A device and method for detecting multiple temperatures inside a BDU

Abstract

The application provides a device and method for detecting multiple temperatures in a BDU, comprising a BDU body, a plurality of NTC thermistors arranged at different positions of the BDU body, each of the NTC thermistors having two terminals, a fixed resistance box comprising a plurality of independently arranged fixed resistors, two ends of each of the fixed resistors being electrically connected with the two terminals of the NTC thermistors in a one-to-one correspondence to form a plurality of closed-loop structures, and a multi-channel resistance measuring instrument, an input end of which is electrically connected with a common end of the closed-loop structures in a one-to-one correspondence. The multi-channel resistance measuring instrument is used to measure the resistance values of the closed-loop structures corresponding to each heating position of the BDU body in a power-off state or a power-on state. The resistance values of the closed-loop structures are different from each other, so that different internal positions of the BDU and the heating conditions thereof can be distinguished, and the NTC thermistors can be prevented from being incorrectly arranged or selected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicles, and particularly relates to a device and method for detecting multiple temperatures in a BDU. BACKGROUND

[0002] With the development of electric vehicles, users have higher and higher performance requirements for electric vehicles. The vehicle acceleration 0-100km / h requirement is ≤4 seconds, and the charging time requirement is ≤15 min when the electric quantity is 30-80%. Therefore, 4C or 6C high-current charging electric vehicles gradually appear on the market, and the charging current is as high as 600A. This poses a great challenge to the power distribution part in the battery pack of the electric vehicle. The power distribution in the battery pack mainly depends on the BDU, i.e., the Battery Disconnect Unit. The BDU internally contains high-voltage relays, fuses, pre-charging resistors, pre-charging relays, and copper busbars. Due to the limitation of the internal space of the battery pack, the power of the devices and the busbar cannot be increased indefinitely. When the current increases, the temperature of the busbar and other electrical devices will increase. If there is a problem of loose screw connection and poor contact at the electrical connection of the heating device, a safety problem may occur due to excessive temperature. Therefore, multiple temperature sensors are installed at the electrical connection of the heating device in the BDU. By monitoring the temperature of the monitoring points in the BDU and cooperating with the vehicle control strategy, the risk of thermal runaway caused by temperature abnormalities can be effectively prevented. The temperature sensors in the BDU usually use NTC thermistors. At normal temperature, these NTC thermistors installed at different positions in the BDU have the same resistance. It is not possible to determine whether each NTC thermistor sensor is incorrectly installed at the position by the electrical performance test method during the factory FCT test. Once the NTC thermistor is incorrectly installed at a non-corresponding position in the BDU, it may not correctly reflect the temperature of the corresponding part of the circuit, resulting in ineffective identification after thermal runaway, and in severe cases, it may lead to the risk of BDU or vehicle recall. Figure 1 As shown in the figure, when multiple identical NTC thermistors are used to measure the temperature of different parts in the BDU, it is difficult to troubleshoot if the NTC thermistor is incorrectly installed at the position.

[0003] The Chinese patent application with the publication number CN109580026A discloses an NTC temperature transmitter, which comprises a shell, an NTC thermistor, a VREF, a resistor R, an A / D circuit, a single-chip microcomputer, a D / A circuit and a V / I circuit. The NTC thermistor and the resistor R are connected in parallel and input a VERF signal. The voltage signal at the connection point is processed by the A / D circuit and then sent to the single-chip microcomputer, and then an analog output is output through the D / A circuit. The scheme is for the NTC thermistor and the resistor R arranged in parallel in one way, and is not applicable to the scheme of multi-channel collection. Similarly, if the NTC thermistor and the resistor R arranged in parallel in multiple ways are of the same specification, it is still impossible to determine whether the NTC thermistor is incorrectly installed. Therefore, it is necessary to provide a device and method for detecting multi-channel temperature inside a BDU, and to distinguish whether the model or performance of the NTC thermistor is reliable. SUMMARY

[0004] Therefore, the present application provides a method suitable for a BDU with multiple NTC temperature sensors inside, which can better detect the multi-channel temperature of different parts inside the BDU.

