Battery equalization method

Abstract

The invention relates to a battery equalization method, belongs to the technical field of battery management, and solves the problem in the prior art that the performance of a battery pack becomes poor due to the fact that the consistency difference of battery pack monomers is too large after the battery pack is charged and discharged for multiple times. The method comprises the steps of integrally discharging a battery pack; in response to the fact that the total voltage of the battery pack or the voltage of at least one single battery drops to the discharge cut-off voltage, overall discharge of the battery pack is stopped, and the single batteries which are not dropped to the discharge cut-off voltage in the battery pack are discharged one by one; in response to the fact that all the single batteries in the battery pack are reduced to the discharge cut-off voltage, the battery pack is wholly charged; in response to the fact that the total current of the battery pack or the current of at least one single battery reaches the charging cut-off current, overall charging of the battery pack is stopped, and the single batteries which do not reach the charging cut-off current in the battery pack are charged one by one; and stopping charging the single batteries in response to the fact that all the single batteries in the battery pack reach the charging cut-off current.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and in particular to a battery balancing method and battery system. Background Technology

[0002] Lithium-ion batteries have high power density and energy density, and are widely used in energy storage systems. The voltage of a single cell is usually below 5V, which is generally sufficient for consumer electronics. However, energy storage systems require several batteries to be connected in series and parallel to form a high-voltage, high-capacity battery pack. Therefore, the consistency of the battery pack is particularly important.

[0003] As the number of charge-discharge cycles increases, the differences between individual cells in the battery pack become more pronounced during repeated charging and discharging, leading to decreased battery consistency and a "weakest link" effect, which in turn causes a decline in battery pack performance. Furthermore, batteries with smaller capacity are characterized by lower capacity and higher internal resistance, resulting in the highest heat generation during both charging and discharging, making them more susceptible to thermal runaway and safety issues.

[0004] Therefore, there is an urgent need for a battery balancing method that can solve the problem of excessive differences in the consistency of individual battery cells, which leads to a deterioration in battery pack performance. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a battery balancing method to solve the problem of excessively large differences in the consistency of individual cells in existing battery packs after multiple charge and discharge cycles, which leads to deterioration in battery pack performance.

[0006] On one hand, embodiments of the present invention provide a battery balancing method, comprising the following steps:

[0007] The battery pack is discharged as a whole, wherein the battery pack comprises multiple string-connected individual cells;

[0008] In response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, the overall discharge of the battery pack is stopped, and the individual cells in the battery pack that have not dropped to the discharge cutoff voltage are discharged one by one.

[0009] In response to all individual cells in the battery pack dropping to the discharge cutoff voltage, the battery pack is charged as a whole;

[0010] In response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, the overall charging of the battery pack is stopped, and the individual cells in the battery pack that have not reached the charging cutoff current are charged one by one; and

[0011] In response to all individual cells in the battery pack reaching the charging cutoff current, charging of the individual cells is stopped.

[0012] Based on a further improvement to the above method, before discharging the entire battery pack, the method further includes:

[0013] The battery management system of the battery pack obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell; and...

[0014] Discharging the entire battery pack or discharging individual cells one by one includes:

[0015] The maximum allowable discharge current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell.

[0016] Based on the maximum allowable discharge current, the battery pack is discharged as a whole or the individual cells are discharged one by one using a constant current method.

[0017] A further improvement to the above method involves charging the entire battery pack as a whole, including:

[0018] The battery management system of the battery pack obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell.

[0019] The maximum allowable charging current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell.

[0020] When the total voltage of the battery pack or the voltage of at least one of the individual cells reaches the charging cutoff voltage, the battery pack is switched to constant voltage charging mode to charge the entire battery pack according to the maximum allowable charging current.

[0021] A further improvement to the above method involves charging individual cells in the battery pack that have not reached the charging cutoff current, including:

[0022] When the voltage of a single battery cell reaches the charging cutoff voltage, the system switches to constant voltage charging mode to charge the single battery cell.

