WO2026015069A1

WO2026015069A1 - A circuit board of a battery pack for interconnecting battery cells, a battery pack and a method therefor

Info

Publication number: WO2026015069A1
Application number: PCT/SE2025/050676
Authority: WO
Inventors: Sebastian THUNÉ
Original assignee: Zparq AB
Current assignee: Zparq AB
Priority date: 2024-07-12
Filing date: 2025-07-11
Publication date: 2026-01-15
Anticipated expiration: 2027-01-12

Abstract

The present invention relates to a circuit board for interconnecting battery cells of a battery pack, comprising a substrate comprising: a contact area of the substrate configured to be connected to a pole of a battery cell for interconnecting battery cells; a contact temperature sensor operable to measure a temperature of the contact area; a substrate temperature sensor operable to measure a temperature of the substrate; wherein the circuit board further comprises a controller comprising: a measurement module operable to measure signals representing measured temperatures from the contact and substrate temperature sensors; and a communication module configured to send information about the measured temperatures to a battery management system.

Description

A CIRCUIT BOARD OF A BATTERY PACK FOR INTERCONNECTING BATTERY CELLS, A BATTERY

PACK AND A METHOD THEREFOR

TECHNICAL FIELD

The present disclosure generally relates to the field of circuit boards for interconnecting batteries in a battery pack and more specifically to a circuit board for interconnecting battery cells with improved monitoring and cooling.

BACKGROUND

In battery packs i.e. a plurality of interconnected battery cells. The battery cells are often connected in series or in parallel. Conventionally, this interconnection is performed by means of a bus-bar, which may be a solid bar of a metal with low resistivity, such as copper, to which the terminals of the battery cells are welded or screwed. Thermal management within the battery pack is of utmost importance for reliable operation of the battery pack. Various solutions exist to enhance the cooling of a battery pack in operation, or during charging. Quite often forced cooling is required and utilizes fans for increased air flow, or liquid cooling for transporting heat to a heat sink. However, in many applications there is a need for a sealed battery pack without any fans or liquid cooling, in such applications there is a need for passive cooling that utilizes heat transfer from the battery cells to the surroundings using passive means and no forced media for heat transfer. In such sealed battery packs there is a large need for tight temperature management and increased monitoring of the internal temperatures of the battery pack.

In the art known solutions exists for monitoring the temperature of various components of the battery pack. An example of such a solution is disclosed in CN209822826 in which temperature sensors are arranged on the bus-bar.

Other solutions such as the one disclosed in WO23231880A1 provides a solution for monitoring the internal temperatures of the battery pack. WO23231880A1 utilizes flexible circuit boards with temperature sensors arranged between neighboring battery cells. These temperature sensors are used to determine if a thermal runaway condition is present in the battery pack and/or to determine the direction of thermal flow in the battery pack.

These solutions do not indicate the cause of thermal runaway nor the exact position of the hot-spot.

SUMMARY

An object of the present disclosure is to provide a circuit board for interconnecting battery cells of a battery pack which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and to provide an improved circuit board.

This object is obtained by a circuit board for interconnecting battery cells of a battery pack, comprising a substrate. The substrate comprises a contact area configured to be connected to a pole of a battery cell for interconnecting battery cells, a contact temperature sensor operable to measure a temperature of the contact area, a substrate temperature sensor operable to measure a temperature of the substrate. The circuit board further comprises a controller comprising a measurement module operable to measure signals representing measured temperatures from the contact and substrate temperature sensors, and a communication module configured to send information about the measured temperatures to a battery management system.

According to an aspect, the substrate further comprises a further contact area, and a further contact temperature sensor operable to measure the temperature of the further contact area. This way an efficient solution for interconnecting battery cell is achieved without having to rotate the circuit board 90 degrees, every other board.

According to an aspect, at least one of the temperature sensors is an electrically conducting path formed as a trace in a conductive layer arranged on a carrier board of the substrate. This way a planar sensor is achieved that provides a good connection to the surroundings and simultaneously the sensor area may easily be adapted. The relation between resistance and temperature is well known for all suitable metals and alloys. This way the temperature may easily be calculated using a formula and the measured temperature. According to an aspect, the substrate temperature sensor comprises a plurality of temperature sensors configured to sense the temperature of different regions of the substrate. This way a more precise position of a hotspot may be detected.

