Battery string equalization circuit and method and battery string charging and discharging device

Abstract

The invention discloses a battery string equalization circuit and method and a battery string charging and discharging device, relates to the field of battery equalization, and is used for reducing the complexity of a battery string equalization circuit and improving the equalization efficiency. The equalization circuit comprises a control circuit, and a charging and discharging circuit, a switching circuit, a current sampling circuit and a first voltage sampling circuit which are respectively connected with the control circuit, the switching circuit comprises a first switch and a second switch which are respectively connected with the positive electrode and the negative electrode of each single battery, and the current sampling circuit is connected in series with a main loop of the charging and discharging circuit; the first voltage sampling circuit collects voltages at the two ends of each single battery. And the control circuit independently turns on the switches of the single batteries with low / high SOC to control the charging and discharging circuit to independently charge / discharge the single batteries. According to the invention, the circuit topology is simple, the electric quantity equalization efficiency is high, part of batteries can be independently charged, discharged and equalized, and the overall service life of the battery string is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of battery balancing, and in particular to a battery string balancing circuit, method and battery string charging and discharging device. Background Art

[0002] A battery string is formed by connecting multiple single cells in series. In the application of battery strings, there is a phenomenon that the state of charge (SOC) of single cells is inconsistent due to factors such as manufacturing differences and uneven temperature distribution among single cells. If the state of charge differences among the single cells in the battery string are too large, it may cause risks such as capacity attenuation, shortened lifespan, and even thermal runaway of the battery string. Through battery balancing technology, the differences in the state of charge of each single cell can be controlled within a certain range, so as to ensure that each single cell maintains the same state during normal use and avoid overcharging or over-discharging.

[0003] Currently, battery balancing technology is divided into two types: passive balancing and active balancing.

[0004] Passive balancing discharges the electricity of the battery with a higher state of charge through a resistor, so as to achieve the effect of balancing with the battery with a lower state of charge. This method has certain limitations on the resistance value design of the discharge resistor, the balancing efficiency is low, the resistor discharge method will also cause energy waste, and the heat generated during the resistor discharge process will also increase the additional thermal management burden.

[0005] Active balancing is to balance the electricity among single cells. The currently known active balancing method is to transfer the electricity from the single cell with a higher charge to the single cell with a lower charge, so as to achieve energy balance. Active balancing often uses a capacitor or an inductor as a temporary storage device for energy transfer between single cells. It first obtains energy from the single cell with a higher charge and then transfers it to the single cell with a lower charge. This method needs to be turned on and off with each single cell one by one, requires a complex topology structure to support, and the circuit cost is relatively high; moreover, since it can only obtain energy from the high-charge single cell first and then transfer it to the low-charge single cell each time, the balancing efficiency is low.

[0006] In addition, in common existing technologies, almost all trigger balancing through the voltage difference between single cells and cannot dynamically track the actual capacity differences of each single cell. Summary of the Invention

[0007] The object of the present invention is to: in view of all or part of the above problems, provide a battery string balancing circuit, method and battery string charging and discharging device to reduce the circuit complexity of battery string balancing and improve the balancing efficiency.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A battery string balancing circuit, wherein the battery string is formed by connecting a plurality of single cells in series; the balancing circuit comprises:

[0010] A charging and discharging circuit, which is controlled by the control circuit to charge or discharge the battery string;

[0011] A switch circuit, comprising a first switch between the positive electrode of each of the single cells and the positive electrode of the charge-discharge circuit, and a second switch between the negative electrode of each of the single cells and the negative electrode of the charge-discharge circuit;

[0012] A current sampling circuit, connected in series to the main loop of the charging and discharging circuit;

[0013] A first voltage sampling circuit is used to respectively collect the voltage at both ends of each of the single cells;

[0014] The control circuit is respectively connected to the charging and discharging circuit, the switching circuit, the current sampling circuit and the first voltage sampling circuit.