[0023] Based on a further improvement of the above method, the method further includes:

[0024] The battery management system of the battery pack obtains the real-time total voltage and real-time total current of the battery pack, as well as the real-time voltage and real-time current of each individual cell.

[0025] Based on further improvements to the above method, discharging the battery pack as a whole includes discharging each individual cell in the battery pack simultaneously; charging the battery pack as a whole includes charging each individual cell in the battery pack simultaneously.

[0026] Based on a further improvement of the above method, the discharge circuit structure used for discharging the battery pack as a whole or discharging the individual cells in the battery pack one by one is as follows:

[0027] The circuit consists of a first LC filter circuit, a first-stage buck circuit, a second LC filter circuit, a second-stage boost circuit, and a load power fine-tuning circuit, all cascaded in sequence.

[0028] Based on a further improvement of the above method, the charging circuit structure used for charging the battery pack as a whole or charging the individual cells in the battery pack one by one is as follows:

[0029] The circuit consists of a common-mode inductor filter, a power factor correction circuit, an LLC half-bridge resonant circuit, a synchronous rectifier circuit, and a capacitor filter, all cascaded in sequence.

[0030] On the other hand, embodiments of the present invention provide a battery system, including:

[0031] One or more battery packs, the battery packs comprising multiple string-connected individual cells and a battery management system, the battery management system being used to monitor the total voltage and total current of the battery pack and the voltage and current of all individual cells; and

[0032] A charging and discharging maintenance device, comprising a controller, a string charging and discharging module, and one or more individual charging and discharging modules; wherein...

[0033] The string charge / discharge module is configured to perform overall charge and discharge of the battery pack.

[0034] The single-cell charge / discharge module is configured to perform charging and discharging of the single-cell battery.

[0035] The controller is configured to perform:

[0036] The string charging and discharging module is controlled to discharge the battery pack as a whole.

[0037] In response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, the string charging and discharging module is controlled to stop discharging the battery pack as a whole, and based on the monitoring data of the battery management system, the individual cell charging and discharging module is controlled to discharge the individual cells in the battery pack that have not dropped to the discharge cutoff voltage one by one.

[0038] In response to all individual cells in the battery pack dropping to the discharge cutoff voltage, the string charging and discharging module is controlled to charge the entire battery pack.

[0039] In response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, the string charging / discharging module is controlled to stop charging the entire battery pack, and based on monitoring data from the battery management system, the individual cell charging / discharging module is controlled to charge the individual cells in the battery pack that have not reached the charging cutoff current one by one; and

[0040] In response to all individual cells in the battery pack reaching the charging cutoff current, the individual cell charging and discharging module is controlled to stop charging the individual cells.

[0041] Based on further improvements to the above system, the controller is also configured to perform:

[0042] Before controlling the string charging and discharging module to discharge the battery pack as a whole, the battery management system obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell.

[0043] The maximum allowable discharge current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell.

[0044] Based on the maximum allowable discharge current, the string charging and discharging module is controlled to discharge the battery pack as a whole or the individual cell charging and discharging module is controlled to discharge the individual cells one by one using a constant current method.

[0045] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0046] The battery balancing method and battery system provided by this invention can reduce the capacity differences between individual batteries and make them more consistent by balancing the voltage differences between batteries, thereby restoring the performance of the battery pack and improving its lifespan.

[0047] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0048] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0049] Figure 1 This is a schematic flowchart of a battery balancing method according to an embodiment of the present invention.

[0050] Figure 2A schematic system block diagram illustrating the discharge circuit structure according to an embodiment of the present invention is provided.

[0051] Figure 3 A schematic block diagram of a charging circuit system according to an embodiment of the present invention is shown.

[0052] Figure 4 A schematic diagram of a battery system according to an embodiment of the present invention is shown. Detailed Implementation

[0053] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0054] One specific embodiment of the present invention discloses a battery balancing method, such as... Figure 1 As shown, it includes the following steps:

[0055] Step 101: Discharge the entire battery pack.

