Monitoring system of battery pack and battery pack

Abstract

The embodiment of the present disclosure provides a kind of battery pack monitoring system and battery pack, belong to new energy automobile technical field.The monitoring system includes first optical fiber, multiple first fiber grating temperature sensors, broadband light source and demodulator, and the multiple first fiber grating temperature sensors are arranged along the circumferential direction of the battery pack box body;The broadband light source and the demodulator are located in the battery pack box body, and the first optical fiber is connected with the output end of the broadband light source and the demodulator respectively.The embodiment of the present disclosure can monitor the temperature of battery pack, so as to determine whether the temperature in battery pack meets the requirements in real time.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of new energy vehicles, and particularly relates to a battery pack monitoring system and a battery pack. BACKGROUND

[0002] As one of the core components of the three-electricity system of a new energy vehicle, the electrical performance and safety of a battery pack have a decisive effect on the performance and reliability of the vehicle. In a hybrid electric vehicle, the battery pack has a complex structure, a large volume and mass, and is usually fixedly installed at the bottom of the vehicle. The exhaust pipe of the engine is usually arranged on one side of the battery pack. When the engine is working, the temperature of the exhaust pipe is as high as 400 ℃ to 500 ℃, so the temperature on the side of the battery pack close to the exhaust pipe is relatively high, while the temperature on the side of the battery pack away from the exhaust pipe is basically not affected, thus a large temperature difference is formed between the two sides of the battery pack. In order to avoid the situation that the performance and service life of the battery pack are affected due to the temperature difference, the vehicle thermal management needs to effectively regulate and control the temperature to balance the temperature of the battery pack. Moreover, the battery pack in the battery pack is generally best in electrochemical performance at 15 ℃ to 40 ℃. The high temperature of the exhaust pipe can seriously affect the performance of the battery pack and accelerate the aging of the battery pack, thereby shortening the service life, and in severe cases, can even cause thermal runaway, causing the battery to catch fire, explode and other safety problems. This further requires the vehicle thermal management to timely cool the battery pack.

[0003] In related technologies, in order to quickly determine whether the battery pack has a temperature abnormality (including the above-mentioned temperature imbalance or excessively high temperature), the temperature in the battery pack generally needs to be monitored. During monitoring, the electrical sensor is mainly relied on, such as a thermistor, a thermal resistance and a thermocouple. During monitoring, the electrical sensor is encapsulated and pasted at multiple positions in the battery pack, so as to monitor the temperature at different positions in the battery pack.

[0004] However, the above electrical sensor has the problems of few measurement position points, slow response speed and low measurement accuracy when arranged, and it is difficult to accurately and timely obtain the temperature field information of the outer surface of the battery pack. SUMMARY

[0005] The present disclosure provides a battery pack monitoring system and a battery pack, which can increase the monitoring points and improve the monitoring accuracy of the temperature field information of the battery pack. The technical solution is as follows:

[0006] The embodiment of the present disclosure provides a battery pack monitoring system, the battery pack comprising a battery cell and a battery pack box body, the battery cell being connected in the battery pack box body; the monitoring system comprising a first optical fiber, a plurality of first fiber grating temperature sensors, a broadband light source and a demodulator, the plurality of first fiber grating temperature sensors being located in the battery pack box body and being arranged at intervals along the circumference of the battery pack box body, the plurality of first fiber grating temperature sensors being connected with the battery pack box body; the first optical fiber being located in the battery pack box body, the first optical fiber sequentially connecting the plurality of first fiber grating temperature sensors together; the broadband light source and the demodulator both being located in the battery pack box body, and one end of the first optical fiber being connected with the output end of the broadband light source and the demodulator respectively.

[0007] In another implementation manner of the present disclosure, the first optical fiber and the plurality of first fiber grating temperature sensors are both located in the battery pack box body, and the plurality of first fiber grating temperature sensors and the first optical fiber are both connected with the inner wall of the battery pack box body.

[0008] In another implementation manner of the present disclosure, the first optical fiber is bonded on the inner wall of the battery pack box body, the inner wall of the battery pack box body is arranged with a plurality of grooves along the circumference thereof, the first optical fiber is arranged along the plurality of grooves, and the plurality of first fiber grating temperature sensors are arranged in one-to-one correspondence with the plurality of grooves, the first fiber grating temperature sensor is located in the corresponding groove and is bonded and fixed with the groove wall of the corresponding groove.

[0009] In another implementation manner of the present disclosure, the first optical fiber and the plurality of first fiber grating temperature sensors are both located outside the battery pack box body, and the plurality of first fiber grating temperature sensors and the first optical fiber are both connected with the outer wall of the battery pack box body.

[0010] In another implementation manner of the present disclosure, the battery pack further comprises an outer protective container, the outer protective container being arranged along the extension of the circumference of the outer wall of the battery pack box body and being connected with the outer wall of the battery pack box body, the middle part of the plurality of first fiber grating temperature sensors and the first optical fiber being located in the outer protective container, both ends of the first optical fiber being located outside the outer protective container, and the outer protective container being filled with a heat-conducting structural adhesive.