[0015] The present invention also provides a battery string balancing method based on the above-mentioned battery string balancing circuit, which comprises:

[0016] Using the control circuit to turn on only the first switch and the second switch connected to the single cells at both ends of the battery string; using the control circuit to control the charge and discharge circuit to charge or discharge the battery string;

[0017] Using the control circuit to evaluate the state of charge of each of the single cells according to the voltage collected by the first voltage sampling circuit and the current collected by the current sampling circuit; judging whether the state of charge of each single cell is in the first state or the second state based on the relative size of the state of charge of all the single cells;

[0018] Using the control circuit to only turn on the first switch and the second switch at both ends of the first single cell or the sub-cell string of the first single cell in the first state of charge, and control the charge and discharge circuit to charge the battery string until the first single cell leaves the first state;

[0019] And / or, the control circuit is used to turn on only the first switch and the second switch at both ends of the second single cell with a second state of charge or a sub-cell string of second single cells connected in series, and control the charge and discharge circuit to discharge the cell string until the second single cell leaves the second state.

[0020] The present invention further provides a battery string charging and discharging device, which comprises the above-mentioned battery string balancing circuit, and a second voltage sampling circuit for collecting voltages at both ends of the battery string, wherein the second voltage sampling circuit is connected to the control circuit.

[0021] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0022] The battery string equalization circuit designed in this application is uniformly managed by a control circuit. By collecting the current on the main circuit and the voltages of each single battery, the state of charge of each single battery during the charging or discharging process can be accurately grasped. Then, strictly following the principle of state-of-charge equalization, the dynamic equalization of the actual capacities between single batteries is achieved. In this application, by controlling the conduction of the corresponding switches in the switching circuit and the charging or discharging state of the charge and discharge circuit, the equalization of the battery string is quickly realized. Moreover, in this application, the method of transferring electric quantity one by one between two single batteries in the traditional active equalization is abandoned. The charge and discharge circuit can charge or discharge one or more single batteries simultaneously with a relatively large current, greatly improving the equalization efficiency of the battery string. The equalization circuit of this application has a simple structure and can realize the independent charging, discharging, and equalization of some single batteries in the battery string, improving the overall service life of the battery string. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described by way of examples with reference to the accompanying drawings, where:

[0024] Figure 1 is the structural diagram of the battery string equalization circuit provided by the embodiment of this application.

[0025] Figure 2 is the schematic diagram of charging equalization for a single battery in the embodiment of this application.

[0026] Figure 3 is the schematic diagram of discharging equalization for a single battery in the embodiment of this application.

[0027] Figure 4 is the schematic diagram of charging equalization for multiple single batteries in the embodiment of this application.

[0028] Figure 5 is the schematic diagram of discharging equalization for multiple single batteries in the embodiment of this application.

[0029] Figure 6 is the schematic diagram of normal charging and discharging of the battery string in the embodiment of this application.

[0030] Figure 7 is the schematic diagram of discharging of the remaining battery string after bypassing with battery 2 as the target single battery in the embodiment of this application.

[0031] Figure 8 is the flowchart of the battery string equalization method provided by the embodiment of this application.

[0032] Figure 9 is the structural diagram of the battery string charging and discharging device provided by the embodiment of this application. Specific embodiments

[0033] All features disclosed in this specification, or steps in all methods or processes disclosed, can be combined in any way, except for mutually exclusive features and / or steps.

[0034] Any feature disclosed in this specification (including any appended claims, abstract) can be replaced by other equivalent or similar-purpose alternative features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only an example of a series of equivalent or similar features.

[0035] Regarding the problems in current known battery equalization technologies, where the passive equalization method has low equalization efficiency and causes energy waste and thermal management burden, and the active equalization method has a complex topology and low equalization efficiency, this application provides a battery string equalization circuit, method, and battery string charge and discharge device, aiming to reduce the complexity of the battery equalization circuit. On this basis, improve the battery equalization efficiency and extend the overall service life of the battery string.

[0036] The battery string equalization circuit proposed in this application includes:

[0037] A charge and discharge circuit. The charge and discharge circuit is connected to the control circuit and, under the action of the control circuit, charges or discharges the battery string. In the embodiments of this application, the charge and discharge circuit is responsible for actively charging or discharging all or part of the single cells in the battery string, and the charge and discharge target depends on the switch conducted by the switch circuit.

[0038] A switch circuit. The switch circuit includes a first switch between the positive electrode of each single cell and the positive electrode of the charge and discharge circuit, and a second switch between the negative electrode of each single cell and the negative electrode of the charge and discharge circuit. The switch circuit is connected to the control circuit and, under the action of the control circuit, conducts or turns off each first switch or second switch.

