Battery cell temperature measuring method for lithium battery and lithium battery

Abstract

The invention provides a battery cell temperature measuring method for a lithium battery, the lithium battery comprises a battery cell group and a controller, according to a first equivalent conductive thermal resistance R1 between the controller and the battery cell group, a second equivalent conductive thermal resistance R2 between the battery cell group and the environment and a third equivalent conductive thermal resistance R3 between the controller and the environment, the temperature of the battery cell group is measured according to the first equivalent conductive thermal resistance R1, the second equivalent conductive thermal resistance R2 and the third equivalent conductive thermal resistance R3; constructing a thermal model of the battery cell group, the controller and the environment; calculating the initial temperature of the battery cell group according to the initial environment temperature and the thermal model, and determining the current environment temperature according to the actually measured current temperature of the controller; and determining the temperature change of the battery cell group according to the current environment temperature, the current temperature of the controller and the initial temperature of the battery cell group, and determining the current temperature of the battery cell group according to the temperature change of the battery cell group. According to the technical scheme, a temperature sensor arranged in the battery cell of the lithium battery in the prior art can be omitted, so that the production cost is effectively reduced; and meanwhile, wire harnesses in the battery are reduced, the internal structure of the battery is simplified, and the arrangement of the controller BMS is more flexible.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and particularly to a method for measuring the temperature of a battery cell for a lithium battery and a lithium battery. Background Art

[0002] In the prior art, if it is necessary to measure the temperature of a battery cell of a lithium battery, it is necessary to arrange an unequal number of temperature sensors inside the battery, connect them to the battery internal control system, and measure the temperature change of the battery cell inside the battery by means of analog sampling. This method not only requires setting multiple sensors inside the battery, increasing the production cost, but also has complex wiring harnesses, which is not conducive to later maintenance and repair. Summary of the Invention

[0003] In order to overcome the above technical defects, an object of the present invention is to provide a method for measuring the temperature of a battery cell for a lithium battery, where the lithium battery includes a battery cell group and a controller, and includes:

[0004] Construct a thermal model of the battery cell group, the controller, and the environment according to a first equivalent conduction thermal resistance R1 between the controller and the battery cell group, a second equivalent conduction thermal resistance R2 between the battery cell group and the environment, and a third equivalent conduction thermal resistance R3 between the controller and the environment:

[0005] The temperature change ΔTcell(t) of the battery cell group is related to the first equivalent conduction thermal resistance R1, the first heat generated when the battery cell group operates, and the second equivalent conduction thermal resistance R2; the change ΔTBms(t) of the current temperature T BMS (t) of the controller is related to the first equivalent conduction thermal resistance R1, the second heat generated when the controller operates, and the third equivalent conduction thermal resistance R3;

[0006] According to the initial ambient temperature TEnv0, where Tenv0 = Tcell0 = Tbms0 at this time, the thermal model calculates the initial temperature Tcell(1) of the battery cell group, the current temperature TBms(1) of the controller obtained by actual measurement, and ΔTBms(1) to determine the current ambient temperature TEnv1, where Tcell(1) is the sum of TCell(0) and the first heat generated when the battery cell group operates, and TCell(0) is the same as the initial ambient temperature TEnv0;

[0007] Determine the temperature change ΔTcell(1) of the battery cell group according to the current ambient temperature TEnv1, the current temperature TBms(1) of the controller, and the initial temperature Tcell(1) of the battery cell group, and determine the current temperature Tcell(2) of the battery cell group according to the temperature change ΔTcell(1) of the battery cell group;

[0008] Periodically update and measure the current temperature \(T_{Bms}(t)\) of the controller, and determine the ambient temperature \(T_{Env}(t)\) of the current period according to \(T_{Bms}(t)\) and \(\Delta T_{Bms}(t)\) and \(T_{cell}(t)\) calculated based on the thermal model in the previous period.

