Battery equilibration between modules using minimum cell voltage for selecting battery sub-module for supplying a power to load

Abstract

To provide a new technique of detecting, relaxing, and / or avoiding a problem related to a battery in a whole electrically-driven aircraft (or the other transportation means).SOLUTION: The present invention relates to each battery sub-module in a plurality of battery sub-modules, where a voltage related to a cell in each battery sub-module is received, and each battery sub-module in the plurality of battery sub-modules contains a plurality of cells. Each battery sub-module is selected based at least in part on the received voltages, and a set of one or more loads, which draws power from the selected battery sub-module and is not powered by any other battery sub-module in the plurality of battery sub-modules, is configured so that the set of loads at least temporarily does not draw power from the selected battery sub-module.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] New types of aircraft are being developed that are all-electric. Due to differences in how batteries tend to be designed (e.g., aircraft batteries must satisfy the Federal Aviation Administration, which may have greater concerns about single points of failure and degree of redundancy compared to the National Highway Traffic Safety Administration) and / or how the vehicles are used, there may be some battery-related issues that were not previously exposed with respect to electric vehicles but are exposed as all-electric aircraft are developed. New techniques for detecting, mitigating, and / or avoiding such battery-related issues in all-electric aircraft (or other vehicles) would be desirable.

[0002] Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0003] [Figure 1] 1 is a flow chart illustrating one embodiment of a process for inter-module balancing. [Diagram 2] 1 is a diagram illustrating one embodiment of a battery system including battery submodules connected in series with each battery submodule including cells connected in series with each other. [Figure 3A] 1 is a diagram showing one embodiment of an uncapped battery submodule. [Figure 3B] 1 is a diagram showing one embodiment of a covered battery submodule. [Figure 4] 11 is a flow chart illustrating an embodiment of a process for inter-module balancing that includes turning off electronics. [Diagram 5]1 is a flow chart illustrating an embodiment of a process for inter-module balancing that includes configuring a set of electronics to draw power from a non-selected battery sub-module. [Figure 6] 1 is a diagram showing an example of cell voltages in a battery submodule in a battery system. [Figure 7] 1 is a flow chart illustrating one embodiment of a process for selecting battery sub-modules using voltage thresholds. [Figure 8] 10 is a flow chart illustrating one embodiment of a process for selecting a battery sub-module using a voltage threshold and a maximum value of minimum cell voltages. [Figure 9] 1 is a flow chart illustrating an embodiment of a process for selecting a battery sub-module using a voltage threshold and a maximum value of maximum cell voltage. [Figure 10A] 1 is a diagram illustrating an embodiment in which balancing is performed both before and after charging. [Figure 10B] 1 is a diagram illustrating an embodiment in which balancing is performed only after charging. [Figure 11] 1 is a flow chart illustrating an embodiment of a process for determining when to perform balancing on a charging process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0004] The present invention may be implemented in numerous ways, including as a process, an apparatus, a system, a composition, a computer program product embodied on a computer-readable storage medium, and / or as a processor, such as a processor configured to execute instructions stored in and / or provided by a memory coupled to the processor. These implementations, or any other form the present invention may take, may be referred to herein as techniques. In general, the order of steps of a disclosed process may be varied within the scope of the present invention. Unless otherwise noted, components such as a processor or memory described as configured to perform a task may be implemented as general components temporarily configured to perform the task at a given time, or as specific components manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions.

[0005] A detailed description of one or more embodiments of the present invention is provided below along with accompanying figures illustrating the principles of the present invention. While the present invention will be described in connection with such embodiments, the present invention is not limited to any of the embodiments. The scope of the present invention is limited only by the claims, and the present invention encompasses numerous alternatives, modifications, and equivalents. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. These details are provided for the purpose of example, and the present invention may be practiced according to the claims without some or all of these specific details. For the purposes of clarity, technical materials known in the art related to the present invention have not been described in detail so as not to unnecessarily obscure the present invention.

[0006] Various examples of techniques for balancing battery sub-modules in a battery system are described herein. In some examples, the balancing is performed by receiving, for each battery sub-module in a plurality of battery sub-modules (e.g., connected in series with one another), a voltage associated with a cell in the battery sub-module, where each battery sub-module in the plurality of battery sub-modules includes a plurality of cells (e.g., connected in series with one another). A battery sub-module is selected from the plurality of battery sub-modules based at least in part on the received voltage. A set of one or more loads (e.g., electronic devices or other power consumers) that draw power from the selected battery sub-module and are not powered by other battery sub-modules in the plurality of battery sub-modules is configured such that the set of one or more loads does not draw power from the selected battery sub-module, at least temporarily.

[0007] In some applications, this technique is used to select which battery sub-modules will not (e.g., at least temporarily) provide standby or standby power to corresponding electronics during times when a primary load (e.g., lift fans in an all-electric aircraft) is not drawing power from the battery system. In the long run, if this process is performed, the battery sub-modules will be more balanced than if the process was not performed (e.g., a more balanced battery sub-module will perform better) and / or permanent damage to the battery sub-modules may be avoided.

[0008] 1 is a flow chart illustrating one embodiment of a process for inter-module balancing. In some embodiments, the process is performed by and / or on a battery system having multiple sub-modules connected in series with each other, each battery sub-module, in turn, including multiple cells connected in series with each other.