According to an aspect, the substrate temperature sensor has a sensor area of at least 10 % of the area of the substrate.

According to an aspect, the contact area and/or the further contact area is formed in the conductive layer.

According to an aspect, the substrate further comprises a further conductive layer in which at least one of the temperature sensors and/or contact areas is formed. This way a denser circuit board may be achieved.

According to an aspect, the further conductive layer is formed on an opposite side of the carrier board than the conductive layer.

The object is also obtained by a battery pack for an electrical vehicle comprising a plurality of circuit boards according to embodiments disclosed herein. The battery pack further comprises a plurality of battery cells interconnected by means of the plurality of circuit boards. The battery pack also comprises a frame configured to mount the circuit boards between battery cells in a sandwich structure, wherein each battery cell is in physical contact with a corresponding face of a circuit board, and wherein the substrate temperature sensor is in physical contact with the battery cell. The battery pack also comprises a cooling structure in physical contact with the frame for heat transfer from the frame to the cooling structure. Further, the battery pack comprises a battery management system, BMS, operable for charging and monitoring of the battery cells, wherein the BMS is operable to receive information about the measured temperatures from the plurality of circuit boards, the BMS is further operable to generate a control signal for controlling the power to, or from, the battery pack in response to said received information about the measured temperatures.

According to an aspect, the frame is in physical contact with at least a part of the periphery of each circuit board. This way the circuit board transfer heat generated by the battery cells in physical contact with the circuit board. The object is also attained by a method of a battery management system for a battery pack according to embodiments disclosed herein. The method comprising receiving measured temperatures from the controllers of the plurality of circuit boards, and generating a control signal, CS, operable to control electrical power from, or to, the battery pack in response to the received measured temperatures.

According to an aspect, the step of generating a control signal further comprises determining if any one of the received measured temperatures is above a threshold, and generating an alarm if one of the received measured temperatures is above said threshold.

According to an aspect, the step of generating an alarm further comprises generating a contact area alarm if the temperature above the threshold is a temperature measured by one of the contact temperature sensors, and/or generating a battery cell alarm if the temperature above the threshold is a temperature measured by one of the substrate temperature sensors.

According to an aspect, the step of generating a control signal further comprises a step of disconnecting the battery pack from a load, or entering a low power mode of operation that causes the measured temperatures to decrease below the threshold temperature in response to the generated alarm.

The object is also obtained by an electrical propulsion system for a boat, comprising a battery pack according to embodiments disclosed herein for supplying an electric motor of the boat with electric power for propulsion via a motor controller, wherein the motor controller is operable to receive the control signal from the battery management system.

The object is also obtained by a computer program product comprising instructions, which when the program is executed by a processor of a battery management system of a battery pack according to embodiments disclosed herein, causes the processor to execute the method according to embodiments of the present disclosure.

Further objects and advantages may be found in the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1 is a schematic drawing of a circuit board according to one embodiment of the present invention;

Figure 2 is a schematic view of a cross section of a substrate along line A-A' for a circuit board according to one embodiment of the present invention;

Figure 3 is a schematic view of a cross section of a substrate along line A-A' for a circuit board according to one embodiment of the present invention;

Figure 4 is a schematic illustration of a battery pack according to one embodiment of the present invention.

Figure 5 is a schematic illustration of a battery pack according to one embodiment of the present invention.

Figure 6 is a flow diagram illustrating a method according to one embodiment of the present invention; and

Figure 7 is a schematic illustration of a boat according to one embodiment of the present invention.

DETAILED DESCRIPTION

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatus and method disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

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

In this disclosure the term 'physical contact' should be interpreted as a direct contact between two elements, or a contact between two elements that may comprise a media such as cooling paste, glue or the like. A physical contact should provide low thermal resistance and be suited for thermal heat flow.

