Lithium battery temperature acquisition and detection method and preparation method

Abstract

The invention discloses a lithium battery temperature acquisition and detection method, which comprises the following steps of: 1) replacing an original acquisition line (sheet) for acquiring the voltage of each monomer in an original battery pack (pack) with a copper / constantan double-core wire (bimetallic strip), welding an acquisition point on a monomer cell by adopting laser fusion welding or ultrasonic welding, and forming a standard T-shaped thermocouple at the welding point; after welding is completed, welding spots are isolated through epoxy resin or silica gel, and stability is guaranteed; 2) the copper wire (sheet) of the double-core wire can still be used for original single voltage acquisition signals, and functions of the copper wire (sheet) are kept unchanged; a constantan wire (sheet) is taken as a single cell temperature acquisition signal, and the temperature correction of a thermocouple formed on a cell utilizes a plurality of standing time periods in the production process of a battery pack (pack) and is completely corrected by a BMS (battery management system); and 3) repeatedly arranging a small number of NTC thermistors on key points in the battery and the thermocouples manufactured in the above mode for dynamic calibration and cold end temperature compensation of the thermocouples in the use process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for collecting and detecting the temperature of a lithium battery and a preparation method thereof. Background Art

[0002] Currently, existing lithium batteries are sensitive to temperature, and independent temperature sensors are required for detection and monitoring during use. Especially in the fields of energy storage and new energy, when the system voltage is high and multiple battery strings are required, many temperature sensors must be deployed to monitor the temperature to ensure battery safety. However, they are generally only installed on battery cells in key locations. In this way, the temperature monitoring of battery cells where sensors are not installed may not be monitored or may be delayed, which poses a risk. Increasing the number of temperature sensors will result in too many signal harnesses, which will reduce the reliability of the connection, layout, and BMS temperature acquisition circuits and increase costs.

[0003] To this end, a lithium battery temperature acquisition and detection method and a preparation method are proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a lithium battery temperature acquisition and detection method and a preparation method, which, on the basis of safety, reliability and cost-effectiveness, reduces wiring and monitors the temperature of all battery cells, thereby improving the safety of lithium batteries during use.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The lithium battery temperature collection and detection method includes the following steps:

[0007] 1) Replace the original voltage collection wire (sheet) for each cell in the original battery pack (pack) with a copper / constantan double-core wire (bimetallic sheet). The collection point is laser welded or ultrasonically welded to the single cell. The welding point forms a standard T-type thermocouple. After welding, the welding point is isolated with epoxy resin or silicone to ensure its stability.

[0008] 2) The copper wire (sheet) of the dual-core wire can still be used for the original single-cell voltage acquisition signal, retaining its function unchanged; the constantan wire (sheet) is used as the single-cell temperature acquisition signal, and the temperature calibration of the thermocouple formed on the cell utilizes multiple static time periods during the battery pack (pack) production process, and the BMS performs all calibrations on it;

[0009] 3) A small number of NTC thermistors are placed repeatedly at key points inside the battery and at the thermocouples made in the above manner to ensure dynamic calibration of the thermocouples and cold-end temperature compensation during use.

[0010] 4) Transmit the temperature and voltage signals to the BMS via a dual-core cable. Use time-division multiplexing technology to separate the signals. Establish a three-dimensional temperature field reconstruction model in the BMS firmware, and verify the data validity using the temperature gradient of adjacent thermocouple nodes.

[0011] 5) Establish a multi-level calibration system: Initial calibration is performed in a constant temperature chamber during the initial stage. Contact resistance compensation correction is performed using a laser heating device during module assembly. After system integration, online temperature field calibration is performed using an NTC array or a thermal imager, forming a three-level calibration database.

[0012] 6) BMS Intelligent Diagnosis Strategy: When an abnormal change in the resistance of a constantan wire in a channel is detected exceeding ±5%, it automatically switches to a thermopile consisting of several adjacent thermocouples for redundant measurement, triggering a warning signal and recording the coordinates of the failure location.