[0009] At 100, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module is received, and each battery sub-module in the plurality of battery sub-modules includes a plurality of cells. In one example, the battery system is used to power an all-electric aircraft. For various reasons, the battery system powering the aircraft may consist of a plurality of battery sub-modules connected in series with each other. For example, by having a plurality of battery sub-modules connected in series with each other to form an overall battery system, the battery sub-modules may be easily replaced as needed or desired, and relatively high voltages (e.g., on the order of several hundred volts required by the lift fan) as well as lower voltages (e.g., on the order of a few volts required by the avionics and / or electronics) may be simultaneously available. In contrast, these desirable properties and / or characteristics are not present when the battery system comprises a(n)monolithic battery. An exemplary battery system including battery sub-modules (connected in series with each other), which in turn include cells (also connected in series with each other), is described in more detail below.

[0010] At 102, a battery sub-module is selected from the plurality of battery sub-modules based at least in part on the received voltage. For example, the selected battery sub-module may be selected because it is undesirable for the battery sub-module to continue to power one or more loads (e.g., electronics, motors, solenoids, etc.) operating on the selected battery sub-module. In some embodiments, more than one battery sub-module is selected. Some examples of how the selection may be performed are described in more detail below.

[0011] At 104, a set of one or more loads that draw power from the selected battery sub-module and are not powered by any other battery sub-module in the plurality of battery sub-modules is configured such that the set of one or more loads at least temporarily does not draw power from the selected battery sub-module. As described in more detail below, in some embodiments, the loads include electronics that are turned off such that they no longer draw (e.g., standby) power from the selected and / or associated battery sub-module. Alternatively, electronics associated with the selected battery sub-module may be configured such that they draw power from some other battery sub-module other than the selected one.

[0012] Conceptually and / or generally, the above process attempts to balance the voltage levels in the various sub-modules and / or cells by selectively allowing some (but not all) of the battery sub-modules to power their associated loads, e.g., during any dormant or stationary state in which the aircraft (or other loads) are not consuming significant amounts of power. This reduces the voltage levels in sub-modules and / or cells (e.g., those that are better equipped and / or in a better state to provide power) so that the voltage levels in selected sub-modules and / or selected cells may be preserved.

[0013] In one example of why balancing is important and / or useful, if balancing was not performed (e.g., according to the process of FIG. 1), some battery sub-modules in the battery system would permanently fail if the battery system was left alone for about 20 days. This could entirely happen if the battery system is used in an aircraft. For example, a pilot could fly the aircraft to some remote location with no charging stations, where the aircraft would sit unused for about 20 days and the batteries would not be charged during that time. Or the aircraft could be left in a hangar for a long period of time, and thus maintenance requiring human intervention would be quite inconvenient.

[0014] Another benefit of keeping the battery submodules balanced is that for a battery with submodules in series, keeping the battery submodules balanced increases the capacity of the battery since the capacity of the battery is determined by the smallest capacity cell. This is because discharging the battery below its minimum capacity would damage it. In the same vein, keeping the submodules balanced reduces the time it takes the battery to charge since in a balanced state the cells are at a uniform and higher voltage than in an unbalanced state. Finally, by maintaining a balanced battery, the overall life of the battery can be increased. Cells with reduced voltage may deteriorate more quickly than their neighbors, and when one of the constituent cells of a submodule reaches a critical point of deterioration, the submodule must be replaced. Additionally, in embodiments that allow the submodules to be discharged in parallel, submodules of different voltages will provide different currents to the load, and submodules that must provide excess current will experience accelerated deterioration. The process of FIG. 1 can be repeated as needed or desired. For example, when the non-selected battery sub-modules provide power, the voltage levels stored in those cells and / or battery sub-modules will decrease, resulting in different voltage levels and, therefore, different degrees and / or states of imbalance. In one example, the battery sub-module selected in step 102 will not provide power for (for example) 15 minutes during step 104, after which the process of Figure 1 is repeated with updated voltages. As a result, the different battery sub-modules may be selected in step 102 to no longer provide power, at least temporarily, to their corresponding electronics.

[0015] In some embodiments, the exemplary balancing process described above is performed when the primary loads (e.g., lift fans in an all-electric aircraft) are not drawing power. For example, the draws by the primary loads on the battery system may change very rapidly, and therefore it may be difficult and / or expensive to sample the battery system fast enough to accurately determine what state the battery system is in when the primary loads are drawing power. For this reason, it may be simpler and / or easier to perform balancing when the primary loads are off.

[0016] In some embodiments, the exemplary balancing process described above is performed before and / or after charging of the battery system is performed. For example, balancing the battery system (e.g., according to the process of FIG. 1) before charging of the battery system is performed may aid in the charging process itself by repairing or otherwise reducing larger imbalances (if any) between the battery sub-modules (e.g., that may be undesirable during the charging process). If balancing is performed (e.g., according to the process of FIG. 1) after the battery system is charged, smaller imbalances (if any) between the battery sub-modules may be repaired or otherwise reduced.

[0017] It may be helpful to describe an example battery system that implements the process of Figure 1. The following diagram describes one such example battery system.

[0018] 2 is a diagram illustrating an embodiment of a battery system including battery submodules connected in series with each battery submodule including cells connected in series with each other. In this example, the battery system is used to power an all-electric aircraft.

[0019] In this example, there are M battery sub-modules, namely a first battery sub-module (200a), a second battery sub-module (200b), and an Mth battery sub-module (200c), which are connected in series with each other to generate a high voltage power supply (e.g., on the order of several hundred volts) to power high voltage loads (202), such as the lift fans of an aircraft.