[0009] Determine the temperature change \(\Delta T_{cell}(t)\) of the battery cell pack according to the current ambient temperature \(T_{Env}(t)\), the current temperature \(T_{Bms}(t)\) of the controller, and the current temperature \(T_{cell}(t)\) of the battery cell pack, and determine the temperature \(T_{cell}(t + 1)\) of the battery cell pack in the next period according to the temperature change \(\Delta T_{cell}(t)\) of the battery cell pack.

[0010] Preferably, constructing the thermal model of the battery cell pack, the controller, and the environment includes:

[0011] The thermal model includes:

[0012]

[0013]

[0014] Where \(C_{m1}\) is the heat capacity of the battery cell pack, \(C_{m2}\) is the heat capacity of the controller, \(PV1\) represents the heat generated when the battery cell pack is working, \(PV2\) represents the heat of the controller shunt when current passes through, and \(t\) is the cycle time;

[0015] Periodically update and measure the current temperature \(T_{Bms}(t)\) of the controller, and determine the ambient temperature \(T_{Env}(t)\) of the current period according to \(T_{Bms}(t)\) and \(\Delta T_{Bms}(t)\) and \(T_{cell}(t)\) calculated based on the thermal model in the previous period according to formula (2).

[0016] Determine the temperature change \(\Delta T_{cell}(t)\) of the battery cell pack according to the current ambient temperature \(T_{Env}(t)\), the current temperature \(T_{Bms}(t)\) of the controller, and the current temperature \(T_{cell}(t)\) of the battery cell pack according to formula (1), and determine the temperature \(T_{cell}(t + 1)\) of the battery cell pack in the next period according to the temperature change \(\Delta T_{cell}(t)\) of the battery cell pack.

[0017] Preferably, calculate \(PV1\) and \(PV2\) according to formulas (3) and (4):

[0018] \(PV1 = |U - V|*I\) Formula (3)

[0019] \(PV2 = I*I*R_{shunt}\) Formula (4)

[0020] U is the terminal voltage of the lithium battery, V is the open-circuit voltage of the lithium battery, I is the current flowing through the lithium battery, and Rshunt is the resistance of the shunt resistor in the controller.

[0021] The present invention also discloses a lithium battery, including a battery cell group and a controller. The controller includes a controller temperature sensor and a microprocessor. The controller temperature sensor is used to detect the current temperature of the controller, and the microprocessor is used to measure the temperature of the battery cell group according to any one of the above-mentioned methods for measuring the temperature of the battery cells of the lithium battery.

[0022] After adopting the above technical solution, compared with the prior art, it has the following beneficial effects:

[0023] 1. It is possible to eliminate the temperature sensor disposed inside the battery cells of the lithium battery in the prior art, effectively reducing the production cost;

[0024] 2. At the same time, it reduces the wiring harness inside the battery, simplifies its internal structure, makes the layout of the controller BMS more flexible, and is beneficial to later maintenance and repair;

[0025] 3. It is possible to estimate the current temperature of the battery cells according to their different positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the internal structure of a lithium battery in the prior art;

[0027] Figure 2 is a schematic diagram of the thermal model in the method for measuring the temperature of the battery cells of the lithium battery according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of the internal structure of a lithium battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The advantages of the present invention are further elaborated below in conjunction with the accompanying drawings and specific embodiments.

[0030] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0031] The terms used in this disclosure are for the purpose of describing particular embodiments only and are not intended to limit the disclosure. The singular forms "a", "the", and "said" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0032] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0033] In the prior art, as Figure 1 shown, the battery pack of a lithium battery includes battery cells, a controller, and a battery cell temperature sensor. The battery cell temperature sensor is relied on to detect the current temperature of the battery cells at different positions and transmit the temperature information to the controller to achieve the monitoring of the temperature change of the battery cells. However, since the positions of the battery cells are different, their temperatures will also be different, and a lithium battery usually has multiple battery cells, so a corresponding number or a similar number of sensors need to be set to accurately obtain the temperatures of the battery cells arranged at different positions and different regions. This results in a need to set a plurality of temperature sensors inside the lithium battery, the cost of the lithium battery is too high, there are more internal wiring harnesses, and the layout space of the controller is limited.

