AU2020388957B2

AU2020388957B2 - Bypassing a battery management system in a submarine in the event of an emergency

Info

Publication number: AU2020388957B2
Application number: AU2020388957A
Authority: AU
Inventors: Boris Nagorny; Marc Pein
Original assignee: ThyssenKrupp AG; ThyssenKrupp Marine Systems GmbH
Current assignee: ThyssenKrupp AG; ThyssenKrupp Marine Systems GmbH
Priority date: 2019-11-19
Filing date: 2020-11-12
Publication date: 2023-01-12
Anticipated expiration: 2040-11-12
Also published as: DE102019217796A1; KR20220024841A; EP4062517A1; WO2021099204A1; AU2020388957A1

Abstract

The invention relates to an energy storage device (20), said energy storage device (20) having a load output (60) for dispensing electric energy to at least one load. The energy storage device (20) has at least one first battery (50) and a second battery (50), and the energy storage device (20) has at least one first battery management system (80) for the first battery (50) and a second battery management system (80) for the second battery (50). A first load switch (70) is arranged between the first battery (50) and the first battery management system (80), and a second load switch (70) is arranged between the second battery (50) and the second battery management system (80), wherein first load switch (70) connects the first battery (50) to the load output (60), and the second load switch (70) connects the second battery (50) to the load output (60). The invention is characterized in that the energy storage device (20) has an emergency switch (30), said emergency switch (30) being designed to establish an electric connection between the load output (60) and the first load switch (70) and to establish an electric connection between the load output (60) and the second load switch (70).

Description

BYPASSING A BATTERY MANAGEMENT SYSTEM IN A SUBMARINE IN THE EVENTOFANEMERGENCY

1. FIELD OF THE INVENTION The invention relates to a method for bypassing a battery management system in the event of an emergency, in order to provide energy to a submarine in the event of an emergency for correspondingly necessary maneuvers.

2. BACKGROUND OF THE INVENTION Lithium-based batteries are becoming increasingly interesting, for example owing to the high energy density. However, for large energy storage systems in particular, there are two fundamental differences compared to, for example, lead-sulfuric acid batteries. On the one hand, the individual cells cannot simply be enlarged arbitrarily. This results in a multiplicity of batteries regularly being assembled to form a larger module. On the other hand, thermal runaway is a particular problem with these batteries. Since a large amount of gas is also created in this case, this signifies a great risk, in particular in critical environments, as has been shown in batteries in aircrafts, for example.

O Battery management systems are used in order to protect the batteries. A battery management system in particular prevents a deep discharge which could result in damage to the batteries, as well as in a power dissipation which is too strong and which could result in overheating and therefore in thermal runaway. A battery management system therefore protects the batteries and ensures a long lifespan. At ?5 the same time, the environment is thus also protected, so that fire can thus be regularly avoided.

However, there can be hazardous situations in which it may be more important to use the energy reserves which are still available and therefore accept damage to the batteries through a deep discharge and even fire. One example of this is a submarine which is immersed and, as a result of its mission, without energy reserves. In this

19214176_1 (GHMatters) P117870.AU case, it is expedient to use the energy reserves which are still available through deep discharge in order to surface the submarine, in order to be able to evacuate the crew.

However, one important point in this case is that an override of this type usually constitutes a very high risk if this override were to be activated outside of a hazardous situation of this type and therefore all safety systems would be deactivated.

One further complication is that an override of this type is only required in a situation in which hardly any energy is available anymore. In particular, the voltage which is provided by a battery depends on the charge state and drops significantly in particular in the case of very low charge states. However, this may result in the voltage falling below that which is necessary for a circuit of the control electronics or the voltage not being stable enough in order to carry out a switching process. It is then no longer possible to connect the battery to the electrical network by its own power.

A battery system of a submarine with at least two battery modules is known from patent document DE 10 2004 045 897 Al. Each module provides on-board power supply of the submarine and each module is connected via a switch to the on-board electrical system of the submarine which enables the associated battery module to be connected to and disconnected from the on-board electrical system.