[0020] Each battery submodule in turn includes N cells connected in series with each other. For example, the first battery submodule (200a) includes a first cell (204a), a second cell (204b), an (N-1)th cell (204c), and an Nth cell (204d). The voltage across each battery submodule in this example is on the order of tens of volts. In this example, there are 36 battery submodules and 12 cells per battery submodule. The following diagram shows an exemplary battery submodule:

[0021] FIG. 3A is a diagram showing one embodiment of an uncapped battery submodule. In the example shown, the battery submodule includes layers of cells (300) interleaved with layers of (e.g., flame-retardant) insulating material (302). In this example, the cells are resistant to pressure (e.g., about 0.21-0.35 kgf / cm 2 A pouch cell is a battery sub-module that performs better when subjected to a pressure of (3-5 PSI). More specifically, the cycle life of a pouch cell can be extended by applying pressure to the pouch cell. Thus, the battery sub-module is encased in a metal can (304) that applies pressure to the contained pouch cell.

[0022] Each cell has two tabs (306) extending upwardly from the cell, a positive tab and a negative tab. The tabs are connected to each other such that the cells are electrically connected in series with each other. See, for example, FIG. 2.

[0023] 3B is a diagram showing one embodiment of a covered battery submodule. In this example, a cover (350) is attached to the battery submodule such that only a single positive connection and a single negative connection are exposed. In the above-described example where the battery system is included in an aircraft, each battery submodule may be physically and electrically connected to one another within the aircraft such that a single battery submodule may be swapped out and replaced as needed or desired.

[0024] Returning to FIG. 2, each battery sub-module (200a-200c) has a set of electronics (206a-206c) associated with it and powered by it (e.g., even when the aircraft is not flying and the high voltage load (202) is not consuming power). For example, a first set of electronics (206a) is powered by the first battery sub-module (200a), a second set of electronics (206b) is powered by the second battery sub-module (200b), and an Mth set of electronics (206c) is powered by the Mth battery sub-module (200c). For the sake of brevity and to preserve readability of the figure, a voltage converter (e.g., to step down the voltage generated by the battery sub-module to a voltage level expected by the electronics) is not shown herein, but may be used if needed or desired.

[0025] The electronics (206a-206c) in this example include a battery management system (BMS) that monitors and / or records metrics and / or measurements associated with the cells in the associated battery sub-module over time. In some embodiments, the battery management system monitors and / or tracks the voltage of each of the cells in the associated battery sub-module over time. The electronics controller (208) controls the various electronics (206a-206c) in a manner described in more detail below.

[0026] This type of battery configuration may be better suited for aircraft applications compared to automotive applications. For example, the Federal Aviation Administration may have very strict requirements regarding redundancy and / or potential single points of failure. By configuring multiple battery sub-modules in series with backup connections, not shown, if one of the battery sub-modules fails, the entire battery system can still operate and output a high voltage signal for the high voltage load (202). In contrast, the National Highway Traffic Safety Administration may pay less attention to redundancy and / or potential single points of failure because if a battery fails, the aircraft will crash, but the car can simply coast and pull over. For these and other reasons, battery systems for electric vehicles tend to be more monolithic (e.g., relatively fewer battery sub-modules and / or relatively fewer cells per battery sub-module compared to battery systems for aircraft).

[0027] Due to slight differences between the various cells and the various battery sub-modules, the voltages across the cells and battery sub-modules may not all be the same. Furthermore, with the configurations shown herein, while the high voltage loads (202) are off and the electronics (206a-206c) are on (e.g., when the aircraft is powered down), the battery sub-modules with less charge are used to provide more power than the battery sub-modules with more charge (e.g., when no inter-module balancing is performed, one example of which is illustrated in FIG. 1). To use an analogy, the rich (sub-modules) stay rich and the poor (sub-modules) stay poor. To address this, the electronics controller 208 (including, for example, a BMS controller) performs the balancing process of FIG. 1.

[0028] In the context of this exemplary system, step 100 of Figure 1 begins when the electronics controller (208) determines to execute the process of Figure 1. As explained above, balancing may be performed before and / or after charging, but (e.g., for simplicity and / or to avoid costly sampling equipment) balancing is not performed when high voltage loads are drawing power from the battery system.

[0029] 1 begins, the electronics controller (208) signals each set of electronics (206a-206c) to send back one or more voltages associated with the cells in the associated battery submodule. For example, the voltage sent back to the electronics controller may be the minimum (e.g., lowest) voltage of all the cells in that battery submodule, sometimes referred to herein as the minimum cell voltage (e.g., for a given battery submodule). In some other embodiments, some other type of cell voltage is sent to the electronics controller in addition to and / or instead of the minimum cell voltage (e.g., as a maximum cell voltage or a median or average cell voltage). Using the voltages received from the electronics (206a-206c), the electronics controller selects at least one set of electronics. In one example, the electronic device with the global minimum cell voltage is selected (e.g., the controller picks the minimum of the minimum cell voltages) (e.g., because continuing to draw power from the battery sub-module may permanently damage the battery sub-module if the cell with the minimum cell voltage falls below a threshold and / or irrecoverable cell voltage level). This is one example of step 102 in FIG. 1.

[0030] In this example, there are two paths between each set of electronics (206a-c) and the electronics controller (208): one path is for communication and / or control, and the other path is for power supply. The latter incorporates a switch to interrupt power from a given battery sub-module and / or set of electronics to the electronics controller. The control and / or communication path is always connected and available (e.g., to allow the controller to query cell voltages and control the state of the aforementioned switches in response to voltage measurements).