[0034] To solve the problems in the prior art, an embodiment of the present invention provides a method for measuring the temperature of battery cells for a lithium battery. By constructing a thermal equilibrium model, the temperature of the battery cells is calculated according to the actually measurable temperature of the controller. Specifically, it includes:

[0035] As Figure 2 shown, according to the first equivalent conduction thermal resistance R1 between the controller and the battery cell group, the second equivalent conduction thermal resistance R2 between the battery cell group and the environment, and the third equivalent conduction thermal resistance R3 between the controller and the environment, a thermal model of the battery cell group, the controller, and the environment is constructed:

[0036] The temperature change ΔTcell(t) of the battery cell group is related to the first equivalent conduction thermal resistance R1, the first heat generated when the battery cell group operates, and the second equivalent conduction thermal resistance R2; the current temperature T of the controller BMSThe change in (t), ΔTBms(t), is related to the first equivalent conduction thermal resistance R1, the second heat generated when the controller operates, and the third equivalent conduction thermal resistance R3. That is, when the controller with a relatively close physical position heats up and current flows through the battery cells, both will cause the temperature of the battery cell group to rise, and the rise in the temperature of the battery cell group will dissipate heat to the environment. Therefore, the temperature change of the battery cell group is affected by the above processes. A thermal model is constructed based on this heat transfer process. It should be noted that in actual hardware, the controller includes multiple electronic components, and its main heat source is the shunt resistor. Therefore, the parameters related to the heat calculation of the controller, such as the temperature of the controller in the present invention, are simplified to the corresponding parameters of the shunt resistor. For example, the resistance of the controller can also be the resistance of the shunt resistor in the present invention.

[0037] In the actual calculation process, the first equivalent conduction thermal resistance R1, the second equivalent conduction thermal resistance R2, and the third equivalent conduction thermal resistance R3 can use common thermal resistance measurement methods in the art, and the present invention does not limit this here.

[0038] Based on the initial ambient temperature TEnv0, the thermal model calculates the initial temperature Tcell(1) of the battery cell group, the currently measured temperature TBms(1) of the controller, and ΔTBms(1) to determine the current ambient temperature TEnv1, where Tcell(1) is the sum of TCell(0) and the first heat generated when the battery cell group operates, and TCell(0) is the same as the initial ambient temperature TEnv0;

[0039] Based on the current ambient temperature TEnv1, the currently measured temperature TBms(1) of the controller, and the initial temperature Tcell(1) of the battery cell group, determine the temperature change ΔTcell(1) of the battery cell group, and based on the temperature change ΔTcell(1) of the battery cell group, determine the current temperature Tcell(2) of the battery cell group;

[0040] Periodically update the measurement of the currently measured temperature TBms(t) of the controller, and based on TBms(t) and Tcell(t) calculated according to the thermal model in the previous period, determine the ambient temperature TEnvt of the current period;

[0041] Based on the current ambient temperature TEnvt, the currently measured temperature TBms(t) of the controller, and the current temperature Tcell(t) of the battery cell group, determine the temperature change ΔTcell(t) of the battery cell group, and based on the temperature change ΔTcell(t) of the battery cell group, determine the temperature Tcell(t + 1) of the battery cell group in the next period.

[0042] Specifically, in this embodiment, the thermal model is constructed as follows:

[0043]

[0044]

[0045] Among them, Cm1 is the heat capacity of the battery cell group, Cm2 is the heat capacity of the controller, and the heat capacity data can be found according to the properties of the components. PV1 represents the heat generated when the battery cell group works, PV2 represents the heat of the controller when current passes through, and t is the cycle time.

[0046] Among them, PV1 and PV2 are calculated according to formulas (3) and (4):

[0047] PV1 = |U - V| * I Formula (3)

[0048] PV2 = I * I * Rshunt Formula (4)

[0049] U is the terminal voltage of the lithium battery, V is the open - circuit voltage of the lithium battery, I is the current flowing through the lithium battery, and Rshunt is the resistance of the shunt resistor in the controller. Among them, U, V, and Rshunt are all data that can be actually measured or found.

