Method of balancing battery modules

Abstract

The present invention relates to a method for improving the operational efficiency of a battery pack (100) comprising at least two battery modules (10, 10', 10"), wherein each battery pack is configured to have a common gas space (29). The method comprises the steps of obtaining (101) data about the battery modules (10, 10', 10"), wherein the data relates to the number of battery cells of each battery module, the number of battery modules, the temperature of each battery module, and the energy capacity of the battery modules; obtaining (102) an indication of the internal resistance (R i1 , R i2 , R i3 ) of the battery modules; determining (104) an oxygen fill amount to be filled into the battery pack in case the difference of the indicated parameters between any of the battery modules exceeds a first threshold value; and initiating (107) a filling of the battery pack based on the determined oxygen fill amount.

Description

Technical Field

[0001] This invention generally relates to batteries, particularly nickel-metal hydride (NiMH) batteries. The invention relates to a method for using a battery pack, wherein hydrogen, oxygen, or hydrogen peroxide is added to improve performance. Furthermore, the invention specifically relates to the field of increasing the lifespan of battery packs. Background Technology

[0002] Nickel-metal hydride (NiMH) batteries exhibit long cycle life and rapid charging and discharging capabilities. During charging and discharging, the electrodes interact via an alkaline electrolyte as hydrogen is transported between them in the form of water molecules. During discharge, hydrogen is released from the negative electrode and allowed to migrate to the positive electrode (nickel electrode) where it is embedded. This binding results in the release of energy. During charging, this hydrogen migration is reversed.

[0003] In particular, NiMH batteries are designed with nickel electrodes limited by a starved electrolyte. This is done to avoid overcharging and over-discharging of the battery cells by controlling the cell chemistry and state of charge via the gas phase.

[0004] When the battery is charged, hydrogen is transported from nickel hydroxide to the metal hydride via water molecules in the aqueous alkaline electrolyte. During discharge, hydrogen is transported back to the nickel hydroxide electrode as water molecules.

[0005] PCT Publication WO 2017 / 069691 describes that a proper balance between the capacity of the nickel electrode and the metal hydride electrode, along with an appropriate amount of overcharge and over-discharge reserves, is necessary for a functional battery module to achieve stable, long-term charge / discharge performance. Adding oxygen, hydrogen, or hydrogen peroxide can provide appropriate overcharge and discharge reserves and replenish the electrolyte, thereby extending the battery module's lifespan and increasing the possible cycle life.

[0006] Oxygen is preferably added when the battery module is not in operation. Therefore, to optimize battery module operation, oxygen filling should preferably be performed in a manner that optimizes not only battery module capacity but also operating time. Summary of the Invention

[0007] The object of the present invention is to provide a method for improving operating efficiency by adding oxygen to a battery pack comprising at least two battery modules, wherein each battery module comprises at least one battery cell, which at least mitigates one of the disadvantages of the prior art.

[0008] This objective is achieved by the method according to the independent claim.

[0009] Other advantages of the invention are provided by the features of the dependent claims.

[0010] According to a first aspect of the invention, a method is provided for improving the operating efficiency of a battery pack comprising at least two battery modules, wherein each battery module comprises at least one battery cell. Each battery module has a housing surrounding the at least one battery cell and enclosing a gas space, wherein the gas spaces of the battery modules are interconnected to form a common gas space. Each battery cell includes a first electrode, a second electrode, a porous separator, and an aqueous alkaline electrolyte disposed between the first and second electrodes, wherein the porous separator, the first electrode, and the second electrode are configured to allow the exchange of hydrogen and oxygen by allowing gas migration between the electrodes. At least one housing includes a gas inlet for adding gas or liquid to the common gas space of the housing. The method is characterized by including a step of obtaining data about the battery modules, wherein the data relates to the number of battery cells in each battery module, the number of battery modules, the temperature of each battery module, and the energy capacity of the battery modules. The method is characterized by further comprising the steps of: obtaining an indication parameter related to the internal resistance of at least two battery modules in the battery module; and, if the difference between the indication parameters between any two battery modules in the battery module exceeds a predetermined first threshold, determining the amount of oxygen to be filled into the battery module based on the indication parameters and data about the battery modules, so as to reduce the difference indication parameter between any two battery modules to a level below the first threshold.

[0011] The method may also include the step of initiating the filling of the battery pack with the determined oxygen filler quantity. Initiation may include the step of placing an order to send a gas container containing the correct amount of oxygen at the correct pressure to the battery module. Alternatively, if the battery module is connected to an oxygen supply, initiation may include initiating the filling of oxygen from the oxygen supply.

[0012] The method according to the first aspect of the invention can improve the operating efficiency of the battery compared to methods according to the prior art. Operating efficiency means increased battery module lifespan while maintaining low oxygen refill times. For different battery modules, properly balancing the internal resistance of each cell can extend lifespan. By setting a threshold for the imbalance between the internal resistances of each cell in different battery modules, the battery is prevented from operating with high internal resistance, while also avoiding excessively short refill times.

[0013] This method can be implemented in a control unit that may include a computer.

[0014] The step of obtaining indication parameters, such as data for determining the internal resistance or state of health (SOH) of at least two battery modules in the battery module, is preferably achieved by receiving data from a measuring component configured to obtain indication parameters for at least two battery modules in the battery module. The number of battery cells in the battery module is obtained from data about the battery module. The determined number of cells is subject to practical limitations. Typically, only the terminal contacts of the battery module are accessible. Therefore, indication parameters, such as SOH or internal resistance, are determined for all battery cells in the battery module.

[0015] The step of obtaining data about the battery module (which is at least related to the number of battery cells and the energy capacity of the battery module) can be accomplished in many different ways. One alternative is to configure a measuring component to send data about the battery module to a computer device performing the method. Data can be sent from the measuring component, but to minimize the complexity of the measuring component, it is preferable that the measuring component only sends an identification number. After receiving the identification number from the measuring component, the data can be retrieved from, for example, memory. As mentioned above, the data is at least related to the number of battery cells in the battery module, the temperature of each battery module, and the energy capacity of the battery module. This data is necessary to determine the amount of oxygen to be filled into the battery module. However, the actual number of battery cells or the energy capacity of the battery module does not need to be used in the determination. According to one alternative, a control component can consult a lookup table in memory to retrieve data about the battery corresponding to the identification number of the battery module. In one example, the data about the battery could be a type number identifying the battery type. The control component can then retrieve the necessary oxygen filling amount from different lookup tables based on the determined indication parameters, temperature, and type number. The necessary oxygen filling amount in the lookup table can, in turn, be based on earlier experiments using similar battery types. The type number defines a battery module having a predetermined number of battery cells, a predetermined energy capacity, and optionally a predetermined volume of common gas space.

