Apparatus and method for energy maximization in secondary battery system

Abstract

A battery system includes a plurality of batteries including a plurality of rechargeable battery cells, the plurality of batteries selectively connected in parallel to the bus, and a bus. The battery management system monitors an operation limit of a rechargeable battery cell of the plurality of batteries, generates a signal indicating that the operation limit of the rechargeable battery cell of one of the plurality of batteries is being reached to perform a turn-back operation of the battery, and initiates the turn-back operation. The controller is configured to generate a signal for disconnecting the battery associated with the signal of the battery management system from the bus.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and interest in provisional application US 63 / 527,269, filed July 17, 2024, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to secondary battery systems, and more specifically to maximizing energy in secondary battery systems. Background Technology

[0004] Unlike primary batteries, which are typically used and discarded, secondary batteries are rechargeable batteries. Currently, lithium-ion batteries are the most commonly used secondary batteries due to their high voltage potential, safety, and commercial viability. Research into secondary batteries is ongoing due to increasing demand in electric vehicles and energy storage systems, aiming to reduce dependence on fossil fuels, decrease pollution, and protect the environment.

[0005] A battery system typically has multiple secondary batteries connected in series and / or in parallel, which are suitable for charging from a power source and discharging to a load or grid.

[0006] However, battery systems composed of these secondary batteries will be affected by aging during their service life, which manifests as capacity degradation. If all secondary batteries perform and age at the same rate, their voltage and current profiles will be identical because they are following essentially the same power curve. However, in reality, during a typical lifespan, some secondary batteries will age faster than others, resulting in different voltages and currents on some batteries compared to others with similar power curves. This can create an imbalance among the secondary batteries, which can negatively impact the system's energy capacity in a way that cannot be resolved by simply subtracting the sum of individual capacity losses from the total capacity.

[0007] Furthermore, during system operation, some secondary cells may exhibit a greater temperature increase than others due to various reasons such as uneven cooling distribution or different internal impedances. These secondary cells with temperatures exceeding the expected levels may also affect the system's energy capacity, an effect that cannot be addressed by the average temperature response during system operation.

[0008] Additionally, there are conditions that typically result from manufacturing consistency and quality variations of the battery assemblies, and that are not attributable to system design functionality, that can result in secondary batteries exhibiting different current, voltage, and temperature conditions (or variations) while operating under substantially similar environmental and operating conditions during normal operation of the battery system. These differences can result in unexpectedly reduced discharge and charge capacity and affect system performance. SUMMARY

[0009] The present disclosure describes a battery system and method for maximizing system capacity in the event of imbalanced conditions among secondary batteries in the battery system.

[0010] In one aspect, the power capacity of a battery system can be maximized by not allowing an imbalanced secondary battery in the battery system to limit the charge or discharge capacity of the battery system.

[0011] It is one objective contemplated by the present disclosure to increase the power capacity in a battery system that is limited by various imbalanced conditions of the secondary batteries in the battery system, and thereby deliver power at a higher capacity and for a relatively longer period of time.

[0012] However, the present disclosure is not limited to achieving the above-mentioned objectives, and other objectives not described herein can be achieved by a person skilled in the art based on the knowledge obtained from the following description.

[0013] According to one aspect, a battery system includes a plurality of batteries including a plurality of rechargeable battery cells, a bus to which the plurality of batteries are selectively connected in parallel, a battery management system configured to monitor operating limits of the rechargeable battery cells of the plurality of batteries, generate a signal indicating that an operating limit of one rechargeable battery cell of one of the plurality of batteries is being reached for a turnaround operation of the battery, and initiate the turnaround operation, and a controller configured to generate a signal for disconnecting the battery associated with the signal of the battery management system from the bus.

[0014] The operating limits can include at least one of a voltage limit and a temperature limit.

[0015] The battery management system can include a current limiting device for disconnecting the battery associated with the signal of the battery management system from the bus.

[0016] The controller can be configured to determine current limits of the remaining plurality of batteries on the bus, and control to allow incremental current to the remaining plurality of batteries on the bus based on the current limits of the remaining plurality of batteries not exceeding a maximum allowable current limit.

[0017] The controller can be configured to calculate an increasing current to the remaining plurality of batteries on the bus before the battery associated with the signal of the battery management system is disconnected from the bus.

[0018] The controller can be configured to generate the signal to disconnect the battery from the bus during a foldback operation.

[0019] The controller can be configured to generate the signal to disconnect the battery from the bus closer to the end of the foldback operation than the beginning of the foldback operation.

[0020] The controller can be configured to monitor the foldback operation and generate the signal to disconnect the battery from the bus near the end of the foldback operation.

[0021] The controller can be configured to determine a rate of change of current during the foldback operation for determining generation of the signal to disconnect the battery from the bus.

[0022] The battery system can include a buffer zone near the end of the foldback operation in which the rate of change of current is reduced.

[0023] According to another aspect, a method of controlling a battery system, the battery system including a plurality of batteries and a bus, the plurality of batteries including a plurality of rechargeable battery cells, the plurality of batteries being selectively connected in parallel to the bus, the method including: monitoring operational limits of the rechargeable battery cells of the plurality of batteries; generating a signal indicating that an operational limit of one rechargeable battery cell of one of the plurality of batteries is being reached for a foldback operation of the battery; initiating the foldback operation; and disconnecting the battery associated with the signal from the bus.

