Bridging a battery management system in a submarine in the event of an emergency

Description

[0001] The invention relates to a method for bridging a battery management system in the event of danger in order to provide a submarine with energy for the necessary maneuvers in the event of danger.

[0002] Lithium-based batteries are becoming increasingly attractive, for example due to their high energy density. However, especially for large energy storage systems, there are two fundamental differences compared to lead-sulfuric acid batteries, for example. Firstly, the individual cells cannot simply be enlarged at will. This leads to the frequent combination of multiple batteries into a larger module. Secondly, these batteries are particularly susceptible to the problem of thermal runaway. Since this process also generates a large amount of gas, this poses a significant risk, especially in critical environments, as has been demonstrated, for example, with batteries in aircraft.

[0003] Battery management systems are used to protect the batteries. A battery management system specifically prevents deep discharge, which could lead to battery damage, as well as excessive power dissipation, which could cause overheating and thermal runaway. Thus, a battery management system protects the batteries and ensures a long service life. At the same time, it also protects the surrounding area, thus regularly preventing fires.

[0004] However, there may be dangerous situations in which it may be more important to utilize the remaining energy reserves, even if this means accepting the risk of battery damage due to deep discharge and even fire. An example of this is a submerged submarine that is without energy reserves due to its mission. In this case, it is expedient to use the energy reserves still available due to deep discharge to surface the submarine so that the crew can be evacuated.

[0005] An important point here, however, is that such an override would normally represent a very high risk if it were to be activated outside of such a dangerous situation and thus deactivate all safety systems.

[0006] Further complicating the situation is the fact that such override is only required in a state where hardly any energy is available. In particular, the voltage provided by a battery depends on the charge level and drops significantly, especially at very low charge levels. This may result in the voltage falling below the level required to switch the control electronics, or the voltage may not be stable enough to perform a switching operation. Connecting the battery to the electrical grid under its own power is then no longer possible.

[0007] From DE 10 2004 045 897 A1, a battery system of a submarine with at least two battery modules is known, each of which has the on-board network voltage of the submarine and is each connected to the on-board network of the submarine via a switch, which makes it possible to connect and disconnect the associated battery module to the on-board network.

[0008] A torpedo with a battery for power supply is known from DE 101 06 521 C1.

[0009] From DE 10 2017 009 527 A1, a propulsion network of a submarine for supplying a propulsion system with electrical energy is known, wherein at least two DC-DC converters are assigned to the propulsion system for transmitting the electrical energy.

[0010] JP 2016 163536 A discloses an energy supply for a mobile object.

[0011] A battery system for a submarine is known from EP 1 641 066 A2.

[0012] The object of the invention is to provide a method for providing the last energy reserves on a submarine, whereby in the event of danger, the last energy reserves can be used, for example to surface the submarine and thus evacuate the crew, even if this may result in damage to the accumulators.

[0013] This object is achieved by the method having the features specified in claim 1 and by the energy storage device having the features specified in claim 6. Advantageous further developments emerge from the subclaims, the following description, and the drawings.

[0014] For the inventive method for providing energy on a submarine, a submarine with an energy storage device is selected. The energy storage device has at least a first accumulator and a first battery management system. The first battery management system controls the first accumulator and thus prevents, in particular, overheating, deep discharging, and overcharging, and thus damage to the first accumulator. This corresponds to the normal functioning of a battery management system. To provide the energy, the first battery management system of the first accumulator is bypassed. This serves to enable deep discharging of the first accumulator.In this way, even the last remaining stored electrical energy can be made available in the event of danger, whereby permanent damage to the first accumulator and possibly also a fire triggered by thermal runaway are accepted. A discharged first accumulator is selected as the first accumulator. In this context, discharging is to be understood as the first accumulator being discharged to such an extent that the battery management system, in order to protect against deep discharge and thus possible damage to the first accumulator, prevents further discharge of this accumulator, for example by disconnecting the first accumulator from a load output. In particular, the battery management system has disconnected the first accumulator from a load output of the energy storage device using a first load switch.A discharged accumulator within the meaning of the invention is therefore never truly completely and absolutely discharged, but always retains a certain residual charge, whereas a deeply discharged accumulator within the meaning of the invention no longer retains any residual charge that can be delivered to the connected loads. Even in a deeply discharged state, the accumulator may still retain a minimal electrical charge, but this can no longer be utilized due to the low voltage in the accumulator and the electrical properties of the connected loads, since no current can be delivered to them, even though the loads are electrically connected to the accumulator.In this context, discharging means, for example, that the accumulator only has a voltage that is specified in the battery management system as a limit value, in the form of the final discharge voltage, so that the accumulator is disconnected from the grid by the battery management system and thus protected from further discharging. The first accumulator is thus disconnected from the load output of the energy storage device by the first battery management system connected to it, so that no further electrical charge is drawn and the first accumulator is not deeply discharged and damaged. An emergency switch is used to bypass the first battery management system, whereby a switching voltage is applied (or given) to a first load switch by the emergency switch. By applying the voltage to the first load switch, the first load switch connects the first accumulator to a load output of the energy storage device.