A torpedo with a battery for supplying current is known from patent document ?5 DE10106521C1.

A propulsion network of a submarine for supplying a propulsion system with electrical energy is known from patent document DE 10 2017 009 527 Al, wherein at least two DC-DC converters are allocated to the propulsion system for transmitting the electrical energy.

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Patent document JP 2016 163536 A discloses an arrangement for providing energy to a mobile object.

Patent document EP 1 641 066 A2 discloses a battery arrangement with battery management system in a submarine.

It will be understood that reference to the above patent documents is not intended to indicate that the documents or their contents is well-known to the skilled addressee in Australia or other countries and are merely referenced herein as prior art documents.

It would be advantageous to provide a method for making available last energy reserves on a submarine, whereby in the event of an emergency, having accepted damage to the batteries will result from making such energy reserves available, the last energy reserves can be used to still surface the submarine and thus evacuate the crew, for example.

3. SUMMARY OF THE INVENTION In accordance with a first aspect there is provided a method for providing energy on a submarine in an emergency situation from an energy storage device. The energy storage device has at least one first battery and one first battery management system. The first battery management system controls the first battery and thus prevents in particular overheating, deep discharging and overcharging and therefore damage to the first battery. This corresponds to the normal mode of operation of a battery management system. In order to provide emergency energy, a bypassing of ?5 the first battery management system of the first battery is carried out. This serves to enable a deep discharge of the first battery. This makes it possible to provide even the last remnant of stored electrical energy in the event of an emergency, wherein permanent damage to the first battery and possibly also a fire triggered by a thermal runaway is accepted. A discharged first battery is selected as the first battery. In this context, discharged is intended to be understood to mean that the first battery is discharged to such an extent that, in order to protect against a deep discharge and thus possible damage to the first battery, the battery management system prevents a

19214176_1 (GHMatters) P117870.AU discharge of this battery beyond a threshold value, by disconnecting the first battery from a load output of the energy storage device. The battery management system disconnects the first battery from the load output of the energy storage device via a first load switch. A discharged battery as defined in the invention is therefore never really completely and absolutely discharged, but rather it still has a certain residual charge, while a deeply discharged battery as defined in the invention no longer has any residual charge which can be output to an energy consumer connected via the load output to the energy storage device. The battery may still have a minimum electrical charge even in the deeply discharged state, but this charge can no longer be utilized as a result of the low voltage in the battery and as a result of the electrical properties of the connected consumers, since no more current can be output to these, despite the fact that the consumers are electrically connected to the battery. In this context, discharging means, for example, that the battery only has a voltage which is specified in the battery management system as a limit value, in the form of the end-of-discharge voltage, such that the battery has been disconnected from the network by the battery management system and has thus been protected from further discharge. The first battery thus has been 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 thus the first battery is not deeply discharged and damaged. An emergency switch is provided and used for bypassing the first battery management system in case of an emergency during which discharged batteries are re-connected, wherein a switching voltage is applied (or given) to a first load switch by means of the emergency switch. By imprinting the voltage on the first load switch, the first load switch connects the first battery to the ?5 load output of the energy storage device.

A battery as defined in the method according to the invention can be an individual electrochemical cell (a secondary element). However, it can also be a module which is composed of a plurality of batteries. Similarly, it can also be a so-called string, in which a plurality of modules are interconnected.

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The term emergency switch as defined in the invention serves to identify this switch unambiguously and therefore to linguistically differentiate it from other switches. In this case, the emergency switch can be constructed as a switch such as an emergency stop switch, it can be constructed as a switch which is mechanically secured against unintentional switching, for example as a key switch, or it can also be controlled by software as switching logic. However, the emergency switch is preferably a manually actuatable switch, because it will only be used in extreme emergency situations.

O Deep discharge as defined in the invention is the withdrawal of current from the battery until almost complete exhaustion of the capacity of the battery. The deep discharge takes place up to below the end-of-discharge voltage and can take place as far as is technically possible based on the electrical properties of the connected network and its consumers.