[0050] Periodically update and measure the current temperature TBms(t) of the controller. According to TBms(t) and Tcell(t) calculated according to the thermal model in the previous period, determine the ambient temperature TEnvt of the current period according to formula (2);

[0051] According to the current ambient temperature TEnvt, the current temperature TBms(t) of the controller, and the current temperature Tcell(t) of the battery cell group, determine the temperature change ΔTcell(t) of the battery cell group according to formula (1). According to the temperature change ΔTcell(t) of the battery cell group, the temperature Tcell(t + 1) of the battery cell group in the next period can be determined.

[0052] In another embodiment, it can be actually measured that R1 is 3K / W, R2 is 0.4K / W, R3 is 100K / W, the current of the lithium battery is 1A, the terminal voltage is 12V, the open - circuit voltage V is 13V, Rshunt is 100uΩ, Cm1 is 20000J / K, Cm2 is 5J / K, and the cycle time is 1s. The initial ambient temperature TEnv0 is 20°C.

[0053] In the initial state or sleep mode, the lithium battery and the controller can be regarded as in an un - working state. At this time, the temperature values of the controller, the ambient temperature, and the battery cell group are regarded as equal, all being 20°C.

[0054] When the battery cell group and the controller start to power on and enter the normal working mode, voltage and current flow through the battery cell group and the controller, that is, PV1 and PV2 generate heat, causing a thermal effect, and the three temperature values are updated at a frequency of once per second.

[0055] First, calculate PV1 and PV2 according to formulas (3) and (4):

[0056] PV1 = |U - V| * I = |12 - 13| V * 1 A = 1 W

[0057] PV2 = I * I * Rshunt = 1 * 1 * 100 * 10 -6 = 10 -4 W.

[0058] Then

[0059] Then Tcell(1) = TEnv0 + ΔTcell(1) = 20 + 0.00005 = 20.00005 °C

[0060] Substitute into formula (2). Given that Tcell(1) = 20.00005 °C at this time, ΔTBms is the difference between the measured shunt temperatures in this cycle and the next cycle, and TBms(1) is the measured value of the shunt temperature in this cycle. At this time, TEnv1 at this time can be obtained.

[0061] Substitute into formula (1) again. Given TEnv1 at this time, and Tcell(1) = 20.00005 °C and TBms(1) at this time, ΔTcell(2) between this cycle and the next cycle can be calculated, and ΔTcell(2) = Tcell(2) - Tcell(1). From this, the battery cell group temperature Tcell(2) in the next cycle can be calculated.

[0062] Repeat the above process to continuously update the controller temperature, ambient temperature, and battery cell group temperature at each second.

[0063] In addition, it should be noted that since the battery cell group usually includes multiple battery cells, the positions of the battery cells will affect the value of the equivalent conduction thermal resistance. Therefore, in the actual calculation process, the specific values of the first equivalent conduction thermal resistance R1 between the controller and the battery cell group and the second equivalent conduction thermal resistance R2 between the battery cell group and the environment corresponding to different positions of the battery cells can be measured to achieve accurate estimation. In addition, in another embodiment, after calculating the corresponding battery cell temperatures for different battery cells, the average value of the battery cell temperatures can be further calculated as the real-time temperature of the battery cell group. This invention will not elaborate here.

[0064] Another embodiment of the present invention provides a lithium battery, such as Figure 3As shown, it includes a battery cell and a controller. The controller includes a controller shunt, an NTC temperature sensor, and a microprocessor. The controller temperature sensor is used to detect the current temperature of the shunt of the controller, and the microprocessor is used to estimate the temperature of the battery cell according to any one of the above methods for measuring the temperature of the battery cell in the lithium battery.

[0065] In the embodiments of the present invention, the temperature sensor disposed in the lithium battery cell in the prior art can be omitted, effectively reducing the production cost; at the same time, the internal wiring harness of the battery is reduced, the internal structure is simplified, the layout of the controller BMS is made more flexible, which is beneficial to later maintenance and repair; the current temperature of the battery cell can be estimated accordingly according to different positions of the battery cell, improving the accuracy of the estimation.

