sub-charge mechanism will reach the balance before the traditional sub-charge. The segmented split charging mechanism has a short space between the same cell rechargeable batteries and relatively little heat accumulation time, and can use the remaining battery cells to cool down during the split charging period, which solves the problem of balanced charging of the same cell for a long time. Caused by temperature rise. The present invention can also solve the unbalanced shortcomings caused by the lack of electricity in the sub-charging core when the sub-charging of the conventional technology is not completed. The charging mechanism of the conventional technology needs to complete a complete second stage of charging in order to achieve a fully charged balance of each battery cell. Therefore, if the charging mechanism is not completed, the battery pack may not reach the full charge state of all the battery cells. There is a gap in the battery capacity, and the balance of the invention is the first important point. Because the battery pack is balancedly charged using voltage segments, the difference in energy between the cells is smaller when each segment is charged.

The above-mentioned embodiments are merely illustrative for describing the features and effects of the present invention, and are not intended to limit the scope of the essential technical content of the present invention. Anyone skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention should be listed in the scope of patent application described later.

Claims (10)

A battery segmented charging method is used for charging a battery pack having a plurality of battery cells. The steps of the battery segmented charging method include: (a) performing charging on the battery pack until any one of the battery packs is charged; When the voltage of a battery cell reaches the full voltage, the charging operation is stopped; (b) All the battery cells of the battery pack are sorted according to the current voltage level. Starting from the lowest voltage battery cell, all the battery cells are charged to First segment voltage; (c) Charge all battery cells to the second segment voltage according to the sequence; (d) Charge all battery cells to the third segment voltage according to the sequence to complete the division of the battery pack Step charging. The battery segment charging method according to claim 1, wherein the third segment voltage is a fully charged voltage of the battery cell. The battery charging method according to claim 1, wherein the step (a) further comprises: detecting the voltages of all the battery cells at the same time when charging the battery pack, and when the voltages of one battery cell and the other battery cells are When the difference exceeds a first balance setting value, the battery cell is supplemented with electricity for balance, so that the voltage difference between the battery cell and other battery cells is less than the second balance setting value, and then the electricity supply is stopped. The battery charging method according to claim 3, wherein the first balance setting value is 50 mV. The battery charging method according to claim 3, wherein the second balance setting value is 30 mV. A battery segmented charging system includes: a balanced power source, which imports power from an external power source; a plurality of balanced switches, which are electrically connected to the balanced power source, and each balanced switch is separately connected to the battery pack; Each battery cell; a plurality of voltage measurement units electrically connected to each of the battery cells for measuring the voltages of the battery cells; and a control unit electrically connected to the balance switches and the voltage measurements Unit, the control unit controls the balance switches to perform the battery segmented charging as described in claim 1 according to the battery cell voltage information returned by the voltage measurement unit. The battery segmented charging system according to claim 6, wherein the balanced power source has a DC-DC Forward Converter. The battery segmented charging system according to claim 6, wherein the external power source is mains power. The battery segmented charging system according to claim 6, wherein the external power source is a solar power generation system, a wind power generation system, or another type of green power generation system. The battery segmented charging system according to claim 6, wherein the external power source is an energy storage battery.