Method for carrying out a deep discharge of a battery by means of a deep discharge device, computer program product, computer-readable storage medium, and deep discharge device

Abstract

The invention relates to a method for carrying out a deep discharge (16) of a battery (12) by means of a deep discharge device (10), having the steps of: providing the battery (12) with an emptied state of charge (VSoC0%); applying a specified first discharge current (18) to the emptied battery (12) up to a specified first voltage value (20) of the battery (12) by means of an electronic computing device (14) of the deep discharge device (10); reversing the polarity of the battery (12) by means of the deep discharge device (10) when the specified first voltage value (20) is reached; and applying a second discharge current (18) up to a specified second voltage value (22) by means of the electronic computing device (14) when the polarity of the battery (12) is reversed, the second voltage value (22) being a negative voltage value. The invention also relates to a computer program product, to a computer-readable storage medium, and to a deep discharge device (10).

Description

[0001] Description

[0002] Method for performing a deep discharge of a battery using a deep discharge device, computer program product, computer-readable storage medium and deep discharge device

[0003] The following invention relates to a method for performing a deep discharge of a battery using a deep discharge device according to claim 1. The invention further relates to a computer program product, a computer-readable storage medium and a deep discharge device.

[0004] The safe and efficient recycling of batteries is a topic of growing importance given their increasing use in electrical devices and the growing number of electric vehicles. The term "battery" is used here to refer to individual cells, cell assemblies, battery modules, and battery packs. Among the various steps of the recycling process, battery disassembly, often automated using a shredder, plays a crucial role before the actual recovery of raw materials using hydro- and pyrometallurgical processes. If batteries are fed into the shredding process without prior deactivation, or without controlled deactivation, two key problems arise.

[0005] Lithium-based batteries can pose hazards if handled improperly. During the mechanical shredding process, energy still stored in the battery is suddenly released, which can lead to fires and explosions, for example. This presents a safety risk to personnel and the machinery used by the recycler. If a large battery pack is to be manually disassembled into smaller modules, a multi-stage, usually manual, disassembly process is necessary. When loosening screws, opening covers, and exposing cables and contacts, the battery's energy can discharge uncontrollably. This poses a risk to the processing personnel, for example, from electric shock.

[0006] Furthermore, every battery, even at zero percent charge, retains a significant amount of residual energy. If this energy is not drawn from the battery in a controlled manner, it is converted into heat. This prevents the energy from being fed back into the building's electrical system, the wider power grid, or the DC link for battery discharge to allow for analysis measurements. One way to extract this residual energy is through deep discharge. In this process, batteries with a residual voltage are delivered to a recycler's factory, for example, and connected to power electronics for discharge. If the battery type and datasheet are known, it is generally safe to discharge to the lower voltage limit. The battery is then discharged continuously at the same current to a lower voltage, for example, zero volts.This process is controlled by a constant current. The lower voltage value from the previous step, for example zero volts, can be maintained for a specific period to achieve a more thorough discharge of the battery. The battery is then disconnected from the power electronics to be sent on to the next stage of the recycling process. During this process, the battery voltage returns to a significantly positive value.

[0007] While the residual energy of a single cell may not pose a problem, the individual voltages of cells connected in series within a module or pack can add up to a dangerous total voltage. The deep discharge performed so far does not yet create safe conditions for further use. Potential hazards such as electric shocks upon contact, fires due to thermal runaway, or explosions during shredding or manual disassembly remain.

[0008] Particularly when the battery is electrically deactivated before further processing, the recycler uses power electronics to discharge it to the discharge cut-off voltage of zero volts, as previously described. However, it has been shown that this method does not extract all the remaining energy from the battery, as evidenced, for example, by the excessively positive values ​​of the relaxing voltage. Therefore, safety risks for both people and machinery remain.