[0015] A battery within the meaning of the method according to the invention can be a single electrochemical cell (a secondary cell). However, it can also be a module composed of several batteries. It can also be a so-called string, in which several modules are connected together.

[0016] The term "emergency switch" is used in the context of the invention to clearly identify this switch and thus linguistically distinguish it from other switches. The emergency switch can be designed as a switch such as an emergency stop switch, it can be designed as a switch mechanically protected against unintentional activation, for example, as a key switch, or it can be controlled by software as a switching logic. However, the emergency switch is preferably a manually operated switch, as this will only be used in extreme emergency situations.

[0017] Deep discharge, as defined by the invention, is the withdrawal of current from the accumulator until its capacity is almost completely exhausted. Deep discharge occurs below the final discharge voltage and can be carried out as far as technically possible given the electrical properties of the connected network and its loads.

[0018] Essential to the invention is that bypassing the battery management system, a load connection is created between the first accumulator and a load output, and thus a network, in order to be able to release the entire stored energy from the first accumulator without a safety device limiting the energy release on the accumulator side. In particular, a battery management system is intended to disconnect a accumulator from a consumer when, for example, the temperature at the accumulator is too high or the residual capacity is too low, in order to protect the accumulator from damage.In the simplest case, the battery management system continues to operate but can no longer disconnect the accumulator, for example, because a parallel connection to the load is established or because a control line from the battery management system to a switching element is set to a potential by the bridge, at which the switching element allows a connection between the accumulator and a load. Thus, an electrical connection is provided for discharging, not for charging the first accumulator. Bridging can therefore be understood, for example, to mean that all control interventions of the battery management system are no longer taken into account and have no effect on the further discharge of the accumulator or the load switch.

[0019] The voltage of a rechargeable battery depends, to a first approximation, on its state of charge. The lower the state of charge, the lower the voltage. Therefore, the voltage provided by a rechargeable battery can also be considered a measure of the state of charge. A discharged rechargeable battery, as defined by the invention, is a rechargeable battery that has reached or fallen below a voltage specified by the battery management system, which is close to the end-of-discharge voltage or is the end-of-discharge voltage itself. The level of the end-of-discharge voltage depends on the respective rechargeable battery type.

[0020] Alternatively, a discharged accumulator within the meaning of the invention is an accumulator that has reached or fallen below a first predetermined voltage specified by the battery management system, wherein the predetermined voltage lies between a first predetermined voltage and a second predetermined voltage. Preferably, the first predetermined voltage is in a range of 1% to 5% above the final discharge voltage, and the second voltage is in a range of 0% to 1% above the final discharge voltage. The level of the final discharge voltage depends on the respective accumulator type.

[0021] Battery management systems are particularly common for lithium-ion batteries due to their complex charging characteristics. Typical functions of a battery management system include cell protection, charge control, load management, determination of the state of charge, determination of cell health (especially aging, residual capacity, internal resistance, and the like), balancing of multiple cells, recording of history, communication with other ship systems, temperature monitoring, and adjustment of the final charge voltage.