[0024] The method can include controlling a current limiting device to disconnect the battery from the bus.

[0025] The method can include determining current limits of the remaining plurality of batteries on the bus; and controlling to allow an increasing current to the remaining plurality of batteries on the bus based on the current limits of the remaining plurality of batteries not exceeding a maximum allowable current limit.

[0026] The method can include calculating an increasing current to the remaining plurality of batteries on the bus before the battery is disconnected from the bus.

[0027] The method can include disconnecting the battery from the bus during a foldback operation.

[0028] The method can include disconnecting the battery from the bus closer to the end of the foldback operation than the beginning of the foldback operation.

[0029] The method can include monitoring the turn around operation; and disconnecting the battery from the bus near the end of the turn around operation.

[0030] The method can include determining a rate of change of current during the turn around operation for determining to disconnect the battery from the bus.

[0031] The method can include determining a rate of change at a buffer zone near the end of the turn around operation, in which the rate of change of current decreases.

[0032] According to another aspect, a non-transitory computer readable medium comprising computer executable instructions stored therein, which, when executed by one or more processors, cause the one or more processors to perform a method of controlling a battery system, the battery system comprising a plurality of batteries and a bus, the plurality of batteries comprising a plurality of rechargeable battery cells, the plurality of batteries being selectively connected in parallel to the bus. The method comprises: monitoring an operational limit of a rechargeable battery cell in the plurality of batteries; generating a signal indicating that an operational limit of a rechargeable battery cell of a battery among the plurality of batteries is being reached for a turn around operation of the battery; initiating the turn around operation; and disconnecting the battery associated with the signal from the bus.

[0033] It should be noted that the technical effects obtainable by the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood by those skilled in the art from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings illustrate exemplary aspects of the present disclosure and together with the following detailed description, provide further understanding of the technical spirit of the present disclosure. However, the present disclosure should not be construed as being limited to the accompanying drawings.

[0035] Figure 1 is a schematic diagram illustrating an exemplary battery system.

[0036] Figure 2 is a graph illustrating time series of voltages, states of charge (SOC), and charging currents of battery cells Cell 1-4 connected in series.

[0037] Figure 3 is a schematic diagram illustrating a battery system according to an aspect of the present disclosure.

[0038] Figure 4 is a schematic diagram illustrating a battery module connection and disconnection structure of a battery system according to an aspect of the present disclosure in more detail.

[0039] Figure 5 is a schematic diagram illustrating a control system according to an aspect of the present disclosure.

[0040] Figure 6 FIG. 9 is a flowchart illustrating a method for controlling a plurality of modules by a controller according to an aspect of the present disclosure.

[0041] Figure 7 FIG. 10 is a diagram illustrating a module disconnection timing performed by a controller according to an aspect of the present disclosure.

[0042] Figure 8 FIG. 14 is a flowchart illustrating another method for controlling a plurality of battery modules by a controller according to another aspect of the present disclosure.

[0043] Figure 9 FIG. 15 is a diagram illustrating a module disconnection timing performed by a controller according to another aspect of the present disclosure.

[0044] Figure 10 FIG. 16 is a flowchart illustrating a method performed by a controller to reconnect a disconnected module or modules with a bus according to an aspect of the present disclosure. DETAILED DESCRIPTION

[0045] The present disclosure can vary in various ways and have various aspects, and the specific aspects disclosed in detail herein serve to facilitate the understanding of the present disclosure for those skilled in the art.

[0046] Therefore, it should be understood that the present disclosure is not intended to be limited to the particular aspects disclosed, but is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

[0047] In the present application, it should be understood that terms such as "include" or "have" are intended to indicate that the specifications described in the specification include the features, numbers, steps, operations, components, parts or combinations thereof, and they do not exclude the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.

[0048] Figure 1 FIG. 1 is a schematic diagram illustrating an exemplary battery system. The battery system 100 includes a battery management system 10 and a battery module 20 including a plurality of rechargeable battery cells (secondary battery) Cell 1-4 connected in series. The battery module can be a package including a plurality of battery cells or an assembly of only battery cells. The exemplary battery system 100 is introduced to describe a turn-back operation of a battery system.

[0049] Battery management systems, or BMSs, are found in electric vehicles, energy storage systems, and electronic devices to manage one or more rechargeable battery cells. The battery management system monitors key data such as voltage, temperature, and current of the battery cells. The battery cells are typically monitored at all times during charging or discharging. The battery management system typically includes a controller and various sensors that sense the voltage, temperature, and current of the battery cells, which are then signaled to the controller. The controller can then calculate the state of charge (SOC) and state of health (SOH) of the one or more battery cells, among other things.