[0031] The electronics controller then configures the selected electronics such that the selected electronics does not draw power from its associated battery sub-module (e.g., to the extent possible, since there is typically some level of standby power consumption even when the thing is “turned off”). In some embodiments, the electronics controller turns off the selected electronics to achieve this goal. Alternatively, the electronics controller in some other embodiments configures the selected electronics (and / or any other components) such that power from a given battery sub-module is not sent to the upstream electronics controller (208). For example, even if the electronics 206a is in a power minimization mode and is not providing power to the controller (208), the controller (208) can still query the battery management system 206a about the voltage of that electronics, etc. This may be desirable in applications where it is desirable to keep the electronics accessible. For example, as described above, the battery management system tracks and / or monitors metrics associated with the associated battery sub-module and / or cells therein. It may be desirable to continue to track such metrics and / or measurements, for example, by obtaining power from another battery sub-module. These are some examples of how step 104 in FIG. 1 may be performed.

[0032] Without balancing, one or more of the battery sub-modules can become irreparably damaged in as little as about 20 days. For example, if power continues to be drawn from a cell when the cell's voltage level drops below a certain voltage level, the cell will become irreparably damaged, resulting in the need to replace the entire battery sub-module.

[0033] The following figures more generally and / or formally describe some of the examples discussed above in flow chart form.

[0034] Figure 4 is a flow chart illustrating one embodiment of a process for inter-module balancing including turning off electronics. Figure 4 relates to Figure 1 and, for convenience, related steps are indicated using similar or the same reference numbers.

[0035] In 100, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module is received, with each battery sub-module in the plurality of battery sub-modules including a plurality of cells. For example, the electronics controller (208) in FIG. 2 receives at least one voltage from each of the electronics (206a-206c), with each received voltage associated with one cell in the corresponding or associated battery sub-module (200a-200c).

[0036] At 102, a battery sub-module is selected from the plurality of battery sub-modules based at least in part on the received voltage. Some examples of how the selection may be performed are described in more detail below. In some embodiments, multiple battery sub-modules are selected.

[0037] In 104a, a set of one or more loads that draw power from the selected battery submodule and are not powered by any other battery submodule in the plurality of battery submodules may be configured to at least temporarily not draw power from the selected battery submodule, including configuring the set of loads that draw power from the selected battery submodule to be turned off. For example, if the first battery submodule (200a) in FIG. 2 is selected, the load controller 208 may configure the first set of loads 206a to be turned off and not draw power from the first battery submodule (200a).

[0038] 5 is a flow chart illustrating one embodiment of a process for inter-module balancing that includes configuring a set of electronics to draw power from a non-selected battery sub-module. FIG 5 relates to FIG 1, and for convenience, related steps are indicated using similar or the same reference numbers.

[0039] At 100, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module is received, and each battery sub-module in the plurality of battery sub-modules includes a plurality of cells.

[0040] At 102, a battery sub-module is selected from the plurality of battery sub-modules based at least in part on the received voltage. As discussed above, in some embodiments, the plurality of battery sub-modules is selected (e.g., because if the plurality of battery sub-modules continued to provide power, the plurality of battery sub-modules would become insufficient to provide power and / or would be irreparably damaged and therefore are selected).

[0041] In 104b, a set of one or more loads that draw power from the selected battery sub-module and are not powered by any other battery sub-module in the plurality of battery sub-modules is configured such that the set of one or more loads at least temporarily do not draw power from the selected battery sub-module, including configuring the set of loads that draw power from the selected battery sub-module to draw power from non-selected battery sub-modules.

[0042] In some applications, it is not desirable to turn off the electronics. In the example of FIG. 2, the electronics includes a battery management system that tracks and / or monitors the health and / or other metrics of the battery sub-modules and / or cells, and it is important and / or desirable to track that information at all times. For example, in the case of an aircraft, the aircraft may be powered down during the week and only flown on weekends. The battery management system should operate for a week so that a faulty battery sub-module can be identified and / or the aircraft will not be allowed to fly if necessary or required.

[0043] As discussed above, in some embodiments, a battery sub-module is selected from multiple battery sub-modules to prevent the cells in that battery sub-module from being pulled down to a voltage level where irreparable damage occurs (and, e.g., the entire battery sub-module must be replaced). The following diagram describes some example cell voltages and example techniques for using those cell voltages to select a battery sub-module.

[0044] FIG. 6 is a diagram illustrating an example of cell voltages in battery submodules in a battery system. In this example, there are M battery submodules and N cells per battery submodule, consistent with the example of FIG. 2. In the graph shown, the x-axis indicates cell index (defined by the battery submodule number and the cell number within that battery submodule) and the y-axis indicates the cell voltage of the corresponding cell. Group 600 indicates cell voltages for cells in a first battery submodule, group 602 indicates cell voltages for cells in a second battery submodule, and group 604 indicates cell voltages for cells in the Mth battery submodule.

[0045] For the sake of brevity and ease of explanation, thresholdAssume that there is a voltage level, represented by V, below which a cell would be permanently damaged if power (e.g., standby power or standby power when the aircraft is powered down) continues to be drawn from the cell. For example, cells 2,1 (610) and 2,N (612) are both in the second battery submodule (602) and are connected to a power supply (not shown) between the first and second battery submodules (602) and V threshold (606) or less. To ensure that power is no longer drawn from that battery sub-module, a second battery sub-module will be selected (e.g., in step 102 of FIG. 1) and a corresponding set of electronics (e.g., 206b in FIG. 2) will be configured such that they no longer draw power from the second battery sub-module (e.g., 200b in FIG. 2).