[0009] To avoid this, the terminals of an individual cell or the contacts / BUS bars of a module / pack are short-circuited immediately after discharge or upon reaching a discharge cut-off voltage. However, since insufficient deep discharge means that not all of the battery's energy is extracted, a manual short-circuiting procedure generates heat, which, especially with numerous cells in a group, can reach a critical state and provoke thermal runaway. Although a discharged and short-circuited module exhibits a voltage of zero volts at its edges, individual cells in the series connection within the module may still retain a residual voltage due to the following asymmetries.The state of charge (SoC) can vary within individual batteries. For example, discharging at a constant current can cause individual cells to reverse polarity uncontrollably, resulting in a discharge into the negative voltage range. This polarity reversal triggers chemical reactions, such as electrolyte decomposition. Furthermore, batteries can exhibit different stages of aging. Not all cells within a battery pack age at the same rate. Variations in material and manufacturing properties, as well as the battery's placement within the module, affect its health differently; for instance, there can be variations in the residual electrolyte content.

[0010] Both of these factors cause some batteries within a battery pack to reach or fall below the lower voltage limit of the deep discharge procedure more quickly, i.e., to reverse polarity if the lower voltage limit is zero volts or less. This heats up the module, posing a risk of thermal runaway. Furthermore, batteries can suddenly exhibit infinitely high resistance, for example, if the current interrupt device is triggered by excessive pressure within the battery. In series-connected batteries that are part of the circuit, this creates an open circuit, preventing any further energy from being drawn from the batteries in that circuit. Consequently, manually disassembling such a module would pose a safety risk to personnel and the machinery used at the recycling facility.

[0011] The object of the present invention is to provide a method, a computer program product, a computer-readable storage medium and a deep discharge device by means of which improved deep discharge of the battery can be achieved.

[0012] This problem is solved by a method, a computer program product, a computer-readable storage medium, and a deep discharge device according to the independent claims. Advantageous embodiments are specified in the dependent claims.

[0013] One aspect of the invention relates to a method for performing a deep discharge of a battery using a deep discharge device. The battery is provided in a depleted state of charge. A predetermined first discharge current is applied to the depleted battery by means of an electronic control unit of the deep discharge device until a predetermined first voltage value of the battery is reached. The battery is then reversed by means of the deep discharge device upon reaching the predetermined voltage value, and a second discharge current is applied with the battery reversed until a predetermined second voltage value, wherein the second voltage value is a negative voltage value, is reached by means of the electronic control unit.

[0014] In particular, this method allows for the controlled creation of an internal short circuit during deep discharge of batteries. As a result, the battery is completely discharged. After the battery is removed from the power electronics used for discharging, it is devoid of residual energy, thus posing no safety risk during shredding or dismantling. This internal short circuit is created by a controlled reversal of the battery's polarity into the negative voltage range, i.e., a battery voltage of less than zero volts.

[0015] In particular, the discharged battery is defined by the final voltage specified in the datasheet, at which the battery's state of charge is zero percent. However, even at zero percent state of charge, which corresponds to the discharged state, the battery still retains a certain residual energy. Specifically, after reaching the final voltage, particularly according to the specified datasheet, the predefined discharge current is applied to a predefined second final voltage. During this process, the battery's polarity is reversed. The maximum desired negative final voltage can be selected as the so-called discharge cut-off voltage. This controlled deep discharge with polarity reversal results in significant differences compared to the current state of the art.In particular, recurrent voltage spikes, known as voltage disturbances, which can lead to hazardous situations during further processing after deep discharge of the batteries, can be avoided. This protects both the human employees and the machinery in the recycling plant.

[0016] Deactivated batteries no longer need to be stored or transported in isolation or protection, for example, in designated containers of the appropriate protection class. Transport and handling inside and outside factory buildings are possible with significantly reduced risk. Since the batteries no longer have any residual voltage, they are no longer classified as hazardous goods during transport. Short-circuiting the battery to achieve zero volts is no longer necessary, as the deep discharge with polarity reversal proposed here leads to almost complete deactivation. Hazards from deliberate short circuits at a holding voltage of zero volts or higher, such as uncontrolled temperature increases, are avoided. The residual voltages of the batteries are close to zero volts; therefore, short-circuiting the module / pack is no longer essential.Should this nevertheless be done for safety reasons, no dangerously high temperatures, sparks or thermal runaway will occur.