[0050] In the battery system 100, the battery management system 10 monitors various operating states of the battery cells Cell 1-4. For example, the battery management system 10 can dynamically calculate the charge and discharge current states of the battery cells Cell 1-4 based on the operating states of the individual cells and have the ability to control the current that is pushed or pulled through the series-connected battery cells Cell 1-4. Among the charge and discharge current states of the battery cells Cell 1-4, the charge current limit of the battery cells Cell 1-4 is a function of the maximum cell voltage and / or maximum / minimum temperature of any one of the series-connected battery cells Cell 1-4, while the discharge current limit of the battery cells Cell 1-4 is a function of the minimum cell voltage and / or maximum / minimum temperature of any one of the series-connected battery cells Cell 1-4. Thus, during energy storage charging operations, the maximum voltage limit or maximum / minimum temperature limit of an individual cell can limit the current allowed in the battery cells Cell 1-4. Conversely, during energy storage discharging operations, the minimum cell voltage and / or maximum / minimum temperature of an individual cell can limit the current discharged by the battery cells Cell 1-4.

[0051] When the current through the battery cells Cell 1-4 is reduced due to the current limit, this is referred to as “foldback.” During foldback, the battery management system 10 reduces the current through the battery cells Cell 1-4 in proportion to the extent that the voltage and / or temperature of any one cell approaches its maximum / minimum value. This approach is to ensure the safety of the battery cells Cell 1-4 in the battery system 100. Thus, the charge current limit or discharge current limit of an individual cell can affect the charge or discharge power capacity of the battery system 10.

[0052] Figure 2 Further shown is a foldback operation. Figure 2is a graph showing time series of voltages, state of charge (SOC), and charging current of battery cells Cell 1-4 connected in series. Assume that cell Cell 2 has a higher SOC than cells Cell 1, 3, and 4, which means that, all other conditions being the same, the voltage of cell Cell 2 will be higher than the other three cells Cell 1, 3, and 4. When the battery management system 10 supplies a charging current to cells Cell 1-4, since these cells are connected in series, the current will flow identically through each of these cells, and correspondingly, the respective SOC of cells Cell 1-4 will rise. At some point in time, the voltage of cell Cell 2 will rise to a point close to its maximum voltage value, while the voltages of the other cells Cell 1, 3, and 4 can not be so close, as shown in Figure 2 The battery management system 10, which monitors the individual cell voltages, will determine that the voltage of cell Cell 2 is approaching its maximum voltage value, and will initiate a foldback operation that begins to reduce the charging current to cells Cell 1-4 connected in series. As a result, the charging current flowing through cells Cell 1-4 will be reduced, and in turn, the current through each of cells Cell 1-4 and the rate of increase of their SOC will be reduced.

[0053] At the point where the voltage of cell Cell 2 reaches its maximum voltage value, the battery management system 10 stops the charging process, and the charging current will become zero. At this time, cell Cell 2 is fully charged, while cells Cell 1, 3, and 4 are not fully charged. Therefore, the total energy stored will be less than the total energy in the case where all cells Cell 1, 2, 3, and 4 are fully charged. That is, the total energy stored will be:

[0054] where, is the energy capacity that can be stored in a cell, is the difference between the state of charge of cell Cell 2 and the other three cells Cell 1, 3, and 4 (assuming the other three SOC are the same).

[0055] Figure 3is a schematic diagram illustrating a battery system according to one aspect of the disclosure. The battery system 200 includes a battery management system 50 and a plurality of battery modules MOD 1-3, which include a plurality of battery cells Cell 1-4 connected in series. The battery modules can be a package of battery cells or just an assembly. While three battery modules are shown, it should be understood that there can be fewer or more than three battery modules. A battery pack can refer to a collection of modules / multiple modules, or in some cases, a collection of cells without any individual modules. A rack can refer to a collection of modules / multiple modules, or in some cases, a collection of cells without any individual modules. The plurality of battery modules MOD 1-3 are selectively connected in parallel to a bus 60. The bus 60 can include a positive bus 62 and a negative bus 64. The plurality of battery modules MOD 1-3 can be selectively connected to the bus 60 through current limiting devices 70. The current limiting devices can be relays, contactors, switches, semiconductor switching devices, or the like. In this aspect, the positive terminals of the battery modules are connected to the positive bus 62, and the negative terminals of the battery modules are selectively connected to the negative bus 64 through the current limiting devices. However, in other aspects, the positive terminals of the battery modules can be selectively connected to the positive bus, or both the positive and negative terminals of the battery modules can be selectively connected to the respective positive and negative buses.

[0056] The battery management system 50 is configured to control the current limiting devices 70 to disconnect the battery modules from the bus 60 based on a signal of a controller 80. The controller 80 can be part of the battery management system 50 as shown in Figure 3 or the controller can be external to the battery management system 50. The battery management system 50 is configured to monitor an operating limit of one or more battery cells in the battery modules, generate a signal when the battery cells are reaching the operating limit requiring a foldback operation, and initiate the foldback operation. The controller 80 is configured to generate a signal for disconnecting the battery modules associated with the signal of the battery management system 50 from the bus 60 using the current limiting devices 70. The operating limit of the battery cells can be a voltage limit, a temperature limit, or both a voltage limit and a temperature limit of the battery cells during a charging or discharging operation.