[0056] In this embodiment, the battery pack may contain n individual cells, where n is less than or equal to 32; preferably, n is 4, 6, or 8. The n individual cells in the battery pack are connected in a string configuration. By connecting the n individual cells in series to form the battery pack, a larger voltage and current output can be provided.

[0057] In some embodiments, discharging the battery pack as a whole refers to discharging all n individual cells connected in series as a whole.

[0058] In some embodiments, before discharging the entire battery pack, parameters such as the total voltage of the battery pack, the voltage of individual cells, the temperature of the battery pack, the current of the battery pack, and the state of the cells can be collected. Then, based on these parameters, the maximum allowable discharge current of the battery pack can be determined. Finally, the entire battery pack can be discharged using a constant current method, or individual cells can be discharged one by one. For example, if the maximum allowable discharge current of the battery pack is I1, then a constant current discharge can be performed using a current of I1 / 3.

[0059] In some embodiments, the discharge circuit structure used for discharging the battery pack as a whole or discharging the individual cells in the battery pack one by one is as follows:

[0060] The circuit consists of a first LC filter circuit, a first-stage buck circuit, a second LC filter circuit, a second-stage boost circuit, and a load power fine-tuning circuit, all cascaded in sequence.

[0061] Figure 2 A schematic system block diagram of a discharge circuit structure according to an embodiment of the present invention is shown. Figure 2 As shown, BAT+ and BAT- are the positive and negative terminals of the battery input. After passing through the first LC filter circuit composed of L1 and C1, they are connected to a first-stage buck circuit. The buck circuit consists of V1, V2, L2, and C2. When V1 is on, the battery supplies power to the subsequent load through V1 and L2, and the filter capacitor C2 smooths the output voltage. When V1 is off, the L2 inductor supplies power to the subsequent load through V2, and the filter capacitor C2 smooths the output voltage. By adjusting the width of the PWM pulse and controlling the conduction time of transistor V1, the output voltage and current can be adjusted. For example, if the output voltage after the first-stage step-down is Uo1, the battery voltage is UBT, and the voltage across inductor L2 is UL2, then Uo1 = UBT - UL2. If the switching cycle is T1, the on-time of switch V1 is T1on, and the off-time is T1off, then T1 = T1on + T1off. If the inductance of L2 is L2, and the change in current across the inductor is ΔI1, then UL2 = L2 * ΔI1 / T1on. Assuming the voltage drop across V2 is 0, then Uo1 = L2 * ΔI1 / T1off. Since Uo1 = UBT - UL2, we can calculate Uo1 = UBT * T1on / T1. From the above formula, we can see that by adjusting the on-time, the output voltage can be adjusted; the longer the on-time, the higher the output voltage.

[0062] The first-stage buck circuit, after passing through a second LC filter circuit composed of L3 and C3, is connected to the second-stage boost circuit. The boost circuit consists of V3, V4, V5, L4, and C2. When V3 is on, the battery stores current through V3 and L4, and the filter capacitor C2 smooths the output voltage. When V3 is off, the inductor L4 supplies power to the subsequent load through V4, and the filter capacitor C2 smooths the output voltage. By adjusting the width of the PWM pulse and controlling the conduction time of transistor V3, the output voltage and current can be adjusted. For example, if the output voltage after the two-stage boost is Uo2, the input voltage is Uo1, and the voltage across inductor L4 is UL4, then Uo2 = Uo1 + UL4. If the switching cycle is T2, the on-time of switch V3 is T2on, and the off-time is T2off, then T2 = T2on + T2off. If the inductance of L4 is L4, and the change in current across the inductor is ΔI2, then Uo1 = L4 * ΔI2 / T2on. Assuming the voltage drop across V4 is 0, then UL4 = L4 * ΔI2 / T2off. Therefore, Uo2 = Uo1 * T2 / T2off, or Uo2 = Uo1 * T2 / (T2 - T2on). From the above formula, it can be seen that by adjusting the on-time, the output voltage can be adjusted; the longer the on-time, the higher the output voltage.