Some of the example embodiments presented herein are directed towards a circuit board for a battery pack. As part of the development of the example embodiments presented herein, a problem will first be identified and discussed. In a typical battery pack several battery cells are interconnected in series or in parallel to achieve the desired capacity of the battery pack in terms of output voltage and stored energy. If one of the battery cells is experiencing an error this might be detected by a battery management system that monitors cell voltages. However, in some cases the battery cell might become overheated and this is not easy to detect based on the cell voltage. Furthermore, in a sealed battery pack there is a large need to efficiently cool the battery cells and this is not straightforward in dense battery packs with many battery cells tightly arranged in the sealed environment.

The present inventors realized that these problems may be minimized or even eliminated by a circuit board, as shown in Fig. 1, generally designated 100 for interconnecting battery cells of a battery pack 400. The circuit board comprises a substrate 101 comprising a contact area

102 of the substrate configured to be connected to a pole of a battery cell for interconnecting battery cells. The substrate further comprises a contact temperature sensor

103 operable to measure a temperature of the contact area 104, a substrate temperature sensor 104 operable to measure a temperature of the substrate 101. The circuit board further comprises a controller 105 comprising a measurement module 106 operable to measure signals representing measured temperatures from the contact and substrate temperature sensors, and a communication module 107 configured to send information about the measured temperatures to a battery management system. This allows precise measurements of the substrate temperature as well as the temperature of the contact area. This way a faulty connection from a battery cell to the circuit board may be detected due to the heating of the contact area when the cell delivers power due to ohmic losses in the contact area. A faulty battery cell may also be detected when the substrate temperature deviates.

Optionally, the substrate 101 further comprises a further contact area 108, and a further contact temperature sensor 109 operable to measure the temperature of the further contact area 108.

Optionally, at least one of the temperature sensors is an electrically conducting path formed as a trace in a conductive layer 202 arranged on a carrier board 203 of the substrate 101.

The conductive layer may be a copper layer and the trace may be formed using standard PCB manufacturing techniques such as etching or milling. Advantageously, the carrier board has a good thermal conductivity to provide for efficient heat transfer, an example of such a carrier board is an aluminum substrate.

Optionally, the substrate temperature sensor 104 comprises a plurality of temperature sensors 111, 112, 113, 114 configured to sense the temperature of different regions of the substrate. This way a more precise location of a region with a deviating temperature may be obtained.

Optionally, the substrate temperature sensor 104 have a sensor area of at least 10 % of the area of the substrate. This way the temperature sensor has a sensor area that covers a large portion of a battery cell in contact with the circuit board during operation in a battery pack.

Optionally, the contact area and/or the further contact area is formed in the conductive layer.

Optionally, the substrate 101 further comprises a further conductive layer 302, as shown in Fig. 3, in which at least one of the temperature sensors and/or contact areas is formed. This further conductive layer may provide overlapping sensor areas to sensors formed in the conductive layer.

Optionally, the further conductive layer 302 is formed on an opposite side of the carrier board 203 than the conductive layer 202.

Now with reference made to Fig. 4 in which a battery pack for an electrical vehicle, generally designated 400, is illustrated. Of course this battery pack 400 is suitable for all applications where a sealed battery pack is used. Typically uses are within marine operation or general outdoor use.

The battery pack 400 comprises a plurality of circuit boards 401a-f according to embodiments disclosed herein, and a plurality of battery cells 402a-e interconnected by means of the plurality of circuit boards.

The battery pack 400 comprises a frame 403 configured to mount the circuit boards between the battery cells in a sandwich structure, wherein each battery cell is in physical contact with a corresponding face of a circuit board, and the substrate temperature sensor is in physical contact with the battery cell. Typically the circuit boards are mounted in the frame using a cooling paste such that efficient heat flow from the circuit board to the frame is achieved. This allows efficient cooling of the battery cells through the circuit boards.

The battery pack 400 further comprises a cooling structure 404 in physical contact with the frame 403 for heat transfer from the frame 403 to the cooling structure 404. The cooling structure may be a heat sink in contact with the surroundings of the battery pack.

The battery pack 400 further comprises a battery management system, BMS, 405 operable for charging and monitoring of the battery cells. The BMS is operable to receive information about the measured temperatures from the plurality of circuit boards. The BMS is further operable to generate a control signal 407 for controlling the power to, or from, the battery pack in response to said received information about the measured temperatures. The control signal 407 may be used to control a converter supplied with power from the battery pack.