[0016] Preferably, when the obtained indication parameter is internal resistance (which refers to the internal resistance across multiple battery cells), the average internal resistance of each battery cell is calculated at the measured temperature of the battery pack and / or battery module. The average internal resistance of each battery cell is then compared to a resistance threshold at the measured temperature of a single battery cell. In principle, the difference in internal resistance between different battery modules can be compared to a resistance threshold for that difference, but this is equivalent to comparing the difference in internal resistance between battery cells from different battery modules to a resistance threshold at the measured temperature. A disadvantage of comparing the difference in internal resistance between different battery modules to a resistance threshold is that different resistance thresholds must be supplied depending on the number of battery cells in the battery module.

[0017] The method may further include the following steps: obtaining a voltage indication, such as open-circuit voltage (OCV) or state of charge (SOC), at a measurement temperature of at least one battery module; determining whether the voltage indication of any one of at least two battery modules is within a predetermined voltage range; and determining that filling the battery pack with oxygen is safe only if the obtained voltage indication of each battery module does not exceed the value of the predetermined voltage range. The inventors have recognized that if the battery modules are filled with oxygen when the voltage indication exceeds the voltage range, there is a risk of fire. When OCV is used as a voltage indication, preferably, the average voltage of each battery cell is calculated from the voltage on each battery module. In this way, only a voltage threshold needs to be used.

[0018] The predetermined voltage range is defined by a lower voltage indication threshold and an upper voltage indication threshold, and the voltage indication can be the open-circuit voltage OCV on the battery module or the state of charge SOC of the battery module.

[0019] The method may further include, if it is determined that filling the battery pack with oxygen is unsafe, initiating a step of discharging or charging the battery pack to the voltage of at least one battery module within a voltage range before initiating filling the battery pack with the determined amount of oxygen. According to an alternative, initiating the discharge or charge may involve sending a message to the battery operator to discharge or charge the battery. Alternatively, if the battery modules are connected for automatic discharge or charge, initiation may include the step of starting automatic discharge or charge.

[0020] Filling the battery pack with inert gas can be combined with starting the battery pack by filling it with oxygen, i.e., starting simultaneously. By filling with a combination of oxygen and inert gas, the fire hazard is further minimized. When the battery module is connected to a gas supply, the gas supply preferably contains the correct gas mixture of oxygen and inert gas.

[0021] The method may also include the step of adding hydrogen to the common gas space before filling the battery pack with oxygen if it is determined that filling the battery pack with oxygen is unsafe, which further improves the operating efficiency of the battery module.

[0022] The method may also include the step of adding hydrogen to the common gas space after filling the battery pack with oxygen, which further improves the operating efficiency of the battery module.

[0023] The method may further include the following steps: after filling the battery pack with oxygen, measuring the temperature of the battery pack and / or battery modules, and obtaining post-fill parameters related to the internal resistance of each battery module in the battery modules; determining whether the difference in post-fill parameters between any of the at least two battery modules exceeds a predetermined second threshold at the measurement temperature; and if the difference in post-fill parameters between any of the battery modules exceeds the second threshold, determining, based on the post-fill parameters of the battery modules at the measurement temperature of the battery pack and / or battery modules and data about the battery modules, to fill the battery pack with an additional amount of oxygen to further reduce the difference in post-fill parameters between any two battery modules to a level below the second threshold; and initiating filling of the battery pack with the determined additional amount of oxygen.

[0024] In an embodiment, the step of obtaining the indication parameter includes obtaining the internal resistance of all battery modules in the battery pack at the measured battery pack and / or battery module temperature. The method further includes the steps of: determining whether the difference in internal resistance of each cell between any pair of battery modules in the battery pack exceeds a predetermined first resistance threshold at the measurement temperature; and, if the difference in internal resistance of each cell between any pair of battery modules at the measured battery pack temperature and / or battery module temperature exceeds the predetermined first resistance threshold at a certain temperature, determining, based on the internal resistance of the different battery modules and the obtained data about the battery pack, the amount of oxygen to be filled into the battery pack to reduce the difference in internal resistance of each battery module to below the first resistance threshold. By obtaining the internal resistance of all battery modules, it can be ensured that the maximum difference in internal resistance compensated for for the measured temperature is detected.

[0025] The step of determining the amount of oxygen can determine the amount of oxygen to be filled into the battery module in order to obtain the difference in internal resistance of each battery cell between the battery modules below a second resistance threshold, wherein the second resistance threshold is lower than the first resistance threshold.

[0026] According to a second aspect of the invention, a computer program including instructions is provided for improving the operating efficiency of a battery pack, which, when executed on at least one processor, cause the at least one processor to perform the method according to the first aspect of the invention.

[0027] According to a third aspect of the invention, a computer-readable storage medium is provided, which carries a computer program according to a second aspect of the invention for improving the operating efficiency of a battery pack.

[0028] Preferably, the battery pack includes multiple battery modules having at least one NiMH battery cell.

[0029] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 The diagram illustrates a battery system used to balance a battery pack comprising two battery modules.

[0031] Figure 2 The diagram illustrates a battery system used to balance a battery pack comprising three battery modules.

[0032] Figure 3 A flowchart of a method for balancing a battery module according to an embodiment is shown.

[0033] Figure 4 A graph showing different measurements of resistance and voltage is provided.

[0034] Figure 5 The diagram illustrates the process based on... Figure 2 In a battery pack, how does the voltage on the battery cells change during cycling to ensure battery quality before oxygenation?

[0035] Figure 6 The diagram illustrates the process based on... Figure 2 In a battery pack, how does the voltage on the battery cells change during cycling to ensure the quality of the battery after oxygenation?

[0036] Figure 7 The first example is shown, illustrating how the internal resistance changes when balancing the battery pack.

[0037] Figure 8 A second example is shown, illustrating how the internal resistance changes when the battery pack is balanced. Detailed Implementation

[0038] Reference will be made to the accompanying drawings in the following description of the preferred embodiments. The drawings are not drawn to scale, and some dimensions may be exaggerated to clearly show all features. The same reference numerals will be used for similar features in different drawings.

[0039] The terminology used herein is for the purpose of describing specific aspects of this disclosure only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0040] In this application, terms related to the internal resistance of a battery module indicate parameters including the internal resistance of the battery module and the State of Health (SOH) measurement. The SOH measurement may include internal resistance and other parameters important for determining the condition of the battery module, such as internal pressure.

[0041] The term "internal resistance," which should be interpreted as referring to internal DC resistance, is used collectively in the description as a measure of the state of each battery module and battery cell. Internal resistance is obtained by measuring the voltage drop during controlled discharge using a predetermined discharge current. Subsequently, the internal resistance is calculated based on the measured voltage drop and discharge current. Examples can be found in the following standard: IEC 63115-1, Ed. 1.0 (2020-01), Chapter 7.6.3, Measurement of the internal DC resistance.