[0046] Returning briefly to Figure 2, it would be desirable if the electronics controller (208) could receive cell voltages for only a few cells per battery sub-module, instead of having to receive cell voltages for all cells in a given battery sub-module. This would reduce the amount of traffic or communication exchanged between the electronics controller (208) and the lower level electronics (206a-206c), for example.

[0047] In one example, the minimum cell voltage from each battery sub-module is sent to an electronics controller or other block making the selection. For example, each electronics controller (e.g., a battery management system) may make this selection and upload only the minimum cell voltage to the electronics controller (e.g., a BMS controller). In FIG. 6, this would mean selecting the cell voltage (620) for cell 1, (N-1), which is the minimum cell voltage in the first battery sub-module (600), and sending it to such electronics controller. For the second battery sub-module (602), the minimum cell voltage would be the cell voltage (610) for cell 2, 1, and that cell voltage would be selected and sent to the electronics controller. For the Mth battery sub-module (604), the minimum cell voltage would be the cell voltage (622) for cell M, N, and that cell voltage would be selected and sent to the electronics controller.

[0048] In some embodiments, the battery sub-modules are selected in step 102 of FIG. 1 using a threshold voltage. For example, if any of the battery sub-modules is greater than V threshold If a second battery submodule has a minimum cell voltage below (606), then that battery submodule will be selected such that its corresponding electronics will not continue to draw power from that battery submodule. For the example cell voltages shown in FIG. 6, only the second battery submodule (602) will be selected. Thus, the corresponding electronics will be configured to at least temporarily not draw power from the second battery submodule (e.g., by either turning off the second set of electronics or drawing power from some other battery submodule).

[0049] In some embodiments, the above steps are performed first (e.g., the minimum cell voltage from each battery submodule is V threshold (606), and then Vthreshol From the pool of battery submodules that were above d, the n battery submodules with the n largest (remaining) minimum cell voltages are used to power (at least temporarily), while the remaining battery submodules (V threshold (including battery sub-modules with a minimum cell voltage below ) will not provide power (at least temporarily). This pulls down the n battery sub-modules, thereby making them more balanced relative to the other battery sub-modules.

[0050] In FIG. 6, for example, the Mth battery sub-module (604) generally has a much higher cell voltage compared to the remaining battery sub-modules. By lowering the cell voltage of the Mth battery sub-module (604), this can help lower the Mth battery sub-module (604), i.e., the high-end outlier, without irreparably damaging the second battery sub-module (602), i.e., the low-end outlier. In other words, the first inspection or test (e.g., setting the minimum cell voltage to V threshold ) ensures that nothing is faulty or broken, and the second inspection or test (e.g., drawing power from n battery sub-modules with the n largest minimum cell voltages) is a performance-oriented selection (e.g., the selection will balance better than some other selection techniques, and the performance of balanced battery sub-modules will be better).

[0051] In some embodiments, V thresholdNo battery sub-module has a minimum cell voltage below (606). In some such embodiments, the maximum cell voltage from each battery sub-module is obtained, and the m battery sub-modules with the m largest maximum cell voltages provide power (at least temporarily), while the remaining battery sub-modules do not provide power (at least temporarily). In this situation, no battery sub-module is in danger of being permanently damaged if that battery sub-module continues to provide power, and therefore using the maximum cell voltage from each cell is a better way to balance the sub-modules (e.g., even better than using the largest of the minimum cell voltages). In the context of this type of balancing, it is always beneficial to draw power from higher voltage sub-modules rather than lower voltage sub-modules.

[0052] These examples are more generally and / or formally described in the following flow charts: Suitable techniques may be implemented in various applications and / or implementations.

[0053] 7 is a flow chart illustrating an embodiment of a process for selecting battery sub-modules using voltage thresholds. In some embodiments, battery sub-modules are selected in step 102 of FIG. 1 using the example processes described herein. In this example, receiving a voltage in step 100 of FIG. 1 includes receiving a minimum cell voltage such that a plurality of minimum cell voltages are received for each battery sub-module in a plurality of battery sub-modules connected in series with one another.

[0054] At 700, the minimum cell voltages are compared to voltage thresholds to identify any battery sub-modules with minimum cell voltages that do not exceed the voltage thresholds. For example, in FIG. 6, the minimum cell voltage for cell 1, (N-1) (620), the minimum cell voltage for cell 2, 1 (610), and the minimum cell voltage for cell M, N (622) are V threshold(606). In that example, the only cell with a minimum cell voltage that does not exceed the voltage threshold is cell 2,1 (610).

[0055] At 702, any of the identified battery sub-modules having a minimum cell voltage that does not exceed a voltage threshold is selected. Continuing the example from FIG. 6, the second battery sub-module (602) would be selected. Accordingly, the corresponding electronics would be configured such that they do not, at least temporarily, draw power from the second battery sub-module (602). The second battery sub-module (602) is fragile and may be permanently damaged if the battery sub-module (602) continues to draw power.

[0056] Depending on the design objectives and / or constraints, an appropriate technique for making the selection may be used. For example, the process of FIG. 7 is relatively simple. In some applications, the process of FIG. 7 is used to make the selection when other, more complex processes provide negligible performance improvement.