[0022] A load switch within the meaning of the invention comprises any electrical or mechanical circuit that can establish and break an electrical connection. In addition to a mechanical switch, this also includes semiconductor components that can establish and break or break an electrical connection. For example, the first accumulator is connected to a load output of the energy storage device via a DC-DC converter, also called a DC-DC controller or DC-DC converter, in order to adapt the voltage provided by the first accumulator to the output voltage required at the load output. An example of such a DC-DC converter is shown, for example, in DE 10 2017 009 527 A1 in Figure 4 and the associated description. The DC-DC converter shown in the example has two H-bridges, each with four MOSFETs. For isolation, all eight MOSFETs are preferably non-conductive.During operation, i.e. when the load switch is electrically conductive, two diagonally opposite MOSFETs are always conductive and the other two diagonally opposite are non-conductive, with this circuit constantly alternating. This circuit converts the direct current into alternating current, which is then transformed and converted back into direct current on the other side in an analog manner. The symmetrical design allows both charging and discharging of the first accumulator. The inventive connection of the first accumulator to the load output of the energy storage device by means of the first load switch thus occurs in that the control electronics of the DC-DC converter receives a signal for continuously controlling the DC-DC converter and thus establishes the electrical connection between the first accumulator and the load output of the energy storage device in the sense of a load switch.In semiconductor-based switches, the emergency switch therefore provides a switching voltage that allows the driver circuit of the semiconductor-based switch or the semiconductor-based switch itself to allow current to flow. This example is not intended to be limiting. The term "load switch" encompasses all switchable, bidirectional, and technically known electrical circuit arrangements of DC-DC converters.

[0023] In a further embodiment of the invention, before carrying out the above-mentioned step, a check is carried out to determine whether the stored electrical energy in the entire energy storage device falls below a lower limit value. Preferably, the limit value is less than 5% of the maximum stored electrical energy overall, and particularly preferably, the limit value is less than 3% of the maximum stored electrical energy. This can prevent bridging from occurring at a time when it is not absolutely necessary. Since bridging also deactivates the overheating protection at the same time, the risk of damage to the energy storage device and the area surrounding the energy storage device is extreme, so this operating mode should be avoided at all costs unless it is absolutely necessary due to a dangerous situation.

[0024] In a further embodiment of the invention, the energy storage device comprises at least one second accumulator and a second battery management system, wherein the emergency switch is also designed to bypass the second battery management system. Of course, there can be n accumulators with n battery management systems, with each battery management system monitoring a respective accumulator. The emergency switch serves to simultaneously bypass all battery management systems and thus make available all the remaining energy.

[0025] In a further embodiment of the invention, the energy storage device has a main battery management system that is higher-level than the first battery management system and the second battery management system, with the emergency switch also being designed to bypass the main battery management system. Of course, with a larger number of accumulators, there may also be intermediate levels of battery management systems. Advantageously, all battery management systems are deactivated simultaneously by the one emergency switch.

[0026] In a further alternative embodiment of the invention, the energy storage device comprises at least a second accumulator, a second battery management system, and a second emergency switch, wherein the second emergency switch is designed to bypass the second battery management system. This makes it possible to minimize damage to the accumulators so that, in the event that the submarine can still be salvaged, at least a portion of the accumulators for which the battery management system was not bypassed can be used.

[0027] In a further embodiment of the invention, the battery management system bypass can no longer be removed after the emergency switch has been activated once. Since implementing the method is highly likely to result in serious damage, switching back to the initial state would create a false sense of system safety, which is no longer the case. Therefore, it is advantageous if, after activating the method, there is no way back to normal operation without performing fundamental maintenance and repair of the entire system.

[0028] In a further embodiment of the invention, no further charging can be performed after the emergency switch has been activated once. If charging the first accumulator were possible without a battery management system, the risk of damage would be very high. Therefore, this system is preferably deactivated. Since the method is only carried out in a situation in which no further power is available to the submarine, there will be no need or possibility to recharge the accumulators.

[0029] In a further embodiment of the invention, the emergency switch has a first input device and a second input device, wherein a first input on the first input device and a second input on a second input device are necessary for bridging. By separating the first input device and the second input device, wherein the first input device and the second input device are preferably spaced apart, particularly preferably more than 2 m apart, accidental triggering of the emergency switch can be reliably prevented. This means that the emergency switch is really only actuated in the event of absolute danger and thus the method according to the invention is carried out. The first input and the second input must preferably be made simultaneously.The simultaneity of the first input and the second input, in particular with a sufficient spatial separation of the first input device and the second input device, means that two people are required to carry out the method, which means that two people must simultaneously declare their willingness to accept the disadvantages of the method according to the invention.

[0030] In a further embodiment of the invention, the method establishes a direct electrical connection between the first accumulator and the load output. Normally, a galvanically isolated connection is preferably established. For example, the direct electrical connection can be designed in such a way that recharging of the accumulator is prevented.

[0031] In a further embodiment of the invention, the first accumulator is irreversibly disconnected from the load output after discharging by the method. This is intended to ensure that a accumulator damaged by the method can be recharged and continued to be operated.

