DETERMINATION OF THE AGING STATE OF AN ENERGY STORAGE SYSTEM ON BOARD OF A SUBMERSIBLE BOAT

Description

[0001] The invention relates to a method for the specific measurement of the aging state of an energy storage device on board a submarine.

[0002] Currently, submarines are typically equipped with energy storage devices using lead-based batteries (especially lead-lead(IV)-sulfuric acid). To test the capacity of these energy storage devices, the batteries were discharged with a very low charging current while connected to shore power.

[0003] However, batteries with other technologies are increasingly being used, for example, and especially, lithium-based batteries. Their behavior is completely different, meaning they are better discharged with a high, constant current, which is significantly higher compared to a lead-acid battery. This would, however, result in the amount of current delivered via a shore power connection being considerably greater than the maximum flow rate of a single connection.

[0004] For submarines, compared to other applications such as the automotive sector, removing or replacing the batteries is not a practical option due to the effort involved. Measurements, for example in a test rig, are therefore not feasible. The testing must thus be carried out within the submarine itself, using the available resources.

[0005] From US patent 2021 / 044119 A1, a method for performing a health status assessment for a rechargeable battery energy storage system is known.

[0006] From KR 2019 0043212 A a structure and a method for the design of the safety of the layered battery for submarines are known.

[0007] From DE 10 2009 038 663 A1 a motor vehicle with a plurality of batteries and a method for battery diagnostics is known.

[0008] The object of the invention is to provide a new method for reliably measuring the current maximum capacity and thus the state of aging of energy storage devices with accumulators based on a different material than the previously used lead-based battery, in particular lithium-based batteries. In particular, this method should also take into account the increasingly shorter port stays, so that the method can be carried out independently of special external devices.

[0009] This problem is solved by the method with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0010] The method according to the invention serves to determine the state of health of an energy storage device on board a submarine. The term state of health refers to the age-dependent, currently available capacity. This provides information on the maximum energy that can actually be stored in the energy storage device. Furthermore, changes in this capacity indicate the aging process; in particular, abrupt changes are an indication of emerging problems, so that the development of the time-dependent maximum capacity allows conclusions to be drawn about the state of health.This is usually done continuously in a predictive manner, whereby a ship's battery management system assumes average aging behavior and then considers the number and type of charging cycles, environmental influences such as temperature, and the like, thereby estimating the maximum capacity. However, such a model has only limited accuracy, so according to the invention, the exact condition is recorded from time to time, for example, once a year. This allows the model to be reset to the exact determined starting value for the future. Furthermore, it may even be possible to adjust the model overall. The submarine has at least one first energy storage device, wherein the first energy storage device has more than two strings, preferably 10 to 200 strings. The strings preferably consist of two to ten, more preferably four to eight modules.Each module comprises a plurality of unit cells, preferably connected partly in series and partly in parallel. The modules are preferably connected in series in a string. Each string can preferably be individually connected to the vehicle's electrical system, allowing the strings to be connected in parallel to maximize current draw.

[0011] The method according to the invention comprises the following steps: a) Setting the state of charge of the energy storage device to a value of 45 to 80% of the maximum capacity, preferably to 45 to 60% of the maximum capacity, particularly preferably to 47 to 55% of the maximum capacity. b) Dividing the strings into string groups, each string group containing no more than 50% of the strings. c) Selecting a first string group to determine its state of aging. d) Fully charging the first string group. e) Maintaining the first string group at full charge. f) Fully discharging the first string group at a constant current and determining the capacity of the first string group. g) Charging the first string group.

[0012] The advantage of this method is that only a portion of the strands are selected. This makes it possible to direct and utilize the discharge current within the boat. "Use" in this context specifically includes using it to charge another strand or strand group. This eliminates the need for a shore power connection. Furthermore, it is advantageous that parts of the energy storage system can be measured separately. For example, during a port call, only one strand group can be examined at a time. If the energy storage system is divided into four equally sized strand groups, for instance, one strand group can be examined after each of four port calls, ensuring that all strands have been examined after four calls. This allows for optimal and low-interference integration into normal boat operation, thus avoiding extended port calls.The procedure could also be carried out during the return trip to port over water or during a longer transfer trip.