[0039] A current sampling circuit. The current sampling circuit is connected in series in the main circuit of the charge and discharge circuit to collect the current when the charge and discharge circuit charges or discharges the battery string. For example, the current in the main circuit during the charging or discharging process of the charge and discharge circuit to the battery string. The current sampling circuit is connected to the control circuit to transmit the collected main circuit current to the control circuit.

[0040] The first voltage sampling circuit. The first voltage sampling circuit is used to respectively collect the voltages across each single battery in the battery string. In some feasible embodiments, the first voltage sampling circuit is respectively connected to the positive and negative electrodes of the battery string, as well as each intermediate connection point (such as the connection point between the negative electrode of the previous single battery and the positive electrode of the next single battery), and calculates the voltage across each single battery by detecting the electric potential at the connected place. The first voltage sampling circuit is connected to the control circuit to transfer the voltage across each single battery collected to the control circuit.

[0041] The control circuit is responsible for obtaining sampling data from the connected current sampling circuit and the first voltage sampling circuit, and controlling the charge and discharge circuit and the switch circuit according to these data, so as to complete the charge balance of the battery string.

[0042] Such as Figure 1 shown, taking the battery string including 4 single batteries as an example, the order from the positive electrode to the negative electrode of the battery string is called battery 1, battery 2, battery 3 and battery 4 in turn, with the one closer to the positive electrode of the battery string in the front and the one closer to the negative electrode of the battery string in the back. The battery string composed of more single batteries is designed similarly according to the Figure 1 circuit structure. The positive electrodes of battery 1, battery 2, battery 3 and battery 4 are respectively connected to the positive electrode of the charge and discharge circuit through switches P1, P2, P3 and P4. Switches P1, P2, P3 and P4 are all called the first switches. After each first switch is connected to the same node on the side close to the charge and discharge circuit, it is then connected to the positive electrode of the charge and discharge circuit; the negative electrodes of battery 1, battery 2, battery 3 and battery 4 are respectively connected to the negative electrode of the charge and discharge circuit through switches N1, N2, N3 and N4. Switches N1, N2, N3 and N4 are all called the second switches. After each second switch is connected to the same node on the side close to the charge and discharge circuit, it is then connected to the negative electrode of the charge and discharge circuit. Switches P1, P2, P3, P4, N1, N2, N3 and N4 are respectively connected to the control circuit. On the main circuit of the charge and discharge circuit (represented by the thick line in the figure), the current sampling circuit is connected in series. And the first voltage sampling circuit is respectively connected to the positive electrode of battery 1, the negative electrode of battery 4, as well as the connection point between battery 2 and battery 3 and the connection node between battery 3 and battery 4.

[0043] As an alternative embodiment, in each adjacent pair of single batteries, the second switch connected to the negative electrode of the previous single battery and the first switch connected to the positive electrode of the next single battery are connected to the same node at one end close to the battery string, and then connected to the connection node between the single batteries from this node. In this way, at each connection node between single batteries, only one wire is led out to connect to the charge and discharge circuit, which can reduce the complexity of the circuit, facilitate wiring and reduce the risk of entanglement between lines. Such as Figure 1As shown, after connecting one end of switch P1 and switch N1 close to the battery string to the same node, it is connected to the connection node between battery 1 and battery 2. Similarly, after connecting one end of switch P2 and switch N2 close to the battery string to the same node, it is connected to the connection node between battery 2 and battery 3. After connecting one end of switch P3 and switch N3 close to the battery string to the same node, it is connected to the connection node between battery 3 and battery 4.

[0044] The control circuit performs balancing control based on the collected data. As an alternative implementation, the control circuit is configured to:

[0045] Based on the voltage collected by the first voltage sampling circuit and the current collected by the current sampling circuit, the state of charge of each single battery is evaluated respectively. The first voltage sampling circuit can collect the voltage across each single battery, and the current sampling circuit is on the main circuit. The currents of the single batteries in the series-connected battery string are equal. Therefore, the state of charge of each single battery can be calculated through the voltage and current of each single battery, serving as the trigger source for battery balancing. Compared with the prior art method of triggering balancing based on the difference between the voltages of single batteries, the method of triggering based on the difference in the state of charge in this application is more reliable, and can dynamically track the state of charge of each single battery, ensuring the reliability of the balancing effect, and generally improving the service life of the battery string.