[0032] In a further embodiment of the invention, before bypassing the first battery management system, the communication of the battery management system is checked. For example, this can be used to determine whether known damage to the first accumulator would render bypassing pointless or particularly dangerous. This can be particularly useful in a system comprising a large number of accumulators and a large number of battery management systems. Likewise, previously recorded temperature peaks can indicate an increased risk, provided they have already been detected by the battery management system.

[0033] In a further embodiment of the invention in a system with a plurality of accumulators and a plurality of battery management systems, the charge level of the connected accumulators is first queried in all battery management systems. Only if sufficient capacity is no longer available is the first battery management system bypassed.

[0034] In a further aspect, the invention relates to a method for operating a submarine with an energy storage device, wherein the method according to the invention for bridging a first battery management system of a first accumulator can be carried out with the energy storage device.

[0035] In a further aspect, the invention relates to a submarine with an energy storage device. The energy storage device has a load output for transferring electrical energy to at least one consumer. For example, this is a busbar that collects the electrical energy from various accumulators and transfers it to the on-board electrical system of a submarine, for example. This is the area where the highest voltage is present, as long as even a single accumulator still has sufficient residual charge to provide the minimum voltage required for a switching operation. The energy storage device has at least a first accumulator and a second accumulator. Typically, the energy storage device has a plurality of accumulators. The accumulators can preferably be arranged in groups in modules; more preferably, the modules can be arranged in groups in strings.A submarine, for example, typically has an energy storage device having approximately 10 to 50 strings, each string having approximately 4 to 10 modules. A module can, for example, have 20 to 500 batteries. The energy storage device has at least a first battery management system for the first battery and a second battery management system for the second battery. A first load switch is arranged between the first battery and the first battery management system. A second load switch is arranged between the second battery and the second battery management system. The first load switch connects the first battery to the load output, and the second load switch connects the second battery to the load output. The respective load switch can preferably be a DC-DC converter based on semiconductor switching elements, which can be controlled by the battery management system.The advantage is that such DC-DC converters can convert a variable input voltage into a constant output voltage.

[0036] According to the invention, the energy storage device comprises an emergency switch. The emergency switch is designed to establish an electrical connection between the load output and the first load switch, as well as to establish an electrical connection between the load output and the second load switch.

[0037] In a further embodiment of the invention, the emergency switch has a first input device, wherein the first input device is designed as a switch that is mechanically secured against unintentional switching, for example, as a key switch. The advantage of a switch that is mechanically secured against unintentional switching is that it is practically impossible to trigger it accidentally. With the exemplary key switch, the key can be inserted into the key switch and the key turned, thus ensuring that the user is fully aware that this action actually risks permanent damage to the energy storage device in order to provide the last remaining electrical energy.

[0038] In a further embodiment of the invention, the emergency switch has a second input device. The first input device is preferably also designed as a switch that is mechanically secured against unintentional switching. The first input device and the second input device are at least 2 m apart. By using two input devices, both of which are designed as key switches, for example, the risk of unintentional activation can be further reduced. In particular, if both key switches must be activated simultaneously, this can no longer be done by a single person; instead, a coordinated approach by two people is necessary, which practically eliminates the possibility of accidental activation.

[0039] In a further embodiment of the invention, the energy storage device comprises a plurality of accumulators. The multiple accumulators are combined to form a module, and multiple modules are combined to form a string. Each module has a module battery management system, and each string has a string battery management system. The emergency switch bridges all module battery management systems and all string battery management systems. Such tiered battery management systems are common. Therefore, bridging each instance is necessary.

[0040] In a further embodiment of the invention, the energy storage device comprises a plurality of accumulators. The emergency switch is blocked if less than 50%, preferably less than 80%, of all accumulators are switched off due to their discharge state.

[0041] The invention relates to a submarine with an energy storage device according to the invention. While in practically all other applications there is hardly any need to mobilize the last energy reserves, thereby destroying the energy storage device, and especially to accept the risk of fire, the situation is completely different in a submarine, especially one that is currently submerged. If sufficient energy is still available to surface the submarine, the crew can be evacuated and thus at least their lives can be saved.