It is essential to the invention that a load connection is created between the first battery and a load output by bypassing the battery management system and therefore a network is created, in order to be able to output the total stored energy from the first battery without a safety device limiting the energy output on the battery side. In particular, a battery management system should just disconnect a battery from a consumer if, for example, the temperature at the battery is too high or the residual capacity is too low in order to protect the battery from damage. In the simplest case, the battery management system continues to operate but can no longer disconnect the battery, for example because a parallel connection is made to ?5 the consumer or because a control line from the battery management system to a switch element is set to a potential as a result of the bypassing at which the switch element produces a connection between the battery and a consumer. An electrical connection is therefore provided for discharging, not for charging the first battery. Bypassing is therefore intended to be understood 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 battery or the load switch, for example.

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

O Alternatively, a discharged battery as defined in the invention is a battery which has reached or has fallen below a first voltage specified by the battery management system, wherein the specified voltage is between a first specified voltage and a second specified voltage. The first specified voltage is preferably in a range from 1

% to 5 % above the end-of-discharge voltage and the second voltage in a range from 0 % to 1 % above the end-of-discharge voltage. The level of the end-of-discharge voltage depends on the respective battery type.

Battery management systems are common in particular in the case of lithium-ion batteries, owing to the complex charging characteristics. Typical functions of a battery management system are cell protection, charge control, load management, determining the charge state, determining cell health, in particular ageing, residual capacity, internal resistance and the like, counterbalancing in the case of a plurality of cells, recording the history, communication with other ship systems as well as temperature monitoring and adjusting the end-of-charge voltage.

A load switch as defined in the invention comprises each electrical or mechanical circuit which can produce and disconnect an electrical connection. In addition to a mechanical switch, semiconductor components are thus also included which can produce and disconnect or produce an electrical connection. For example, the first battery is connected to a load output of the energy storage device via a DC-DC converter, also referred to as a DC chopper controller, in order to adjust the voltage provided by the first battery to the output voltage required at the load output. One

19214176_1 (GHMatters) P117870.AU example of a DC-DC converter of this type is shown in DE 10 2017 009 527 Al in figure 4 and the associated description, for example. The DC-DC converter shown in the example has two H-bridges with four MOSFETS respectively. For disconnecting, all eight MOSFETS are preferably non-conductive. During operation, i.e. in the electrically conductive state of the load switch, two diagonally opposite MOSFETS are always conductive in each case and the other two diagonally opposite are non conductive, wherein this circuit is constantly changed. This circuit ensures that the direct current is converted into alternating current, which is then transformed and converted back into direct current on the other side in an analogous manner. In this case, the symmetrical design permits both charging and discharging of the first battery. The connection according to the invention of the first battery to the load output of the energy storage device by means of the first load switch thus takes place in that the control electronics of the DC-DC converter receives a signal for continuous control of the DC-DC converter and in this way produces the electrical connection between the first battery and the load output of the energy storage device in terms of a load switch. In the case of semiconductor-based switches, the emergency switch consequently provides a switching voltage which permits the driver circuit of the semiconductor-based switch or the semiconductor-based switch itself to enable a current flow. The example is not intended to be understood in a restrictive manner. The term load switch includes all electrical circuit arrangements of DC-DC converters which are switchable, bidirectional and are known to the person skilled in the art.

In one further embodiment of the invention, before carrying out the abovementioned step, it is checked whether the stored electrical energy in the entire energy storage ?5 device falls below a lower limit value; preferably the limit value is in total less than 5 % of the maximum stored electrical energy, particularly preferably the limit value is less than 3 % of the maximum stored electrical energy. This makes it possible to prevent bypassing from taking place at a time at which it is not absolutely necessary. Since bypassing also simultaneously deactivates protection against overheating, the risk of damage to the energy storage device and the environment of the energy storage device is extreme, such that this operating mode should be avoided at all costs, provided that it is not absolutely necessary due to a hazardous situation.