[0017] Furthermore, the polarity reversal can be performed in several stages, individually tailored to the battery's characteristics, even with multiple discharge cut-off voltages in the negative voltage range. The individually adjustable deactivation process prevents thermal runaway due to uncontrolled chemical reactions, transport processes, or current-induced heating. Further processing, for example in a shredding process, can then take place without a sudden voltage discharge within the module / pack, which could lead to fire or explosion.

[0018] According to an advantageous embodiment, the first voltage value is essentially zero volts. In other words, the battery is deeply discharged to zero volts, and then a polarity reversal is performed when the voltage reaches zero. This allows a negative voltage value to be reached, enabling the battery to be reliably discharged towards the second voltage value. Thus, reliable battery discharge can be achieved.

[0019] It is also advantageous if a negative final voltage of the battery is specified as the second voltage value. Specifically, a negative final voltage is applied. If the battery is then discharged until the negative final voltage is reached, residual energy within the battery can be prevented, even after the battery has relaxed.

[0020] It has also proven advantageous to perform a battery relaxation phase after reaching the second voltage value. Specifically, no discharge current is applied to the battery during this relaxation phase. The battery relaxes and, in doing so, dissipates the heat that was present when the discharge current was applied. Based on this, a new voltage is established. After relaxation, it can be verified whether the battery has been completely discharged. Furthermore, it has proven advantageous to determine a third voltage value of the relaxed battery. This third voltage value can be determined after relaxation, particularly after a predetermined relaxation time. This allows verification of whether the battery is completely discharged.

[0021] In a further advantageous embodiment, if the third voltage value exceeds a predetermined threshold, a discharge current is applied again, and the polarity is reversed upon reaching the first voltage value. Particularly with aged batteries, residual energy may remain after an initial deep discharge and subsequent relaxation. Should the voltage threshold be exceeded, a discharge current can be applied again, and the battery can be deep-discharged once more, ideally down to the second or a further voltage value. This essentially ensures that the battery is fully discharged.

[0022] It can also be stipulated that after the second discharge step, the battery is relaxed again and a relaxed voltage value is measured again. This can be repeated, in particular, until the battery essentially has zero residual energy.

[0023] It is also advantageous to discharge the battery at a C-rate between 0.1C and 2.0C, particularly at 0.5C. The C-rate depends primarily on the battery's maximum possible discharge current. 1C means, in particular, that the battery's entire energy, especially when charged between zero and 100 percent, is extracted within one hour. Discharging at a rate between 0.1C and 2.0C, especially at 0.5C, ensures that thermal reactions within the battery are prevented. This allows for reliable deep discharge of the battery.

[0024] Another advantageous design provides that the battery is discharged to a completely empty state of charge using the deep discharge device before the deep discharge process. In other words, the battery should not be delivered completely empty, where "empty" specifically means zero percent of the state of charge. The deep discharge device allows the state of charge to be checked beforehand, and a discharge to zero percent, specifically to a completely empty state, to be carried out. This then allows the deep discharge process to be carried out safely.

[0025] It is also advantageous to discharge the battery at a C-rate between 0.5C and 3C, particularly at 1C. This prevents excessive heating of the battery during the discharge process.

[0026] According to a further advantageous embodiment, the battery temperature is monitored, at least during deep discharge. For this purpose, suitable temperature sensors or a thermal imaging camera can be used, for example. This prevents thermal runaway during deep discharge. If the temperature exceeds a certain threshold, the discharge current can be reduced accordingly. If the temperature is not exceeded, the discharge current can be increased, thus accelerating the deep discharge process.

[0027] It has also proven advantageous to maintain the second voltage value for a predefined period upon reaching it. In particular, this allows, for example, the final voltage to be held in the negative range for a predefined period to ensure adequate battery discharge. A relaxation phase can then follow.