[0005] The technical scheme of the present application is as follows: on the one hand, the present application provides a device for detecting multi-channel temperature inside a BDU, which comprises

[0006] a BDU body;

[0007] a plurality of NTC thermistors arranged at different parts of the BDU body; each NTC thermistor has two terminals;

[0008] a fixed resistance box comprising a plurality of independently arranged fixed resistors, the two ends of each fixed resistor being electrically connected to the two terminals of the plurality of NTC thermistors to form a plurality of closed-loop structures;

[0009] a multi-channel resistance measuring instrument, the input end of which is electrically connected to the common end of the plurality of closed-loop structures;

[0010] The multi-channel resistance measuring instrument is used to measure the resistance value of the plurality of closed-loop structures corresponding to each heating part of the BDU body in the power-off state or the power-on state.

[0011] On the basis of the above technical scheme, preferably, the plurality of NTC thermistors are of the same specification; and the resistance values of the fixed resistors of the fixed resistance box are different.

[0012] Preferably, the plurality of NTC thermistors are fixedly arranged inside the BDU body along a preset direction, and the preset direction is the length extension direction or the width extension direction of the BDU body.

[0013] Preferably, the number of the several NTC thermistors is at least five.

[0014] Preferably, the larger value of the corresponding custom resistance values of the two adjacent NTC thermistors closest in straight-line distance inside the BDU body is more than 9 times the smaller value.

[0015] On the basis of the above technical solutions, preferably, the ambient temperature of the BDU body, the fixed-value resistance box and the multi-channel resistance measuring instrument is -40℃ to 26℃.

[0016] On the other hand, the present application also provides a method for detecting multiple temperatures inside a BDU, comprising the following steps:

[0017] S1, configuring the above-mentioned device for detecting multiple temperatures inside a BDU, spacing each NTC thermistor at different heating parts inside the BDU body, and fixedly connecting each NTC thermistor with the heating parts of the BDU body, and leading out the wiring terminals of the several NTC thermistors outside the BDU body; electrically connecting the wiring terminals of each NTC thermistor with the two ends of the fixed-value resistance respectively, so that each NTC thermistor and the fixed-value resistance form a closed loop structure connected at the head and tail;

[0018] S2, obtaining the temperature-resistance characteristic of the NTC thermistor, and further fitting the temperature-resistance characteristic curve of the closed loop structure formed by connecting each NTC thermistor in parallel with the corresponding fixed-value resistance;

[0019] S3, electrically connecting the wiring terminals of each NTC thermistor with the input terminals of the multi-channel resistance measuring instrument respectively;

[0020] S4, keeping the non-powered state of the BDU body, measuring the resistance values of the several closed loop structures by the multi-channel resistance measuring instrument, and obtaining the first resistance values of each closed loop structure composed of the NTC thermistor and the fixed-value resistance under the current state;

[0021] S5, making the BDU body enter the powered state and work for a period of time T1, and then measuring the second resistance values of each closed loop structure composed of the NTC thermistor and the fixed-value resistance under the current state by the multi-channel resistance measuring instrument again, inversely deducing the resistance values of each NTC thermistor under the current state from the second resistance values, and obtaining the current temperature of the heating parts of the BDU body by the infrared temperature measuring instrument, and judging the degree of deviation of the resistance values of each NTC thermistor under the current state from the temperature-resistance curve.

[0022] Preferably, the NTC thermistors at different positions in the BDU body are arranged at intervals, respectively, along the preset direction at the shunt mounting point, the contact of the charging negative relay, the contact of the charging positive relay, the inner surface of the BDU body and the contact of the main fuse.

[0023] Preferably, the step S5 judges the degree of deviation of the resistance value of each NTC thermistor in the current state from the temperature-resistance value curve, that is, whether the corresponding value of the resistance value of each NTC thermistor in the current state deviates from the temperature-resistance value curve by more than 5%, if not, it is considered that the type of NTC thermistor is qualified, if more than 5%, after being powered off and standing for a period of time, under the same current and time, the resistance value of the corresponding NTC thermistor is obtained by the infrared thermometer, if it is found that the resistance value of at least one NTC thermistor deviates from the corresponding value of the temperature-resistance value curve for more than three times, a batch of NTC thermistors of the same specification need to be replaced and assembled with the BDU again, and the steps S1-S5 are repeated.