[0063] Assuming a maximum discharge voltage of 40V and a current of 600mA, the first-stage buck converter has a maximum output voltage of 18V and a maximum PWM duty cycle of 0.9. When the battery voltage is below 20V, the buck converter will no longer adjust and will output according to the actual battery voltage. The second-stage boost converter has a range of 10V to 20V, with a boost output voltage of 30V. When the voltage is below 10V, an undervoltage alarm will be triggered.

[0064] The discharge thermistors (PTC1 to PTC7, as shown in the circuit diagram, are not necessarily seven in number) can be switched between different fine-tuning output load power via MOSFET switches (V6 to V12), while the load power is coarsely adjusted via the two-stage voltage adjustment circuit mentioned above. By combining the two-stage voltage adjustment circuit with the load power fine-tuning circuit composed of PTC resistors, the output voltage and output current can be adjusted more flexibly, thus adapting to different discharge modes and battery types.

[0065] Step 102: In response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, stop discharging the battery pack as a whole, and discharge the individual cells in the battery pack that have not dropped to the discharge cutoff voltage one by one.

[0066] In this embodiment, discharge stops when the total voltage of the battery pack drops to the discharge cutoff voltage or the voltage of at least one individual cell drops to the discharge cutoff voltage.

[0067] Specifically, the discharge cutoff voltage can be determined in the following ways:

[0068] For example, if the battery is a LiFePO4 battery with a rated voltage of 3.2V and an operating voltage range of 2.5V to 3.6V, and the entire battery pack consists of 8 LiFePO4 batteries connected in series, then the rated voltage is 3.2V × 8 = 25.6V, and the operating voltage is 2.5 × 8 = 22.5V to 3.6 × 8 = 20V to 25.6V, so the discharge cutoff voltage is 20V.

[0069] In this embodiment, the discharge circuit system for discharging a single battery cell is as follows: Figure 2 As shown above, since the above has already discussed... Figure 2 The above has already been described, so I will not repeat it here.

[0070] In this embodiment, discharging each individual cell that has not dropped to the discharge cutoff voltage means that each individual cell is discharged through a single discharge circuit, and all individual cells are discharged simultaneously.

[0071] In some embodiments, the real-time total voltage and current of the battery pack, as well as the real-time voltage and current of all individual cells, can be obtained through the battery management system (BMS). A BMS is an electronic device that monitors batteries, collecting and calculating parameters such as voltage, current, temperature, and SOC (State of Charge).

[0072] Step 103: In response to all individual cells in the battery pack dropping to the discharge cutoff voltage, the battery pack is charged as a whole.

[0073] In this embodiment, discharge stops when the voltage of all individual cells in the battery pack drops to the discharge cutoff voltage. Afterward, the battery pack can be left to stand for a period of time (e.g., 1 hour) before starting a full charge.

[0074] In some embodiments, charging the battery pack as a whole refers to charging n individual cells connected in series as a whole.

[0075] In some embodiments, before charging the entire battery pack, parameters such as the total voltage of the battery pack, the voltage of individual cells, the temperature of the battery pack, the current of the battery pack, and the state of the batteries can be collected. Then, based on these parameters, the maximum allowable charging current of the battery pack can be determined. Afterward, the charging current can be determined based on the maximum allowable charging current, and the entire battery pack can be charged using a constant current method. For example, if the maximum allowable charging current of the battery pack is I1', then constant current charging can be performed at a current of I1' / 3.

[0076] In some embodiments, the charging circuit structure used for charging the battery pack as a whole or charging individual cells in the battery pack individually is as follows:

[0077] The circuit consists of a common-mode inductor filter, a power factor correction circuit, an LLC half-bridge resonant circuit, a synchronous rectifier circuit, and a capacitor filter, all cascaded in sequence.