[0013] 7) Optimize welding parameter configuration: Establish a welding energy parameter matrix for different battery cell shell materials (aluminum alloy / nickel-plated steel / copper alloy), and use adaptive impedance matching technology to ensure that the solder joint contact resistance is stable within a certain range;

[0014] 8) Implement a dynamic compensation strategy: During battery pack operation, by monitoring the resistance change of the copper wire and correcting the temperature rise with an additional NTC temperature sensor, a cold-junction compensation function is established to perform real-time correction of the thermocouple electromotive force.

[0015] The lithium battery temperature acquisition and preparation method includes the following steps:

[0016] 1) Preparation of double core wire: Use wire diameter 0.12mm 2 The twisted pair is made of copper core enameled wire and constantan alloy (Cu55Ni45) enameled wire, with an outer layer of FEP fluoroplastic insulation. The overall outer diameter is controlled at 1.6±0.05mm. Crimp terminals are used at both ends of the harness, with a contact resistance of ≤2mΩ.

[0017] 2) Welding process: Use laser welding machine or ultrasonic welding. Weld evenly spaced weld points on each positive column of the battery cell to form a T-type thermocouple array;

[0018] 3) Insulation treatment: The welding points are encapsulated with epoxy resin to form an insulation layer with a thickness of 0.8mm. The withstand voltage test passes the 3kV / 10s standard.

[0019] 4) System calibration:

[0020] 4.1) Initial calibration: Place the module in a constant temperature chamber and let it stand for 2 hours at each of the three temperature points. Record the electromotive force of each thermocouple and create a temperature-voltage correspondence table.

[0021] 4.2) Dynamic Calibration: During module assembly, a fiber laser is used to compensate for contact resistance of 10% of random solder joints. The compensation amount is automatically calculated based on the ΔR value monitored in real time.

[0022] 4.3) Static calibration: After packaging, a thermal imager is used to perform dot matrix calibration on 100 solder joints;

[0023] 5) BMS integration: A 24-bit Δ-Σ ADC is used for signal acquisition, with a sampling rate of 4kSPS. TDM time division multiplexing technology is used to separate voltage and temperature signals.

[0024] Furthermore, in step 6), the abnormal change in resistance of the constantan wire exceeds ±5%.

[0025] Furthermore, in step 7), the contact resistance of the solder joint is stabilized within the range of 0.1-0.3 mΩ.

[0026] Furthermore, the purity of the copper core enameled wire in step 1) is ≥99.99%.

[0027] Furthermore, in step 2), the contact resistance after welding is tested to be 0.15-0.25 mΩ.

[0028] Furthermore, the three constant temperature points in step 4.1) are -20°C, 25°C, and 60°C.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This technical solution can monitor the temperature of all cells in a battery pack (pack) at a very low cost and with little increase in wiring complexity and wiring difficulty, unlike traditional battery packs (packs) which can only monitor a few cells at key points; BMS can better manage and safely use batteries;

[0031] The battery cell temperature monitoring coverage rate has been increased from the maximum 53% of the conventional solution to 100%, and the accuracy of temperature anomaly positioning has been improved from 3-4 battery cells or modules to a single battery cell and a single solder point.

[0032] Through the dynamic compensation algorithm and the additional redundant NTC temperature sensor for compensation, the reliability and accuracy of temperature monitoring can be guaranteed even when individual temperature points fail. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0034] Example 1:

[0035] The present invention provides a technical solution, a lithium battery temperature acquisition and detection method, comprising the following steps:

[0036] 1. Replace the original collection line (sheet) for collecting the voltage of each cell in the original battery pack (pack) with a copper / constantan double-core wire (bimetallic sheet). The collection point is laser welded or ultrasonically welded to the single cell. The welding point forms a standard T-type thermocouple. After welding, the welding point is isolated with epoxy resin or silicone to ensure its stability.

[0037] 2. The copper wire (sheet) of the dual-core cable can still be used for the original single-cell voltage acquisition signal, retaining its function unchanged; the constantan wire (sheet) is used as the single-cell temperature acquisition signal;

[0038] 3. The temperature calibration of the thermocouples formed on the battery cells is carried out by the BMS using multiple static time periods during the battery pack production process;

[0039] 4. A small number of NTC thermistors are placed repeatedly at key points inside the battery and at the thermocouples made in the above manner to facilitate dynamic calibration of the thermocouples and cold-end temperature compensation during use.