[0024] Preferably, the step S5 makes the BDU body enter the powered state, that is, the current flowing through the BDU body is 400A.

[0025] The BDU internal multi-channel temperature detection device and method provided by the application has the following beneficial effects compared with the prior art:

[0026] The present application sets the same specification NTC thermistors in the BDU body, and sets different groups of fixed value resistors and NTC thermistors outside the box to form a closed loop structure in parallel, so that each closed loop structure has a significantly different resistance value at the same temperature and can be reliably measured, which can effectively avoid the phenomenon of incorrect installation of NTC thermistors, and avoid the quality defects of the existing embodiments that cannot effectively identify the heat loss position after being installed.

[0027] Further, by means of the non-powered state and the powered state for a period of time, the resistance value of each NTC thermistor changes significantly, and further by means of the multi-channel resistance measuring instrument, the resistance value of the parallel connection of the NTC thermistor and the fixed value resistor before and after the current is turned on is measured, the performance of the NTC thermistor is judged whether it deviates from the temperature-resistance value curve and the degree of deviation, and whether the type of the NTC thermistor is used incorrectly can be further judged. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0029] Figure 1 A schematic diagram of an existing BDU multi-channel temperature detection device;

[0030] Figure 2 A schematic diagram of a connection of an NTC thermistor, a fixed resistor and a multi-channel resistance measuring instrument of a BDU internal multi-channel temperature detection device of the present application;

[0031] Figure 3 A schematic diagram of the arrangement position of each temperature detection unit of a BDU internal multi-channel temperature detection device of the present application in the BDU;

[0032] Figure 4 A flow chart of a BDU internal multi-channel temperature detection method of the present application;

[0033] Figure 5 A schematic diagram of a connection of a power-on detection state of a BDU internal multi-channel temperature detection method of the present application;

[0034] Figure 6 A schematic diagram of a connection of another power-on detection state of a BDU internal multi-channel temperature detection method of the present application;

[0035] Figure 7 A temperature-resistance value curve of a ring structure composed of an NTC thermistor and a fixed resistor arranged at a heating part in a BDU body of a BDU internal multi-channel temperature detection method of the present application;

[0036] Figure 8 A temperature-resistance value curve of a ring structure composed of an NTC thermistor and a fixed resistor arranged at another heating part in a BDU body of a BDU internal multi-channel temperature detection method of the present application;

[0037] Figure 9 A temperature-resistance value curve of a ring structure composed of an NTC thermistor and a fixed resistor arranged at still another heating part in a BDU body of a BDU internal multi-channel temperature detection method of the present application;

[0038] Figure 10 A temperature-resistance value curve of a ring structure composed of an NTC thermistor and a fixed resistor arranged at yet another heating part in a BDU body of a BDU internal multi-channel temperature detection method of the present application;

[0039] Figure 11 The temperature-resistance curve of the ring structure formed by the NTC thermistor arranged at another heating position in the BDU body and the fixed-value resistor. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0041] As shown in Figure 2 and Figure 3 The present application provides a device for detecting multiple temperatures in a BDU, comprising:

[0042] The BDU body, i.e. Figure 2 the dashed box on the left side;

[0043] A plurality of NTC thermistors are arranged at different positions of the BDU body respectively; each NTC thermistor has two connection terminals; the NTC thermistor has a negative temperature coefficient, i.e. the resistance decreases with the increase of temperature.

[0044] A fixed-value resistor box includes a plurality of independently arranged fixed-value resistors, and the two ends of each fixed-value resistor are electrically connected to the two connection terminals of the plurality of NTC thermistors to form a plurality of closed-loop structures; the fixed-value resistor box is used to make the fixed-value resistors independent of each other and not interfere with each other, and a constant temperature environment can be used inside the fixed-value resistor box to eliminate the temperature drift of different fixed-value resistors.

[0045] A multi-channel resistance measuring instrument, the input end of which is electrically connected to the common end of the plurality of closed-loop structures respectively; the multi-channel resistance measuring instrument can be a commercially available product.