[0013] The division of the strands into strand groups according to step b) can, for example, be performed once during the construction of the energy storage device and thus be fixed. However, it can also be performed dynamically, for example, if the state of charge is higher than that set according to step a). Thus, if, for example, only an average state of charge of 75% can be achieved, preferably four to six strand groups are selected, while at a state of charge of 50%, preferably three strand groups are selected.

[0014] The order of steps a) and b) is arbitrary, and in particular step b) can be performed only once. However, it may still be useful to check whether an adjustment could be beneficial.

[0015] To carry out the procedure, the submarine typically has a control unit that regulates the process. For example, the control unit puts the circuits into a corresponding operating mode. Furthermore, the submarine has an evaluation unit that determines, evaluates, stores, and compares the aging state from the measured currents. The evaluation unit may also have a predictive module that forecasts the aging state between two measurements based on a computational model stored within the evaluation unit.

[0016] Preferably, each string has a string battery management system capable of detecting the currents flowing into and out of the string. It may also be possible to additionally measure the voltage at the string's output.

[0017] In a further embodiment of the invention, steps d) to g) are performed independently for each strand of the first strand group. In practical terms, this means that as soon as a strand of the first strand group is fully charged in step d), the charge for that strand is held in step e), and then the strand is discharged in step f). Thus, for example, the strand of the first strand group with a higher residual charge may go through the steps more quickly than another strand of the first strand group with a lower residual charge at the beginning of the process. This can result in steps d) to g) being performed simultaneously for the individual strands, while steps a) to c) are performed in parallel for all strands simultaneously, and step d) is also started for all strands of the first strand group.

[0018] During the execution of the method according to the invention, the other boat systems can be reliably and independently supplied with energy in three ways. In a first embodiment, the submarine is supplied with energy via a shore power connection. In a second embodiment, there are two energy storage devices, one of which carries out the method according to the invention and the other of which supplies the boat with energy. In a third embodiment, the energy storage device has three strand groups, a first strand group of which carries out the method according to the invention, a second strand group serves as a source or sink for the energy of the first strand group for the method, and the third strand group supplies the boat with energy.

[0019] In a further embodiment of the invention, the method additionally comprises the following steps: h) Selecting a second string group to determine the aging state, i) Fully charging the second string group, j) Holding the second string group at full charge, k) Fully discharging the second string group at constant current and measuring the capacity of the second string group, l) Charging the second string group

[0020] If sufficient time is available, the procedure can of course be continued with a second strand group. Alternatively, the second strand group can also be measured at a later time, as already described.

[0021] If sufficient time is available, the procedure can be continued for all further strand groups, allowing the exact state of all strands to be determined simultaneously in a single transaction.

[0022] Analogous to steps d) to g), steps i) to l) can also be carried out individually for each strand of the second strand group, so that steps i) to l) can also be carried out simultaneously for the individual strands.

[0023] In a further embodiment of the invention, if a fault occurs in one strand, the process continues for the strand group, and only the affected strand is removed from the group. This allows a measurement to be obtained for the remaining strands in the group, thus utilizing the available time. The strand in which a fault has occurred is typically separated and examined first. For the purposes of this invention, "fault" is to be interpreted broadly and includes not only classic error messages but also, for example, exceeding a certain temperature, such as in the cooling water. Similarly, a temperature sensor intended to detect thermal runaway may have triggered an alarm, requiring an initial check to determine whether one of the unit cells is damaged.Therefore, errors in this context also include, for example, ambient temperatures that are completely uncritical for normal operation, but are too high for an accurate measurement of the capacity.

[0024] In a further embodiment of the invention, the strand groups, with the exception of the selected strand group in step d) and step i), respectively, provide the energy to fully charge the selected strand group and absorb the energy from the selected strand group in step f) and step k), respectively. An advantage of this embodiment is that electrical energy is converted only within the energy storage device. This allows the process to be carried out completely independently of other ship equipment or a shore power connection.