[0046] The control circuit turns on the first switch and the second switch at both ends of the first single battery or the sub-battery string in series with the first single battery in the switch circuit whose state of charge is in the first state, and controls the charge and discharge circuit to charge the battery string. Or, turn on the first switch and the second switch at both ends of the second single battery or the sub-battery string in series with the second single battery in the switch circuit whose state of charge is in the second state, and control the charge and discharge circuit to discharge the battery string. The first state and the second state are judged based on the relative magnitudes of the states of charge of all single batteries. In some feasible implementations, the first state is judged based on whether the distance from the highest reference value of the state of charge exceeds the first threshold, and if it exceeds, it belongs to the first state; the second state is judged based on whether the distance from the lowest reference value of the state of charge exceeds the second threshold, and if it exceeds, it belongs to the second state. When the state of charge of a single battery changes from exceeding the first threshold / second threshold from the highest reference value / lowest reference value to within the first threshold / second threshold, it is called exiting the first state / second state.

[0047] For example, Figure 2The figure shows a schematic diagram of charging equalization for a single cell taking cell 1 as an example. Suppose it is calculated that the state of charge of cell 1 is 50%, while the states of charge of cell 2, cell 3, and cell 4 are all 60%. In comparison, the state of charge of cell 1 is significantly lower than that of other single cells by 10%. Assuming the first threshold is 5%, the state of charge of cell 1 is classified into the first state for charging equalization here. The control circuit turns on switches P1 and N1 at both ends of cell 1 in the switch circuit, and at this time the remaining switches (switches P2, P3, P4, N2, N3, and N4) are all turned off; the control circuit controls the charge and discharge circuit to charge the battery string. Since only switches P1 and N1 are turned on, charging for cell 1 alone is achieved to increase the power of cell 1 and achieve the charging equalization effect.

[0048] As Figure 3 The figure shows a schematic diagram of discharging equalization for a single cell taking cell 1 as an example. Suppose it is calculated that the state of charge of cell 1 is 60%, while the states of charge of cell 2, cell 3, and cell 4 are all 50%. In comparison, the state of charge of cell 1 is significantly higher than that of other single cells by 10%. Assuming the second threshold is also 5%, the state of charge of cell 1 is classified into the second state for discharging equalization here. The control circuit still turns on switches P1 and N1 at both ends of cell 1 in the switch circuit and turns off the remaining switches; the control circuit controls the charge and discharge circuit to discharge the battery string, thereby discharging cell 1 alone to reduce the power of cell 1 and achieve the discharging equalization effect.

[0049] The above methods of charging equalization or discharging equalization for a single cell are to charge or discharge the individual cell when the states of charge of most single cells are equivalent and only the state of charge of an individual cell is significantly lower or higher. In this way, battery equalization can be achieved with as few operations on the single cells as possible. However, in the embodiments of the present application, it is also allowed to perform overall charging equalization or discharging equalization on most single cells with equivalent states of charge.

[0050] As Figure 4 As shown in the figure, suppose it is calculated that the state of charge of cell 1 is 70%, while the states of charge of cell 2, cell 3, and cell 4 are all 60%. In comparison, the state of charge of cell 1 is significantly higher than that of other single cells. The first threshold is still 5%. Here, the states of charge of cell 2, cell 3, and cell 4 are classified into the first state for charging equalization. The control circuit turns on switch P2 connected to the positive electrode of cell 2 and switch N4 connected to the negative electrode of cell 4 in the switch circuit. At this time, the remaining switches (switches P1, P3, P4, N1, N2, and N3) are all turned off; the control circuit controls the charge and discharge circuit to charge the battery string, thereby overall charging the sub-battery string composed of cell 2, cell 3, and cell 4 to increase the power of cell 2, cell 3, and cell 4 and achieve the charging equalization effect.