[0066] It should be noted that the embodiments of the present invention have better implementability and do not impose any form of limitation on the present invention. Any person skilled in the art may use the disclosed technical content to change or modify it into equivalent effective embodiments. However, as long as it does not depart from the technical solution of the present invention, any modification, equivalent change, or modification made to the above embodiments according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for measuring the temperature of a battery cell for a lithium battery, the lithium battery comprising a battery cell group and a controller, characterized in that, Construct a thermal model of the battery cell group, the controller, and the environment based on a first equivalent conduction thermal resistance R1 between the controller and the battery cell group, a second equivalent conduction thermal resistance R2 between the battery cell group and the environment, and a third equivalent conduction thermal resistance R3 between the controller and the environment: The temperature change ΔTcell(t) of the battery cell group is related to the first equivalent conduction thermal resistance R1, the first heat generated when the battery cell group operates, and the second equivalent conduction thermal resistance R2; the temperature change ΔTBms(t) of the current temperature T BMS (t) of the controller is related to the first equivalent conduction thermal resistance R1, the second heat generated when the controller operates, and the third equivalent conduction thermal resistance R3; Determine the current ambient temperature TEnv1 according to the initial ambient temperature TEnv0, calculate the initial temperature Tcell(1) of the battery cell group using the thermal model, the currently measured temperature TBms(1) of the controller, and ΔTBms(1), where Tcell(1) is the sum of TCell(0) and the first heat generated during the operation of the battery cell group, and TCell(0) is the same as the initial ambient temperature TEnv0; Determine the temperature change ΔTcell(1) of the battery cell group according to the current ambient temperature TEnv1, the currently measured temperature TBms(1) of the controller, and the initial temperature Tcell(1) of the battery cell group, and determine the current temperature Tcell(2) of the battery cell group based on the temperature change ΔTcell(1) of the battery cell group; Periodically update the measurement of the currently measured temperature TBms(t) of the controller, and determine the ambient temperature TEnvt of the current period according to TBms(t) and Tcell(t) calculated using the thermal model in the previous period; Determine the temperature change ΔTcell(t) of the battery cell group according to the current ambient temperature TEnvt, the currently measured temperature TBms(t) of the controller, and the current temperature Tcell(t) of the battery cell group, and determine the temperature Tcell(t + 1) of the battery cell group in the next period based on the temperature change ΔTcell(t) of the battery cell group.

2. The method for measuring the temperature of a battery cell for a lithium battery according to claim 1, wherein: The construction of the thermal model of the battery cell group, the controller, and the environment includes: The thermal model includes: where Cm1 is the heat capacity of the battery cell group, Cm2 is the heat capacity of the controller, PV1 represents the heat generated during the operation of the battery cell group, PV2 represents the heat of the controller when current passes through, and t is the cycle time; Periodically update the measurement of the currently measured temperature TBms(t) of the controller, and determine the ambient temperature TEnvt of the current period according to TBms(t), ΔTBms(t), and Tcell(t) calculated using the thermal model in the previous period according to formula (2); Determine the temperature change ΔTcell(t) of the battery cell group according to the current ambient temperature TEnvt, the currently measured temperature TBms(t) of the controller, and the current temperature Tcell(t) of the battery cell group according to formula (1), and determine the temperature Tcell(t + 1) of the battery cell group in the next period based on the temperature change ΔTcell(t) of the battery cell group.

3. The method for measuring the temperature of a battery cell for a lithium battery according to claim 2, wherein: Calculate PV1 and PV2 according to formulas (3) and (4): PV1 = |U - V| * I Formula (3) PV2 = I * I * Rshunt Equation (4) U is the terminal voltage of the lithium battery, V is the open-circuit voltage of the lithium battery, I is the current flowing through the lithium battery, and Rshunt is the resistance of the shunt resistor in the controller.

4. A lithium battery, comprising a battery cell group and a controller, characterized in that the controller includes a controller temperature sensor and a microprocessor, the controller temperature sensor is used to detect the current temperature of the controller, and the microprocessor is used to measure the temperature of the battery cell group according to the method for measuring the temperature of the battery cells of a lithium battery as described in any one of claims 1-3.

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