[0057] 8 is a flow chart illustrating an embodiment of a process for selecting a battery sub-module using a voltage threshold and a maximum value of minimum cell voltages. In some embodiments, a battery sub-module is selected in step 102 of FIG. 1 using an exemplary process described herein. In this example, receiving a voltage in step 100 of FIG. 1 includes receiving a minimum cell voltage such that a plurality of minimum cell voltages are received for each battery sub-module in a plurality of battery sub-modules connected in series with one another.

[0058] At 800, the plurality of minimum cell voltages are compared to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold. See, for example, FIG. 6, where a second battery sub-module (602) has a minimum cell voltage (610) that does not exceed a voltage threshold (606).

[0059] At 802, one or more maximum values ​​are selected from the plurality of minimum cell voltages to obtain one or more maximum values ​​of the minimum cell voltages. For example, in FIG. 6, the minimum cell voltages include voltage for cell 1, (N-1) (620), voltage for cell 2, 1 (610), and voltage for cell M, N (622), with the maximum of those voltages being voltage for cell M, N (622). For simplicity and ease of explanation, it will be assumed in this example of step 802, and thereafter in step 804, that only one maximum value is selected.

[0060] At 804, any of the identified battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold, as well as battery sub-modules that do not correspond to one of the maximum minimum cell voltages, are selected. For example, the second battery sub-module (602) would be selected because it has a minimum cell voltage (610) that does not exceed the voltage threshold (606). Also, the first battery sub-module (600) does not correspond to the maximum minimum cell voltage, and therefore, the first battery sub-module would also be selected. In other words, the first battery sub-module (600) and the second battery sub-module (602) would not need to provide power (at least temporarily), but the Mth battery sub-module (604) would provide power (e.g., during the time period). Intuitively, this makes sense, since the Mth battery sub-module (604) tends to have a higher cell voltage compared to the other battery sub-modules.

[0061] In some applications, the process of FIG. 8 is used instead of the process of FIG. 7 because it does not require obtaining additional cell voltages for each battery submodule (e.g., according to FIG. 9) but allows for better and / or faster balancing compared to FIG. 7.

[0062] 9 is a flow chart illustrating an embodiment of a process for selecting a battery sub-module using a voltage threshold and a maximum value of maximum cell voltages. In some embodiments, a battery sub-module is selected in step 102 of FIG. 1 using an example process described herein. In this example, receiving a voltage in step 100 of FIG. 1 includes receiving a minimum cell voltage and a maximum cell voltage such that a plurality of minimum cell voltages and a plurality of maximum cell voltages are received for each battery sub-module in a plurality of battery sub-modules connected in series with each other.

[0063] At 900, the plurality of minimum cell voltages are compared to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold, see, for example, FIG.

[0064] At 902, it is determined whether there is a battery sub-module with a minimum cell voltage that does not exceed the voltage threshold. For example, for the cell voltages shown in Figure 6, the determination would be "yes" because the minimum cell voltages for cells 2 and 1 (610) do not exceed the voltage threshold (606). In this example, the process would then proceed to step 802 in Figure 8.

[0065] However, if the determination at step 902 is "no" (e.g., because all of the minimum cell voltages exceed the voltage threshold), then one or more maximum values ​​are selected from the plurality of maximum cell voltages to obtain one or more maximum values ​​of the maximum cell voltages at 904. For example, the plurality of maximum cell voltages in Figure 6 includes the cell voltage for cell 1,2 (630), the cell voltage for cell 2,(N-1) (632), and the cell voltage for cell M,1 (634). If only one maximum value is selected, then the maximum of the maximum cell voltages would be the cell voltage for cell M,1 (634).

[0066] At 906, a battery sub-module that does not correspond to one of the maximum maximum cell voltage values ​​is selected. In other words, the battery sub-module that corresponds to the maximum maximum cell voltage value will provide power (at least temporarily) for a period of time. Continuing with the example from above, the Mth battery sub-module will provide power (at least temporarily) while the remaining battery sub-modules will not provide power (at least temporarily).

[0067] In some applications, this technique requires the use of both minimum and maximum cell voltages, which allows for best and / or faster balancing, but requires more information to be exchanged between the (local) electronics (e.g., battery management system) and the electronics controller (e.g., BMS controller). Depending on the specific design goals and / or constraints of a particular application, an appropriate technique may be selected. For example, if performance is critical and more and / or additional exchanges are an acceptable trade-off, the process of FIG. 9 may be used.

[0068] As explained above, in some embodiments, balancing is performed before and / or after charging. The following figures describe some example scenarios in which balancing is performed both before and after charging, as well as only after charging.

[0069] FIG. 10A is a diagram illustrating an embodiment in which balancing is performed both before and after charging. In the illustrated example, the battery system has a large imbalance between the various battery sub-modules and / or between the cells underlying those battery sub-modules at time 0. For example, assume that the BMS controller calculates an imbalance metric that represents the degree or amount of imbalance in the battery system, and that the metric is relatively high and / or above some imbalance threshold. As explained above, it is important that the battery system is balanced (e.g., sufficiently) before charging. Thus, in this example, at 1000, a first pass of balancing (e.g., according to any of the balancing techniques discussed above) is performed. For example, some battery sub-modules provide power to various electronics in the system, while other battery sub-modules do not provide power for some predefined amount of time and / or until some desired imbalance metric is reached.

[0070] A first pass or iteration of balancing is then performed at 1000 before the battery system is charged at 1002 .