[0051] As Figure 5 shown, assume that after calculation, the state of charge of battery 1 is 50%, while the states of charge of battery 2, battery 3, and battery 4 are all 60%. In comparison, the state of charge of battery 1 is significantly lower than that of other single cells, and the second threshold is still 5%. Here, the states of charge of battery 2, battery 3, and battery 4 are classified into the second state for discharge equalization. The control circuit still turns on switch P2 connected to the positive electrode of battery 2 and switch N4 connected to the negative electrode of battery 4 in the switch circuit, and at this time, the rest of the switches are all turned off; the control circuit controls the charge and discharge circuit to discharge the battery string, so as to overall discharge the sub-battery string composed of battery 2, battery 3, and battery 4, in order to reduce the power of battery 2, battery 3, and battery 4 and achieve the effect of discharge equalization.

[0052] It can also be found from the above embodiments that the present application can perform charge equalization or discharge equalization on multiple single cells at the same time, rather than transferring the power from the single cell with high power to the single cell with low power each time. This greatly improves the battery equalization efficiency. Moreover, the embodiments of the present application can all achieve equalization during the charging process or the discharging process of the battery string, without the need to separately implement the equalization process.

[0053] It can be found from the various embodiments listed above that in the present application, the state of charge of the single cell with the lowest state of charge among the single cells is determined as the first state. In fact, it is also possible to determine the states of charge of more single cells with the lowest state of charge as the first state. By setting the first threshold, among all single cells, the state of charge of the single cell whose difference from the highest reference value (in pure charge equalization, the highest reference value is selected as the highest state of charge among all single cells) exceeds the first threshold is determined as the first state. For example, assume that the states of charge of battery 1, battery 2, battery 3, and battery 4 are 50%, 65%, 45%, and 60% respectively, and the first threshold is set to 5%, then the states of charge of battery 1 and battery 3 may both be determined as the first state. In addition, in the above embodiments, the state of charge of the single cell with the highest state of charge among the single cells is determined as the second state. In fact, it is also possible to determine the states of charge of more single cells with the highest state of charge as the first state. By setting the second threshold, among all single cells, the state of charge of the single cell whose difference from the lowest reference value (in pure discharge equalization, the lowest reference value is selected as the lowest state of charge among all single cells) exceeds the second threshold is determined as the second state. In the above example, the states of charge of battery 2 and battery 4 may both be determined as the second state.

[0054] In a traditional battery equalization circuit, for the charging and discharging of a battery string, as Figure 6As shown, all are carried out with the battery string as a whole, and independent charging and discharging of partial single cells cannot be performed. When some single cells are damaged, the entire battery string will fail completely. In the balancing circuit provided in this application, partial single cells are allowed to be independently charged and discharged, and partial single cells are also allowed to independently perform charge balancing.

[0055] As an optional implementation manner, in the battery string balancing circuit, by turning on the first switch connected to the negative electrode of the sub-battery string formed by connecting the target single cell and all the previous single cells in series, and turning on the second switch connected to the negative electrode of the last single cell, the target single cell is bypassed. Of course, all the previous single cells thereof will also be bypassed, and only the battery string after the target single cell is retained for continued use. By turning on the second switch connected to the positive electrode of the sub-battery string formed by connecting the target single cell and all the subsequent single cells in series, and turning on the first switch connected to the positive electrode of the first single cell, the target single cell (and all the subsequent single cells) is bypassed, and the battery string before the target single cell is retained for continued use.

[0056] For example, assuming that battery 2 is damaged, in the embodiment of this application, the control circuit can turn on switch P1 and switch N1 to bypass battery 2, battery 3, and battery 4, as Figure 2 Or Figure 3 shown. Or, the control circuit can also turn on switch P3 and switch N4 to bypass battery 1 and battery 2, and retain the battery string composed of battery 3 and battery 4 for continued use, as Figure 7 shown. If battery 1 or battery 4 is damaged, it is more convenient. Only by bypassing battery 1 or battery 4 can the number of single cells that can continue to be used be maximally retained. By turning on switch P2 and switch N4, or turning on switch P1 and switch N3, battery 1 or battery 4 can be bypassed. When the remaining battery string contains two or more single cells, the method of battery string balancing is still the same as described above.

[0057] As Figure 8 shown, this application also provides a battery string balancing method for the battery string balancing circuit based on the above embodiment. The method includes the following processes:

[0058] S1. Use the control circuit to only turn on the first switch and the second switch connected to the single cells at both ends of the battery string; use the control circuit to control the charge and discharge circuit to charge or discharge the battery string.