[0042] The example embodiments given herein are for methods of balancing battery cells, preferably battery cells with MH electrodes, and more preferably NiMH battery cells. As part of the development of the example embodiments given herein, problems will first be identified and discussed.

[0043] During the charging and discharging of a battery pack comprising multiple battery modules, such as a NiMH battery module (each module containing at least one cell), the performance of each cell will degrade due to electrolyte desiccation. It has been found that the addition of oxygen restores the electrolyte, resulting in a decrease in internal pressure during use, as gas recombination reactions are improved. Therefore, the battery module becomes less sensitive to unintentional overcharging and over-discharging. Electrolyte-deficient designs mean that only a minimal amount of electrolyte is available in the battery module. Any loss of electrolyte impairs performance, primarily manifested as increased internal resistance. Electrolyte desiccation is a major cause of limited cycle life. Electrolyte desiccation is mainly caused by excessive internal pressure within the cell, which may open a safety valve, releasing oxygen or hydrogen depending on misuse of overcharging or over-discharging and the negative electrode corrosion that consumes electrolyte and forms hydrogen. When two or more cell modules are gaseous, the cell will lose electrolyte unevenly. This can also be extended to battery modules with multiple cells.

[0044] The primary cause of this is uneven charging of the battery cells, as they are not 100% identical. This results in some cells heating up before others, and water (in gaseous form) migrates between the gaseous-connected battery cells, condensing in areas where the temperature is not too high. Consequently, water moves within the battery module and even between battery modules. As a result, one battery module will exhibit a faster increase in internal resistance than the others. This increase in internal resistance can lead to a reduction in the battery module's lifespan. The uneven increase in internal resistance between battery modules can lead to uneven battery module lifespan, thus reducing the lifespan of the entire battery pack.

[0045] Figure 1A battery system 50 is shown, comprising two battery modules 10, 10' connected in series to form a battery pack 100. Each battery module 10, 10' includes at least one battery cell 12 (preferably a nickel-metal hydride battery cell). Each battery module 10, 10' has a housing 30 that houses the at least one battery cell and seals off a gas space. Each battery cell 12 in the battery modules 10, 10' includes a first positive electrode, a second negative electrode, a porous separator, and an aqueous alkaline electrolyte disposed between the first and second electrodes. The separator, the first electrode, and the second electrode are configured to allow the exchange of hydrogen and oxygen by allowing gas to migrate between the two electrodes. Each battery module 10, 10' includes a positive terminal 11 and a negative terminal 12 that are in electrical contact with at least one battery cell 12 in each battery module, wherein the battery cells are preferably connected in series. The positive terminal 11 of the first module 10 constitutes the positive terminal of the battery pack 100, as indicated by the plus sign, and the negative terminal 12 of the last module 10' constitutes the negative terminal of the battery pack 100, as indicated by the minus sign.

[0046] The battery pack 100 is also configured to connect the gas spaces of each battery module 10, 10' to create a common gas space 29. The battery pack 100 also includes a gas inlet 25 for adding gas or liquid to the common gas space 29. Figure 1 A measuring component 13 is also shown, connected to the positive terminal 11 and negative terminal 12 of each battery module, and configured to obtain data needed to calculate indicative parameters related to the internal resistance of the battery modules 10, 10' between the positive terminal connector 11 and the negative terminal connector 12. The data obtained by the measuring component 13 may include voltage drop during discharge to determine internal resistance, temperature, internal pressure, and current, in the case of a current sensor included within the measuring component 13. The measuring component 13 can also be configured to measure the open-circuit voltage OCV between the positive terminal 11 and the negative terminal 12 in each battery module 10, 10'. Alternatively, the measuring component 13 can be connected to obtain data for only one battery cell 12. However, manufacturing a battery module with this functionality is very expensive. An inlet valve 16 is connected to a gas inlet 25. Figure 1 In this configuration, an optional gas container 17 is connected to an inlet valve 16. A local control unit 20 is connected to both the measuring unit 13 and the inlet valve 16, and can be configured to calculate indication parameters based on data provided from the measuring unit 13. A safety valve 24 (e.g., a rupture disc) is connected to a common space 29. The safety valve prevents the accumulation of hazardous gas pressure in the common gas space 29. A pressure sensor 23 can also be connected to the safety valve 24 to measure the internal pressure in the common gas space 29. The pressure sensor 23 is also connected to the local control unit 20.

[0047] Local control unit 20 communicates with control unit 14 via a wired or wireless connection. One or more intermediate units may also be present between local control unit 20 and control unit 14. Alternatively, the local control unit may be omitted, and control unit 14 may be directly connected to inlet valve 16 and measuring unit 13. Control unit 14 may be located in a remote location, such as at a battery module manufacturer. Central control unit 14 is connected to or includes memory 26.

[0048] Control unit 14 is configured to use measuring unit 13 to initiate measurements of temperature, pressure, voltage, and current at predetermined time intervals to calculate indication parameters (such as the internal resistance between positive terminal 11 and negative terminal 12) required for each battery module 10, 10', and to send this information, along with information identifying the battery module 10, 10', to control unit 14. To achieve this, control unit 14 sends a request to local control unit 20, which returns information related to the current indication parameters of the battery modules 10, 10', and optionally also returns the open-circuit voltage on the battery modules 10, 10' as a response. The internal resistance is not directly measured by measuring unit 13. It measures the voltage drop during discharge at a predetermined discharge current and then calculates the internal resistance, as described above.

[0049] During the use of battery modules 10 and 10', the battery modules are discharged and charged via the terminals of the battery pack marked with positive and negative signs in the diagram. The internal resistance of the battery modules increases with the number of charge and discharge cycles.

[0050] In the first example (not shown), battery module 10 is a standalone battery module having a housing that creates a gas space for all battery cells within the module, as disclosed in publications assigned to the applicant, WO2006 / 104442 or WO2007 / 093626. In the standalone battery module, the cells are configured in a bipolar configuration. In this example, the cells are connected in series with two plates to form a battery cell stack. The battery module has a housing that accommodates the battery cells and encloses the gas space. Connecting conduits must be provided to connect the gas space of the battery module to a common gas space.

[0051] In a second example (not shown), the battery modules are connected in series in a bipolar configuration. In this case, resistance is minimized by placing the positive terminal of the first battery module 10 opposite the negative terminal of the second module 10' to electrically connect the battery modules, thereby utilizing the entire surface of the respective end plates when the two battery modules are connected in series. No connecting tubes are required. Alternatively, sealing O-rings are placed between the modules to ensure a sealed configuration between the gas spaces within each battery module. These types of battery modules are disclosed in WO 2018 / 111182, assigned to the applicant.