[0011] In another implementation manner of the present disclosure, the monitoring system further comprises a second optical fiber and a plurality of second fiber grating temperature sensors, the second optical fiber is arranged in parallel with the first optical fiber along a central axis of the battery pack case body, and the second optical fiber is connected with the battery pack case body; the plurality of second fiber grating temperature sensors are arranged in the battery pack case body and arranged in a circumferential direction of the battery pack case body, and the plurality of second fiber grating temperature sensors are connected with the battery pack case body, the second optical fiber sequentially connects the plurality of second fiber grating temperature sensors, and one end of the second optical fiber is connected with the output end of the broadband light source and the demodulator respectively.

[0012] In another implementation manner of the present disclosure, the monitoring system further comprises an optical circulator, the optical circulator is arranged in the battery pack case body and connected between the broadband light source and the first optical fiber and between the first optical fiber and the demodulator, a first port of the optical circulator is connected with the output end of the broadband light source, a second port of the optical circulator is connected with one end of the first optical fiber, and a third port of the optical circulator is connected with the demodulator, and the first port, the second port and the third port of the optical circulator are sequentially arranged along a light wave transmission direction in the optical circulator.

[0013] In another implementation manner of the present disclosure, the monitoring system further comprises a control device, the control device is arranged in the battery pack case body, an input end of the control device is connected with an output end of the demodulator, and an output end of the control device is connected with a battery management system of the battery pack.

[0014] In another implementation manner of the present disclosure, the optical circulator, the broadband light source, the demodulator and the control device are integrated in the battery management system.

[0015] In another implementation manner of the present disclosure, a battery pack is further provided, the battery pack comprises a monitoring system, a battery pack case body and a cell, the cell is arranged in the battery pack case body, the monitoring system is connected with the battery pack case body, and the monitoring system is the monitoring system provided in the present disclosure.

[0016] The technical scheme provided by the present disclosure has the following beneficial effects:

[0017] When the monitoring system provided by the present disclosure monitors the temperature in the battery pack, the plurality of fiber grating temperature sensors are arranged in the circumferential direction of the battery pack case body and connected with the battery pack case body, so that the plurality of fiber grating temperature sensors can monitor a plurality of different positions in the circumferential direction of the battery pack, and the real-time temperature changes corresponding to different positions of the inner wall of the battery pack case body can be obtained according to the monitoring results of the plurality of fiber grating temperature sensors.

[0018] And, since the monitoring system further comprises an optical fiber, a broadband light source and a demodulator, and the optical fiber connects the plurality of fiber grating temperature sensors in sequence, and one end of the optical fiber is connected with the output end of the broadband light source and the demodulator, so that the plurality of fiber grating temperature sensors are connected together through the optical fiber, the broadband light source and the demodulator, so that the broadband light source emits a broadband light signal, the broadband light signal passes through each fiber grating temperature sensor through the optical fiber, and when the broadband light signal passes through each fiber grating temperature sensor, a reflected light is reflected back, the reflected light reflected back is transmitted to the demodulator, and the demodulator obtains the temperature change value of the plurality of positions on the periphery of the battery pack according to the information of the center wavelength of the reflected light reflected back by each fiber grating temperature sensor.

[0019] Therefore, the fiber grating temperature sensor can be arranged at intervals on the periphery of the battery pack to monitor the temperature of the entire circumference of the battery pack, thereby increasing the monitoring points and greatly improving the monitoring accuracy. Once the temperature of the battery pack is abnormal, the position information of the battery pack where the abnormal temperature occurs can be quickly obtained through the above monitoring system, so as to timely determine whether the temperature of the battery pack is abnormal and ensure the safe use of the battery pack. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 A structural schematic diagram of the monitoring system provided by the embodiments of the present disclosure is shown in the figure.

[0022] Figure 2 A structural schematic diagram of the battery pack box provided by the embodiments of the present disclosure is shown in the figure.

[0023] Figure 3 A structural schematic diagram of another battery pack box provided by the embodiments of the present disclosure is shown in the figure.

[0024] The meanings of the symbols in the figure are as follows:

[0025] 200, battery pack; 201, battery cell; 202, battery pack box; 2020, groove; 203, outer protection container;

[0026] 1, first optical fiber; 2, first fiber grating temperature sensor; 3, broadband light source; 4, demodulator; 6, optical circulator; 51, second optical fiber; 52, second fiber grating temperature sensor; 7, control device; 71, analog-to-digital conversion module; 72, communication module. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present disclosure clearer, the present disclosure embodiments will be further described in detail below with reference to the drawings.

[0028] In order to clearly illustrate the battery pack monitoring system provided by the embodiments of the present disclosure, the detection principle of the fiber grating temperature sensor will be briefly described first.