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In one further embodiment of the invention, 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. Of course, there can be n batteries with n battery management systems, wherein each respective battery management system monitors one battery in each case. The emergency switch is used to bypass all battery management systems at the same time and thus to provide the total energy which is still available.

O In one further embodiment of the invention, the energy storage device has a main battery management system which is superordinate to the first battery management system and the second battery management system, wherein the emergency switch is also designed for bypassing the main battery management system. Of course, there may also be intermediate levels of battery management systems in the case of a larger number of batteries. All battery management systems are advantageously deactivated at the same time by the one emergency switch.

In one further alternative embodiment of the invention, the energy storage device has at least one second battery, one second battery management system and one second emergency switch, wherein the second emergency switch is designed for bypassing the second battery management system. This makes it possible to attempt to reduce damage to the batteries to a minimum, in order to subsequently be able to fall back on at least one part in which the battery management system was not bypassed, in the event that the submarine can still be saved.

In one further embodiment of the invention, bypassing the battery management system can no longer be cancelled after the single input by the emergency switch. Since there is a high probability of serious damage when carrying out the method, switching back to the initial state would simulate an apparent safety of the system which is no longer met. It is therefore advantageous if after activating the method, there is no way back to normal operation without basic maintenance and repair of the overall system taking place.

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In one further embodiment of the invention, a charging process can no longer be performed after the single input by the emergency switch. If charging the first battery were possible without a battery management system, the risk of damage would be very high. It is therefore preferably deactivated. Since the method is only carried out in a situation in which there is no more energy available for the submarine, there is also no need and no possibility for recharging the batteries.

In one further embodiment of the invention, 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. Disconnecting the first input device and the second input device, wherein the first input device is preferably spaced apart from the second input device, particularly preferably they are spaced apart by more than 2 m, makes it possible to avoid accidental triggering of the emergency switch in a reliable manner. This means that the emergency switch is really only actuated in the event of an absolute emergency and thus the method according to the invention is performed. The first input and the second input preferably must take place at the same time. The simultaneity of the first input and the second input, in particular with a sufficient spatial distance of the first input device and the second input device, force two people to be required in order to carry out the method, whereby two people must simultaneously declare that they are willing to accept the disadvantages of the method according to the invention.

In one further embodiment of the invention, the method produces a direct electrical ?5 connection between the first battery and the load output. Usually, a galvanically isolated connection is preferably produced. For example, the direct electrical connection can be designed in such a way that it prevents recharging of the battery.

In one further embodiment of the invention, the first battery is irreversibly disconnected from the load output after discharge by means of the method. This should guarantee that a battery damaged by the method may be recharged and operated again.

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In one further embodiment of the invention, the communication of the battery management system is checked before bypassing the first battery management system. For example, it can be queried in this case whether damage to the first battery which is already known would make a bypassing pointless or particularly dangerous. This may be useful in particular in a system made up of a multiplicity of batteries and a multiplicity of battery management systems. Temperature spikes which are already registered can also indicate an increased risk if they have already been detected by the battery management system.

In one further embodiment of the invention, in a system with a multiplicity of batteries and a multiplicity of battery management systems, the charge state of the connected batteries is firstly queried in the case of all battery management systems. Bypassing the first battery management system is only carried out if a sufficient capacity is no longer available in this case.

In one 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 bypassing a first battery management system of a first battery can be carried out with the energy storage device.