Optionally, the frame 403 is in physical contact with at least a part of the periphery of each circuit board 401a-f. This way the frame transfer heat generated by the battery cells to the cooling structure. The BMS may monitor the efficiency of the cooling of the battery pack. The BMS may use a serial interface for reading the measured temperatures from the communication module of the circuit boards. This allows the BMS in addition to obtaining the temperatures to determine the physical position of each circuit board in the battery pack. Further means to obtain the physical position may of course be used such as providing the controller 105 with position information during configuration, other solutions may involve setting the position using the connected wiring harness. The controller may be galvanic isolated from the other parts of the battery pack.

Fig. 5 discloses schematically a battery pack 500 comprising a plurality of circuit boards 501a- g interconnecting a plurality of battery cells 502a-f in series. The battery pack have a positive terminal 504 and a negative terminal 503. The circuit boards 501a-g have contact areas in a first end of each circuit board, and a further contact area in a second end of each circuit board. This allows efficient routing of the wiring harness as can be seen in this figure. The polarity of every other battery cell is changed by rotating the battery cell which causes an efficient series connection. If the battery cells are not rotated a parallel connection of all cells are obtained of course with one pole on the contact area and the other pole on the further contact area.

Fig. 6 discloses a flow diagram illustrating a method 600 of a battery management system 405 for a battery pack 400, 500 according to embodiments disclosed herein.

The method 600 comprises the steps of:

Receiving 55 measured temperatures from the controllers of the plurality of circuit boards.

Generating S10 a control signal, CS, 407 operable to control electrical power from, or to, the battery pack in response to the received measured temperatures.

Optionally, the step of generating a control signal S10 further comprises: determining S15 if any one of the received measured temperatures is above a threshold; and generating S20 an alarm if one of the received measured temperatures is above said threshold.

Optionally, the step of generating S20 an alarm further comprises:

Generating a contact area alarm if the temperature above the threshold is a temperature measured by one of the contact temperature sensors, and/or generating a battery cell alarm if the temperature above the threshold is a temperature measured by one of the substrate temperature sensors.

Optionally, the step of generating a control signal S10 further comprises a step S25 of disconnecting the battery pack from a load, or entering a low power mode of operation that causes the measured temperatures to decrease below the threshold temperature in response to the generated S10 alarm. This way the load may be supplied with a limited amount of power which may keep the load at least partly operational.

Fig. 7 shows schematically an electrical propulsion system 700 for a boat 702, comprising a battery pack 701 according to embodiments for supplying an electric motor 703 of the boat with electric power for propulsion via a motor controller 705. The motor controller 705 is operable to receive the control signal 407 from the battery management system 405.

With reference made to the boat 702 of Fig. 7, some scenarios will now be described in which some of the advantages of the present invention will be discussed.

In a first scenario, a connection from a battery cell to a circuit board of a battery pack 701 starts to experience a higher resistance than normal. This ohmic loss results in an increased temperature on one of the contact areas which is sensed by a contact area temperature sensor of a circuit board. In response to that, the BMS generates a control signal to the motor controller 705 which instructs the motor controller 705 to decrease its power. This decrease continues until a safe temperature below the threshold is sensed by the sensor. Furthermore, the BMS trigger a contact area alarm that a service technician may use to detect the position of the faulty connection in the battery pack. This way a hard shutdown in which the battery pack is completely disconnected is not necessary, and the boat may reach its harbor with reduced speed.

In a second scenario, one of the battery cells of the battery pack starts to experience an increased series resistance which will cause the battery cell to heat up. This heat up is sensed by a substrate temperature sensor of a circuit board of the battery pack. In response to that, the BMS generates a control signal which instructs the motor controller to decrease the power withdrawn from the battery pack. This decrease continues until a safe temperature below the threshold is sensed by the sensor. Furthermore, the BMS trigger a battery cell alarm that a service technician may use to detect the position of the faulty battery cell in the battery pack.

In a third scenario, one of the circuit boards of the battery pack has a bad physical contact with the frame. This causes the circuit board to heat up and the sensors indicates a higher temperature than the neighboring sensors. This information may be used in system verification of the final battery pack prior to shipping. This allows a stress test that provides information about the thermal flow within the battery pack during load. The thermal information from the circuit boards may also be used in a digital twin of the battery pack, which may provide detailed information about state-of-charge for example.