[0028] Furthermore, it has proven advantageous to determine and categorize the battery's state of health before deep discharge and to perform the deep discharge accordingly. In particular, this allows for an optional safety assessment of the process before deep discharge with polarity reversal to create an internal short circuit. This assessment specifically estimates the state of health (SoH) of the battery and / or individual cells within the battery, as well as determining the cell internal resistance. This can be done, for example, by measuring the capacity, internal resistance, or electrochemical impedance. All of the aforementioned measurement methods provide a data basis for deciding whether a battery can be subjected to the deep discharge procedure with polarity reversal proposed here.The decision as to whether a battery is functioning correctly or not can be made based on a single parameter or a combination of parameters. It has been shown that simply determining the state of health based on capacity data does not provide sufficient information about the battery's discharge characteristics. Even batteries with a higher state of health can, for example, exhibit problems with deep discharge and reverse polarity if they have high internal resistance. The described method, however, is optional and can also be considered an independent aspect of the invention. All batteries can also be subjected to the deep discharge and reverse polarity test. However, success of the method is not guaranteed. In particular, the battery can be classified as healthy, aged, or corrupt. If the battery is classified as healthy or aged, the method can be performed.If the battery is classified as corrupt, the procedure should not be carried out.

[0029] In particular, the C-rates and final voltages of the deep discharge can thus be selected depending on the state of health.

[0030] The presented method is, in particular, a computer-implemented method. Therefore, a further aspect of the invention relates to a computer program product with program code means which, when the program code means are executed by the electronic computing device, cause a method according to the preceding aspect to be carried out.

[0031] Furthermore, the invention also relates to a computer-readable storage medium containing the computer program product.

[0032] A further aspect of the invention relates to a deep discharge device for performing a deep discharge of a battery, comprising at least one electronic computing device, wherein the deep discharge device is configured to perform a method according to the preceding aspect. In particular, the method is carried out using the deep discharge device.

[0033] Advantageous embodiments of the process are to be regarded as advantageous embodiments of the computer program product, the computer-readable storage medium, and the deep discharge device. The deep discharge device, in particular, possesses specific physical features to enable the execution of the corresponding process steps. A computing unit / electronic computing device can be understood, in particular, as a data processing device containing a processing circuit. The computing unit can thus, in particular, process data to perform arithmetic operations. This may also include operations to perform indexed accesses to a data structure, for example, a lookup table (LUT).

[0034] The computing unit may, in particular, contain one or more computers, one or more microcontrollers, and / or one or more integrated circuits, for example, one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and / or one or more systems on a chip (SoCs). The computing unit may also contain one or more processors, for example, one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs), and / or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit may also include a physical or virtual array of computers or other units of the aforementioned type.

[0035] In various embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more storage units.

[0036] A storage unit can be volatile data storage, for example as dynamic random access memory (DRAM) or static random access memory (SRAM), or as non-volatile data storage, for example as read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or flash EEPROM, ferroelectric random access memory (FRAM), or magnetoresistive random access memory.It can be designed as MRAM (magnetoresistive random access memory) or as phase-change random access memory, PCRAM (phase-change random access memory).

[0037] For use cases or application situations that may arise in a method according to the invention and that are not explicitly described herein, it may be provided that, according to the method, an error message and / or a request for user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0038] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0039] Further features and combinations of features of the invention will become apparent from the figures and their description, as well as from the claims. In particular, further embodiments of the invention need not necessarily include all features of any one of the claims. Further embodiments of the invention may have features or combinations of features not mentioned in the claims.

[0040] This shows:

[0041] FIG 1 shows a schematic block diagram according to one embodiment of a deep discharge device; and

[0042] FIG 2 shows a schematic voltage-current-time diagram during the execution of a deep discharge according to the inventive concept.

[0043] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0044] FIG. 1 shows a schematic block diagram according to an embodiment of a deep discharge device 10. The deep discharge device 10 is designed for deep discharging a battery 12. For this purpose, the deep discharge device 10 has at least one electronic computing unit 14. Furthermore, the deep discharge device 10 has a polarity reversal device. In this example, this is implemented only as software in the electronic computing unit 14. However, the polarity reversal device can also be implemented mechanically, for example, in the form of switching elements. A method for carrying out a deep discharge 16 (FIG. 2) can be carried out using the deep discharge device 10.