[0040] 5. Transmit the temperature and voltage signals to the BMS system via a dual-core cable, using time-division multiplexing technology to separate the signals. Establish a three-dimensional temperature field reconstruction model in the BMS firmware, and verify the data validity through the temperature gradient of adjacent thermocouple nodes.

[0041] 6. Establish a multi-level calibration system: Initial calibration is performed in a constant temperature chamber in the initial stage. Contact resistance compensation correction is performed using a laser heating device during module assembly. After system integration, online temperature field calibration is performed using an NTC array or a thermal imager, forming a three-level calibration database.

[0042] 7. BMS intelligent diagnostic strategy: When detecting an abnormal change in the resistance of a constantan wire in a channel exceeding ±5%, it automatically switches to a thermopile consisting of several adjacent thermocouples for redundant measurement, triggering a warning signal and recording the coordinates of the failure location.

[0043] 8. Optimize welding parameter configuration: Establish a welding energy parameter matrix for different battery cell shell materials (aluminum alloy / nickel-plated steel / copper alloy), and use adaptive impedance matching technology to ensure that the solder joint contact resistance is stable in the range of 0.1-0.3mΩ;

[0044] 9. Implement a dynamic compensation strategy: During battery pack operation, by monitoring the resistance change of the copper wire and correcting the temperature rise with an additional NTC temperature sensor, a cold-junction compensation function is established to perform real-time correction of the thermocouple electromotive force.

[0045] Example 2:

[0046] The present invention provides a technical solution, a lithium battery temperature acquisition and preparation method, comprising the following steps:

[0047] 1. Preparation of double core wire: Use wire diameter 0.12mm 2 The twisted pair is made of copper core enameled wire (purity ≥99.99%) and constantan alloy (Cu55Ni45) enameled wire, with an outer layer of FEP fluoroplastic insulation. The overall outer diameter is controlled at 1.6±0.05mm. Crimp terminals are used at both ends of the wire harness, with a contact resistance of ≤2mΩ.

[0048] 2. Welding process: Use laser welding machine or ultrasonic welding. Each battery cell positive column is welded with evenly spaced weld points to form a T-type thermocouple array. The contact resistance test value after welding is 0.15-0.25mΩ;

[0049] 3. Insulation treatment: The welding points are encapsulated with epoxy resin to form an insulation layer with a thickness of 0.8mm. The withstand voltage test passes the 3kV / 10s standard.

[0050] 4. System calibration:

[0051] a) Initial calibration: Place the module in a constant temperature box and keep it at -20°C, 25°C, and 60°C for 2 hours each. Record the electromotive force of each thermocouple and create a temperature-voltage correspondence table.

[0052] b) Dynamic calibration: During module assembly, a fiber laser is used to compensate for contact resistance of 10% of random solder joints. The compensation amount is automatically calculated based on the ΔR value monitored in real time.

[0053] C) Static calibration: After packaging, a thermal imager is used to perform dot matrix calibration on 100 solder joints;

[0054] 5. BMS integration: A 24-bit Δ-Σ ADC is used for signal acquisition, the sampling rate is set to 4kSPS, and the voltage / temperature signal separation is achieved through TDM time division multiplexing technology.