The invention also concerns a computer program product comprising instructions, which when the program is executed by a processor 406 of a battery management system 404 of a battery pack according to embodiments, causes the processor 406 to execute the method of embodiments disclosed herein.

The disclosure relates to a circuit board for interconnecting battery cells of a battery pack, comprising a substrate comprising: a contact area of the substrate configured to be connected to a pole of a battery cell for interconnecting battery cells; a contact temperature sensor operable to measure a temperature of the contact area; a substrate temperature sensor operable to measure a temperature of the substrate; wherein the circuit board further comprises a controller comprising: a measurement module operable to measure signals representing measured temperatures from the contact and substrate temperature sensors; and a communication module configured to send information about the measured temperatures to a battery management system.

According to some embodiments, the substrate further comprises a further contact area, and a further contact temperature sensor operable to measure the temperature of the further contact area.

According to some embodiments, at least one of the temperature sensors is an electrically conducting path formed as a trace in a conductive layer arranged on a carrier board of the substrate.

According to some embodiments, the substrate temperature sensor comprises a plurality of temperature sensors configured to sense the temperature of different regions of the substrate.

According to some embodiments, the substrate temperature sensor has a sensor area of at least 10 % of the area of the substrate.

According to some embodiments, the contact area and/or the further contact area is formed in the conductive layer. According to some embodiments, the substrate further comprises a further conductive layer in which at least one of the temperature sensors and/or contact areas is formed.

According to some embodiments, the further conductive layer is formed on an opposite side of the carrier board than the conductive layer.

The disclosure also relates to a battery pack for an electrical vehicle, comprising a plurality of circuit boards according to any one of the preceding claims; a plurality of battery cells interconnected by means of the plurality of circuit boards; a frame configured to mount the circuit boards between battery cells in a sandwich structure, wherein each battery cell is in physical contact with a corresponding face of a circuit board, and wherein the substrate temperature sensor is in physical contact with the battery cell; a cooling structure in physical contact with the frame for heat transfer from the frame to the cooling structure; a battery management system, BMS, operable for charging and monitoring of the battery cells, wherein the BMS is operable to receive information about the measured temperatures from the plurality of circuit boards, the BMS is further operable to generate a control signal for controlling the power to, or from, the battery pack in response to said received information about the measured temperatures.

According to some embodiments, the frame is in physical contact with at least a part of the periphery of each circuit board.

According to some embodiments, method comprising: receiving measured temperatures from the controllers of the plurality of circuit boards; generating a control signal, CS, operable to control electrical power from, or to, the battery pack in response to the received measured temperatures.

According to some embodiments, the step of generating a control signal further comprises: determining if any one of the received measured temperatures is above a threshold; and generating an alarm if one of the received measured temperatures is above said threshold.

According to some embodiments, the step of generating an alarm further comprises: generating a contact area alarm if the temperature above the threshold is a temperature measured by one of the contact temperature sensors; and/or generating a battery cell alarm if the temperature above the threshold is a temperature measured by one of the substrate temperature sensors.

According to some embodiments, the step of generating a control signal further comprises a step of: disconnecting the battery pack from a load, or entering a low power mode of operation that causes the measured temperatures to decrease below the threshold temperature in response to the generated alarm.

The disclosure also relates to an electrical propulsion system for a boat, comprising a battery pack according to embodiments for supplying an electric motor of the boat with electric power for propulsion via a motor controller, wherein the motor controller is operable to receive the control signal from the battery management system.

The disclosure also relates to a computer program product comprising instructions, which when the program is executed by a processor of a battery management system of a battery pack according to embodiments, causes the processor to execute the method according to embodiments disclosed herein.

In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the embodiments being defined by the following claims.

The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. The circuit board of the present solution could also be used to heat a battery by means of using the traces of the circuit board acting as a temperature sensor as a resistive heater for the battery pack. This could potentially be useful in low temperatures.