In one further aspect, the invention relates to an energy storage device. The energy storage device has a load output for transferring electrical energy to at least one consumer. For example, it is a busbar in this case which collects the electrical energy ?5 from different batteries and transfers it to the on-board electrical system of a submarine, for example. This is the area at which the highest voltage is applied, provided that even one individual battery still possesses a sufficient residual charge in order to provide the minimum voltage which is necessary for a switching process. The energy storage device has at least one first battery and one second battery. The energy storage device usually has a multiplicity of batteries. The batteries may preferably be arranged in groups of modules; further preferably the modules may be arranged in groups of strings. A submarine usually has an energy storage device, for

19214176_1 (GHMatters) P117870.AU example, which has approximately 10 to 50 strings, wherein each string has approximately 4 to 10 modules. A module can have 20 to 500 batteries, for example. 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. 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 first load output and the second load switch connects the second battery to the load output. In this case, the respective load switch may preferably be a DC-DC converter which is based on semiconductor switch elements and which can be controlled by the battery management system. The advantage is that DC-DC converters of this type can convert a variable input voltage into a constant output voltage.

According to the invention, the energy storage device has an emergency switch. 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.

In one further embodiment of the invention, the emergency switch has a first input device, wherein the first input device is designed as a switch which is mechanically secured against unintentional switching, for example as a key switch. One advantage of a switch which is mechanically secured against unintentional switching is that it practically cannot be triggered accidentally. In the case of the exemplary key switch, ?5 the key can be inserted into the key switch and can be turned, thus ensuring that the user knows precisely that this action results in permanent damage to the energy storage device really being accepted in order to provide the last remnant of electrical energy which is available.

In one further embodiment of the invention, the emergency switch has a second input device. The first input device is preferably also designed as a switch which is mechanically secured against unintentional switching. The first input device and the

19214176_1 (GHMatters) P117870.AU second input device have a distance of at least 2 m. Using two input devices which are both designed as key switches, for example, may further reduce the risk of unintentional triggering. In particular if simultaneous triggering of both key switches is necessary, this can no longer take place with only one individual person, but rather a coordinated approach of two people is necessary, which practically rules out an oversight.

In one further embodiment of the invention, the energy storage device has a multiplicity of batteries. The plurality of batteries are combined to form a module, a plurality of modules are combined to form a string. Each module has a module battery management system based on each string has a string battery management system. The emergency switch bypasses all module battery management systems and all string battery management systems. Battery management systems which are staggered in this way are common. A bypassing is therefore necessary in every instance.

In one further embodiment of the invention, the energy storage device has a multiplicity of the batteries. 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.

In one further aspect, 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 while destroying the energy ?5 storage device and in particular to accept the risk of fire, the situation is completely different in the case of a submarine, in particular one which is currently submerged. If there is still sufficient energy available in order to surface the submarine, the crew can be evacuated and thus the life of said crew can at least be saved.

The above-described embodiments of methodologies for making available last energy reserves on board a submarine according to the invention can be used in submarines having an energy storage device based on batteries as will be explained

19214176_1 (GHMatters) P117870.AU in greater detail hereinafter using exemplary embodiments of such energy storage systems with reference to the accompanying drawings.

4. BRIEF DESCRIPTION OF THE DRAWINGS fig. 1 is a highly schematic illustration of a submarine with an energy storage device; fig. 2 is a highly schematic illustration of a first energy storage device as can be used in the submarine of fig. 1; and fig. 3 is a highly schematic illustration of a second energy storage device as can be used in the submarine of fig. 1.

5. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 schematically shows a submarine 10 in a greatly simplified manner. The submarine 10 has an energy storage device 20 which can be operated using an embodiment of the methodology according to the invention described above, by means of an emergency switch 30. As a result, the last energy which is still available in the energy storage device 20 can be drawn and directed to a motor 40 so that the submarine can surface from a submerged state, in case of an emergency, for example.

Fig. 2 shows a first energy storage device 20 with a string made up of six batteries 50. The batteries 50 themselves may preferably be designed in the form of modules with a plurality of electrochemical cells. The batteries 50 are monitored by a battery management system 80 which detects voltage and temperature, for example. The ?5 electrical energy can be output from the batteries 50 to the submarine's drive (motor 40) 10 via a load output 60. In order to disconnect the string of batteries 50 from the energy supply network, the energy storage device 20 has a load switch 70 which can be switched via the battery management system 80. In order to carry out the method according to the invention, the emergency switch 30 can directly switch the load switch 70, thus bypassing the battery management system 80. It can in fact still report warning messages, for example regarding the charge state and temperature,

19214176_1 (GHMatters) P117870.AU to other systems of the submarine 10 but it can no longer disconnect the string of batteries 50 from the network.