[0025] In In a further embodiment of the invention, the first energy storage device is disconnected from the submarine's electrical system before the start of the process. This is particularly preferably done in combination with the embodiment in which, with the exception of the selected strand group, the strand groups provide the energy to fully charge the selected strand group in step d) and step i) respectively, and receive the energy from the selected strand group in step f) and step k) respectively.

[0026] In In a further embodiment of the invention, the temperature of the first energy storage device is maintained within a range that allows for sufficiently high accuracy of the current measurement, for example, and in particular, within a range of 15 °C to 35 °C. It is particularly preferred that the method is not started if the temperature of the energy storage device is outside this range.

[0027] In In a further embodiment of the invention, steps d) to f) are repeated after step f), or steps i) to k) are repeated after step k). While this doubles the measurement time, it not only allows for a more precise determination of the measured value, but also provides an additional indicator of deviant behavior from the magnitude of the deviation, thus predicting poor forecasting capabilities by a conventional forecasting model.

[0028] In In another embodiment of the invention, the submarine has a second energy storage device. The method according to the invention is also carried out for the second energy storage device.

[0029] In In another embodiment of the invention, the submarine has a second energy storage device. While the inventive method is being carried out for the first energy storage device, the method is simultaneously carried out for the second energy storage device. This embodiment is preferred, for example, if the submarine is supplied with electricity via a shore power connection. This embodiment may also be preferred if the submarine is powered by a diesel generator while surfaced.

[0030] Particularly preferred in a further development of this embodiment is the separate operation of both energy storage devices, isolated from the ship's electrical system. The process is thus carried out separately for each energy storage device and completely independently of the other ship systems. The electrical energy of the process therefore remains within the respective energy storage device.

[0031] In a further alternative embodiment of the invention, the method is carried out for the first energy storage device, while the second energy storage device provides the energy supply for the submarine. This achieves complete independence from a shore power connection or a diesel generator, which would be necessary, for example, in a port that does not have a shore power connection.

[0032] In a further embodiment of the invention, the method can be carried out neither manually nor automatically while the submarine is in combat mode. This ensures that the maximum amount of energy is always available in such a situation.

[0033] In a further embodiment of the invention, the process can be interrupted immediately at any time, thus making any energy available at that time directly available to the energy storage device. This embodiment is preferred, for example, when energy is needed for the operation of the submarine or when immediate combat readiness is required.

[0034] In a further embodiment of the invention, if the process is interrupted, the charge states of the strings are first equalized before the energy storage device releases the energy via the ship's electrical system. This ensures that the energy is available at the highest possible power. This embodiment is preferred if it is foreseeable in the long term that the process cannot be completed, for example, due to changed boundary conditions, such as an earlier departure from port.

[0035] In a further embodiment of the invention, the strands which have a fault or defect are not taken into account during the division in step b) and are therefore not used for the process.

[0036] The method according to the invention is explained in more detail below with reference to an embodiment shown in the drawings. Fig. 1 Submarine with first energy storage device Fig. 2 Submarine with multiple power generators

[0037] In Fig. 1 A submarine 10 is shown. This is shown as being in port, and the ship's electrical system 20 is powered via a shore power connection 30. A propulsion motor 40 is shown as an example of a power consumer. Connectable to the ship's electrical system via a disconnect switch 50, the submarine 10 has an energy storage device 90, which has 12 strands 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71. For the procedure to be carried out, the disconnect switch 50 is set to the disconnect position, so that there is no electrical connection between the first energy storage device 90 and the ship's electrical system 20.

[0038] First, a uniform charge of approximately 50% ± 5% of the maximum capacity is set as an example before the first energy storage device 90 is disconnected from the vehicle electrical system 20 by the disconnect switch 50 (step a)). For the following, it is assumed that all strings have exactly the same capacity and are set to exactly 50% initial charge, and that no electrical energy is lost during the process.

[0039] According to step b), the first strand 60, the second strand 61, the third strand 62 and the fourth strand 63 are combined in a first strand group 80, the fifth strand 64, the sixth strand 65, the seventh strand 66 and the eighth strand 67 are combined in a second strand group 81 and the ninth strand 68, the tenth strand 69, the eleventh strand 70 and the twelfth strand 71 are combined in the third strand group 82.