It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other. It should be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

Claims

1. A circuit board (100; 401a-f;501a-g) for interconnecting battery cells (402a-e;502a-f) of a battery pack (400;500), comprising: a substrate (101) comprising: a contact area (102) of the substrate configured to be connected to a pole of a battery cell for interconnecting battery cells; a contact temperature sensor (103) operable to measure a temperature of the contact area (104); a substrate temperature sensor (104) operable to measure a temperature of the substrate (101); wherein the circuit board further comprises a controller (105) comprising: a measurement module (106) operable to measure signals representing measured temperatures from the contact and substrate temperature sensors; and a communication module (107) configured to send information about the measured temperatures to a battery management system.

2. The circuit board according to claim 1, wherein the substrate (101) further comprises a further contact area (108), and a further contact temperature sensor (109) operable to measure the temperature of the further contact area (108).

3. The circuit board according to any one of claims 1 or 2, wherein at least one of the temperature sensors is an electrically conducting path formed as a trace in a conductive layer (202) arranged on a carrier board (203) of the substrate (101).

4. The circuit board according to claims 1 to 3, wherein the substrate temperature sensor (104) comprises a plurality of temperature sensors (111, 112, 113, 114) configured to sense the temperature of different regions of the substrate.

5. The circuit board according to any one of the preceding claims, wherein the substrate temperature sensor (104) has a sensor area of at least 10 % of the area of the substrate.

6. The circuit board according to claims 3 to 5, wherein the contact area and/or the further contact area is formed in the conductive layer.

7. The circuit board according to any one of the preceding claims 3 - 6, wherein the substrate (101) further comprises a further conductive layer (302) in which at least one of the temperature sensors and/or contact areas is formed.

8. The circuit board according to claim 7, wherein the further conductive layer (302) is formed on an opposite side of the carrier board (203) than the conductive layer (202).

9. A battery pack (400;500;701) for an electrical vehicle, comprising: a plurality of circuit boards (100;401a-f;501a-g) according to any one of the preceding claims; a plurality of battery cells (402a-e;502a-f) interconnected by means of the plurality of circuit boards; a frame (403) configured to mount the circuit boards between battery cells in a sandwich structure, wherein each battery cell is in physical contact with a corresponding face of a circuit board, and wherein the substrate temperature sensor is in physical contact with the battery cell; a cooling structure (404) in physical contact with the frame (403) for heat transfer from the frame (403) to the cooling structure (404); a battery management system, BMS, (405) operable for charging and monitoring of the battery cells, wherein the BMS is operable to receive information about the measured temperatures from the plurality of circuit boards, the BMS is further operable to generate a control signal (407) for controlling the power to, or from, the battery pack in response to said received information about the measured temperatures.

10. The battery pack according to claim 9, wherein the frame (403) is in physical contact with at least a part of the periphery of each circuit board (100;401a-f;501a-g).

11. A method (600) of a battery management system (405) for a battery pack

(400;500;701) according to claim 9 or 10, the method comprising: receiving (S5) measured temperatures from the controllers of the plurality of circuit boards; generating (S10) a control signal, CS, (407) operable to control electrical power from, or to, the battery pack in response to the received measured temperatures.

12. The method according to claim 11, wherein the step of generating a control signal (S10) further comprises: determining (S15) if any one of the received measured temperatures is above a threshold; and generating (S20) an alarm if one of the received measured temperatures is above said threshold.

13. The method according to claim 12, wherein the step of generating (S20) an alarm further comprises: generating a contact area alarm if the temperature above the threshold is a temperature measured by one of the contact temperature sensors; and/or generating a battery cell alarm if the temperature above the threshold is a temperature measured by one of the substrate temperature sensors.

14. The method according to claim 12 or 13, wherein the step of generating a control signal (S10) further comprises a step (S25) of: disconnecting the battery pack from a load, or entering a low power mode of operation that causes the measured temperatures to decrease below the threshold temperature in response to the generated (604) alarm.

15. An electrical propulsion system (700) for a boat (702), comprising a battery pack (701) according to claim 9 or 10 for supplying an electric motor (703) of the boat with electric power for propulsion via a motor controller (705), wherein the motor controller (705) is operable to receive the control signal (407) from the battery management system (405).

16. A computer program product comprising instructions, which when the program is executed by a processor (406) of a battery management system (404) of a battery pack according to claim 9 to 10, causes the processor (406) to execute the method according to any one of claims 11 to 14.