[0045] Figure 2 shows a voltage-current-time (V-T) diagram. The upper part of Figure 2 shows a time-voltage diagram, while the lower part shows a time-current diagram. Specifically, seven different time steps, S1 to S7, are shown, which display both the current and voltage waveforms.

[0046] FIG 2 thus shows the schematic sequence of a deep discharge with several polarity reversal steps. In the first journal S1, for example, battery 12 with a residual voltage Vs0cobisioo% is delivered to the recycler's factory and connected to the deep discharge device 10 for electrical deactivation. The state of charge (SoC) is between zero percent, which means completely discharged, and 100 percent, which means fully charged. With a defined current, for example 1 C, within the specifications of battery 12 in the second journal S2, battery 12 is discharged down to a voltage V. SoThe battery is discharged to the lower voltage limit of battery 12 according to the datasheet. The maximum current depends on the tolerable current specified in the datasheet. If a significant temperature increase is expected for certain batteries 12 after this process, the current for this step can be set lower. This reduces the amount of heat generated in battery 12, eliminating the need for extended pauses to dissipate the heat. This prevents thermal runaway of battery 12 and can save time overall. Specifically, in the third stage, S3, after reaching the final voltage Vs0co% according to the datasheet, the battery is deeply discharged at a lower current, for example, 0.5 C, down to a predefined negative final voltage. During this stage, the polarity of battery 12 is reversed.The maximum desired negative cut-off voltage can be directly selected as the discharge cut-off voltage. For aged batteries 12, it has been shown that this voltage cannot be directly reached due to kinetic limitations within the battery 12. Typically, only a lower voltage V is reached during the first polarity reversal step. S te PiThe maximum negative terminal voltage is reached. For batteries in a high state of health, such as brand new ones, a single polarity reversal step may be sufficient to reach the maximum negative terminal voltage. The selected current depends on the characteristics of battery 12. The higher the current, the faster the process can occur. However, excessively high discharge currents can lead to overheating of battery 12. If the temperature of battery 12 exceeds a defined maximum, the discharge or polarity reversal can be interrupted to allow the battery voltage to relax and the heat to dissipate.

[0047] The negative discharge cut-off voltage V reached in the third journal S3 S t epiThe negative voltage is held for a defined period. Even if, due to inhibition caused by kinetics, polarization, and / or diffusion effects, the maximum defined negative cutoff voltage is not reached in aged batteries 12, kinetic processes still occur within the battery 12, such as the dissolution of copper ions or the copper foil of the current collector at the anode. This promotes the internal short circuit of the battery 12. The duration of the negative voltage can vary. A shorter duration, especially for aged batteries, allows for a faster transition to the second polarity reversal step, in which a lower cutoff voltage can generally be reached, thus enabling the internal short circuit to occur more quickly.

[0048] In the fifth time step S5, particularly to reduce polarization or diffusion effects in the batteries 12, a first relaxation step is initiated. The resulting relaxation voltage V Re iaxi is generally insufficient for safe further processing, especially with aged batteries 12. During the relaxation phase, both the voltage and temperature of the battery 12 decrease. Performing multiple relaxation steps therefore has a positive effect on process safety, but can take more time.

[0049] In a sixth magazine S6, which corresponds in particular to a second polarity reversal step, a defined current, which corresponds, for example, to that of the first polarity reversal step, is applied up to a negative discharge cut-off voltage Vste. P2 discharged. This voltage can be reached quickly through the reduction of the inhibiting effects in the fifth magazine S5 and is generally lower for aged batteries than in the first polarity reversal step, which allows the internal short circuit of battery 12 to be brought about more quickly. V S te P Voltage 2 can be held for a specific time before relaxation occurs. Alternatively, the duration could also be controlled via the current. If the reversal of battery 12 creates sufficient electrically conductive paths between the electrodes to cause a short circuit, the current increases in magnitude to maintain the target voltage. For example, if the threshold is exceeded, the voltage holding process can be terminated and relaxation initiated. In the present seventh time step S7, the voltage V relaxes. Reiax2 more quickly than before, down to a stable value of zero volts. The slope of the relaxation curve allows for a timely determination of whether the polarity reversal was successful. Successful completion of the deep discharge with polarity reversal ensures that battery 12 can be safely processed further.