[0040] Now the first strand group 80 is selected to check the actual maximum capacity (step c)).

[0041] Now, in step d), all strands 60, 61, 62, 63 of the first strand group 80 are fully charged (thus to 100%), and energy is drawn from strands 64, 65, 66, 67, 68, 69, 70, 71 of the second strand group 81 and the third strand group 82, which then have a charge level of 25%. Subsequently, in step e), the full charge is maintained for a predetermined time, for example, 5 minutes.

[0042] Now, in step f), all strands 60, 61, 62, 63 of the first strand group 80 are completely discharged (thus to 0%) and the energy is transferred to strands 64, 65, 66, 67, 68, 69, 70, 71 of the second strand group 81 and the third strand group 82, which then have a state of charge of 75%. This preferably occurs with a constant current, for example, 20% of the maximum current. This current is recorded for each strand 60, 61, 62, 63 by its strand battery management system. This allows the actual capacity of each individual strand 60, 61, 62, 63 of the first strand group 80 to be determined.

[0043] Subsequently, in step g), all strands 60, 61, 62, 63 of the first strand group 80 are recharged to 50% and energy is taken from the strands 64, 65, 66, 67, 68, 69, 70, 71 of the second strand group 81 and the third strand group 82, which thus also have a charge state of 50%.

[0044] Once the submarine 10's layover period is over, it can depart. However, if submarine 10 remains in port, the second strand group should preferably also be measured. Alternatively, this can be done during the next port call. If there is still time, the second strand group 81 will be selected to verify the actual maximum capacity (step h)).

[0045] Now, in step i), all strands 64, 65, 66, 67 of the second strand group 81 are fully charged (thus to 100%), and energy is drawn from strands 60, 61, 62, 63, 68, 69, 70, 71 of the first strand group 80 and the third strand group 82, which then have a charge level of 25%. Subsequently, in step j), the full charge is maintained for a predetermined time, for example, 5 minutes.

[0046] In step k), all strands 64, 65, 66, 67 of the second strand group 81 are completely discharged (thus to 0%) and the energy is transferred to strands 60, 61, 62, 63, 68, 69, 70, 71 of the first strand group 80 and the third strand group 82, which then have a state of charge of 75%. This preferably occurs with a constant current, for example, 20% of the maximum current. This current is recorded for each strand 64, 65, 66, 67 by its strand battery management system. This allows the actual capacity of each individual strand 64, 65, 66, 67 of the second strand group 81 to be determined.

[0047] Subsequently, in step l), all strands 64, 65, 66, 67 of the second strand group 81 are recharged to 50% and energy is taken from the strands 60, 61, 62, 63, 68, 69, 70, 71 of the first strand group 80 and the third strand group 82, which thus also have a charge state of 50%.

[0048] If there is no more time, submarine 10 can now depart. However, if there is still time, the procedure for the third strand group 82 will continue. If there is still time, the third strand group 82 will be selected to verify the actual maximum capacity.

[0049] Now, all strands 68, 69, 70, 71 of the second strand group 81 are fully charged (to 100%), and energy is drawn from strands 60, 61, 62, 63, 64, 65, 66, 67 of the first strand group 80 and the second strand group 81, which then have a charge level of 25%. The full charge is then held for a predetermined time, for example, 5 minutes.

[0050] Now, all strands 68, 69, 70, 71 of the third strand group 82 are completely discharged (thus to 0%) and the energy is transferred to strands 60, 61, 62, 63, 64, 65, 66, 67 of the first strand group 80 and the second strand group 81, which then have a state of charge of 75%. This preferably occurs with a constant current, for example, 20% of the maximum current. This current is recorded for each strand 68, 69, 70, 71 by its strand battery management system. This allows the actual capacity of each individual strand 68, 69, 70, 71 of the third strand group 82 to be determined.

[0051] Subsequently, all strands 68, 69, 70, 71 of the third strand group 82 are recharged to 50% and energy is taken from strands 60, 61, 62, 63, 64, 65, 66, 67 of the first strand group 80 and the second strand group 81, which thus also have a charge level of 50%.