[0052] Figure 2 A battery system 150 is shown, including a battery pack 120 according to an alternative embodiment of the invention. Figure 2 In this embodiment, three battery modules 10, 10', and 10" are connected in series to form a battery pack 120. The battery pack 120 also includes sealing rings (not shown) connecting the gas spaces of the battery modules 10, 10', and 10" to a common gas space 29. The battery pack 120 also includes a gas inlet for adding gas or liquid to the common gas space 29. An inlet valve 16 is connected to the gas inlet. An optional gas container 17 is connected to the inlet valve 16. A safety valve (not shown) may be connected to the common space 29 and may provide a pressure sensor 23 to measure the internal pressure within the common gas space 29.

[0053] The battery system also includes a local control unit 20 connected to the measuring component 13 and the intake valve 16. A safety valve prevents the accumulation of hazardous gas pressure in the common gas space 29. Each battery module 10, 10', 10" also includes a positive terminal and a negative terminal. Electrical connections between different battery modules 10, 10', 10" are provided via contact plates located between the battery modules.

[0054] Local control unit 20 may also be connected to pressure sensor 23, and local control unit 20 communicates with control unit 14, in this example via wired communication. One or more intermediate units may also be present between local control unit 20 and control unit 14. Alternatively, the local control unit may be omitted, and control unit 14 may be directly connected to pressure sensor 23, inlet valve 16, and measuring unit 13. As previously mentioned, control unit 14 may be located in a remote location, such as at, for example, a battery module manufacturer. In this example, central control unit 14 includes memory 26. The measuring unit is configured to obtain deterministic indication parameters (such as a first internal resistance R between the terminals of the first battery module 10). i1 and the optional first open-circuit voltage U1, and the second internal resistance R between the positive terminals of the second battery module 10'. i2 and an optional second open-circuit voltage U2, and a third internal resistance R between the positive terminals of the third battery module 10”. i3 And the data required for the optional third open-circuit voltage U3). The internal resistance is calculated based on the voltage drop during discharge current (as described above). The average internal resistance R of each battery cell in the first battery module 10 ic1 By measuring the internal resistance R i1 Divide by the number in the first battery module 10, i.e., ten battery cells, to determine. Similarly, calculate the internal resistance R of each battery cell in the second battery module 10' and the third battery module 10'". ic2 R ic3It is important to note that the indicated parameters related to internal resistance are temperature-dependent, and the measuring unit needs to measure the temperature of each module, or at least the battery pack temperature, in order to correctly calculate the internal resistance.

[0055] Figure 3 A flowchart of a method for balancing multiple battery modules in a battery pack is shown. The method includes a first step 101 of obtaining data about the battery pack. This can be done in many different ways. An example of how data can be obtained is that a local control unit sends a unique identification number to a control unit. The control unit can then retrieve data about the battery pack from memory. In a second step 102, indication parameters of at least two battery modules are obtained, illustrated here as internal resistance Ri, for example, R... i1 and R i3 According to one embodiment, data for calculating the internal resistance is obtained from a measuring component, and a control circuit system (e.g., a local control component 20) determines the resistance between the positive terminals of each battery module. The local control component then sends data related to the internal resistance to a control component, which may be the internal resistance R calculated for each battery module. i1 R i2 R i3 Or it could be information about measuring voltage drop at a specific discharge current.

[0056] In the third step 103, the control unit 14 determines whether the difference in internal resistance between any of the two battery modules exceeds a predetermined first resistance threshold R. t1 The first resistance threshold R t1 The first resistance threshold R corresponding to each cell at the measured battery pack and / or battery module temperature. tc1 The control unit can calculate the average internal resistance R of each cell in each battery module. ic This is necessary when the battery module includes different numbers of battery cells. However, if the battery module includes the same number of battery cells, this step can be omitted.

[0057] According to some embodiments, the indicator parameters for each battery module need to be higher than a common threshold, for example, corresponding to a level at least twice the internal resistance of a new battery module, in order to perform the process of balancing the battery modules in the battery pack. For example, if the internal resistance of a battery module is 6mΩ when it is new, then a common threshold of at least 12mΩ can be selected.

[0058] Therefore, for battery modules with the same number of battery cells, the absolute difference in the internal resistance between two battery modules, such as modules 10 and 10", can be compared with a predetermined first resistance threshold R. t1The comparison is used to perform the determination in step 103, namely ΔR. i =|R i1 -R i3 │>R t1 Alternatively, based on the internal resistance R of the battery module i1 R i2 R i3 Calculate a comparison between any of the at least two battery modules 10, 10', and 10" to determine whether any difference exceeds a predetermined first resistance threshold R. t1 .

[0059] When the battery module has a different number of battery cells, it is necessary to calculate the average internal resistance of each battery cell in each battery module, i.e., R. ic1 R ic2 R ic3 And by comparing the absolute difference of the average internal resistance between two battery modules (e.g., modules 10 and 10") with a first predetermined unit resistance threshold R tc1 To perform step 103, a comparison is made, for example, ΔR. ic =|R ic1 -R ic3 │>R tc1 Alternatively, based on the average internal resistance R of the battery module ic1 R ic2 R ic3 Calculate a comparison of each cell between any two battery modules to determine if any difference exceeds a predetermined first cell resistance threshold R. tc1 .

[0060] First resistance threshold R t1 This can be stored in memory 26 or implemented within the method, i.e., in the computer program that controls the execution of the method. If the calculation in step 103 is performed for the average internal resistance in the battery module, then it needs to be based on a first resistance threshold R for each battery cell. t1 And data about the battery pack, specifically the number of battery cells in each battery module, to determine the first cell resistance threshold R. tc1 More specifically, the control unit receives an identification number from the local control unit 20 and retrieves data about the battery module from its memory. This data could be that the battery pack includes ten battery cells in each battery module, or that the battery pack comprises three battery modules, such as... Figure 2 The battery pack 120 shown is shown.

[0061] Information regarding the energy capacity of each battery cell, the number of battery cells, and optionally the volume of the common gas space is forwarded from memory to the control unit. The control unit then divides the obtained resistance by the number of battery cells to determine the average internal resistance R of each battery cell in each of the two battery modules. ic1 R ic2 The absolute difference in the internal resistance of the two different battery modules does not exceed a predetermined first resistance threshold R. t1 Alternatively, the average internal resistance of each cell in two different battery modules shall not exceed a predetermined first cell resistance threshold R. tc1 In the case of the control unit waiting time T w During this period, wait for the next opportunity to obtain the updated value of the battery module's internal resistance.