[0057] The operation of the battery system 200 will now be described. Assume that the cell Cell 2 of module MOD 2 has a higher SOC than the cells Cell 1, 3 and 4 of module MOD 2 and all other cells in modules MOD 1 and 3. This means that, all other conditions being equal, the voltage of MOD 2 / Cell 2 will be higher than the voltage of the other eleven cells. When modules MOD 1-3 are being charged by the battery management system 50, the current flows approximately equally through each cell (assuming they are approximately the same capacity, age and temperature). Therefore, each of their SOCs will rise at approximately the same rate. At some point, the voltage of MOD 2 / Cell 2 will rise to a point very close to its maximum recommended voltage, while the voltage of the other cells will not be so close. The battery management system 50, which monitors the individual cell voltages, will determine that the voltage of MOD 2 / Cell 2 is approaching the maximum voltage value, and will initiate a foldback operation to start reducing the charging current to all modules MOD 1, 2 and 3.

[0058] If no interruption is made, the current in each module will decrease, so the current of each cell will also decrease, and the rate of rise of their SOCs will decrease with it. Although the condition of modules MOD 1 and 3 is well within the operating range, the current to modules MOD 1, 2 and 3 will depend on the condition of the cell closest to its maximum voltage limit, i.e. MOD 2 / Cell 2.

[0059] This approach is to ensure the safety of the battery cells in the battery system 200, so that no cell exceeds its safety limit. However, this can severely reduce the amount of energy that the battery system is able to store and deliver to a load or grid. In this example, the amount of total energy not stored when MOD 2 / Cell 2 stops the charging process is:

[0060] where ΔSOC1to ΔSOC 11 is the difference in SOC between the highest charged cell and the other eleven cells. In this example, if the SOC difference is only 1% on average, the total lost charging energy is about 10% of the total system energy.

[0061] While the operating limit described so far is the voltage limit, a similar situation can occur when any of these cells experiences a higher temperature than the others and if that temperature approaches the absolute maximum operating condition of the cell. For example, if one cell reaches its maximum temperature limit while the others have not during charging or discharging, a foldback operation can be initiated to reduce the current in modules MOD 1, 2 and 3, thereby limiting the total power capacity of the battery system when all cells reach the operating limit at the same time.

[0062] according to Figure 3 With proper configuration, battery system 200 can be configured to extend the time during which discharge or charging power remains within a desired level. This time extension can be applied to any battery system at any age / degradation, i.e., not only to battery systems at the beginning of their life (BOL), but also to battery systems at any point in their lifespan.

[0063] As an example, during discharge, the desired level could be a design standard where specifications require maintaining a specific power output. In another example, at many storage sites, contractual terms may require the battery system to operate within a specified power output throughout the discharge period. That is, any point in time where the battery system's power output has subsequently fallen below the specified power output, after a reduction in the battery system's power due to one or more modules entering foldback operation, will not be considered compliant with the contractual terms. The same operating standard applies during battery system charging, where the contract stipulates that the power input should be maintained within a specified power level, taking into account situations where the power output falls below that level due to module foldback.

[0064] The battery system 200 can be configured such that when the battery management system 50 encounters the operating limit of the MOD / Cell during charging or discharging and needs to perform a turnback operation, the controller 80 is configured to monitor the turnback operation of the module with the MOD / Cell that is reaching the operating limit, disconnect the module from the bus 60, and allow the battery management system 50 to continue charging or discharging the remaining modules with consideration for the desired power level.

[0065] Since the modules are connected in parallel to each other on bus 60, the current associated with each module will be a relatively constant ratio to the total bus current. Assuming each module has the same current, the bus current will be:

[0066] in, This is the number of modules connected to the bus.

[0067] Therefore, in this example, the bus current limit of the battery system 200 Simply multiply the minimum current limit of any module by the number of modules connected to the bus.

[0068]

[0069] During any charging or discharging operation, the battery management system 50 can calculate the current limit of each module. What it should be can depend on multiple variables. For example, the variables can include its individual cell current limit, its individual cell temperature, and individual cell voltage. The current limit gradually decreases as the control parameter approaches its absolute limit.

[0070]

[0071] When the battery management system 50 adjusts the current limit of the bus to be less than its maximum allowable current , then it is referred to as “going into a foldback”. The current limit is dominated by the minimum of the current limits among the modules. Therefore, any module that goes into foldback will start decreasing . By setting the current limit of the bus to the decreasing , the battery management system ensures that the current of each individual module does not exceed the adjusted current limit.

[0072] However, when the adjusted current limit is reduced to a point close to or equal to the operating current associated with the desired power level of the battery system, the battery management system 50 will disconnect the modules that are causing the foldback operation from the bus 60, and the current that was previously flowing through all the modules before going into foldback will be distributed to the remaining modules that are connected to the bus 60.

[0073] The redistribution of current will increase the current of each module, and as more modules are disconnected, more current will be redistributed. The battery management system 50 should ensure that it does not disconnect any additional modules if the redistributed current will exceed the current limit of the remaining modules.

[0074] To maintain the same power, the increase in current of each module that is still connected to the bus will be:

[0075] where, and is the number of connected modules before and after one or more modules are disconnected.

[0076] This formula will be referred to as the “current formula”.