[0071] After charging (1002) is completed, there may still be some imbalance in the battery system (e.g., carried over from the end of the first balancing pass) and / or additional imbalances may have been introduced by the charging process. Thus, a second pass or iteration of balancing (e.g., by any of the techniques described above) is performed at 1004, but this time to address smaller and / or minor imbalances in the battery system.

[0072] FIG. 10B is a diagram illustrating an embodiment in which balancing is performed only after charging. In this example, the battery system has a relatively small amount or degree of imbalance between the battery submodules (and / or the underlying cells) when the entire process begins. In other words, at time 0, the battery submodules are sufficiently balanced such that charging can be performed immediately (e.g., without having to first perform a balancing process). As previously mentioned, the BMS controller may have determined an imbalance metric and compared the imbalance metric to a threshold to conclude that the battery system is sufficiently balanced to proceed with charging. Thus, charging (1050) is performed immediately at time=0. After charging is completed, balancing (1052) is performed (e.g., according to any of the techniques described above) to address the relatively small and / or minor imbalances present in the battery system at that time.

[0073] A third possible scenario (not shown here for simplicity) is to perform balancing before charging but not after charging.

[0074] The following figures explain the above examples more generally and / or formally in a flow chart.

[0075] 11 is a flow chart illustrating an embodiment of a process for determining when to perform balancing on a charging process. In some embodiments, the process is performed by the BMS controller 208 in FIG.

[0076] At 1100, an imbalance metric is determined that is related to the degree of imbalance between the battery sub-modules in the plurality of battery sub-modules. One example of an imbalance metric is the difference between the maximum cell state of charge and the minimum cell state of charge in a battery, referred to herein as RANGE(SOC). Another metric in this example is the amount of imbalance that can be handled over the duration of a single charge, referred to herein as maxImbalance. Straightforwardly, if RANGE(SOC)>maxImbalance, it would be beneficial to balance before charging. If balancing was not performed before charging, the battery would be charged until the maximum voltage cell reached a maximum cell voltage threshold that would damage the cell if exceeded. At this point, the battery would still be unbalanced and all high voltage cells would need to be depleted until they reached the same voltage as the minimum voltage cell. After this, another charge would be performed until the now balanced battery reached its maximum cell voltage.

[0077] This is not really an issue if the aircraft is left attached to the charging station for an extremely long period of time. In this case, the batteries can be trickle charged and kept fully charged while the batteries themselves balance. However, in high throughput environments (e.g., air taxi or shared use applications) where the time the aircraft needs to spend on the charging station needs to be minimized, it is beneficial to pre-balance the batteries (e.g., because the batteries do not need to be connected to the charging station during that time).

[0078] Note that maxImbalance is actually a variable, not a fixed value. If the aircraft is fully discharged, it may nominally take 1.25 hours to charge. Balancing may be performed while charging and balancing occurs at a set rate, so logic dictates that if less than 1.25 hours worth of balancing is required, charging should proceed or otherwise be performed without fear of downtime. Otherwise, if it is desired to minimize time on the charging device, it would be beneficial to perform balancing beforehand. If only 0.5 hours worth of charging is required (i.e., the airplane was only partially discharged), the threshold would be correspondingly smaller.

[0079] At 1102, it is determined whether the imbalance metric exceeds an imbalance threshold. In this example, an imbalance metric with a greater value corresponds to a greater degree or amount of imbalance in the battery system and an imbalance metric with a lesser value corresponds to a lesser degree or amount of imbalance in the battery system. In other words, the imbalance threshold is used to determine whether the battery system is sufficiently charged to immediately begin charging or whether some balancing needs to be performed first.

[0080] If the imbalance metric exceeds an imbalance threshold at 1102 (e.g., the battery system is not sufficiently balanced for charging), then pre-charging balancing is performed at 1104. For example, any of the balancing techniques described above (e.g., in FIG. 1) may be used. After pre-charging balancing is performed at 1104, the multiple battery sub-modules are charged at 1106.

[0081] If the imbalance metric does not exceed the imbalance threshold at 1102 (e.g., the battery system is sufficiently balanced for charging), then the multiple battery sub-modules are charged at 1106 (e.g., without first performing balancing at step 1104).

[0082] In some embodiments, after the battery sub-modules are charged in step 1106, post-charging balancing is performed in 1108 (e.g., using any of the balancing techniques described above, such as in FIG. 1). Alternatively, the post-charging balancing step in 1108 may be skipped (e.g., because the degree or amount of imbalance in the battery system after charging does not warrant repeated balancing).

[0083] Although the above embodiments have been described in some detail for the purpose of clarity of understanding, the present invention is not limited to the details given. There are many alternative ways to implement the present invention. The disclosed embodiments are illustrative and not restrictive.

Claims

1. A processor; a memory coupled to the processor; wherein the memory, when executed, receiving, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module, each battery sub-module in the plurality of battery sub-modules including a plurality of cells; selecting a battery sub-module from the plurality of battery sub-modules based at least in part on the received voltage; configuring one or more loads that draw power from the selected battery sub-module and that are not powered by any other battery sub-module in the plurality of battery sub-modules such that the set of one or more loads does not draw power from the selected battery sub-module, at least temporarily; A system configured to provide instructions to the processor to cause the processor to:

2. 2. The system of claim 1, wherein configuring the set of one or more loads comprises configuring to turn off the set of loads that draw power from the selected battery submodule.