[0078] Figure 2 A schematic block diagram of a charging circuit system according to an embodiment of the present invention is shown. Figure 2As shown, the AC input undergoes input filtering (i.e., common-mode inductor filtering) to suppress internal interference signals from interfering with external signals, while also preventing external signals from interfering with the power supply itself. The AC input is then boosted and rectified into DC by a PFC (Power Factor Correction) circuit. The boosted DC is then converted into high-frequency AC by an LLC half-bridge resonant circuit, and further stepped down by a transformer for isolation. Afterward, it is rectified into DC by a synchronous rectifier circuit, and finally filtered into smooth DC by an output filter circuit (e.g., a capacitor filter). Furthermore, output sampling controls the resonant frequency of the LLC half-bridge resonant circuit to stabilize the voltage across the transformer, thus achieving voltage regulation.

[0079] The charging circuit system of this invention adopts an LLC circuit design. The LLC power supply realizes zero-voltage turn-on (ZVS) of the two main switches on the primary side and zero-current turn-off (ZCS) of the rectifier diodes on the secondary side. Through soft-switching technology, the switching losses of the power supply can be reduced, and the efficiency and power density of the power converter can be improved.

[0080] Step 104: In response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, stop charging the battery pack as a whole, and charge the individual cells in the battery pack that have not reached the charging cutoff current one by one.

[0081] In this embodiment, the overall charging of the battery pack is stopped when the total current of the battery pack or the current of at least one individual cell reaches the charging cutoff current.

[0082] Specifically, the charging cutoff voltage can be determined first by the following method:

[0083] For example, if the battery is a LiFePO4 battery with a rated voltage of 3.2V and an operating voltage range of 2.5V to 3.6V, and the entire battery pack consists of 8 LiFePO4 batteries connected in series, then the rated voltage is 3.2V × 8 = 25.6V, and the operating voltage is 2.5 × 8 = 22.5V to 3.6 × 8 = 20V to 25.6V. Therefore, the charging cut-off voltage is 25.6V.

[0084] Then, the battery pack is charged using constant current charging until the total voltage of the battery pack or the voltage of at least one individual cell reaches the charging cutoff voltage. When the total voltage of the battery pack or the voltage of at least one individual cell reaches the charging cutoff voltage, the battery pack is charged using constant voltage charging until the total current of the battery pack or the current of at least one individual cell reaches the charging cutoff current.

[0085] In some embodiments, the real-time total voltage and current of the battery pack, as well as the real-time voltage and current of all individual cells, can be obtained through the battery management system (BMS). A BMS is an electronic device that monitors batteries, collecting and calculating parameters such as voltage, current, temperature, and SOC (State of Charge).

[0086] In this embodiment, the charging circuit system for charging individual batteries is as follows: Figure 3 As shown above, since the above has already discussed... Figure 3 The above has already been described, so I will not repeat it here.

[0087] Step 105: In response to all individual cells in the battery pack reaching the charging cutoff current, stop charging the individual cells.

[0088] In this embodiment, charging stops when all individual cells in the battery pack reach the charging cutoff current.

[0089] Specifically, the charging cutoff voltage can be determined first by the following method:

[0090] For example, if the battery is a LiFePO4 battery with a rated voltage of 3.2V and an operating voltage range of 2.5V to 3.6V, and the entire battery pack consists of 8 LiFePO4 batteries connected in series, then the rated voltage is 3.2V × 8 = 25.6V, and the operating voltage is 2.5 × 8 = 22.5V to 3.6 × 8 = 20V to 25.6V. Therefore, the charging cut-off voltage is 25.6V.

[0091] Then, the individual cells are charged one by one using constant current charging until their voltage reaches the charging cutoff voltage. When the voltage of an individual cell reaches the charging cutoff voltage, constant voltage charging is then used to continue charging the individual cell until its current reaches the charging cutoff current.

[0092] It is understood that the battery equalization method provided in this application can reduce the capacity difference between individual batteries and make them more consistent by equalizing the voltage differences between batteries, thereby restoring the performance of the battery pack and improving its lifespan.