[0055] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A lithium battery temperature acquisition and detection method, characterized in that: The following steps are involved: 1) Replace the original voltage collection wire (sheet) for each cell in the original battery pack (pack) with a copper / constantan double-core wire (bimetallic sheet). The collection point is laser welded or ultrasonically welded to the single cell. The welding point forms a standard T-type thermocouple. After welding, the welding point is isolated with epoxy resin or silicone to ensure its stability. 2) The copper wire (sheet) of the dual-core wire can still be used for the original single-cell voltage acquisition signal, retaining its function unchanged; the constantan wire (sheet) is used as the single-cell temperature acquisition signal; the temperature calibration of the thermocouple formed on the cell utilizes multiple static time periods during the battery pack (pack) production process, and the BMS performs all calibrations on it; 3) A small number of NTC thermistors are placed repeatedly at key points inside the battery and at the thermocouples made in the above manner to ensure dynamic calibration of the thermocouples and cold-end temperature compensation during use. 4) Transmit the temperature and voltage signals to the BMS via a dual-core cable. Use time-division multiplexing technology to separate the signals. Establish a three-dimensional temperature field reconstruction model in the BMS firmware, and verify the data validity using the temperature gradient of adjacent thermocouple nodes. 5) Establish a multi-level calibration system: Initial calibration is performed in a constant temperature chamber during the initial stage. Contact resistance compensation correction is performed using a laser heating device during module assembly. After system integration, online temperature field calibration is performed using an NTC array or a thermal imager, forming a three-level calibration database. 6) BMS Intelligent Diagnosis Strategy: When an abnormal change in the resistance of a constantan wire in a channel is detected exceeding ±5%, it automatically switches to a thermopile consisting of several adjacent thermocouples for redundant measurement, triggering a warning signal and recording the coordinates of the failure location. 7) Optimize welding parameter configuration: Establish a welding energy parameter matrix for different battery cell shell materials (aluminum alloy / nickel-plated steel / copper alloy), and use adaptive impedance matching technology to ensure that the solder joint contact resistance is stable within a certain range; 8) Implement a dynamic compensation strategy: During battery pack operation, by monitoring the resistance change of the copper wire and correcting the temperature rise with an additional NTC temperature sensor, a cold-junction compensation function is established to perform real-time correction of the thermocouple electromotive force.

2. The lithium battery temperature acquisition and preparation method according to claim 1, characterized in that: The following steps are involved: 1) Preparation of double core wire: Use wire diameter 0.12mm 2 The twisted pair is made of copper core enameled wire and constantan alloy (Cu55Ni45) enameled wire, with an outer layer of FEP fluoroplastic insulation. The overall outer diameter is controlled at 1.6±0.05mm. Crimp terminals are used at both ends of the harness, with a contact resistance of ≤2mΩ. 2) Welding process: Use laser welding machine or ultrasonic welding. Weld evenly spaced weld points on each positive column of the battery cell to form a T-type thermocouple array; 3) Insulation treatment: The welding points are encapsulated with epoxy resin to form an insulation layer with a thickness of 0.8mm. The withstand voltage test passes the 3kV / 10s standard. 4) System calibration: 4.1) Initial calibration: Place the module in a constant temperature chamber and let it stand for 2 hours at each of the three temperature points. Record the electromotive force of each thermocouple and create a temperature-voltage correspondence table. 4.2) Dynamic Calibration: During module assembly, a fiber laser is used to compensate for contact resistance of 10% of random solder joints. The compensation amount is automatically calculated based on the ΔR value monitored in real time. 4.3) Static calibration: After packaging, a thermal imager is used to perform dot matrix calibration on 100 solder joints; 5) BMS integration: A 24-bit Δ-Σ ADC is used for signal acquisition, with a sampling rate of 4kSPS. Voltage / temperature signal separation is achieved through TDM time division multiplexing technology.

3. The lithium battery temperature acquisition and detection method according to claim 1, characterized in that: In step 6), the abnormal change in resistance of the constantan wire exceeds ±5%.

4. The lithium battery temperature acquisition and detection method according to claim 1, characterized in that: In step 7), the solder joint contact resistance is stabilized within the range of 0.1-0.3 mΩ.

5. The lithium battery temperature acquisition and preparation method according to claim 2, characterized in that: The purity of the copper core enameled wire in step 1) is ≥99.99%.

6. The lithium battery temperature acquisition and preparation method according to claim 2, characterized in that: The contact resistance test value after welding in step 2) is 0.15-0.25 mΩ.

7. The lithium battery temperature acquisition and preparation method according to claim 2, characterized in that: The three constant temperature points in step 4.1) are -20°C, 25°C, and 60°C.