[0042] The submarine according to the invention is explained in more detail below using an embodiment shown in the drawings. Fig. 1Submarine Fig. 2First energy storage device Fig. 3Second energy storage device

[0043] Fig. 1 shows a highly simplified schematic of a submarine 10 according to the invention. The submarine 10 has an energy storage device 20, which can be operated according to the invention by means of an emergency switch 30. This allows the last remaining energy to be directed, for example, to a motor 40, allowing the submarine to surface.

[0044] Fig. 2 shows a first energy storage device 20 with a string of six accumulators 50. The accumulators 50 themselves can preferably be designed in the form of modules with a plurality of electrochemical cells. The accumulators 50 are monitored by a battery management system 80, which, for example, records voltage and temperature. The electrical energy can be delivered from the accumulators 50 to the submarine 10 via the load output 60. To disconnect the string from the grid, the energy storage device 20 has a load switch 70, which can be switched via the battery management system 80. To carry out the method according to the invention, the emergency switch 30 can switch the load switch 70 directly and thus bypasses the battery management system 80. Although the battery management system 80 can still report warning messages, for example regarding the state of charge and temperature, to other systems of the submarine 10, it can no longer disconnect the string from the grid.

[0045] The Fig. 3 The second energy storage device 20 shown differs in that it has two strings, each with six accumulators and each with its own battery management system 80. Both load switches 70 can be actuated together and simultaneously by the emergency switch 30, so that both battery management systems 80 are bypassed simultaneously.

[0046] Reference symbol: 10Submarine 20Energy storage device 30Emergency switch 40Motor 50Accumulator 60Load output 70Load switch 80Battery management system

Claims

1. A method for providing energy on a submarine, wherein the method on the submarine with an energy storage device is applied, wherein the energy storage device has at least one first battery and one first battery management system, wherein for providing the energy, a bypassing of the first battery management system of the first battery is carried out in order to enable a deep discharge of the first battery, wherein a discharged first battery is selected as a first battery, wherein the battery management system has disconnected the first battery from a load output of the energy storage device with a first load switch, characterized in that an emergency switch is used for bypassing the first battery management system, wherein a switching voltage is applied to a first load switch by means of the emergency switch, whereby the first load switch connects the first battery to a load output of the energy storage device.

2. The method as claimed in claim 1, characterized in that before carrying out the bypassing, it is checked whether the stored energy in the energy storage device corresponds to less than 5 % of the maximum stored energy, preferably less than 3 % of the maximum stored energy.

3. The method as claimed in one of the preceding claims, characterized in that the energy storage device has at least one second battery and one second battery management system, wherein the emergency switch is also designed for bypassing the second battery management system.

4. The method as claimed in one of the preceding claims, characterized in that the emergency switch has a first input device and a second input device, wherein a first input at the first input device and a second input of a second input device is necessary for bypassing, wherein the first input and the second input preferably must take place at the same time.

5. The method as claimed in one of the preceding claims, characterized in that bypassing the battery management system can no longer be cancelled after the single input by the emergency switch.

6. Submarine having an energy storage device wherein the energy storage device has a load output for transferring electrical energy to at least one consumer, wherein the energy storage device has at least one first battery and one second battery, wherein the energy storage device has at least one first battery management system for the first battery and one second battery management system for the second battery, wherein a first load switch is arranged between the first battery and the first battery management system, wherein a second load switch is arranged between the second battery and the second battery management system, wherein the first load switch connects the first battery to the load output, wherein the second load switch connects the second battery to the load output, characterized in that the energy storage device has an emergency switch to enable deep discharge of the first accumulator, wherein the emergency switch is designed for producing an electrical connection between the load output and the first load switch as well as for producing an electrical connection between the load output and the second load switch.

7. The submarine as claimed in claim 6, characterized in that the emergency switch has a first input device, wherein the first input device is designed as a key switch.

8. The submarine as claimed in claim 7, characterized in that the emergency switch has a second input device, wherein the first input device is designed as a key switch, wherein the first input device and the second input device have a distance of at least 2 m.

9. The submarine as claimed in one of claims 6 to 8, characterized in that the energy storage device has a multiplicity of batteries, wherein a plurality of batteries are combined to form a module, wherein a plurality of modules are combined to form a string, wherein each module has a module battery management system, wherein each string has a string battery management system, wherein the emergency switch bypasses all module battery management systems and all string battery management systems.

10. The submarine as claimed in one of claims 6 to 9, characterized in that the energy storage device has a multiplicity of the batteries, wherein the emergency switch is blocked provided that less than 50 %, preferably less than 80 % of all batteries are switched off as a result of the discharge state.