[0046] The multi-channel resistance tester is used to measure the resistance of the plurality of closed-loop structures corresponding to each heating position of the BDU body in a power-off state or a power-on state. Each closed-loop structure has an NTC thermistor and a fixed-value resistor connected in parallel. In order to further facilitate the corresponding connection of the NTC thermistor and the fixed-value resistor, a connector assembly can be further provided to better match and fix the terminals of the NTC thermistor and the fixed-value resistor through the connector, and the common terminal is led out to the input end of the multi-channel resistance tester, and the input end of the multi-channel resistance tester is electrically connected to a closed-loop structure in pairs, as shown in Figure 2The terminal 1 and the terminal 11 are electrically connected to the same closed loop structure, the terminal 2 and the terminal 22 are electrically connected to the same closed loop structure, and so on.

[0047] In order to ensure the accuracy of the measurement, the specifications of the selected several NTC thermistors are completely the same, preferably, each NTC thermistor selects the same model of thermistor product of the same manufacturer and the same batch, and the consistency of each NTC thermistor is good, in order to make the resistance values of each closed loop structure different from each other, the resistance values of each fixed resistor of the fixed resistor box are different from each other.

[0048] The NTC thermistors in the BDU body are arranged at intervals, and each NTC thermistor is fixedly arranged in the BDU body along a preset direction, which is the length extension direction or the width extension direction of the BDU body.

[0049] As shown in Figure 3 As a preferred embodiment, the number of NTC thermistors used in the present scheme is at least five. The five temperature detection units are arranged at intervals along the extension direction of the BDU. In addition to the NTC thermistors installed inside the BDU cavity, the remaining NTC thermistors are fixed to the heating part and fixedly connected to the heating part, such as fastening connection.

[0050] The larger value of the corresponding custom resistance value of the two adjacent NTC thermistors with the closest straight-line distance in the BDU body is more than 9 times the smaller value.

[0051] In order to facilitate testing, the present scheme sets the ambient temperature of the BDU body, the fixed resistor box and the multi-channel resistance measuring instrument to -40℃~26℃, which covers the daily temperature range of most areas, and serves as the starting temperature for the multi-channel resistance tester to measure the resistance value of each closed loop structure.

[0052] As shown in Figure 4 In combination with Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown in

[0053] S1, the above-mentioned BDU internal multi-channel temperature detection device is configured, different heating parts in the BDU body are respectively and interval arranged with each NTC thermistor, and each NTC thermistor is fixedly connected with the heating part of the BDU body, and the terminal of a plurality of NTC thermistors is respectively led out of the BDU body;The terminal of each NTC thermistor is respectively and electrically connected with the two ends of the certain value resistance, so that each NTC thermistor and the certain value resistance form a closed loop structure with the tail connected to the head.

[0054] The NTC thermistors described herein are respectively and interval arranged at different positions in the BDU body, that is, the NTC thermistors are respectively and interval arranged at the shunt mounting point, the contact of the charging negative relay, the contact of the charging positive relay, the inner surface of the BDU body and the contact of the main fuse along the preset direction, and the five mounting positions correspond to the NTC thermistor numbers NTC1, NTC2, NTC3, NTC4 and NTC5 in Figure 1 、 Figure 2 、 Figure 3 、 Figure 5 and Figure 6 .

[0055] S2, the temperature-resistance characteristic of the NTC thermistor is obtained, and the temperature-resistance characteristic curve of the closed loop structure formed by further fitting each NTC thermistor and the corresponding constant value resistance in parallel is further fitted;The temperature-resistance characteristic of the NTC thermistor can be obtained from the product manual or the official website.

[0056] S3, the terminal of each NTC thermistor is respectively and electrically connected with the input end of the multi-channel resistance measuring instrument.

[0057] S4, keep the non-powered state of the BDU body, measure the resistance value of each closed loop structure by the multi-channel resistance measuring instrument, and obtain the first resistance value of each closed loop structure composed of the NTC thermistor and the constant value resistance in the current state.