[0050] Should the voltage rise to an unsatisfactory level, where a risk to personnel and machinery cannot be ruled out, additional polarity reversal steps can be performed. These can be based on the process already described. In particular, a discharge in the negative range up to the known final voltage V can be carried out. S t ep 2. This gives battery 12 additional time to complete all internal processes that take place during the polarity reversal. This leads to the final deactivation.

[0051] Furthermore, a discharge in the negative range can occur at a lower final voltage value than V. st ep2 is implemented. This ensures that the processes inside the battery, such as the formation of electrically conductive copper bridges, can take place completely during the polarity reversal. This can be helpful if the battery 12, for example, has different properties than known due to its history or area of ​​application. An instantaneous deep discharge 16 down to the negative voltages proposed here can lead to an uncontrolled temperature rise. Therefore, for process reliability, it is beneficial if the discharge cut-off voltage is reduced gradually.

[0052] In particular, FIG. 2 shows the method for carrying out the deep discharge 16. At least one battery 12 is provided with the discharged state of charge according to the second journal S2. A predetermined first discharge current 18 is then applied to the discharged battery 12 by means of the electronic computing device 14 until a predetermined first voltage value 20 is reached, and the polarity of the battery 12 is reversed by means of the deep discharge device 10 when the predetermined first voltage value 20 is reached. A second discharge current, which may, for example, substantially correspond to the first discharge current 18, is then applied with the battery 12 reversed until a predetermined second voltage value 22 is reached, where the second voltage value 22 is a negative voltage value, by means of the electronic computing device 14. The first voltage value 20 may be essentially zero volts.Furthermore, a negative final voltage of the battery 12 can be specified as the second voltage value 22. After reaching the second voltage value 22, a relaxation 24 of the battery 12 can be carried out. After the relaxation 24, a third voltage value 26 of the battery 12 can be determined. Should the third voltage value 26 exceed a predetermined threshold, another discharge current 28 can be applied, and a polarity reversal can be performed upon reaching the first voltage value 20.

[0053] In particular, the battery 12 can be discharged by means of the deep discharge device 10 before the deep discharge 16 to the empty state of charge in accordance with the journals S1 and S2.

[0054] Furthermore, it may be provided that the temperature of battery 12 is monitored at least during deep discharge.

[0055] It can also be provided that when the second voltage value 22 is reached, the second voltage value 22 is maintained for the predefined period.

[0056] In particular, the negative terminal voltages of time steps S4 and S6 depend on the total voltage of the battery 12 being discharged. This should be in the range of -100 to -1000 millivolts per module / pack of individual cells. Compared to the operating voltage of a lithium-ion cell, especially around 3.2 to 3.7 volts, depending on the cathode chemistry used, even small negative voltages are sufficient to benefit from the effects of the polarity reversal. When selecting the negative voltage range, to avoid inhibition due to polarization and diffusion within the cells in aged batteries, a stepwise polarity reversal with intermediate relaxation steps is advantageous. The negative voltage range or the sustained charge voltage from time step S4 can be adjusted for each step to prevent extreme temperature increases.The relaxation steps also allow for the regular reduction of internal blockages in the battery and the dissipation of heat. The discharge stages should remain within predefined current and voltage ranges. Therefore, the discharge electronics must be able to control the current and voltage. Depending on the cell type, the discharge current should be in the range of 0.1 to 2 C. For example, a discharge current of 0.5 C has proven advantageous for batteries with nickel-manganese-cobalt oxide or lithium iron phosphate cathodes.