[0029] The fiber grating temperature sensor is a kind of optical fiber sensing technology based on reflected light wavelength information, and its sensing unit is fiber grating. The temperature tested by the fiber grating temperature sensor depends not only on the demodulator of the fiber grating, but also on the fiber grating.

[0030] In detection, the fiber grating is connected with the light source and the demodulator through the optical fiber respectively. When the broadband light emitted by the light source passes through the fiber grating, the fiber grating will reflect back a narrowband light of a certain center wavelength (the wavelength of the narrowband light depends on the grating pitch of the fiber grating. Its mathematical expression is: λ=2nΛ, where λ is the center wavelength of the narrowband light reflected back by the fiber grating; n is the effective refractive index of the fiber grating; Λ is the grating pitch). When the fiber grating senses a change in temperature, thermal strain and thermal-optic effect will occur, the thermal strain will cause the grating pitch Λ to change, and the thermal-optic effect will cause the effective refractive index n of the fiber grating to change, thereby causing the center wavelength of the reflected narrowband light to shift (i.e. wavelength drift) relative to the original center wavelength (the so-called original center wavelength is the center wavelength of the narrowband light reflected back by the fiber grating when it has not sensed temperature). The measured temperature can be obtained by demodulating the reflected narrowband light.

[0031] Among them, the demodulator can be integrated with the light source, and the optical detection module, signal demodulation module and data processing module can also be integrated. The demodulator can be directly connected with the computer. In this way, the wavelength drift of the fiber grating can be read on the computer, and the measured temperature can be obtained.

[0032] The present disclosure embodiments provide a battery pack monitoring system, as shown in Figure 1 The battery pack 200 includes the battery cell 201 and the battery pack box 202, and the battery cell 201 is connected in the battery pack box 202.

[0033] The monitoring system comprises a plurality of first optical fibers 1, a plurality of first fiber grating temperature sensors 2, a broadband light source 3 and a demodulator 4. The plurality of first fiber grating temperature sensors 2 are arranged in the battery pack box 202 and are spaced along the circumference of the battery pack box 202, and are connected to the battery pack box 202. The first optical fiber 1 is located in the battery pack box 202, and the plurality of first fiber grating temperature sensors 2 are sequentially connected in series by the first optical fiber 1. The broadband light source 3 and the demodulator 4 are both located in the battery pack box 202, and one end of the first optical fiber 1 is connected to the output end of the broadband light source 3 and the demodulator 4, respectively.

[0034] The monitoring system provided by the embodiment of the present disclosure can monitor the temperature in the battery pack. Since the monitoring system comprises a plurality of first fiber grating temperature sensors 2, which are spaced along the circumference of the battery pack box 202 and are connected to the battery pack box 202, the plurality of different positions on the circumference of the battery pack 200 can be monitored by the plurality of first fiber grating temperature sensors 2, so that the temperature changes corresponding to different positions on the inner wall of the battery pack box 202 can be obtained according to the monitoring results of the plurality of first fiber grating temperature sensors 2.

[0035] In addition, since the monitoring system further comprises a first optical fiber 1, a broadband light source 3 and a demodulator 4, and the plurality of first fiber grating temperature sensors 2 are sequentially connected in series by the first optical fiber 1, and one end of the first optical fiber 1 is connected to the output end of the broadband light source 3 and the demodulator 4 at the same time, the plurality of first fiber grating temperature sensors 2 can be connected together with the broadband light source 3 and the demodulator 4 by the first optical fiber 1, so that a broadband light signal can be emitted by the broadband light source 3, the broadband light signal can pass through each first fiber grating temperature sensor 2 through the first optical fiber 1, and when the broadband light signal passes through each first fiber grating temperature sensor 2, a reflected light can be reflected back correspondingly, the reflected light reflected back can be transmitted through the first optical fiber 1 to the demodulator 4, and the demodulator 4 can obtain the temperature change values of the plurality of positions on the periphery of the battery pack according to the information of the center wavelength of the reflected light reflected back by each first fiber grating temperature sensor 2.

[0036] Therefore, since the first fiber grating temperature sensors 2 can be spaced and arranged on the inner wall of the battery pack box 202 to monitor the temperature on the entire circumference of the battery pack 200, the number of monitoring points can be increased, and the monitoring accuracy can be greatly improved. That is, once a temperature anomaly occurs in the battery pack 200, the position information of the battery pack 200 where the abnormal temperature occurs can be quickly obtained by the above monitoring system, so that whether the temperature anomaly of the battery pack 200 occurs can be determined in time, and the safe use of the battery pack 200 can be ensured.

[0037] As Figure 2As shown, the first optical fiber 1 and the plurality of first fiber grating temperature sensors 2 are located in the battery pack box 202, and the first optical fiber 1 and the plurality of first fiber grating temperature sensors 2 are connected to the inner wall of the battery pack box 202.