[0062] The internal resistance ΔR of any two different battery modules i The absolute difference exceeds the predetermined first resistance threshold R. t1 In this case, the control unit is based on the internal resistance R of the battery module. i1 R i2 R i3 Based on the data about the battery pack, determine the amount of oxygen to be added to the battery pack (step 104) in order to reduce the internal resistance R between any two battery modules. i1 R i2 R i3 The difference, in order to reduce the difference below the first resistance threshold R. t1 The level, or preferably below the predetermined second resistance threshold R. t2 The level where the second threshold is lower than the first threshold, R t1 >R t2 Alternatively, in cases where the battery module contains varying numbers of battery cells, this is performed using the average internal resistance. The data used to determine the necessary amount of oxygen is preferably related to information about the energy capacity of each battery cell and the number of battery cells within each battery module, and optionally, the volume of the common gas space. The necessary amount of oxygen can be determined in many different ways, as described below.

[0063] According to one alternative, the control unit relies on early measurements to determine the necessary amount of oxygen to be filled into the common space of the battery pack. The control unit can consult a lookup table in memory to retrieve data about the battery pack corresponding to its identification number. In one example, the data about the battery pack could be a type number identifying the type of battery pack. The control unit can then retrieve the necessary amount of oxygen from different lookup tables based on the measured resistance and type number. The necessary oxygen amount in the lookup tables can, in turn, be based on earlier experiments using similar battery pack types.

[0064] According to another alternative, the control unit obtains the data needed to calculate the oxygen quantity from a lookup table. The data in the lookup table may include the number of battery cells in each battery module, the number of battery modules in the battery pack, the energy capacity of each battery cell, and the volume of an optional common gas space.

[0065] The method may also include obtaining a voltage indication U on each of at least two battery modules. n Optional step 105, where n equals the number of battery modules in the battery pack, such as U1, U2, U3. The voltage indication can be the open-circuit voltage OCV on the battery module or a measure of the state of charge (SOC) indicating whether adding oxygen to the battery module is safe. In this example, OCV will be used, and the determination in step 105 is made by measuring the open-circuit voltage U on the battery module. n And subsequently, determining whether the voltage on each of at least two battery modules in the battery module is within a predetermined voltage range, U t0 n t1 This can be performed as an optional step. Alternatively, for example, when the battery module contains different numbers of battery cells, the value of each battery cell U is determined. ci Step 105. In this case, the control unit 14 needs to have information about the number of battery cells included in the voltage measurement in order to obtain the average battery cell voltage and compare it with a predetermined cell voltage threshold U. ct Compare them.

[0066] like Figure 1 and Figure 2 As shown in the embodiments, voltage measurements are typically performed only across the entire battery module. If the module voltage U is determined... n Not exceeding the predetermined voltage threshold U t Therefore, it is safe to fill the battery pack with oxygen. On the other hand, if the battery module voltage is not within the voltage range, then an optional step of adjusting the module voltage of the battery module by charging or discharging the battery pack is performed before repeating step 105. This means that if the battery module voltage is higher than or equal to the upper limit voltage indication threshold U, n ≥U t1 Then the battery pack discharges (step 106a), and if the battery module voltage is lower than or equal to the lower limit voltage indication threshold U... n ≤U t0 ​​Then the battery pack is charged (step 106b). Performing these optional steps 105, 105a, and 106 is advantageous to reduce the risk of fire if oxygen is introduced into the battery pack when the voltage on the battery cells is too high. Such a fire could be caused by the fact that the oxygen recombination rate becomes too high at high voltages on the battery cells. If the battery module voltage becomes too low, oxygen will react directly with the negative electrode, which is not protected against hydrogen intercalation.

[0067] Figure 4 This refers to the resistance R of the battery module at room temperature (i.e., 20℃±2℃). in and the corresponding open-circuit voltages OCV and U on the nth battery module n A graph showing multiple measurements. Figure 4 The data in this document applies to NiMH battery modules with 10 cell units. The module's voltage threshold U... t It is the resistor R on the battery module. in functions, such as Figure 4 As shown in the diagram. The four surrounding points 27 indicate measurements where the voltage is too high to fill with oxygen.

[0068] As described above, in cases where it is determined that filling the battery pack with oxygen is unsafe, the method may include an optional intermediate step 106 of adjusting the battery module voltage. This is performed by charging or discharging the battery pack to a certain voltage before initiating the filling of the battery pack with the determined amount of oxygen in step 107 to ensure that the open-circuit voltage on each battery module in the battery pack is within an indicated voltage range. As an example, at a temperature of +20°C ± 2°C, the upper voltage indication threshold is 1.39V / cell, and the lower voltage indication threshold is 1.3V / cell. The upper and lower voltage indication thresholds depend on the temperature and can be normalized to a predetermined temperature range (such as room temperature) to ensure that the OCV is within the voltage range of 1.3-1.39V / cell. Otherwise, thresholds for different temperatures are needed to determine whether filling the battery modules with oxygen is safe.

[0069] When using SOC to determine whether it is safe to fill a battery module with oxygen, the upper SOC threshold is 95%, and the lower SOC threshold is 50%.

[0070] Battery modules 10, 10', and 10" can be filled with inert gas while the battery modules are being filled with oxygen, which reduces the risk of fire during the filling process. Figure 1 The diagram shows the use of gas container 17, which can be connected to gas inlet 25 via inlet valve 16. Control unit 14 can be configured to initiate filling by sending container 17 to the positions of battery modules 10, 10', 10"

[0071] According to some embodiments, the battery pack filling step may also include adding hydrogen to the common gas space before filling the battery pack with oxygen, which further improves the operating efficiency of the battery module. However, this step can only be performed when the voltage indication is within the voltage indication range and it is safe to fill the battery module with oxygen.

[0072] As a precaution, after filling the battery modules with oxygen in step 107, the method optionally includes an eighth step 108, wherein the control unit 14 obtains post-fill parameters related to the internal resistance after filling the at least two battery modules 10, 10', 10" in the battery pack. In an optional ninth step 109, it is determined whether the difference in internal resistance between any two battery modules 10, 10', 10" exceeds a predetermined second threshold, such as a second resistance threshold R. t2 If this is the case, then the method returns to step 104, where the amount of additional oxygen to be added to the battery pack is determined in order to reduce the difference in post-fill parameters between two of the at least two battery modules in the battery pack 100 to below a second resistance threshold R. t2 The level. The additional amount is the amount of oxygen to be filled into the battery pack in step 107. These optional steps provide a more robust approach because they allow for adjustments to the internal resistance R of the battery module. i1 R i2 R i3 Exceeding the first resistance threshold R again t1 Further cycles of the battery prior to this. The optional feedback loop from steps 109 to 104 should theoretically be unnecessary, but if it is necessary to add any additional oxygen to the battery pack, the battery pack is filled with the determined amount of oxygen. For this step to be meaningful, it is necessary to fill the oxygen more or less immediately. In cases where container 17 must be sent for filling, there may be a delay of several hours to several days before the battery pack is filled with oxygen.