[0057] Reversing the polarity of battery 12 typically reverses the polarity of each individual battery 12 within the battery. This results in a significantly faster relaxation of the voltage after the contact is broken, allowing for a rapid safety assessment in multi-step processes. After successful completion of the process, the relaxation voltage can be close to zero volts, thus preventing any residual energy from remaining during further processing of battery 12.

[0058] If battery 12 is in a negative voltage range and negative currents are present, energy is supplied to the battery. This ensures that the necessary energy for the internal short circuit is available, for example, for corrosion of the current collector and ion migration. Furthermore, energy recuperation via an intermediate circuit is conceivable for the polarity reversal steps. In this case, the energy extracted during the discharge of battery 12 in a voltage range greater than zero volts can be used to perform the polarity reversal.

[0059] Furthermore, it may be provided that the state of health of the battery 12 is determined and categorized before the deep discharge 16 is carried out, and that the deep discharge 16 is performed depending on this determined state of health. For example, as already mentioned, before the deep discharge 16 is carried out by reversing the polarity of the battery 12 to create an internal short circuit, an optional safety assessment of the process may take place. In particular, the state of health (SoH) of the battery 12 and / or of individual batteries within the battery is estimated, and the internal cell resistance is determined.

[0060] For this purpose, a capacity determination can be performed, for example. According to the datasheet for battery 12, below the maximum permissible current and below the tolerable voltage limits, the discharge capacity, in particular the amount of charge when discharging from 100 percent state of charge (SoC) to zero percent, is determined and compared with the nominal capacity from the datasheet. The percentage of the discharge capacity relative to the nominal capacity defines the battery's state of health.

[0061] Furthermore, an internal resistance determination can be performed. For a defined time, for example one minute, a positive or negative current, the maximum intensity of which can be found in the datasheet, is applied to battery 12. After this time, a sudden voltage relaxation occurs, so that the internal resistance of battery 12 can be calculated according to Ohm's law R = dll / dl ​​and compared with the values ​​in the datasheet.

[0062] Furthermore, electrochemical impedance measurement is also possible. Within a defined frequency range, for example, from ten kilohertz to one hertz, an impedance spectrum is recorded using a specific current-controlled excitation with an amplitude that is based on the battery's capacity, for example, C / 20. Based on the data from this spectrum, characteristic values ​​at specific frequencies, for example, one kilohertz, can be compared with the specifications in the datasheet. For a more detailed analysis, the curve of the data can also be analyzed using a fitting. This is particularly helpful if data on the electrochemical impedances of the battery type under investigation are already available. A comparison then reveals irregularities that can be used to inform decision-making.

[0063] All described measurement methods provide a data basis for deciding whether a battery 12 can be subjected to the deep discharge procedure with reverse polarity proposed here. The decision of whether or not the battery is suitable can be made based on a single parameter or a combination of parameters. It has been shown that simply determining the battery's health based on capacity data does not provide sufficient information about its discharge characteristics. Even batteries 12 with a high state of health can, for example, experience problems with deep discharge 16 with reverse polarity if they have high internal resistance. However, the described procedure is optional. All batteries 12 can also be subjected to the deep discharge procedure with reverse polarity, but this does not guarantee that the procedure will be successful.

[0064] The batteries can be categorized into three health states. A first health state is "healthy." In this case, the battery has a high health state of over 95 percent and a low internal resistance, where "low" is defined as corresponding to the datasheet specification with a slight deviation, for example, plus ten percent. Impedance spectroscopy reveals only minor anomalies compared to a brand-new, high-quality cell that was previously classified as "good." A second health state is "aged." The battery has a lower health state than a healthy cell because it has already been used for some time, for example, in a battery-powered vehicle. However, the internal resistance corresponds to the datasheet specification or shows only slight deviations, for example, plus ten percent.The impedance spectroscopy analysis shows no abnormalities compared to a battery that has a similar state of aging and was previously classified as OK.