[0038] In the above implementation, the first optical fiber 1 and the first fiber grating temperature sensors 2 are closely attached to the inner wall of the battery pack box 202, so as to monitor the temperature of the entire circumference of the battery pack 200 in real time.

[0039] Optionally, the first optical fiber 1 is attached to the inner wall of the battery pack box 202, the inner wall of the battery pack box 202 has a plurality of grooves 2020 along the circumference thereof, the first optical fiber 1 is arranged along the plurality of grooves 2020, and the plurality of first fiber grating temperature sensors 2 are arranged in one-to-one correspondence with the plurality of grooves 2020, the first fiber grating temperature sensors 2 are located in the corresponding grooves 2020 and are attached and fixed to the groove walls of the corresponding grooves 2020.

[0040] In the above implementation, the first optical fiber 1 and the first fiber grating temperature sensors 2 are connected to the inner wall of the battery pack box 202 in the above manner, so that the first fiber grating temperature sensors 2 can be accommodated by the grooves 2020, and the first fiber grating temperature sensors 2 are convenient to arrange.

[0041] Alternatively, in other embodiments, the inner wall of the battery pack box 202 is not provided with grooves for accommodating the first fiber grating temperature sensors 2, and the first optical fiber 1 and the plurality of first fiber grating temperature sensors 2 are attached to the inner wall of the battery pack box 202 by an optical fiber tape.

[0042] The first optical fiber 1 and the plurality of first fiber grating temperature sensors 2 are attached to the inner wall of the battery pack box 202 by the optical fiber tape, so that the grooves can be omitted on the inner wall of the battery pack box 202, and the optical fiber tape is directly pasted, which is convenient and fast.

[0043] Of course, the fixing manner of the above first fiber grating temperature sensors 2 and the first optical fiber 1 can also be other situations, such as an annular groove is provided on the inner wall of the battery pack box 202, the annular groove extends along the circumference of the battery pack box 202, and the first fiber grating temperature sensors 2 and the first optical fiber 1 are attached in the annular groove by an adhesive. Or the inner wall of the battery pack box 202 is connected to a plurality of fixing supports, and each first fiber grating temperature sensor 2 is connected to the corresponding fixing support in sequence by a fastener such as a bolt.

[0044] That is, as long as the first fiber grating temperature sensors 2 and the first optical fiber 1 can be connected to the inner wall of the battery pack box 202 without affecting the normal use of the first fiber grating temperature sensors 2, the connection manner is not limited in the present disclosure.

[0045] For example, in order to protect the optical fiber, the inner wall of the battery pack box body 202 can be provided with a layer of stainless steel sheet, copper sheet or aluminum alloy sheet, so that the groove 2020 is a stainless steel groove, a copper groove or an aluminum alloy groove. Correspondingly, the first fiber grating temperature sensor 2 can be fixed in the groove 2020 by a heat-conducting structural adhesive or adhesive. Of course, the first optical fiber 1 can also be directly bonded to the inner wall of the battery pack box body 202 by a heat-conducting structural adhesive or adhesive.

[0046] As shown in Figure 3 Optionally, the first optical fiber 1 and the plurality of first fiber grating temperature sensors 2 are located outside the battery pack box body 202, and the plurality of first fiber grating temperature sensors 2 and the first optical fiber 1 are connected to the outer wall of the battery pack box body 202.

[0047] In the above implementation, the first fiber grating temperature sensor 2 and the first optical fiber 1 are arranged on the outer wall of the battery pack box body 202, and the temperature of the outer periphery of the battery pack 200 can also be monitored by the plurality of first fiber grating temperature sensors 2.

[0048] Optionally, the battery pack 200 further comprises an outer protection containing member 203, which is arranged along the circumference of the outer wall of the battery pack box body 202 and connected to the outer wall of the battery pack box body 202.

[0049] The middle part of the plurality of first fiber grating temperature sensors 2 and the first optical fiber 1 is located in the outer protection containing member 203, and the two ends of the first optical fiber 1 are located outside the outer protection containing member 203, and the outer protection containing member 203 is filled with heat-conducting structural adhesive.

[0050] In the above implementation, by arranging the outer protection containing member 203 on the outer wall of the battery pack box body 202, the first fiber grating temperature sensor 2 and the first optical fiber 1 can be accommodated together in the outer protection containing member 203 for protection and convenient arrangement.

[0051] The outer protection containing member 203 can be a protection pipe. That is, a ring-shaped through hole is first formed in the outer wall of the battery pack box body 202. Alternatively, a ring-shaped groove is formed in the outer wall of the battery pack box body 202, and then the outer protection containing member 203 is installed in the corresponding hole or groove, and the first fiber grating temperature sensor 2 and the first optical fiber 1 are arranged together in the protection pipe. Of course, the outer protection containing member 203 can also be directly welded to the outer wall of the battery pack box body 202 or directly connected to the outer wall of the battery pack box body 202 by a fixing member.