[0077] The power delivered or absorbed by the battery system and each module is calculated by the following equation: where,

[0078] ​The battery management system 50 can safely reconnect the disconnected module(s) to the bus 60 at the appropriate time, such as when the direction of bus current changes from discharge to charge or vice versa, in order to keep the battery system 200 operating at maximum availability.

[0079] Figure 4 is a schematic diagram showing a battery module connection and disconnection structure of a battery system according to one aspect of the disclosure in more detail.

[0080] Reference Figure 4 The battery module is connected to the bus 60 by a current limiting device 70. The current limiting device 70 includes a high side contactor 72 that selectively connects the positive terminal of the module to the positive bus 62 and a low side contactor 74 that selectively connects the negative terminal of the module to the negative bus 64. While this aspect shows a high side contactor and a low side contactor, the current limiting device is not limited to this configuration. For example, the current limiting device can have only a high side contactor or the current limiting device can have only a low side contactor. The current limiting device generally has a configuration suitable for selectively connecting the module to the bus and disconnecting the module from the bus. The battery management system 50 controls the high side contactor 72 and the low side contactor 74 of the current limiting device 70. When the battery management system 50 encounters an operating limit of the MOD / Cell during charging or discharging, the battery management system 50 sends a signal to the controller 80 indicating that the operating limit is being reached for a turn around operation. Based on the control method, as will be further described below, the controller 80 sends a signal to the battery management system 50 to disconnect the module having the MOD / Cell reaching the operating limit from the bus 60. The battery management system 50 sends a signal to the current limiting device 70, which disconnects the module from the bus 60. In an alternative configuration, the controller 80 sends a signal to the current limiting device 70 to disconnect the module from the bus.

[0081] To maximize the achievable capacity of the battery system, the timing of the module disconnection needs to be considered. For example, disconnecting one or more modules too early reduces the chargeable or dischargeable energy, while disconnecting one or more modules too late reduces the power capability of the battery system, thereby failing to maximize the power capability of the battery system. Accordingly, the control method of the controller provides the logic behind when the battery management system disconnects the limiting module(s) to maximize the battery system.

[0082] Figure 5 is a schematic diagram showing a control system according to one aspect of the disclosure. According to Figure 5The controller 80 is coupled to a memory 90. The memory 90 stores computer executable instructions that, when executed by the controller 80, cause the controller to perform the control method that will be described below. The controller 80 and memory 90 can be part of the BMS, or it can be a separate control system. In the case where the controller is separate from the BMS, the controller 80 can interface with the BMS by wired or wireless means. When the BMS encounters a run limit of a MOD / Cell during charging or discharging, the battery management system 50 sends a signal to the controller 80 indicating that a run limit is being reached for a foldback operation and initiates the foldback operation. The controller 80 can receive the adjusted current limit applied by the battery management system to the module continuously or at intervals. The controller 80 uses this information to determine when to disconnect the module with the MOD / Cell that is reaching a run limit based on the control method stored in the memory 90. When this determination is made, the controller can send a signal to the BMS to disconnect the module from the bus, or alternatively, the controller can send a signal to the current limiting device 70 to disconnect the module from the bus. See Figure 4 .

[0083] An example of the control method stored in the memory 90 will now be described.

[0084] Figure 6 is a flowchart illustrating a method for controlling a plurality of battery modules by a controller according to one aspect of the present disclosure. Figure 7 is a graph illustrating module disconnect timing performed by a controller according to one aspect of the present disclosure. Reference is made to Figure 6 and Figure 7 In step S100, the battery management system monitors the cells of a plurality of battery modules connected to a bus of a battery system during a charging or discharging operation. In step S110, the battery management system determines whether a run limit of a MOD / Cell of the plurality of battery modules is being reached. If the battery management system determines that the cells of the plurality of battery modules are operating within the run limit, the battery management system returns to step S100 to monitor the cells of the plurality of battery modules. Otherwise, if the battery management system determines that the MOD / Cell of the plurality of battery modules is reaching the run limit, in step S120, the battery management system sends a signal to the controller indicating that a run limit is being reached for a foldback operation.

[0085] In step S130, the battery management system initiates the foldback operation. In step 140, the controller monitors the foldback operation and, in particular, monitors whether the MOD / Cell reaching the operating limit has reached the operating current of the battery system. When the controller determines that the MOD / Cell reaching the operating limit has reached the operating current of the battery system, in step S150, the controller determines whether it can disconnect the module with the MOD / Cell reaching the operating limit from the bus and allow the remaining connected modules to continue the charging or discharging operation without violating their current limits. The controller will determine the maximum allowable current limits of the other connected modules on the bus. If the controller determines that the maximum allowable current limits of the other connected modules will not be violated, in step S160, the controller sends a signal to the battery management system to disconnect the module with the MOD / Cell reaching the operating limit from the bus. During the foldback operation, the first limiting module is disconnected at point B in Figure 7 The battery management system sends a signal to the current limiting device to disconnect the module from the bus. Alternatively, the controller sends a signal to the current limiting device to disconnect the module from the bus. In step S170, the battery management system distributes the total current in the bus across the remaining modules, for example, according to the current formula described above, after the module with the MOD / Cell reaching the operating limit is disconnected. The battery management system returns to step S100 to monitor the cells of the remaining modules connected to the bus.