[0065] Furthermore, battery 12 can also be classified as corrupt. In this case, battery 12 typically has a lower state of health (SoH) than a healthy cell, as it has either already been used or was manufactured under faulty conditions. In rare cases, even a battery 12 with a 100% state of health can be classified as corrupt. A corrupt battery 12 is classified as such if it is deemed unsuitable for the deep discharge test with reverse polarity based on experience or suspicious quality characteristics. Additionally, battery 12 exhibits anomalies in the determination of its internal cell resistance. These deviations from a healthy or aged battery 12 can have various origins. When determined using a DC pulse, the internal resistance can be calculated after different decay times and compared with the value in the datasheet or with one's own experience.Impedance spectroscopy also allows the determination of resistance values ​​at different excitation frequencies. These values ​​can be compared either with the datasheet or with empirical values ​​for healthy and aged batteries.

[0066] Specifically, only batteries of category 12 (healthy and aged) are suitable for deep discharge 16 with polarity reversal. Batteries of category 3 (corrupt) cannot be deactivated using the proposed method.

[0067] Reference symbol list

[0068] 10 Deep discharge device

[0069] 12 Battery 14 Electronic computing device

[0070] 16 Deep discharge

[0071] 18 first discharge current

[0072] 20 first voltage value

[0073] 22 second voltage value 24 relaxation

[0074] 26 third voltage value

[0075] 28 additional discharge current

[0076] Voltage

[0077] I current t time

Claims

Patent claims 1. Method for performing a deep discharge (16) of a battery (12) using a deep discharge device (10), comprising the steps: - Providing the battery (12) with a depleted charge level (V So co%); - Applying a predetermined first discharge current (18) to the discharged battery (12) by means of an electronic computing device (14) of the deep discharge device (10) up to a predetermined first voltage value (20) of the battery (12); - Reversing the polarity of the battery (12) using the deep discharge device (10) when the predetermined first voltage value (20) is reached; and - Applying a second discharge current (18) with reversed polarity of the battery (12) up to a predetermined second voltage value (22), where the second voltage value (22) is a negative voltage value, using the electronic computing device (14).

2. Method according to claim 1, characterized in that the first voltage value (20) is essentially set to 0 volts.

3. Method according to claim 1 or 2, characterized in that the second voltage value (22) is essentially a negative final voltage of the battery (12).

4. Method according to one of the preceding claims, characterized in that after reaching the second voltage value (12) a relaxation (24) of the battery (12) is carried out.

5. Method according to claim 4, characterized in that after relaxation (24) a third voltage value (26) of the relaxed battery (12) is determined.

6. Method according to claim 5, characterized in that, should the third voltage value (26) exceed a predetermined threshold, a discharge current (28) is applied again and a polarity reversal is carried out when the first voltage value (20) is reached.

7. Method according to one of the preceding claims, characterized in that the battery (12) is discharged with a C-rate between 0.1 C and 2.0 C, in particular with 0.5 C.

8. Method according to one of the preceding claims, characterized in that by means of the deep discharge device (10) the battery (12) is discharged to a completely empty state of charge (V) before the deep discharge (16). So co%) is unloaded.

9. Method according to claim 8, characterized in that the battery (12) is discharged with a C-rate between 0.5 C and 3 C, in particular with 1 C.

10. Method according to one of the preceding claims, characterized in that at least during the deep discharge (16) a temperature of the battery (12) is monitored.

11. Method according to one of the preceding claims, characterized in that when the second voltage value (20) is reached, the second voltage value (20) is maintained for a predefined period of time.

12. Method according to one of the preceding claims, characterized in that, prior to carrying out the deep discharge (16), the health status of the battery (12) is determined and categorized, and the deep discharge (16) is carried out depending on the determined health status.

13. Computer program product comprising program code means which cause an electronic computing device (14) to perform a method according to one of claims 1 to 12 when the program code means are processed by the electronic computing device (14).

14. Computer-readable storage medium comprising at least one computer program product according to claim 13.

15. Deep discharge device (10) for carrying out a deep discharge (16) of a battery (12), comprising at least one electronic computing device (14), wherein the deep discharge device (10) is configured for carrying out a method according to one of claims 1 to 12.

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