[0052] The outer protection containing member 203 can be a protection pipe. That is, a ring-shaped through hole is first formed in the outer wall of the battery pack box body 202. Alternatively, a ring-shaped groove is formed in the outer wall of the battery pack box body 202, and then the outer protection containing member 203 is installed in the corresponding hole or groove, and the first fiber grating temperature sensor 2 and the first optical fiber 1 are arranged together in the protection pipe. Of course, the outer protection containing member 203 can also be directly welded to the outer wall of the battery pack box body 202 or directly connected to the outer wall of the battery pack box body 202 by a fixing member.

[0053] With reference to the foregoing Figure 2 Optionally, the monitoring system further comprises a second optical fiber 51 and a plurality of second fiber Bragg grating temperature sensors 52, the second optical fiber 51 is arranged in parallel with the first optical fiber 1 along the central axis of the battery pack case 202, and the second optical fiber 51 is connected to the battery pack case 202.

[0054] The plurality of second fiber Bragg grating temperature sensors 52 are arranged in the battery pack case 202 and along the circumference of the battery pack case 202, and the plurality of second fiber Bragg grating temperature sensors 52 are connected to the battery pack case 202, and the second optical fiber 51 sequentially connects the plurality of second fiber Bragg grating temperature sensors 52. One end of the second optical fiber 51 is connected to the output end of the broadband light source 3 and the demodulator 4, respectively.

[0055] In the above implementation, the second optical fiber 51 and the second fiber Bragg grating temperature sensor 52 are arranged, and the temperature of the outer periphery of the battery pack 200 is monitored by the plurality of first fiber Bragg grating temperature sensors 2 connected to the first optical fiber 1 and the plurality of second fiber Bragg grating temperature sensors 52 connected to the second optical fiber 51 at the same time, so as to make a more accurate judgment on the current temperature state through two groups of temperature data (the values monitored by the first fiber Bragg grating temperature sensors 2 on the first optical fiber 1 are the first group of data, and the values monitored by the second fiber Bragg grating temperature sensors 52 on the second optical fiber 51 are the second group of data).

[0056] Of course, in the above manner, only one of the optical fibers can be used, or both of the optical fibers can be used at the same time. When only one of the optical fibers (such as the first optical fiber 1) is used, if the optical fiber is accidentally broken (such as broken), the demodulator 4 will locate the broken point position through the optical frequency domain reflectometry (OFDR) technology, and then immediately start using the other optical fiber (the second optical fiber 51), so as to ensure that the above monitoring system can always monitor the temperature change of the battery pack, thereby ensuring that the battery pack works at a suitable temperature. If both of the optical fibers are used at the same time, the test points can be increased to increase the temperature monitoring accuracy of the outer periphery of the battery pack.

[0057] Of course, the monitoring system can further comprise a third optical fiber, a fourth optical fiber, and a fifth optical fiber, and the third optical fiber, the fourth optical fiber, and the fifth optical fiber are connected with fiber Bragg grating temperature sensors, respectively. The connection mode of the third optical fiber, the fourth optical fiber, and the fifth optical fiber is the same as that of the second optical fiber, which will not be described here.

[0058] In this embodiment, the first optical fiber 1 and the second optical fiber 51 are the same in structure. The first fiber grating temperature sensor 2 and the second fiber grating temperature sensor 52 are the same in structure. Hereinafter, for the convenience, the first fiber grating temperature sensor 2 and the second fiber grating temperature sensor 52 are collectively referred to as a fiber grating temperature sensor. The first optical fiber 1 and the second optical fiber 51 are collectively referred to as an optical fiber.

[0059] The fiber grating temperature sensor adopts time division multiplexing technology, and has the advantages of long distance, large capacity and low cost.

[0060] Exemplarily, and along the circumference of the battery pack case 202, the spacing between two adjacent fiber grating temperature sensors is within the range of 1 cm ± 0.1 cm.

[0061] In this way, the reflectivity of the fiber grating can be maintained while effectively suppressing the transmission loss of the optical fiber, thereby improving the multiplexing capacity of the fiber grating temperature sensor.

[0062] In this embodiment, the multiplexing capacity of the fiber grating temperature sensor used is as high as 4800 (that is, a maximum of 4800 fiber grating temperature sensors can be arranged), which meets the monitoring needs of the battery pack 200.

[0063] Exemplarily, the spacing between two adjacent fiber grating temperature sensors is the same, and the center wavelengths of the plurality of fiber grating temperature sensors are the same. In this way, the fiber grating temperature sensor does not need to switch the mask plate when it is made, thereby improving the preparation efficiency of the fiber grating temperature sensor.