[0073] In the case where this method aims to obtain the internal resistance difference between any two different battery modules (e.g., 10, 10") below a second resistance threshold, the absolute difference ΔR of the internal resistance of each battery module between the two different battery modules 10 and 10" is... i =|R i1 -R i3 │It should be lower than the second resistance threshold R t2 ΔR i <R t2 .

[0074] Step 109 can be replaced by a QA step because the internal resistance is determined as part of the QA step.

[0075] The control unit may execute step 101 of obtaining data about the battery pack differently depending on the length of time elapsed since the last data acquisition. The data may be stored briefly in the working memory of the control unit 14.

[0076] The above description has already described how the control unit 14 can perform the method - the control unit may include at least one processor 14'. Figure 1 The processor can be programmed with a computer program including instructions that, when executed on at least one processor, cause the processor to perform methods for improving the operating efficiency of the battery pack. The methods at the control unit can be implemented by a computer.

[0077] Example

[0078] Figure 5 The diagram illustrates the process based on... Figure 2 In a battery pack, how does the voltage on the battery cells change during cycling to ensure battery quality before oxygenation?

[0079] Figure 6 The diagram illustrates the process based on... Figure 2 In a battery pack, how does the voltage on the battery cells change during cycling to ensure the quality of the battery after oxygenation?

[0080] The table below includes details about oxygenation into the battery pack (an example of initiating the battery pack filling step). Figure 4 Step 107) and details about the internal resistance of each battery cell in different battery modules.

[0081]

[0082]

[0083] Table 1

[0084] Table 1 above shows the resistance of each battery cell in different battery modules 1-3 at different times during the balancing of the battery pack 120. As can be seen from the first column, oxygen is added in four steps. Before the first step, the internal resistance R of each battery cell is obtained through the battery modules connected in the battery pack. ic1 R ic2 R ic3 The difference in the fifth column refers to the internal resistance R of each battery cell between the first battery module 10 and the third battery module 10". ic1 R ic2 R ic3 The difference lies in the internal resistance R of each battery cell after the fourth oxygen charge. ic1 R ic2 Ric3 The biggest difference is with Figure 2 The maximum value is between the first battery module 1 and the third battery module 3 corresponding to battery module 10 and 10”.

[0085] Before the first oxygenation, perform the following: Figure 5 The quality assurance cycle is shown. The first voltage curve 31 of the first battery module 1 is clearly separated from the second voltage curve 32 of the second battery module 2 and the third voltage curve 33 of the third battery module 3. This is due to the average internal resistance R of each battery cell in the first battery module 1. ic1 The average internal resistance R of each battery cell in the second and third battery modules ic2 R ic3 The significant differences between the second voltage curve 32 and the third voltage curve 33 are due to the similar average internal resistance R of each battery cell. ic2 R ic3 And they get closer to each other.

[0086] After the fourth filling of oxygen into the battery pack 120, the internal resistance R of each battery cell between different battery modules ic1 R ic2 R ic3 The differences are significantly smaller, as shown in the last row of the table above. From Figure 6 This subtle difference can also be observed, with the first voltage curve 31, the second voltage curve 32, and the third voltage curve 33 being very close to each other. This indicates that the repeated QA steps are the same as the repeated quality assurance steps, including the charging and discharging of the battery module.

[0087] Figure 7 The first example is shown, illustrating how the internal resistance changes when balancing a battery pack. In Table 2 below, the battery pack resistance measurements (used as data to determine the amount of filler required to balance the battery) are expressed as the average K-factor and its standard deviation. The K-factor reflects the increase in average internal resistance from the initial average resistance of the battery pack. As an example, a K-factor of 2.5 indicates an increase in internal resistance from 4 mΩ to 10 mΩ.

[0088] Furthermore, equation (1) has been used to determine the required oxygen filling amount:

[0089] Y=(C1·x-C2)·M (1)

[0090] Where Y is the amount of oxygen filled in liters, C1 and C2 are constants, x is the average K-factor of the battery pack, and M is the number of modules in the battery pack. The constants are determined based on data about the battery modules, such as the number of battery cells in each module and the battery capacity. In this example, C1 = 5.8958, C2 = 5.3106, and M = 12 result in equation (2).

[0091] Y=(5.8958·x-5.3106)·12 (2)

[0092]

[0093] Table 2

[0094] When the difference in internal resistance (ΔR) i =R max -R min When ΔR is greater than a predetermined value, or when the standard deviation of the internal resistance exceeds a predetermined value, the battery pack filling process can be initiated. In this example, when ΔR... i >3.5mΩ (e.g.) Figure 7 When curve 40 is shown, the process is activated and the required amount of oxygen is calculated. In this example, the maximum oxygen filling is limited to 72 liters, and therefore performed in two steps. The result after the first filling of 72 liters is shown by curve 41, and an additional amount of oxygen is calculated after the first filling (37.9 liters), resulting in a second filling of 40 liters. The result after the second filling of 40 liters is shown by curve 42. In Table 2, it can be seen that the standard deviation of the internal resistance has been reduced to below the initial standard deviation of 0.020, and the battery pack is considered balanced.

[0095] Figure 8 A second example is shown, illustrating how the internal resistance changes when balancing the battery pack. Formula (2) has been used to calculate the amount of oxygen to be filled, and Table 3 shows the battery pack resistance measurements, the calculated filling amount of the balanced battery pack, the amount filled, and the internal resistance deviation.

[0096]

[0097]

[0098] Table 3

[0099] In this example, when ΔR i >2.5mΩ (e.g.) Figure 8When curve 50 is shown, the process is activated and the required amount of oxygen is calculated. The calculated volume of 107.8 liters is greater than the capacity of the filling equipment, so the filling step is performed in two separate steps, where the filling amount in the first filling step is selected to be approximately half of the calculated amount, i.e., 53 liters. The result after the first filling of 53 liters is shown in curve 51, and an additional amount of oxygen is calculated after the first filling (39.9 liters), resulting in a second filling of 40 liters. The result after the second filling of 40 liters is shown in curve 52. As can be seen in Table 3, after the second filling, the standard deviation of the internal resistance has decreased to below the initial standard deviation of 0.040, and the battery pack is considered balanced.

[0100] After this, the battery pack cycles, and the internal resistance within the battery pack increases, as does the difference in internal resistance between the battery modules, until it exceeds 2.5 mΩ (e.g., Figure 8 (See curve 55). The amount of oxygen required to balance the battery pack was calculated to be 67.6 liters. The results after the third fill of 68 liters are shown in curve 56. As can be seen in Table 3, after the third fill, the standard deviation of the internal resistance has decreased to below 0.030, and the battery pack is considered balanced.