[0058] S5, make the BDU body enter the powered state and work for a period of time T1, then measure the second resistance value of each closed loop structure composed of the NTC thermistor and the constant value resistance in the current state by the multi-channel resistance measuring instrument again, deduce the resistance value of each NTC thermistor in the current state from the second resistance value, and obtain the current temperature of the heating part of the BDU body by the infrared thermometer, and judge the degree of deviation of the resistance value of each NTC thermistor in the current state from the temperature-resistance curve.

[0059] The BDU body described herein enters the powered state, that is, the current flowing through the BDU body is 400A.

[0060] Step S5 judges the degree of deviation of the resistance value of each NTC thermistor in the current state from the temperature-resistance curve, that is, whether the resistance value of each NTC thermistor in the current state deviates from the corresponding value of the temperature-resistance curve by more than 5%. If not, it is considered that the model of the NTC thermistor is qualified. If more than 5%, after being powered off and standing for a period of time, under the same current and time, the resistance value of the corresponding NTC thermistor is obtained by the infrared thermometer. If it is found that the resistance value of at least one NTC thermistor deviates from the corresponding value of the temperature-resistance curve for more than three times, a batch of NTC thermistors of the same specification need to be replaced and assembled with the BDU again, and steps S1-S5 are repeated until the resistance values of the NTC thermistors of the corresponding closed-loop structure at each input end of the multi-channel resistance tester do not deviate from the corresponding value of the temperature-resistance curve by more than 5%.

[0061] In order to better distinguish and verify the current state, as shown in Figure 5 , by connecting the output short relay and the large current constant current source, closing the charging positive relay and the charging negative relay forms the BDU charging circuit shown in the dashed line. In this case, the current flows through the two contacts of the charging positive relay. In the current state, the contact resistance and thermal resistance of each NTC thermistor are different, and the temperature rise rate also has differences. By adjusting the current time of the BDU, such as 60 seconds, the temperature of the mounting position of each NTC thermistor can be obviously different, and the second resistance value of each closed-loop structure formed by the corresponding fixed resistance is recorded. The infrared thermometer can verify the temperature of the heating position. In this scheme, the infrared thermometer is a combination of a digital infrared temperature sensor, a single-chip microcomputer and a display screen. The infrared temperature sensor is installed on the inner surface of the BDU opposite to each NTC thermistor. The measurement point of the infrared temperature sensor is aligned with the position where each NTC thermistor is installed, and the actual temperature of each heating position in the current state is obtained as a reference. The temperature is calculated from the second resistance value of each closed-loop structure, so as to detect whether the model of the NTC thermistor is installed incorrectly or the precision is poor.

[0062] Similarly, as shown in Figure 6 , by connecting the fast charging short relay and the large current constant current source, closing the charging positive relay and the charging negative relay forms the BDU charging circuit shown in the dashed line, and forms the BDU discharge circuit shown in the dashed line. In this case, the current flows through one contact of the charging positive relay, and the other contact is short-circuited by the output short relay. In the current state, the contact resistance and thermal resistance of each NTC thermistor are different, and the temperature rise rate also has differences. By adjusting the current time of the BDU, the temperature of the mounting position of each NTC thermistor can be obviously different, and the second resistance value of each closed-loop structure formed by the corresponding fixed resistance is recorded. Its detection process is the same as the above Figure 5The process is similar and will not be repeated here. It should be noted that the BDU charging circuit and the BDU discharging circuit are not switched continuously during use. Power-on verification can only begin after all NTC thermistors have reached the same set starting temperature.

[0063] The temperature-resistance characteristic curve of the closed-loop structure is calculated by combining the known temperature-resistance characteristics of the NTC thermistor with the resistance value of the fixed resistor at discrete temperatures. The equivalent resistance of the closed-loop structure at each discrete temperature is obtained, and the characteristic curve is further fitted to obtain the expression for the corresponding curve. For example... Figure 3 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, the equivalent resistance characteristic curves of the closed-loop structure corresponding to the mounting positions of each NTC thermistor in the BDU body are fitted, and the following expressions are obtained.