[0064] The center wavelengths of the fiber grating temperature sensors are the same, and the demodulator 4 identifies and demodulates each fiber grating temperature sensor according to the time when the reflected light reflected by each fiber grating temperature sensor reaches the demodulator 4. That is, the broadband light source emits one light signal, and each fiber grating temperature sensor on the optical fiber reflects one reflected light signal. Since there is a delay in the reflection of light by each fiber grating temperature sensor in the optical fiber, the demodulator 4 can identify and locate the fiber grating temperature sensor from which the reflected light signal comes according to the size of the time delay of the received reflected light signal.

[0065] In addition, the overall outer diameter of the fiber grating temperature sensor is ≤2 mm. In this way, the fiber grating temperature sensor has a small volume and a light weight, and the number of fiber grating temperature sensors arranged in a limited space can be increased, thereby further increasing the monitoring accuracy.

[0066] The plurality of fiber grating temperature sensors are written in series on the corresponding optical fiber. The fiber grating temperature sensor is formed by writing the grating on the core of the optical fiber by using a phase mask (that is, the phase mask method).

[0067] The prepared phase mask plate of glass material is placed in front of the optical fiber, and then a laser with a specified working wavelength (usually an excimer laser or a femtosecond laser) passes through the phase mask plate. After the laser passes through the phase mask plate, it is diffracted onto the optical fiber to form interference fringes, which directly act on the fiber core to form a periodic modulation of the refractive index of the fiber core, thereby forming a grating, i.e. an optical fiber grating temperature sensor.

[0068] The optical fiber grating temperature sensor is a homogenous weak reflection grating with a center wavelength of 1550 nm, a reflectivity of 0.1%, a resolution of 0.05℃, an accuracy of ±0.5℃, and a response time of 1200 ms. The homogenous weak reflection grating can reduce the reflection loss of the grating and effectively increase the multiplexing capacity of the optical fiber grating temperature sensor due to its low reflectivity.

[0069] In this embodiment, the optical fiber sequentially includes a fiber core, a cladding, and a protective coating from the inside to the outside. The cladding is a fluorine-doped silica cladding. The refractive index of the cladding is less than that of the fiber core. In this way, light can be totally reflected between the fiber core and the cladding. The doping can reduce the refractive index of silica. The protective coating is a polyimide layer. The polyimide coating is coated outside the cladding. Polyimide has good thermal stability and can be used in a high-temperature environment of 400℃. It also has strong mechanical properties and a low thermal expansion coefficient, and has an excellent protective effect on the fiber core.

[0070] The optical fiber can also use a germanium-doped silica fiber core and a silica cladding. Germanium doping can increase the refractive index of silica.

[0071] In this embodiment, the broadband light source 3 is used to emit a pulsed light signal. The pulsed light signal is reflected by the optical fiber grating temperature sensor and then returned to the demodulator 4 for demodulation.

[0072] In addition, the repeatability of the demodulator 4 is 3-5 pm, the resolution is less than 0.5 pm, and the center wavelength is consistent with that of the broadband light source 3. The reflected light signal is demodulated in real time using the optical frequency domain reflectometry (OFDR) technology, which can enhance the spatial resolution of the optical fiber grating temperature sensor and improve the temperature demodulation accuracy.

[0073] In combination with Figure 1Optionally, the monitoring system further comprises an optical circulator 6, the optical circulator 6 is located in the battery pack box 202 and is connected between the broadband light source 3 and the first optical fiber 1 and the first optical fiber 1 and the demodulator 4, the first port of the optical circulator 6 is connected with the output end of the broadband light source 3, the second port of the optical circulator 6 is connected with one end of the first optical fiber 1, and the third port of the optical circulator 6 is connected with the demodulator 4, and the first port, the second port and the third port of the optical circulator 6 are arranged in sequence along the direction of light wave transmission in the optical circulator 6.

[0074] In the above implementation, the optical circulator 6 can realize one-way transmission of reflected light. When the light emitted by the broadband light source 3 enters the optical circulator 6 through the first port of the optical circulator 6, then the light enters the first optical fiber 1 and the first optical fiber grating temperature sensor 2 through the second port of the optical circulator 6, and the light reflected in the first optical fiber grating temperature sensor 2 forms reflected light, which enters the demodulator 4 through the third port of the optical circulator 6 for demodulation, so that the light is transmitted in one direction.

[0075] Of course, the optical circulator 6 is also connected with one end of the second optical fiber 51. In this way, when the light emitted by the broadband light source 3 enters the optical circulator 6 through the fourth port of the optical circulator 6, then the light enters the second optical fiber 51 and the second optical fiber grating temperature sensor 52 through the fifth port of the optical circulator 6 for reflection, and the reflected light formed after reflection enters the demodulator 4 through the sixth port of the optical circulator 6 for demodulation, so that the light is transmitted in one direction through the optical circulator 6.

[0076] Similarly, the optical circulator 6 is also connected with the third optical fiber, the fourth optical fiber and the like. When the optical circulator 6 is connected with multiple optical fibers at the same time, the connection ports corresponding to each optical fiber are different. That is, one optical fiber corresponds to a set of connection ports. For convenience, one optical fiber can also directly correspond to one optical circulator.