3. 2. The system of claim 1, wherein configuring the set of one or more loads includes configuring the set of loads that draw power from the selected battery sub-module to draw power from a non-selected battery sub-module.

4. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; selecting any of the identified battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; The system of claim 1 , comprising:

5. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; selecting one or more maximum values ​​from the plurality of minimum cell voltages to obtain one or more maximum values ​​of the minimum cell voltages; selecting any of the identified battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold, as well as battery sub-modules that do not correspond to one of the maximum values ​​of the minimum cell voltages; The system of claim 1 , comprising:

6. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; in response to determining that no battery sub-module has a minimum cell voltage that does not exceed the voltage threshold; selecting one or more maximum values ​​from the plurality of maximum cell voltages to obtain one or more maximum values ​​of the maximum cell voltages; selecting a battery sub-module that does not correspond to one of the maximum values ​​of the maximum cell voltages; The system of claim 1 , comprising:

7. The memory, when executed, causes the processor to: determining an imbalance metric relating to a degree of imbalance between battery sub-modules in the plurality of battery sub-modules; determining whether the imbalance metric exceeds an imbalance threshold; in response to determining that the imbalance metric exceeds the imbalance threshold, for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a pre-charge balancing step, charging the plurality of battery sub-modules; charging the plurality of battery sub-modules in response to determining that the imbalance metric does not exceed the imbalance threshold; The system of claim 1 , further configured to provide instructions to the processor to:

8. The memory, when executed, causes the processor to: determining an imbalance metric relating to a degree of imbalance between battery sub-modules in the plurality of battery sub-modules; determining whether the imbalance metric exceeds an imbalance threshold; in response to determining that the imbalance metric exceeds the imbalance threshold, for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a pre-charge balancing step, charging the plurality of battery sub-modules; for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and configuring said set of one or more loads; performing a post-charge equilibration, in response to determining that the imbalance metric does not exceed the imbalance threshold; charging the plurality of battery sub-modules; for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a post-charge equilibration, The system of claim 1 , further configured to provide instructions to the processor to:

9. The system of claim 1 further comprising the plurality of battery sub-modules and the set of one or more loads.

10. receiving, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module, each battery sub-module in the plurality of battery sub-modules including a plurality of cells; selecting a battery sub-module from the plurality of battery sub-modules based at least in part on the received voltage; configuring one or more loads that draw power from the selected battery sub-module and that are not powered by any other battery sub-module in the plurality of battery sub-modules such that the set of one or more loads does not draw power from the selected battery sub-module, at least temporarily; A method comprising:

11. 11. The method of claim 10, wherein configuring the set of one or more loads comprises configuring to turn off the set of loads that draw power from the selected battery submodule.

12. 11. The method of claim 10, wherein configuring the set of one or more loads includes configuring the set of loads that draw power from the selected battery sub-module to draw power from a non-selected battery sub-module.

13. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; selecting any of the identified battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; The method of claim 10, comprising:

14. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; selecting one or more maximum values ​​from the plurality of minimum cell voltages to obtain one or more maximum values ​​of the minimum cell voltages; selecting any of the identified battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold, as well as battery sub-modules that do not correspond to one of the maximum values ​​of the minimum cell voltages; The method of claim 10, comprising:

15. selecting the battery sub-module, comparing the plurality of minimum cell voltages to a voltage threshold to identify any battery sub-modules having a minimum cell voltage that does not exceed the voltage threshold; in response to determining that no battery sub-module has a minimum cell voltage that does not exceed the voltage threshold; selecting one or more maximum values ​​from the plurality of maximum cell voltages to obtain one or more maximum values ​​of the maximum cell voltages; selecting a battery sub-module that does not correspond to one of the maximum values ​​of the maximum cell voltages; The method of claim 10, comprising:

16. determining an imbalance metric relating to a degree of imbalance between battery sub-modules in the plurality of battery sub-modules; determining whether the imbalance metric exceeds an imbalance threshold; in response to determining that the imbalance metric exceeds the imbalance threshold, for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; Configuring said set of one or more loads. performing a pre-charge balancing step, charging the plurality of battery sub-modules; charging the plurality of battery sub-modules in response to determining that the imbalance metric does not exceed the imbalance threshold; The method of claim 10 further comprising:

17. determining an imbalance metric relating to a degree of imbalance between battery sub-modules in the plurality of battery sub-modules; determining whether the imbalance metric exceeds an imbalance threshold; in response to determining that the imbalance metric exceeds the imbalance threshold, for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a pre-charge balancing step, charging the plurality of battery sub-modules; for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a post-charge equilibration, in response to determining that the imbalance metric does not exceed the imbalance threshold; charging the plurality of battery sub-modules; for each battery sub-module in the plurality of battery sub-modules, receiving a voltage associated with a cell in that battery sub-module; selecting the battery sub-module; and Configuring said set of one or more loads. performing a post-charge equilibration, The method of claim 10 further comprising:

18. A computer program product embodied in a non-transitory computer-readable storage medium, comprising: receiving, for each battery sub-module in the plurality of battery sub-modules, a voltage associated with a cell in that battery sub-module, each battery sub-module in the plurality of battery sub-modules including a plurality of cells; selecting a battery sub-module from the plurality of battery sub-modules based at least in part on the received voltage; configuring one or more loads that draw power from the selected battery sub-module and that are not powered by any other battery sub-module in the plurality of battery sub-modules such that the set of one or more loads does not draw power from the selected battery sub-module, at least temporarily; 23. A computer program product comprising computer instructions for:

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