[0064] Y1= e -10 x1 5 – 6e -8 x1 4 + e -5 x1 3 - 0.0003x1 2 - 0.0883x1 + 7.2454; (Expression 1)

[0065] Where x1 and Y1 are the horizontal and vertical axes of the temperature-resistance curve of NTC1 at the shunt mounting point, and e is the base of the natural logarithm.

[0066] Y2 = -9e -10 x2 5 +5e -7 x2 4 - 0.0001x2 3 + 0.0152x2 2 - 0.909x2 + 24.443; (Expression 2)

[0067] Where x2 and Y2 are the horizontal and vertical axes of the NTC2 temperature-resistance curve at the contact of the charging negative relay;

[0068] Y3 = 3e -10 x3 5 - e -7 x3 4 + 2e -5 x3 3 + 0.0003x3 2 - 0.2177x3 + 12.093; (Expression 3)

[0069] wherein x3 and Y3 are the horizontal axis and the vertical axis of the temperature-resistance curve of NTC3 at the contact of the charging positive pole relay;

[0070] Y4 = -3e -9 x5 5 + 2e -6 x5 4 - 0.0003x5 3 + 0.0295x5 2 - 1.2535x5+ 25.58; (Expression 4)

[0071] wherein x4 and Y4 are the horizontal axis and the vertical axis of the temperature-resistance curve of NTC4 at the inner surface of the BDU body;

[0072] Y5 = -4e -12 x5 5 + 9e -8 x5 4 - 4e -5 x5 3 + 0.0082x5 2 - 0.6767x5+ 21.943; (Expression 5)

[0073] wherein x5 and Y5 are the horizontal axis and the vertical axis of the temperature-resistance curve of NTC5 at the main fuse of the BDU.

[0074] Regardless of whether the BDU body is in the non-energized state or the energized state, the resistance of the NTC thermistor should theoretically follow the temperature-resistance characteristic of the NTC thermistor and change with temperature.

[0075] In the non-energized state, the temperature difference of each NTC thermistor in the BDU body is small, and the first resistance of each closed loop structure composed of the NTC thermistor and the fixed resistance is recorded and saved. The first resistance is compared with the temperature-resistance characteristic curve of the closed loop structure to determine the deviation of the corresponding point on the temperature-resistance characteristic curve. In order to obtain more measurement points, in addition to maintaining the current environmental temperature in the BDU, the BDU can be further placed in different heating boxes, and each fixed resistance in the fixed resistance box is kept at a constant temperature. After the temperature of the BDU body is raised as a whole and stabilized, the first resistance of each closed loop structure at the current temperature is measured. Then the temperature inside the BDU is raised again and stabilized, and the first resistance of each closed loop structure at the current temperature is obtained again. In this way, the deviation of each first resistance after interval heating from the corresponding point on the temperature-resistance characteristic curve of the closed loop structure is determined.