[0059] See appendix Figure 6, in the state where only switch P1 and switch N4 are turned on, the charge-discharge circuit charges the battery string. Then, the first voltage sampling circuit samples the voltages of each single battery during the charging state, and the current sampling circuit samples the currents of each single battery during charging. If the charge-discharge circuit discharges the battery string, the first voltage sampling circuit and the current sampling circuit sample the voltages and currents of each single battery during the discharging state.

[0060] S2. Use the control circuit to evaluate the state of charge of each single battery respectively according to the voltage sampled by the first voltage sampling circuit and the current sampled by the current sampling circuit. Based on the relative magnitudes among the states of charge of all single batteries, determine whether the state of charge of each single battery is in the first state or the second state.

[0061] The control circuit receives respectively the voltage sampled by the first voltage sampling circuit and the current sampled by the current sampling circuit, and calculates the state of charge of each single battery in the case of charging or discharging accordingly. After knowing the state of charge of each single battery, the control circuit decides, based on the magnitude relationship among the states of charge of each single battery, whether to determine the state of charge of the single battery or more single batteries with the lowest state of charge as the first state, or to determine the state of charge of the single battery or more single batteries with the highest state of charge as the second state. For the single batteries in the first state, charge equalization is required, and for the single batteries in the second state, discharge equalization is required.

[0062] S3. Use the control circuit to turn on only the first switch and the second switch at both ends of the first single battery or the sub-battery string in series with the first single battery with the state of charge in the first state, and control the charge-discharge circuit to charge the battery string until the first single battery gets out of the first state; and / or, use the control circuit to turn on only the first switch and the second switch at both ends of the second single battery or the sub-battery string in series with the second single battery with the state of charge in the second state, and control the charge-discharge circuit to discharge the battery string until the second single battery gets out of the second state. The so-called first single battery refers to the single battery with the state of charge in the first state, and the second single battery refers to the single battery with the state of charge in the second state.

[0063] The first half of step S3 is for the charge equalization of the single battery with a low state of charge, and the second half is for the discharge equalization of the single battery with a high state of charge. Although both equalization methods may be executed in step S3, it should be understood that it only means that these two equalization methods may be adopted simultaneously. It is not that the two equalization methods are executed simultaneously. Each charging or discharging process can only execute one of them, and each time it can only be carried out for a single battery or a sub-battery string in series with more single batteries.

[0064] In addition, in step S3, whether it is charge balancing or discharge balancing, during the balancing process, the first voltage sampling circuit and the current sampling circuit continue to collect the voltage and current of the balancing object (the single cell that is charged or discharged individually), and the control circuit can dynamically monitor the charge state of the balancing object. After its charge state reaches the set target, the control circuit will stop charging or discharging it.

[0065] As an optional implementation, the above-mentioned control of the charge-discharge circuit to charge the battery string until the first single battery is out of the first state is: control the charge-discharge circuit to charge the battery string until the charge state of at least one first single battery is reached. Figure 2 In the embodiment shown, when battery 1 is charged to a state of charge of 55%, the control circuit controls the charge and discharge circuit to stop charging battery 1 and turns off switch P1 and switch N1. For another example, in the embodiment described above, in which the initial measured states of charge of battery 1, battery 2, battery 3 and battery 4 are 50%, 65%, 45% and 60% respectively, battery 1 can be charged and balanced first, and when the state of charge of battery 1 reaches 60%, the control circuit controls the charge and discharge circuit to stop charging the battery string, changes the switch that is turned on, and then controls the charge and discharge circuit to charge and balance battery 3, and when the state of charge of battery 3 reaches 60%, the control circuit controls the charge and discharge circuit to stop charging the battery string and turns off all switches.

[0066] Alternatively, the above-mentioned controlling the charge-discharge circuit to discharge the battery string until the second single battery is out of the second state is: controlling the charge-discharge circuit to discharge the battery string until the charge state of at least one second single battery is out of the second state. Figure 3 In the embodiment shown, when battery 1 is discharged to a state of charge of 55%, the control circuit controls the charge-discharge circuit to stop discharging battery 1 and turns off switch P1 and switch N1. For another example, in the embodiment described above, in which the initial measured states of charge of battery 1, battery 2, battery 3, and battery 4 are 50%, 65%, 45%, and 60%, respectively, the control circuit can first control the switch circuit and the charge-discharge circuit to discharge and balance battery 2, and when the state of charge of battery 2 reaches 50%, change the switch that is turned on, control the charge-discharge circuit to discharge and balance battery 4, and when the state of charge of battery 4 reaches 50%, the control circuit controls the charge-discharge circuit to stop discharging the battery string and turns off all switches.