[0093] This application also provides a battery system. Figure 4 A schematic diagram of a battery system according to an embodiment of the present invention is shown. Figure 4 As shown, the battery system includes multiple battery packs and a charge / discharge maintenance device. Each battery pack comprises multiple string-connected individual cells (i.e.,...) Figure 4The battery pack includes batteries 1, 2, 3, ..., n, and a battery management system (BMS). The BMS monitors the total voltage and current of the battery pack, as well as the voltage and current of each individual battery cell. The charge / discharge maintenance equipment includes a controller, a string charge / discharge module, and one or more individual charge / discharge modules. The string charge / discharge module is configured to perform overall charge / discharge of the battery pack. The individual charge / discharge modules are configured to perform charge / discharge of the individual battery cells. The controller is configured to: control the string charge / discharge module to discharge the battery pack as a whole; in response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, control the string charge / discharge module to stop discharging the battery pack as a whole, and control the individual cell charge / discharge module to discharge the individual cells in the battery pack that have not dropped to the discharge cutoff voltage one by one, based on monitoring data from the battery management system; in response to all individual cells in the battery pack dropping to the discharge cutoff voltage, control the string charge / discharge module to charge the battery pack as a whole; in response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, control the string charge / discharge module to stop charging the battery pack as a whole, and control the individual cell charge / discharge module to charge the individual cells in the battery pack that have not reached the charging cutoff current one by one, based on monitoring data from the battery management system; in response to all individual cells in the battery pack reaching the charging cutoff current, control the individual cell charge / discharge module to stop charging the individual cells.

[0094] Specifically, the controller can perform the following operations:

[0095] 1. After the charging maintenance equipment is turned on, it will first perform a self-test, which will check each functional module of the charging maintenance equipment. After passing the self-test, the following operations will be performed.

[0096] 2. Obtain parameters such as total battery pack voltage, individual cell voltage, battery pack temperature, and battery pack current collected by the BMS, and also obtain the maximum allowable discharge current provided by the BMS.

[0097] 3. Based on the discharge current value confirmed in step 2, perform constant current discharge on the battery pack using a string charging module. Discharge stops when the total voltage of the battery pack drops to the cutoff voltage or when the voltage of at least one individual cell drops to the cutoff voltage.

[0098] 4. Set aside.

[0099] 5. Switch to single-cell discharge mode. The single-cell charge / discharge module discharges each individual cell that has not reached the discharge cutoff voltage. When the discharge cutoff voltage is reached, the discharge stops, and all individual cells reach the discharge cutoff voltage, ending the discharge process.

[0100] 6. Set aside.

[0101] 7. The battery pack is charged via a string charging / discharging module. When the total voltage of the battery pack or at least one individual cell reaches the charging cutoff voltage, constant voltage charging is switched to the charging cutoff current, and charging stops when the charging cutoff current is reached.

[0102] 8. Switch to single-cell charging mode. The single-cell charging and discharging module charges and discharges each individual cell that has not reached the charging cutoff voltage. When the charging cutoff voltage is reached, it switches to constant voltage charging. When the charging cutoff current is reached, charging stops. Once all individual cells have reached the charging cutoff current, the charging process ends.

[0103] 9. Other battery packs will complete the discharge-charge process in succession according to the above process.

[0104] The battery system provided in this application embodiment can reduce the capacity difference between individual batteries and make them more consistent by balancing the voltage differences between them, thereby restoring the performance of the battery pack and improving its lifespan.

[0105] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0106] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for battery equalization, characterized in that, Includes the following steps: The battery pack is discharged as a whole, wherein the battery pack comprises multiple string-connected individual cells; In response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, the overall discharge of the battery pack is stopped, and the individual cells in the battery pack that have not dropped to the discharge cutoff voltage are discharged one by one. In response to all individual cells in the battery pack dropping to the discharge cutoff voltage, the battery pack is charged as a whole; In response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, the overall charging of the battery pack is stopped, and the individual cells in the battery pack that have not reached the charging cutoff current are charged one by one; and In response to all individual cells in the battery pack reaching the charging cutoff current, charging of the individual cells is stopped.

2. The battery equalization method according to claim 1, characterized in that, Before discharging the entire battery pack, the method further includes: The battery management system of the battery pack obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell; and... Discharging the entire battery pack or discharging individual cells one by one includes: The maximum allowable discharge current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell. Based on the maximum allowable discharge current, the battery pack is discharged as a whole or the individual cells are discharged one by one using a constant current method.