[0101] This disclosure relates to a method for improving the operating efficiency of a battery pack comprising at least two battery modules 10, 10', 10" and wherein each battery module comprises at least one battery cell. Each battery module has a housing surrounding the at least one battery cell and enclosing a gas space, wherein the gas spaces of the battery modules are interconnected to form a common gas space 29. Each battery cell includes a first electrode, a second electrode, a porous separator, and an aqueous alkaline electrolyte disposed between the first and second electrodes, and the porous separator, the first electrode, and the second electrode are configured to allow the exchange of hydrogen and oxygen by allowing gas migration between the electrodes. At least one housing includes a gas inlet for adding gas or liquid to the common gas space. The method includes the steps of: obtaining data about the battery modules, wherein the data relates to the number of battery cells and the number of battery modules in each battery module, the temperature of each battery module, and the energy capacity of the battery modules (10, 10', 10"); and obtaining the internal resistance R of at least two battery modules in the battery modules (10, 10', 10"). i1 R i2 R i3 The relevant indicator parameters; if the difference in indicator parameters between battery modules exceeds a predetermined first threshold, based on the indicator parameters and data about the battery modules, determine the amount of oxygen to be filled into the battery modules, so that the difference in indicator parameters between any two battery modules is brought below the first threshold; and - initiate the filling of the battery pack based on the determined amount of oxygen.

[0102] According to some embodiments, the indicator parameter is selected as the internal resistance R of at least two of the battery modules 10, 10', and 10" i1 R i2 R i3 And the first threshold is the first resistance threshold R. t1 The process of filling the battery pack with oxygen reduces the difference in internal resistance between any two battery modules in battery modules 10, 10', and 10" to below a first resistance threshold R. t1 The level.

[0103] According to some embodiments, the indicator parameters are related to the state of health (SOH) of the battery module.

[0104] According to some embodiments, based on the indication parameters of each battery module and the number of battery cells in each battery module, the indication parameters of battery modules 10, 10', and 10" and a first threshold are determined for each battery cell.

[0105] According to some embodiments, the method further includes the following steps: obtaining voltage indicators U1, U2, and U3 on each of the at least two battery modules 10, 10', and 10" of 105; and determining whether the voltage indicators U1, U2, and U3 on any of the at least two battery modules of 105a exceed a predetermined upper limit voltage indicator threshold U. t1 ; and when the voltage indication of each of the at least two battery modules is lower than a predetermined upper voltage indication threshold U t1 At that time, the step of filling 107 is performed before the step of initiating 107 to fill the battery pack with the determined amount of oxygen.

[0106] According to some embodiments, a predetermined voltage indication threshold U t1 It is the internal resistance R of the at least two battery modules 10, 10', 10" i1 R i2 R i3 Functions that indicate relevant parameters.

[0107] According to some embodiments, when the voltage indication obtained on any of the at least two battery modules is equal to or higher than a predetermined upper limit voltage indication threshold U t1 The method further includes the following steps: discharging the battery pack 106a before initiating 107 to fill the battery pack with the determined amount of oxygen to reduce the voltage on the at least two battery modules 10, 10', 10" to a level below a predetermined upper limit voltage indication threshold.

[0108] According to some embodiments, the method further includes the step of: determining whether the voltage indication on any of the at least two battery modules 10, 10', 10" of 105a is lower than or equal to a predetermined lower limit voltage indication threshold U. t0 ; and when the voltage indication obtained on each of the at least two battery modules exceeds a predetermined lower voltage indication threshold (U t0 When ), execute the step of initiating filling 107.

[0109] According to some embodiments, when the voltage indication obtained on any of the at least two battery modules 10, 10', 10" is lower than or equal to a predetermined lower limit voltage indication threshold U t0 The method further includes the following steps: prior to initiating the step of filling battery module 107 with the determined oxygen filling amount, charging the battery pack 106b to increase the voltage on the at least two battery modules 10, 10', 10" to above the lower limit voltage indication threshold U. t0 The level.

[0110] According to some embodiments, the step of initiating filling 107 further includes filling the battery pack with hydrogen before filling the at least two battery modules with oxygen.

[0111] According to some embodiments, the voltage indication is selected as the open-circuit voltage on the at least two battery modules, and the upper voltage indication threshold and the lower voltage indication threshold depend on the temperature.

[0112] According to some embodiments, the voltage indication is related to the state of charge (SOC) of the battery module.

[0113] According to some embodiments, battery packs 100 and 150 are filled with inert gas along with battery packs 100 and 150 filled with oxygen.

[0114] According to some embodiments, the inert gas is selected as any combination of the following: argon, nitrogen, helium, and / or air.

[0115] According to some embodiments, the step of initiating filling 107 further includes initiating the preparation of container 17 with the determined oxygen filling amount to reduce the difference in indicated parameters between the at least two battery modules. The pressure of the gas in the container depends on the volume of the container and the amount of gas in the container. For small containers, the amount of gas in the container is approximately the same as the oxygen filling amount. However, after filling the container with oxygen, a residual amount of oxygen will always remain in the container. The flow of gas from the container to the battery modules will continue until the pressure in the container is the same as the pressure in the common gas space of the battery modules. Therefore, the amount of gas in the container must be slightly greater than the filling amount.

[0116] According to some embodiments, after filling the battery pack with oxygen, the step further includes: obtaining the internal resistance R of the battery pack after filling. i1 R i2 R i3 The relevant post-fill parameters determine whether the post-fill parameters between any of the at least two battery modules 10, 10', 10'" exceed a predetermined second threshold. If the difference in post-fill parameters between any of the battery modules exceeds the second threshold, based on the post-fill parameters of the battery modules and data about each battery module, the additional amount of oxygen to be added to the battery pack is determined in order to reduce the difference in post-fill parameters between any two battery modules to below a second resistance threshold R. t2 The level; and filling the battery pack with the determined amount of additional oxygen.

[0117] According to some embodiments, the method is performed on a battery pack comprising nickel metal hydride (NiMH) battery cells.

[0118] This disclosure also relates to a computer program including instructions for improving the operating efficiency of a battery pack, which, when executed on at least one processor 14', cause at least one processor 14' to perform the method described above.

[0119] This disclosure also relates to a computer-readable storage medium carrying a computer program as described above for improving the operating efficiency of a battery pack.

[0120] This disclosure also relates to a container 17 for balancing battery packs 100 and 150, wherein the container is filled with at least a certain amount of pressurized oxygen for filling the battery pack with the amount of oxygen to perform the above-described method.

[0121] Various aspects of this disclosure are described with reference to the accompanying drawings, such as block diagrams and / or flowcharts. It should be understood that several entities in the drawings, such as blocks in the block diagrams, and combinations of entities in the drawings, can be implemented by computer program instructions that can be stored in a computer-readable storage medium and can also be loaded onto a computer or other programmable data processing apparatus. Such computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, and / or other programmable data processing apparatus to produce a machine such that the instructions, which execute via the processor of the computer and / or other programmable data processing apparatus, create means for implementing the functions / actions specified in the block diagrams and / or one or more flowchart blocks.