[0067] In addition, in a scenario where both charge equalization and discharge equalization exist simultaneously, it is planned to charge the single battery with the lowest state of charge (SOC) to the intermediate SOC and discharge the single battery with the highest SOC to the intermediate SOC. In fact, this is equivalent to performing charge equalization and discharge equalization sequentially. Taking the example of performing charge equalization first and then discharge equalization, first set the SOC range of normal batteries. Then, among all the single batteries, using the highest SOC of normal batteries as the highest reference value, determine the SOC of single batteries with an SOC lower than the highest reference value by more than the first threshold as the first state, and determine the SOC of the remaining single batteries as the normal state. Perform charge equalization on the single batteries in the first state until they are out of the first state. Then, among all the single batteries, using the lowest SOC of normal batteries as the lowest reference value, determine the SOC of single batteries with an SOC higher than the lowest reference value by more than the second threshold as the second state, and determine the SOC of the remaining single batteries as the normal state. Perform discharge equalization on the single batteries in the second state until they are out of the second state. At this time, taking the embodiment where the initial measured SOCs of battery 1, battery 2, battery 3, and battery 4 are 50%, 65%, 45%, and 60% respectively as an example, set the SOC of normal state batteries in the range of 55% - 60%. It is planned to perform charge equalization on battery 1 and battery 3 and discharge equalization on battery 2. First, perform charge equalization on battery 1 and battery 3 respectively. At this time, use 60% (the highest SOC of the normal state) as the highest reference value. After the SOCs of battery 1 and battery 3 both reach 55%, then perform discharge equalization on battery 2. At this time, use 55% (the lowest SOC of the normal state) as the lowest reference value. When the SOC of battery 2 reaches 60%, the control circuit controls the charge and discharge circuit to stop charging and discharging the battery string and turns off all switches. At this time, the SOCs of all batteries are 55%, 60%, 55%, and 60% in sequence, all reaching the normal state and meeting the requirements of the equalization state.

[0068] Based on the design concept of the present application, an embodiment of the present application also proposes a battery string charge and discharge device. In addition to including the battery string equalization circuit in the previous embodiment, the battery string charge and discharge device further includes a second voltage sampling circuit. As Figure 9 shown, the second voltage sampling circuit is used to collect the voltage across the battery string. The second voltage sampling circuit is connected to the control circuit to transmit the collected voltage across the battery string to the control circuit to trigger corresponding operations.

[0069] For example, the control circuit receives the voltage of the battery string collected by the second voltage sampling circuit. When the voltage of the battery string is lower than the third threshold, turn on the first switch and the second switch connected across the battery string, and control the charge and discharge circuit to charge the battery string. In this way, automatic charging when the battery string is short of power is achieved.

[0070] In addition, it should be noted that in the case where some of the single battery cells are damaged (the case without damage is also applicable), the control circuit can calculate the total voltage based on the voltages of the single battery cells collected by the first voltage sampling circuit. When the total voltage is lower than the fourth threshold (which is calculated by converting the proportion of the remaining battery cells after bypassing the damaged single battery cell (and the single battery cells before or after it) based on the third threshold), the first switch and the second switch at both ends of the remaining battery string are turned on to control the charge and discharge circuit to charge the battery string. In this way, even in the case where some of the battery cells are damaged, the remaining battery string can still be charged, discharged, and the battery power can be balanced.

[0071] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new method or process step or any new combination disclosed.

Claims

1. A battery string equalization circuit, wherein the battery string is formed by connecting a plurality of single cells in series; characterized in that, The equalization circuit includes: A charge and discharge circuit that charges or discharges the battery string under the action of a control circuit; A switch circuit including a first switch between the positive electrode of each single battery and the positive electrode of the charge and discharge circuit, and a second switch between the negative electrode of each single battery and the negative electrode of the charge and discharge circuit; A current sampling circuit connected in series in the main circuit of the charge and discharge circuit; A first voltage sampling circuit that respectively samples the voltages across each single battery; A control circuit connected to the charge and discharge circuit, the switch circuit, the current sampling circuit, and the first voltage sampling circuit respectively.