[0086] Otherwise, in step S150, if the controller determines that disconnecting the module with the MOD / Cell reaching the operating limit will violate the maximum allowable current limits of the remaining connected modules, in step S180, the controller sends a signal to the battery management system to not disconnect the module with the MOD / Cell reaching the operating limit. Alternatively, the controller can not send a signal at all and, as a result, the battery management system does not disconnect the module. Alternatively, the controller does not send a signal to the current limiting device to disconnect the module. The battery management system then terminates the charging or discharging operation when the foldback operation is complete.

[0087] If the post-disconnection current in each of the remaining modules is less than the maximum allowable current limit of the remaining modules, during the foldback operation, the first limiting module is disconnected at point B in Figure 6 The controller sends a signal indicating that the first limiting module can be disconnected, where the battery management system sends a signal to the current limiting device of the first limiting module to disconnect.

[0088] After the first limiting module is disconnected, the operating current of each module is incremented (S170).

[0089] Referring toFigure 7 , assuming that the second module thereafter also reaches its operating limit like the first limiting module, the battery management system sends a signal to the controller indicating that a turn-back operation should be performed. During the turn-back operation, when the current limit of the second limiting module reaches the incremented operating current at point B', the second limiting module is disconnected from the bus at point B'. The process continues to repeat until at point B''', where the disconnection of another module would cause the operating current to exceed the maximum allowable current limit of all remaining modules. In this case, no more modules are disconnected (S180) and the charging or discharging operation ends.

[0090] Figure 8 is a flowchart illustrating another method for controlling a plurality of battery modules by a controller according to another aspect of the present disclosure. Figure 9 is a graph illustrating module disconnection timing performed by a controller according to another aspect of the present disclosure.

[0091] Figure 9 The graph of illustrates performing a turn-back operation on the plurality of battery modules beyond the operating current of the plurality of battery modules. Technically, the battery system can operate with modules connected to the bus until the current limit of the module reaches zero (see Figure 9 point C in ). In this operation, when the MOD / Cell of the plurality of battery modules is entering a turn-back operation, the operating current limit of the battery system does not change even if the current limit of the MOD / Cell is reduced or reaches zero. The MOD / Cell participates in charging or discharging until its current limit reaches or approaches zero. This is to ensure that the energy from the MOD / Cell under the turn-back operation is used up until its current limit reaches or approaches zero and thus maximizes the overall capacity of the battery system.

[0092] Referring to Figure 8 and Figure 9 , in step S200, the battery management system monitors the cells of the plurality of battery modules connected to the bus of the battery system during a charging or discharging operation. In step S210, the battery management system determines whether the operating limit of the MOD / Cell of the plurality of battery modules is being reached. If the battery management system determines that the cells of the plurality of battery modules are operating within the operating limit, the battery management system returns to step S200 to monitor the cells of the plurality of battery modules. Otherwise, if the battery management system determines that the MOD / Cell of the plurality of battery modules is reaching the operating limit, in step S220, the battery management system sends a signal to the controller indicating that the operating limit is being reached for a turn-back operation.

[0093] In step S230, the battery management system initiates the foldback operation. In step S240, the controller monitors the foldback operation and, in particular, monitors whether the MOD / Cell reaching the operating limit is reaching the zero current limit threshold of the battery system.

[0094] When the controller determines that the MOD / Cell reaching the operating limit is reaching the zero current limit threshold of the battery system, in step S250, the controller determines whether it can disconnect the module with the MOD / Cell reaching the operating limit from the bus and allow the remaining connected modules to continue the charging or discharging operation without violating their current limits. The controller will determine the maximum allowable current limits of the other connected modules on the bus. If the controller determines that the maximum allowable current limits of the other connected modules will not be violated, in step S260, the controller sends a signal to the battery management system to disconnect the module with the MOD / Cell reaching the operating limit from the bus. During the foldback operation, the first limiting module is disconnected at point C in Figure 9 The battery management system sends a signal to the current limiting device to disconnect the module from the bus. Alternatively, the controller sends a signal to the current limiting device to disconnect the module from the bus. In step S270, the battery management system distributes the total current in the bus across the remaining modules, for example, according to the current formula described above, after the module with the MOD / Cell reaching the operating limit is disconnected. The battery management system returns to step S200 to monitor the cells of the remaining modules connected to the bus.

[0095] Otherwise, in step S250, if the controller determines that disconnecting the module with the MOD / Cell reaching the operating limit will violate the maximum allowable current limits of the remaining connected modules, in step S280, the controller sends a signal to the battery management system to not disconnect the module with the MOD / Cell reaching the operating limit. Alternatively, the controller can not send a signal at all and, as a result, the battery management system does not disconnect the module. Alternatively, the controller does not send a signal to the current limiting device to disconnect the module. The battery management system then terminates the charging or discharging operation when the foldback operation is complete.