[0122] In some embodiments and according to some aspects of this disclosure, the functions or steps marked in the boxes may not occur in the order indicated in the operating instructions. For example, two boxes displayed consecutively may actually be executed substantially simultaneously, or these boxes may sometimes be executed in reverse order, depending on the functions / actions involved. Furthermore, according to some aspects of this disclosure, the functions or steps marked in the boxes may be executed consecutively in a loop.

[0123] Exemplary aspects of this disclosure have been shown in the accompanying drawings and description. However, many variations and modifications can be made to these aspects without substantially departing from the principles of this disclosure. Therefore, this disclosure should be considered illustrative rather than restrictive, and is not limited to the specific aspects discussed above. Thus, while specific terms have been used, they are used in a general and descriptive sense only and not for limiting purposes.

Claims

1. A method for improving the lifespan of a battery pack (100; 150) comprising at least two nickel metal hydride (NiMH) battery modules (10, 10', 10''), wherein each battery module comprises at least one battery cell, wherein each battery module (10, 10', 10'') has a housing surrounding the at least one battery cell and enclosing a gas space, wherein the gas spaces of the battery modules (10, 10', 10'') are interconnected to form a common gas space (29), wherein each battery cell comprises a first electrode, a second electrode, a porous separator, and an aqueous alkaline electrolyte disposed between the first and second electrodes, wherein the porous separator, the first electrode, and the second electrode are configured to allow the exchange of hydrogen and oxygen by allowing gas migration between the electrodes, and wherein at least one housing comprises a gas inlet for adding gas or liquid to the common gas space; characterized in that, The method includes the following steps: - Obtain data (101) regarding the battery modules (10, 10', 10''), wherein the data relates to the number of battery cells in each battery module (10, 10', 10'') and the number of battery modules (10, 10', 10''), the temperature of each battery module, and the energy capacity of the battery modules (10, 10', 10''). - Obtain the internal resistance (R) of at least two of the battery modules in the (102) battery modules (10, 10', 10''). i1 R i2 R i3 ), - The difference in internal resistance between any battery modules in the battery module exceeds a predetermined first resistance threshold (R). t1 In the case of ), based on the internal resistance and data about the battery modules, determine (104) the amount of oxygen to be filled into the battery modules (10, 10', 10'') so as to reduce the difference in internal resistance between any two battery modules to below a predetermined first resistance threshold (R). t1 ) level, - Initiate battery pack filling based on the determined oxygen filling amount (107).

2. The method according to claim 1, wherein, Based on the internal resistance of each battery module and the number of battery cells in each battery module, the internal resistance of each battery cell in the battery modules (10, 10', 10'') and a predetermined first resistance threshold (R) are determined. t1 ).

3. The method according to claim 1, wherein, The method further includes the following steps: - Obtain voltage indications (U1, U2, U3) on each of the at least two battery modules (10, 10', 10'') as described in (105), and - Determine (105a) whether the voltage indication (U1, U2, U3) on any of the at least two battery modules (10, 10', 10'') exceeds a predetermined upper limit voltage indication threshold (U t1 ),as well as - When the voltage indication of each of the at least two battery modules is lower than a predetermined upper voltage indication threshold (U... t1 When ), perform the filling (107) step.

4. The method according to claim 3, wherein the voltage indication on any of the at least two battery modules is equal to or higher than a predetermined upper limit voltage indication threshold (U). t1 When the method is used, it further includes the following steps: - Before initiating (filling) the battery pack (107) with the determined oxygen filling amount, discharge (106a) the battery pack to reduce the voltage on the at least two battery modules (10, 10', 10'') below a predetermined upper limit voltage indication threshold (U). t1 ) level.

5. The method according to claim 3, further comprising the following step: - Determine (105a) whether the voltage indication on any of the at least two battery modules (10, 10', 10'') is lower than or equal to a predetermined lower voltage indication threshold (U). t0 ),as well as - When the voltage indication on each of the at least two battery modules (10, 10', 10'') exceeds a predetermined lower voltage indication threshold (U... t0 When ), the step of initiating filling (107) is executed.

6. The method according to claim 5, wherein the voltage indication on any of the at least two battery modules (10, 10', 10'') is lower than or equal to a predetermined lower voltage indication threshold (U). t0 When the method is used, it further includes the following steps: - Before performing the step of initiating the filling (107) of the battery modules with the determined oxygen filling amount, the battery pack is charged (106b) to increase the voltage on the at least two battery modules (10, 10', 10'') to above a predetermined lower limit voltage indication threshold (U). t0 ) level.

7. The method according to claim 5, wherein, The step of initiating filling (107) also includes filling the battery pack with hydrogen before filling the at least two battery modules with oxygen.

8. The method according to claim 5, wherein, The voltage indication is selected as the open-circuit voltage on the at least two battery modules, and the upper voltage indication threshold and the lower voltage indication threshold depend on the temperature.

9. The method according to claim 3, wherein, The voltage indication is related to the battery module's state of charge (SOC).

10. The method according to claim 1, wherein, Battery packs (100; 150) filled with inert gas, along with battery packs (100; 150) filled with oxygen.

11. The method according to claim 10, wherein, The inert gas is selected from any combination of the following: argon, nitrogen, helium and / or air.

12. The method according to claim 1, wherein, The step of initiating filling (107) further includes initiating the filling of container (17) with the determined amount of oxygen to reduce the difference in internal resistance between the at least two battery modules.

13. The method of claim 1, further comprising the following steps after filling the battery pack with oxygen: - Obtain the internal resistance (R) of the (108) battery pack after filling. i1 R i2 R i3 ), - Determine whether the difference in the filled internal resistance between any of the at least two battery modules (10, 10', 10'') exceeds a predetermined second resistance threshold (R). t2 ), - The difference in internal resistance after filling between any of the battery modules (10, 10', 10'') exceeds a predetermined second resistance threshold (R). t2 In the case of ), based on the internal resistance of the battery modules after filling and data about each battery module, the amount of additional oxygen to be filled into the battery pack is determined in order to reduce the difference in internal resistance after filling between any two battery modules (10, 10', 10'') to below a second resistance threshold (R). t2 The level of ) and - Fill the battery pack with the determined amount of additional oxygen.

14. A computer program comprising instructions for improving the operating efficiency of a battery pack, wherein, when executed on at least one processor (14'), the instructions cause the at least one processor (14') to perform the method according to any one of claims 1-13.

15. A computer-readable storage medium carrying a computer program for improving the operating efficiency of a battery pack as described in claim 14.

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