[0077] Correspondingly, the broadband light emitted by the broadband light source 3 also enters different optical fibers through multiple output ends respectively. That is, one output end of the broadband light source 3 corresponds to one optical fiber.

[0078] Optionally, the monitoring system further comprises a control device 7, the control device 7 is located in the battery pack box 202, and the input end of the control device is connected with the output end of the demodulator 4, and the output end of the control device 7 is connected with the battery management system of the battery pack.

[0079] In the above implementation, the control device 7 is used to finally transmit the final demodulation result of the demodulator 4 to the battery management system of the battery pack, so that the battery management system of the battery pack can control and manage the thermal management of the battery pack according to the real-time monitored temperature.

[0080] Exemplarily, the control device 7 comprises an analog-digital conversion module 71 and a communication module 72, an input end of the analog-digital conversion module 71 is connected with an output end of the demodulator 4, and an output end of the analog-digital conversion module 71 is connected with an input end of the communication module 72. An output end of the communication module 72 is connected with a battery management system of the battery pack.

[0081] For example, when the heat of the exhaust pipe of the hybrid vehicle is transferred to the battery pack 200, the first fiber grating temperature sensor 2 can sense the temperature of the battery pack case 202, the pulse light signal emitted by the broadband light source 3 enters from the first port end of the optical circulator 6, enters the fiber grating temperature sensor through the second port of the optical circulator 6 to form a reflected light signal. The reflected light signal carrying the temperature information of the periphery of the battery pack case 202 is output from the third port of the optical circulator 6, the demodulator 4 demodulates the reflected light signal into a voltage analog signal and outputs it to the analog-digital conversion module 71, and the analog-digital conversion module 71 converts the voltage analog signal into a digital communication signal and sends it to the communication module 72. The communication module 72 transmits the digital signal carrying the accurate information such as temperature and position to the battery management system (Battery Management System, BMS), and the BMS can automatically start the thermal management according to whether there is an abnormality, so as to ensure that the battery pack 200 works at a normal temperature, and the overall temperature of the battery pack 200 reaches balance through temperature coordination.

[0082] That is, when the battery pack 200 is affected by the heat of the exhaust pipe to cause temperature abnormality, the communication module 72 can transmit the digital signal carrying the accurate information such as abnormal temperature and abnormal position to the BMS, and the BMS can immediately start the thermal management to ensure that the battery pack 200 works at a normal temperature, and the overall temperature of the battery pack 200 reaches balance through temperature coordination.

[0083] Optionally, the optical circulator 6, the broadband light source 3, the demodulator 4 and the control device 7 are integrated in the battery management system.

[0084] In the above implementation manner, the broadband light source 3, the optical circulator 6, the demodulator 4 and the control device 7 are integrated in the BMS, so that the occupied area can be reduced and the arrangement process can be simplified.

[0085] In this embodiment, the fiber is connected to each fiber grating temperature sensor to form a fiber loop, so that the fiber loop is uniformly arranged around the battery pack 200 in a reasonable manner. The advantage of this is that the entire periphery of the battery pack 200 can be monitored in real time. The light emitted by the broadband light source 3 enters the first fiber grating temperature sensor 2 through the first port of the optical circulator 6, and the reflected light carrying wavelength information is output from the third port of the optical circulator 6. The optical signal is converted into a voltage analog signal by the demodulator 4, and the voltage analog signal carrying the battery temperature state is converted into a digital signal by the analog-to-digital conversion module 71 and output to the communication module 72. The communication module 72 determines the battery pack temperature state according to the collected temperature information and the positions of the fiber grating temperature sensors, and sends it to the BMS in real time. When the fiber grating temperature sensor detects an abnormal temperature, the BMS immediately starts the battery pack thermal management system to ensure that the battery always works in the appropriate temperature range, thereby achieving the best electrical performance and prolonging the service life.

[0086] The above monitoring system has the advantages of small size, light weight, high measurement accuracy, sensitive response, good waterproof and pressure resistance, and can accurately reflect the temperature state of the measured surface in real time.

[0087] In addition, compared with other types of temperature sensors, the fiber grating temperature sensor has the advantages of small size, simple monitoring loop arrangement, small transmission loss, flexible monitoring point setting, large information transmission amount, high sensitivity, and anti-electromagnetic interference. In addition, from the nature of the optical fiber itself, the main constituent material of the optical fiber is silicon dioxide and some silicon dioxide compounds, so the optical fiber itself has the advantages of good insulation performance, resistance to various types of corrosion, stable chemical properties, radiation resistance, etc. Moreover, the optical fiber has certain protective measures, which improves the tensile strength of the optical fiber, so that the optical fiber can be used in various types of detection environments, and the monitoring system can be conveniently arranged outside the battery pack 200.