[0052] Fig. 2 The submarine 10 is shown with further components. The first energy storage device 90, which is in Fig. 1 represented by its strands 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, is in Fig. 2 shown only as a single unit. Additionally, the submarine 10 has a second energy storage device 92, which can be connected to the ship's electrical system 20 via a disconnect switch 52. Furthermore, the submarine 10 has a fuel cell device 100 and a diesel generator 110, which can supply power to the ship's electrical system 20 in addition to or as an alternative to the shore power connection 30. Alternatively, the second energy storage device 92 can supply the ship's electrical system while the first energy storage device 90 performs the method according to the invention, or vice versa. Reference sign

[0053] 10 Submarine 20 On-board power supply 30 Shore power connection 40 Traction motor 50 Disconnect switch 52 Disconnect switch 60 First strand 61 Second strand 62 Third strand 63 Fourth strand 64 Fifth strand 65 Sixth strand 66 Seventh strand 67 Eighth strand 68 Ninth strand 69 Tenth strand 70 Eleventh strand 71 Twelfth strand 80 First strand group 81 Second strand group 82 Third strand group 90 First energy storage device 92 Second energy storage device 100 Fuel cell device 110 Diesel generator

Claims

1. Method for determining the state of health of an energy storage device (90, 92) on board a submarine (10), wherein the submarine (10) has at least one first energy storage device (90), wherein the first energy storage device (90) has more than two strings (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71), characterised in that, the method comprises the following steps: a) setting a state of charge of the first energy storage device (90) to a value of 45 to 80 per cent of the maximum capacity, b) dividing the strings (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71) into string groups (80, 81, 82), each string group (80, 81, 82) containing no more than 50% of the strings (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71), c) selecting a first strand group for determining the ageing state, d) Fully charging the first strand group (80), e) Maintaining the first string group (80) at full charge, f) Fully discharging the first string group (80) at a constant current and recording the capacity of the first string group (80), g) charging the first string group (80).

2. Method according to claim 1, characterised in that , the method additionally comprises the following steps: h) Selecting a second string group (81) for determining the ageing state, i) Fully charging the second string group (81), j) Maintaining the second string group at full charge, k) Fully discharging the second string group (81) at a constant current and recording the capacity of the second string group (81), I) charging the second string group (81) to full charge ( ).

3. Method according to claim 2, characterised in that the method is continued for all further string groups (80, 81, 82).

4. Method according to one of the preceding claims, characterised in that, in the event of a fault in a strand (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71), the method is continued for the strand group (80, 81, 82) and only the affected strand (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71) is removed from the strand group (80, 81, 82).

5. Method according to one of the preceding claims, characterised in that the energy for completely charging the selected strand group (80, 81, 82) is provided by the strand groups (80, 81, 82) except for the selected strand group (80, 81, 82) in step d) or step i), respectively, provide the energy for completely charging the selected string group (80, 81, 82) and, in step f) or step k), respectively, absorb the energy from the selected string group (80, 81, 82).

6. Method according to one of the preceding claims, characterised in that the first energy storage device (90) is disconnected from the on-board power supply (20) of the submarine (10) before the start of the method.

7. Method according to one of the preceding claims, characterised in that the temperature of the first energy storage device (90) is maintained within a range of 15 °C to 35 °C.

8. Method according to one of the preceding claims, characterised in that steps d) to f) are repeated after step f) and steps i) to k) are repeated after step k).

9. Method according to one of the preceding claims, characterised in that the submarine (10) has a second energy storage device (92), wherein the method according to one of the preceding claims is also performed for the second energy storage device (92).

10. Method according to claim 9, characterised in that the method is performed simultaneously for the first energy storage device (90) and the second energy storage device (92) while the submarine (10) is supplied with energy from outside via an external connection.

11. Method according to claim 9, characterised in that the method is performed for the first energy storage device (90) while the second energy storage device (92) provides the energy supply for the submarine (10).

12. Method according to one of the preceding claims, characterised in that the method cannot be performed either manually or automatically while the submarine (10) is in combat mode.

13. Method according to one of the preceding claims, characterised in that strands (60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71) which have a fault or defect are not taken into account in the division in step b) and are not used for the method.