[0096] Figure 9 The illustration of FIG. 1 assumes that the foldback operation is performed until the current limit of the MOD / Cell of the limiting module reaches the zero current limit threshold. However, in various cases, at that time, the operating conditions in the plurality of modules connected to the bus can be at their critical levels and the battery system can need to take immediate action because the battery system can not be able to operate at the absolute zero current limit. According to another aspect, the foldback operation can be performed until a point before point C is reached before the limiting module is disconnected from the bus.

[0097] like Figure 9 As shown, a foldback operation can be performed until the current limit of the limiting module is between point D and point C before the limiting module is disconnected from the bus. The controller monitors the foldback operation, and in particular, monitors the current limit until the MOD / Cell of the limiting module reaches the point where the current limit is between point D and point C. When the controller determines that the MOD / Cell reaching the operating limit is reaching the current limit between point D and point C, the controller determines whether it can disconnect the limiting module from the bus and allow the remaining connected modules to continue charging or discharging without violating their current limits. The controller will determine the maximum permissible current limit of the other connected modules on the bus. If the controller determines that the maximum permissible current limit of the other connected modules will not be violated, the controller sends a signal to the battery management system to disconnect the module with the MOD / Cell reaching the operating limit from the bus. During the foldback operation, the limiting module is disconnected at the point between point D and point C. The battery management system sends a signal to the current limiting device to disconnect the module from the bus. Alternatively, the controller sends a signal to the current limiting device to disconnect the module from the bus. The battery management system, for example, distributes the total current in the bus across the remaining modules after a module with a MOD / Cell that has reached its operating limit is disconnected, according to the current formula described above. The battery management system then continues to monitor the individual cells of the remaining modules connected to the bus.

[0098] Otherwise, if the controller determines that disconnecting a module with a MOD / Cell that has reached its operating limit would violate the maximum permissible current limit of the remaining connected modules, the controller signals the battery management system not to disconnect the module with the MOD / Cell that has reached its operating limit. Alternatively, the controller may not send a signal at all, and thus the battery management system will not disconnect the module. Alternatively, the controller may not send a signal to the current limiting device to disconnect the module.

[0099] exist Figure 9 In the example shown, multiple modules are disconnected until the remaining modules can no longer support charging or discharging operations. According to Figure 9 This point is D, where any further disconnection will cause the remaining module to exceed the maximum permissible current limit and will terminate the charging or discharging operation.

[0100] It should be noted that, although Figure 9The limit module is shown disconnected between point D and point C (where point D is close to the absolute zero current limit), but in some design criteria the limit module can be disconnected further from the absolute zero current limit. For example, the limit module can be disconnected between point B and point D. In another design criteria, the limit module can be disconnected between point A and point B.

[0101] In the case where the limit module is disconnected between point D and point C, there can be enough time to disconnect the module before it reaches its zero current limit threshold. According to this aspect, the controller can monitor the rate of change of the current limit over time. The rate of change of the current limit can allow the controller to predict when the current limit will reach the absolute zero current limit, and thus determine when the limit module needs to be disconnected from the bus.

[0102] As shown in Figure 9 , a buffer zone is constructed above the absolute zero current limit, in which the rate of change of the current limit gradually decreases as the current limit approaches its absolute zero limit. An example of a gradual rate of change over time can be seen in Figure 2 , which corresponds to a charging operation. As can be seen, the rate of change of the charging current over time is gradual as the charging current approaches the absolute maximum voltage.

[0103] Referring to Figure 9 , the controller monitors the rate of change of the current limit until the rate of change is equal to or less than a predetermined rate of change. The controller will then determine that the limit module is reaching the absolute zero current limit (which will reduce the ability of the battery system to operate at its capacity), and disconnect the limit module from the bus.

[0104] Figure 10 is a flowchart showing a method performed by a controller to reconnect one or more modules that are disconnected from a bus, according to one aspect of the disclosure.

[0105] In step 300, the controller determines, based on design criteria, whether a charging or discharging operation being performed by the battery system is greater than a predetermined current. If a charging or discharging operation is being performed, in step 310 the controller determines whether the current through the module has changed direction since the one or more modules were disconnected. If the current direction through the module has not changed, the controller returns to step 300 to monitor the charging or discharging operation of the battery system.

[0106] Otherwise, the controller proceeds to step 330, in which the controller determines, based on design criteria, whether the difference between the voltage of the module and the bus voltage is less than a predetermined voltage. If the difference in voltage is less than the predetermined voltage, the controller proceeds to step 340, in which the controller connects the one or more modules that are disconnected to the bus. Otherwise, the controller returns to step 300.

[0107] Returning to step 300, if the charging or discharging operation being performed by the battery system is less than the predetermined current, the controller proceeds to step 320, where the controller determines whether the current of the charging or discharging operation has been less than the predetermined current for a predetermined time based on the design criteria. If the current has been less than the predetermined current for the predetermined time, the controller proceeds to step 330 to perform the method described above. Otherwise, the controller returns to step 300.

[0108] Although the methods have been described above based on flowcharts in which steps or blocks are listed in order, the steps of the present disclosure are not limited to a particular order, and a particular step can be performed at a different step or in a different order or simultaneously with respect to what is described above. Furthermore, it will be understood by those of ordinary skill in the art that the steps of the flowcharts are not exclusive, and another step can be included in the flowcharts or one or more steps in the flowcharts can be deleted without affecting the scope of the present disclosure.