2. The battery string equalization circuit according to claim 1, wherein, Among every two adjacent single batteries, the second switch connected to the negative electrode of the previous single battery and the first switch connected to the positive electrode of the next single battery are connected to the same node at one end close to the battery string.

3. The battery string equalization circuit according to claim 1 or 2, characterized in that, The control circuit is configured to: Respectively evaluate the state of charge of each single battery according to the voltage sampled by the first voltage sampling circuit and the current sampled by the current sampling circuit; Turn on the first switch and the second switch at both ends of the first single battery or the sub-battery string in series with the first single battery whose state of charge is in the first state in the switch circuit, and control the charge and discharge circuit to charge the battery string; or, turn on the first switch and the second switch at both ends of the second single battery or the sub-battery string in series with the second single battery whose state of charge is in the second state in the switch circuit, and control the charge and discharge circuit to discharge the battery string; the first state and the second state are determined based on the relative magnitudes of the states of charge of all single batteries.

4. The battery string equalization circuit according to claim 3, wherein, The control circuit is configured to: Among all single batteries, taking the highest state of charge as the highest reference value, determine the state of charge of the single batteries whose difference from the highest reference value exceeds the first threshold as the first state, and determine the state of charge of the remaining single batteries as the normal state; Or, among all single batteries, taking the lowest state of charge as the lowest reference value, determine the state of charge of the single batteries whose difference from the lowest reference value exceeds the second threshold as the second state, and determine the state of charge of the remaining single batteries as the normal state.

5. The battery string equalization circuit according to claim 2, wherein, By turning on the first switch connected to the negative electrode of the sub-battery string in series with the target single battery and all the previous single batteries, and turning on the second switch connected to the negative electrode of the last single battery; or, by turning on the second switch connected to the positive electrode of the sub-battery string in series with the target single battery and all the subsequent single batteries, and turning on the first switch connected to the positive electrode of the first single battery, to bypass the target single battery.

6. A battery string equalization method based on the battery string equalization circuit according to any one of claims 1-5, characterized in that, Including: Using the control circuit to only turn on the first switch and the second switch connected to the single batteries at both ends of the battery string; Using the control circuit to control the charge and discharge circuit to charge or discharge the battery string; Using the control circuit to respectively evaluate the state of charge of each single battery according to the voltage sampled by the first voltage sampling circuit and the current sampled by the current sampling circuit; Judging whether the state of charge of each single battery is in the first state or the second state based on the relative magnitudes of the states of charge of all single batteries; Using the control circuit to only turn on the first switch and the second switch at both ends of the first single cell or the sub-cell string of the first single cell in the first state of charge, and control the charge and discharge circuit to charge the battery string until the first single cell leaves the first state; And / or, the control circuit is used to turn on only the first switch and the second switch at both ends of the second single cell with a second state of charge or a sub-cell string of second single cells connected in series, and control the charge and discharge circuit to discharge the cell string until the second single cell leaves the second state.

7. The battery string equalization method according to claim 6, wherein Controlling the charge and discharge circuit to charge the battery string until the first single battery is out of the first state comprises: controlling the charge and discharge circuit to charge the battery string until the charge state of at least one first single battery is out of the first state.

8. The battery string equalization method according to claim 6, characterized in that, Controlling the charge and discharge circuit to discharge the battery string until the second single battery leaves the second state comprises: controlling the charge and discharge circuit to discharge the battery string until the charge state of at least one second single battery leaves the second state.

9. A battery string charge and discharge device, characterized in that, It comprises a battery string balancing circuit as claimed in any one of claims 1 to 5, and a second voltage sampling circuit for collecting voltages at both ends of the battery string, wherein the second voltage sampling circuit is connected to the control circuit.

10. The battery string charge and discharge device according to claim 9, characterized in that, The control circuit is configured to: The battery string voltage collected by the second voltage sampling circuit is received, and when the battery string voltage is lower than a third threshold, a first switch and a second switch connected at both ends of the battery string are turned on to control the charge and discharge circuit to charge the battery string.

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