The second energy storage device 20 shown in fig. 3 is different in that here it has two energy supply strings with six batteries each, with each string having its own battery management system 80 and load switch 70. Both load switches 70 can be actuated together and at the same time by the emergency switch 30, such that both battery management systems 80 are bypassed at the same time.

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Reference numbers: 10 submarine 20 energy storage device 30 emergency switch 40 motor 50 battery 60 load output 70 load switch 80 battery management system

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Claims

1. A method for making available energy on a submarine in an emergency situation, wherein the submarine has an energy storage device comprising at least one first battery, a load output with a first load switch arranged to selectively provide energy from the energy storage device via the load output to energy consumers of the submarine, and a first battery management system arranged to prevent deep discharge and therefore damage of the at least one first battery, wherein prior to conducting the method the at least one first battery has been discharged in normal use to an end-of-discharge voltage or predetermined energy discharge level and disconnected from the load output by the first battery management system, the method comprising the steps of: triggering an emergency switch for bypassing the first battery management system, wherein triggering causes a switching voltage to be applied to the first load switch and the first load switch to connect the discharged first battery to the load output of the energy storage and cause a deep discharge of the at least one first battery during which last remnants of stored electrical energy is made available through the load output.

2. The method as claimed in claim 1, further including the step of checking whether stored energy in the energy storage device corresponds to less than 5 % of a maximum stored energy or less than 3 % of the maximum stored energy.

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

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4. The method as claimed in any one of the preceding claims, wherein 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 at the second input device is necessary for causing bypassing of the first battery management system.

5. The method as claimed in claim 4, wherein the first input and the second input must take place at the same time.

6. The method as claimed in any one of the preceding claims, wherein bypassing the battery management system can no longer be cancelled after triggering of the emergency switch.

7. An energy storage device for or on a submarine, comprising a load output for transferring electrical energy to at least one energy consumer of the submarine; at least one first battery and at least one second battery; a first battery management system for the at least one first battery and a second battery management system for the at least one second battery, wherein the first and second battery management systems are configured to (i) allow discharge of the first and second batteries, respectively, in normal use to an end-of-discharge voltage or predetermined energy discharge level, and then (ii) disconnect the respective first and second batteries from the load output to prevent deep discharge and therefore damage of the first and second batteries, respectively; a first load switch arranged between the at least one first battery and the first battery management system and a second load switch arranged between the at least one second battery and the second battery management system, wherein the first load switch connects the at least one first battery to the load output and the second load switch connects the at least one second battery to the load output; and an emergency switch arranged 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, when triggered, such that the 19214176_1 (GHMatters) P117870.AU priorly disconnected first and second batteries are reconnected to the load output of the energy storage to cause a deep discharge of the first and second batteries during which last remnants of stored electrical energy is made available through the load output during an emergency in the submarine.

8. The energy storage device as claimed in claim 7, wherein the emergency switch has a first input device designed as a key switch.

9. The energy storage device as claimed in claim 8, wherein the emergency switch has a second input device designed as a key switch, and wherein the first input device and the second input device have a distance of at least 2 m.

10.The energy storage device as claimed in any one of claims 7 to 9, wherein the energy storage device has a plurality of said first and second batteries, wherein the plurality of batteries are combined to form at least two battery modules, wherein the at least two battery modules are combined to form a string, wherein each module has a module battery management system, wherein the string has a string battery management system, and wherein the emergency switch is arranged to cause bypassing of all of the module battery management systems and the string battery management system.

11.The energy storage device as claimed in any one of claims 7 to 10, wherein the emergency switch is configured to remain blocked provided that less than 50 % or less than 80 % of all first and second batteries are switched off as a result of a discharge state of the batteries.

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