[0088] On the other hand, the present disclosure also provides a battery pack, which comprises a monitoring system, a battery pack box 202 and a battery cell 201. The battery cell 201 is located in the battery pack box 202, and the monitoring system is connected to the battery pack box 202. The monitoring system is the monitoring system described above.

[0089] The above battery pack has the same beneficial effects as described above, which will not be repeated here.

[0090] The above only describes optional embodiments of the present disclosure, and does not limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A battery pack monitoring system, characterized by, The battery pack (200) comprises a battery cell (201) and a battery pack box (202), wherein the battery cell (201) is connected in the battery pack box (202); The monitoring system comprises a first optical fiber (1), a plurality of first fiber grating temperature sensors (2), a broadband light source (3) and a demodulator (4), wherein the plurality of first fiber grating temperature sensors (2) are located in the battery pack box (202) and are arranged along the circumference of the battery pack box (202) at intervals, and the plurality of first fiber grating temperature sensors (2) are connected with the battery pack box (202). The first optical fiber (1) is located in the battery pack box (202), and the first optical fiber (1) sequentially connects the plurality of first fiber grating temperature sensors (2) together. The broadband light source (3) and the demodulator (4) are both located in the battery pack box (202), and one end of the first optical fiber (1) is connected with the output end of the broadband light source (3) and the demodulator (4) respectively. The monitoring system further comprises a second optical fiber (51) and a plurality of second fiber grating temperature sensors (52), wherein the second optical fiber (51) is arranged in parallel with the first optical fiber (1) along the central axis of the battery pack box (202) at intervals, and the second optical fiber (51) is connected with the battery pack box (202). The plurality of second fiber grating temperature sensors (52) are located in the battery pack box (202) and are arranged along the circumference of the battery pack box (202) at intervals, and the plurality of second fiber grating temperature sensors (52) are connected with the battery pack box (202), and the second optical fiber (51) sequentially connects the plurality of second fiber grating temperature sensors (52) together. One end of the second optical fiber (51) is connected with the output end of the broadband light source (3) and the demodulator (4) respectively. The monitoring system further comprises an optical circulator (6), wherein the optical circulator (6) is located in the battery pack box (202) and is connected between the broadband light source (3) and the first optical fiber (1) and between the first optical fiber (1) and the demodulator (4), the first port of the optical circulator (6) is connected with the output end of the broadband light source (3), one end of the first optical fiber (1) is connected with the second port of the optical circulator (6), and the third port of the optical circulator (6) is connected with the demodulator (4), and the first port, the second port and the third port of the optical circulator (6) are arranged in sequence along the direction of light wave transmission in the optical circulator (6).

2. The monitoring system of claim 1, wherein, The first optical fiber (1) and the plurality of first fiber grating temperature sensors (2) are both located in the battery pack box (202), and the plurality of first fiber grating temperature sensors (2) and the first optical fiber (1) are both connected with the inner wall of the battery pack box (202).

3. The monitoring system of claim 2, wherein, The first optical fiber (1) is adhered to the inner wall of the battery pack case (202), the inner wall of the battery pack case (202) is provided with a plurality of grooves (2020) along the circumferential direction of the battery pack case (202), the first optical fiber (1) is arranged along the plurality of grooves (2020), and the plurality of first fiber grating temperature sensors (2) are arranged one-to-one corresponding to the plurality of grooves (2020), the first fiber grating temperature sensor (2) is located in the corresponding groove (2020) and is adhered and fixed with the groove wall of the corresponding groove (2020).

4. The monitoring system of claim 1, wherein, The first optical fiber (1) and the plurality of first fiber grating temperature sensors (2) are located outside the battery pack case (202), and the plurality of first fiber grating temperature sensors (2) and the first optical fiber (1) are connected with the outer wall of the battery pack case (202).

5. The monitoring system of claim 4, wherein, The battery pack (200) further comprises an outer protective container (203) arranged along the extension of the circumferential direction of the outer wall of the battery pack case (202) and connected with the outer wall of the battery pack case (202), the middle part of the plurality of first fiber grating temperature sensors (2) and the first optical fiber (1) are located in the outer protective container (203), and the two ends of the first optical fiber (1) are located outside the outer protective container (203), and the outer protective container (203) is filled with a heat-conducting structural adhesive.

6. The monitoring system of any one of claims 1 to 5, wherein, The monitoring system further comprises a control device (7) located in the battery pack case (202), and the input end of the control device (7) is connected with the output end of the demodulator (4), and the output end of the control device (7) is connected with the battery management system of the battery pack.

7. The monitoring system of claim 6, wherein, The optical circulator (6), the broadband light source (3), the demodulator (4) and the control device (7) are integrated in the battery management system.

8. A battery pack, characterized by, The battery pack (200) comprises a monitoring system, a battery pack case (202) and a battery cell (201), the battery cell (201) is located in the battery pack case (202), the monitoring system is connected with the battery pack case (202), and the monitoring system is the monitoring system of any one of claims 1 to 7.

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