[0076] When the BDU is powered on, after operating for a period of time, the second resistance value of each closed-loop structure formed by the NTC thermistor and the fixed resistor is measured in real time. Since the temperature-resistance characteristics of the NTC thermistor are easily obtained, and the characteristic curves of the equivalent resistance of each closed-loop structure are constrained by expressions, the attached... Figure 5 - Appendix Figure 11 As shown, within the normal operating temperature range of the BDU body, the resistance values ​​of the NTC thermistors in each closed-loop structure are not completely the same, resulting in significant differences in the second resistance values ​​of each closed-loop structure. Under the BDU charging circuit and the BDU discharging circuit, the heat-generating parts of the BDU body are not completely the same. Therefore, each NTC thermistor can be verified twice during the verification process of a single power-on state. Based on the degree of deviation of each second resistance value from the curve of the closed-loop structure, it is easy to distinguish whether each NTC thermistor is installed in the wrong position, has poor precision, or is of the wrong model.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting multiple temperatures inside a BDU, characterized in that, The BDU internal multi-channel temperature detection device comprises: a BDU body; a plurality of NTC thermistors arranged at different positions of the BDU body, each of the NTC thermistors having two terminals; a fixed resistance box comprising a plurality of fixed resistors, the two ends of each of the fixed resistors being electrically connected to the two terminals of one of the NTC thermistors to form a plurality of closed-loop structures; a multi-channel resistance measuring instrument, the input ends of the multi-channel resistance measuring instrument being electrically connected to the common ends of the closed-loop structures. The multi-channel resistance measuring instrument is used to measure the resistance values of the closed-loop structures corresponding to the heating positions of the BDU body in a power-off state or a power-on state. The detection method of the BDU internal multi-channel temperature detection device comprises the following steps: S1. The BDU internal multi-channel temperature detection device is configured, the NTC thermistors are arranged at different positions of the BDU body, the NTC thermistors are fixedly connected to the heating positions of the BDU body, the terminals of the NTC thermistors are led out of the BDU body, the terminals of the NTC thermistors are electrically connected to the fixed resistors, and the NTC thermistors and the fixed resistors form a closed-loop structure. S2. The temperature-resistance characteristic of the NTC thermistor is obtained, and the temperature-resistance characteristic curve of the closed-loop structure formed by the parallel connection of the NTC thermistor and the fixed resistor is further fitted. S3. The terminals of the NTC thermistors are electrically connected to the input ends of the multi-channel resistance measuring instrument. S4. The BDU body is kept in a non-powered state, the resistance values of the closed-loop structures are measured by the multi-channel resistance measuring instrument, and the first resistance values of the closed-loop structures formed by the NTC thermistors and the fixed resistors in the current state are obtained. S5. The BDU body is powered on and works for a period of time T1, the second resistance values of the closed-loop structures formed by the NTC thermistors and the fixed resistors in the current state are measured again by the multi-channel resistance measuring instrument, the resistance values of the NTC thermistors in the current state are inversely deduced from the second resistance values, the current temperature of the heating position of the BDU body is obtained by an infrared temperature measuring instrument, and the degree of deviation of the resistance values of the NTC thermistors in the current state from the temperature-resistance curve is determined.

2. The method for detecting multiple internal temperatures of a BDU according to claim 1, characterized in that, The NTC thermistors have the same specifications, and the fixed resistors of the fixed resistance box have different resistance values.

3. The method for detecting multiple internal temperatures of a BDU according to claim 2, characterized in that, The NTC thermistors are fixedly arranged in the BDU body along a preset direction, and the preset direction is the length extension direction or the width extension direction of the BDU body.

4. The method for detecting multiple internal temperatures of a BDU according to claim 3, characterized in that, The number of the NTC thermistors is at least five.

5. The method of claim 4, wherein the method further comprises: The larger of the resistance values of the fixed resistors corresponding to the two adjacent NTC thermistors closest in straight-line distance in the BDU body is more than 9 times the smaller. ​ 6. The method of claim 1, wherein the BDU is a BDU for a mobile communication terminal. The ambient temperature of the BDU body, the fixed resistance box and the multi-channel resistance measuring instrument is -40℃ to 26℃.

7. The method of claim 1, wherein the BDU is a BDU for a mobile communication terminal. The NTC thermistors are respectively and separately arranged at different positions in the BDU body according to step S1, which means that the NTC thermistors are respectively and separately arranged at the shunt installation point, the contact point of the charging negative relay, the contact point of the charging positive relay, the inner surface of the BDU body and the contact blade of the main fuse along the preset direction.

8. The method for detecting multiple internal temperatures of a BDU according to claim 1, characterized in that, The step S5 judges the degree of the resistance value of each NTC thermistor under the current state deviating from the temperature-resistance value curve, which means that the judgment is made on whether the corresponding value of the resistance value of each NTC thermistor under the current state deviating from the temperature-resistance value curve exceeds 5%, if not, it is considered that the type of the NTC thermistor is qualified, if yes, after the power-off and standing for a period of time, under the same current and time, the resistance value of the corresponding NTC thermistor is obtained by the infrared thermometer, if it is found that the resistance value of at least one NTC thermistor deviates from the corresponding value of the temperature-resistance value curve for more than three times, a batch of NTC thermistors of the same specification need to be replaced and assembled with the BDU again, and the steps S1-S5 are repeated.

9. The method of claim 1, wherein the method comprises: The step S5 makes the BDU body enter the current state, which means that the current flowing through the BDU body is 400 A.

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