3. The battery balancing method according to claim 1, characterized in that, Charging the battery pack as a whole includes: The battery management system of the battery pack obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell. The maximum allowable charging current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell. When the total voltage of the battery pack or the voltage of at least one of the individual cells reaches the charging cutoff voltage, the battery pack is switched to constant voltage charging mode to charge the entire battery pack according to the maximum allowable charging current.

4. The battery equalization method according to claim 1, characterized in that, Charging each individual cell in the battery pack that has not reached the charging cutoff current includes: When the voltage of a single battery cell reaches the charging cutoff voltage, the system switches to constant voltage charging mode to charge the single battery cell.

5. The battery balancing method according to claim 3 or 4, characterized in that, The method further includes: The battery management system of the battery pack obtains the real-time total voltage and real-time total current of the battery pack, as well as the real-time voltage and real-time current of each individual cell.

6. The battery equalization method according to claim 1, characterized in that, Discharging the entire battery pack involves discharging each individual cell within the pack simultaneously; charging the entire battery pack involves charging each individual cell simultaneously.

7. The battery equalization method according to claim 1, characterized in that, The discharge circuit structure used for discharging the battery pack as a whole or discharging the individual cells in the battery pack one by one is as follows: The circuit consists of a first LC filter circuit, a first-stage buck circuit, a second LC filter circuit, a second-stage boost circuit, and a load power fine-tuning circuit, all cascaded in sequence.

8. The battery equalization method according to claim 1, characterized in that, The charging circuit structure used for charging the battery pack as a whole or charging the individual cells in the battery pack one by one is as follows: The circuit consists of a common-mode inductor filter, a power factor correction circuit, an LLC half-bridge resonant circuit, a synchronous rectifier circuit, and a capacitor filter, all cascaded in sequence.

9. A battery system, comprising: One or more battery packs, the battery packs comprising multiple string-connected individual cells and a battery management system, the battery management system being used to monitor the total voltage and total current of the battery pack and the voltage and current of all individual cells; and A charging and discharging maintenance device, comprising a controller, a string charging and discharging module, and one or more individual charging and discharging modules; wherein... The string charge / discharge module is configured to perform overall charge and discharge of the battery pack. The single-cell charge / discharge module is configured to perform charging and discharging of the single-cell battery. The controller is configured to perform: The string charging and discharging module is controlled to discharge the battery pack as a whole. In response to the total voltage of the battery pack or the voltage of at least one of the individual cells dropping to the discharge cutoff voltage, the string charging and discharging module is controlled to stop discharging the battery pack as a whole, and based on the monitoring data of the battery management system, the individual cell charging and discharging module is controlled to discharge the individual cells in the battery pack that have not dropped to the discharge cutoff voltage one by one. In response to all individual cells in the battery pack dropping to the discharge cutoff voltage, the string charging and discharging module is controlled to charge the entire battery pack. In response to the total current of the battery pack or the current of at least one of the individual cells reaching the charging cutoff current, the string charging / discharging module is controlled to stop charging the entire battery pack, and based on monitoring data from the battery management system, the individual cell charging / discharging module is controlled to charge the individual cells in the battery pack that have not reached the charging cutoff current one by one; and In response to all individual cells in the battery pack reaching the charging cutoff current, the individual cell charging and discharging module is controlled to stop charging the individual cells.

10. The battery system according to claim 7, characterized in that, The controller is also configured to perform: Before controlling the string charging and discharging module to discharge the battery pack as a whole, the battery management system obtains the total voltage of the battery pack, the voltage of each individual cell in the string, and the temperature of each individual cell. The maximum allowable discharge current is determined based on the total voltage, the voltage of each individual cell in the string, and the temperature of the individual cell. Based on the maximum allowable discharge current, the string charging and discharging module is controlled to discharge the battery pack as a whole or the individual cell charging and discharging module is controlled to discharge the individual cells one by one using a constant current method.

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