[0109] When aspects of the present disclosure are implemented by software, the above-described methods can be implemented by instructions stored in a memory and executed by a controller. The memory can be installed inside or outside the controller, and can be connected to the controller via various well-known means. The controller can include an application specific integrated circuit (ASIC), other chipsets, logic circuits, and / or electronic processors. The memory can include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

[0110] In the above, the present disclosure has been described in greater detail through the accompanying drawings and aspects. However, the configurations described in the drawings or aspects in the specification are only aspects of the present disclosure and do not represent all technical ideas of the present disclosure. Therefore, it should be understood that various equivalents and modifications to them can exist at the time of filing the present application, and these equivalents and modifications are encompassed by the claims.

Claims

1. A battery system, comprising: Multiple batteries, wherein the multiple batteries include multiple rechargeable battery cells; A bus, wherein the plurality of batteries are selectively connected in parallel to the bus; A battery management system configured to monitor the operating limits of the rechargeable battery cells of the plurality of batteries, generate a signal indicating that the operating limit of one rechargeable battery cell of one of the plurality of batteries is being reached to perform a battery foldback operation, and initiate the foldback operation. as well as A controller configured to generate a signal for disconnecting the battery associated with the signal of the battery management system from the bus.

2. The battery system according to claim 1, wherein, The operating limits include at least one of voltage limits and temperature limits.

3. The battery system of claim 1, further comprising a current-limiting device for disconnecting the battery associated with the signal of the battery management system from the bus.

4. The battery system according to claim 1, wherein, The controller is configured to: Determine the current limits of the remaining multiple batteries on the bus; as well as Control is performed based on the fact that the current limit of the remaining multiple batteries does not exceed the maximum permissible current limit to allow increasing current to the remaining multiple batteries on the bus.

5. The battery system according to claim 4, wherein, The controller is configured to calculate the incremental current to the remaining plurality of batteries on the bus before the battery associated with the signal of the battery management system is disconnected from the bus.

6. The battery system according to claim 1, wherein, The controller is configured to generate a signal for disconnecting the battery from the bus during the foldback operation.

7. The battery system according to claim 6, wherein, The controller is configured to generate a signal to disconnect the battery from the bus closer to the end of the foldback operation than to the beginning of the foldback operation.

8. The battery system according to claim 7, wherein, The controller is configured to monitor the foldback operation and generate a signal to disconnect the battery from the bus near the end of the foldback operation.

9. The battery system according to claim 8, wherein, The controller is configured to determine the rate of change of current during the foldback operation in order to determine the generation of a signal for disconnecting the battery from the bus.

10. The battery system of claim 9, further comprising a buffer near the end of the foldback operation, in which the rate of change of current decreases.

11. A method for controlling a battery system, the battery system comprising a plurality of batteries and a bus, the plurality of batteries comprising a plurality of rechargeable battery cells, the plurality of batteries being selectively connected in parallel to the bus, the method comprising: Monitor the operational limits of the individual rechargeable battery cells among the plurality of batteries; A signal is generated indicating that the operating limit of one of the rechargeable battery cells in one of the plurality of batteries is being reached, so that the battery can be folded back. Initiate the reversal operation; as well as Disconnect the battery associated with the signal from the bus.

12. The method of claim 11, further comprising controlling a current limiting device to disconnect the battery from the bus.

13. The method of claim 11, comprising: Determine the current limits of the remaining multiple batteries on the bus; as well as Control is performed based on the fact that the current limit of the remaining multiple batteries does not exceed the maximum permissible current limit to allow increasing current to the remaining multiple batteries on the bus.

14. The method of claim 13, further comprising calculating the incremental current to the remaining plurality of batteries on the bus before disconnecting the battery from the bus.

15. The method of claim 11, further comprising disconnecting the battery from the bus during the foldback operation.

16. The method of claim 15, further comprising disconnecting the battery from the bus closer to the end of the foldback operation than to the beginning of the foldback operation.

17. The method of claim 16, comprising: Monitor the aforementioned turnaround operation; as well as The battery is disconnected from the bus near the end of the foldback operation.

18. The method of claim 17, further comprising determining the rate of change of current during the foldback operation to determine whether to disconnect the battery from the bus.

19. The method of claim 18, further comprising determining the rate of change at a buffer near the end of the turnaround operation, in which the rate of change of current decreases.

20. A non-transitory computer-readable medium comprising computer-executable instructions stored therein, the computer-executable instructions, when executed by one or more processors, causing the one or more processors to perform a method of controlling a battery system, the battery system comprising a plurality of batteries and a bus, the plurality of batteries comprising a plurality of rechargeable battery cells, the plurality of batteries being selectively connected in parallel to the bus, the method comprising: Monitor the operational limits of the individual rechargeable battery cells among the plurality of batteries; A signal is generated indicating that the operating limit of one of the rechargeable battery cells in one of the plurality of batteries is being reached, so that the battery can be folded back. Initiate the reversal operation; as well as Disconnect the battery associated with the signal from the bus.

Images