Method for measuring specific heat capacity of cylindrical power battery

Abstract

The invention provides a method for measuring the specific heat capacity of a cylindrical power battery. The method comprises the following steps: step 1, drilling a hole in the center of a battery negative plate of the cylindrical power battery; 2, inserting a heating resistance wire into the battery core shaft through the drill hole, and connecting a direct-current power supply; 3, placing the cylindrical power battery into a cavity of the heat insulation calorimeter; 4, starting a direct-current power supply, starting an adiabatic mode of the adiabatic calorimeter, and recording temperature change data; and step 5, finishing measurement, and calculating the specific heat capacity of the battery by using temperature change data. According to the invention, the specific heat capacity of the cylindrical power battery can be measured and calculated, and errors in the specific heat capacity testing process are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of specific heat capacity testing, and in particular to a method for measuring the specific heat capacity of a cylindrical power battery. Background Art

[0002] Specific heat capacity is a parameter that indicates the heat storage capacity of a battery, and its size directly affects the accuracy of temperature calculation during the battery's charge and discharge process. Existing methods mainly use parameter variables or theoretical calculations through the superposition of the specific heat of each battery component, or use heating plates arranged in the gaps of multiple cylindrical batteries in an adiabatic calorimeter for heating measurement. Since the external heating plates cannot fit tightly with all batteries, part of the heat is dissipated into the air instead of being absorbed by the battery, and the repeatability is slightly poor, affecting the measurement accuracy of specific heat capacity.

[0003] Therefore, in order to overcome the above technical defects, the present invention proposes a method for measuring the specific heat capacity of a cylindrical power battery with a built-in heating resistance wire.

[0004] The Chinese invention patent with application number 201410847949.5 discloses a method for determining the specific heat capacity of a lithium-ion battery, and the invention patent with publication number CN108732204A discloses a method and device for testing the specific heat capacity of a power battery. These two patents can only be used to solve the problem of measuring the specific heat capacity of square power batteries, and cannot be used to measure the specific heat capacity of cylindrical power batteries. Summary of the invention

[0005] In view of this, the present invention provides a method for measuring the specific heat capacity of a cylindrical power battery, which can measure the specific heat capacity of the cylindrical power battery and reduce the error in the specific heat capacity testing process.

[0006] In order to solve the above technical problems, the present invention is implemented as follows.

[0007] A method for measuring the specific heat capacity of a cylindrical power battery, comprising:

[0008] Step 1: Drill a hole in the center of the negative electrode of the cylindrical power battery;

[0009] Step 2: Insert the heating resistor wire into the battery mandrel through the drill hole and connect the DC power supply;

[0010] Step 3: Place the cylindrical power battery into the adiabatic calorimeter cavity;

[0011] Step 4: Start the DC power supply, turn on the adiabatic calorimeter to work in adiabatic mode, and record the temperature change data;

[0012] Step 5: After the measurement is completed, use the temperature change data to calculate the specific heat capacity of the battery.

[0013] Preferably, the step 2 is:

[0014] Step S201: Take a heating resistance wire with a length of 120 mm and a diameter of 0.3 mm and measure the resistance value R;

[0015] Step S202: Connect the heating resistance wire to a DC power supply through a wire, and set the current of the DC power supply to 0.114A;

[0016] Step S203: Wrap the resistance wire with an insulating layer and insert it into the power battery core shaft through drilling.

[0017] Preferably, in step 2, after inserting the heating resistance wire into the battery core shaft through the negative electrode drilling hole, further: injecting thermal conductive silicone grease into the battery core shaft, and the thermal conductive silicone grease fills the inside of the power battery core shaft.

[0018] Preferably, the step 3 is:

[0019] Step S301: Fix the power battery in the cavity of the adiabatic calorimeter using thin wires;

[0020] Step S302: attaching a temperature sensor to the outer surface of the power battery to record the temperature change of the power battery;

[0021] Step S303: Set the starting temperature of the adiabatic calorimeter to 20°C and the ending temperature to 60°C, and start the experiment after the temperature stabilizes.

[0022] Preferably, the step 4 is:

[0023] Step S401: Turn on the DC power supply and set the current value to I=0.114A;

[0024] Step S402: The temperature of the power battery starts to rise. After the adiabatic calorimeter detects the temperature change, it turns on the adiabatic mode, tracks the temperature of the power battery, ensures that it is in a nearly adiabatic environment without heat loss, and records the temperature change curve.

[0025] Preferably, the step 5 is:

[0026] Step S501: When the temperature of the power battery reaches the termination temperature, the experiment stops, the DC power supply and the adiabatic calorimeter are turned off, and the temperature data of the adiabatic calorimeter is read;

[0027] Step S502: randomly select two points within the range from the starting temperature to the ending temperature and record them as (T1, t1) and (T2, t2); T1 is the battery measurement temperature at time t1, and T2 is the battery measurement temperature at time t2;

[0028] Step S503: Calculate the thermal capacity of the power battery:

[0029]

[0030] Wherein, C is the heat capacity of the power battery, P is the heating power of the heating resistor, I is the constant current value given by the DC power supply, and R is the resistance value of the heating resistor;

[0031] Step S504: Calculate the specific heat capacity of the power battery according to the mass of the power battery, and the calculation formula is:

[0032]

[0033] Among them, c is the specific heat capacity of the power battery, and m is the mass of the power battery.

[0034] Beneficial effects:

[0035] (1) The specific heat capacity testing method of the present invention utilizes the structure of a cylindrical power battery and drills a hole in the center of the negative electrode of the battery so that the cavity inside the battery core shaft is connected to the outside, thereby providing a space that can accommodate a heating resistor wire. The space volume is suitable for measuring the specific heat capacity of the battery. The heating resistor wire is built into the battery core shaft so that all the heat generated by the heating resistor wire is absorbed by the battery, reducing the loss of heat to the outside of the battery. Therefore, the specific heat capacity of the battery can be obtained more accurately through the temperature rise data of the battery, thereby reducing the error in the specific heat capacity testing process.

[0036] (2) The present invention utilizes the adiabatic environment provided by the adiabatic calorimeter to further reduce temperature loss and reduce errors in the specific heat capacity test process.

[0037] (3) After the heating resistance wire is implanted in the mandrel of the present invention, the battery mandrel is injected with thermal conductive silicone grease, and the thermal conductive silicone grease wraps the resistance wire with the insulating layer and has good contact with the inner wall of the mandrel, thereby removing the air between the insulating layer and the inner wall of the mandrel, improving the heat transfer efficiency, avoiding affecting the experimental accuracy, and reducing the error in the specific heat capacity test process. In particular, in special cases, the heating wire may be very hot, but the external temperature rise is very small, and sufficient heat transfer is required to avoid reducing the experimental accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the specific heat capacity testing method of a cylindrical battery of the present invention;

[0039] Figure 2 is an experimental data curve obtained in an embodiment of the present invention;

[0040] Among them, 1-insulated calorimeter insulated cavity, 2-heating resistance wire, 3-cylindrical power battery, 4-couple sensor. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0042] The present invention provides a method for measuring the specific heat capacity of a cylindrical power battery. The core idea is to utilize the structure of a cylindrical power battery and drill a hole in the center of the negative electrode of the battery so that the cavity inside the battery core shaft is connected to the outside, thereby providing a space that can accommodate a heating resistance wire. The space volume is suitable for measuring the specific heat capacity of the battery. The heating resistance wire is built into the battery core shaft so that all the heat generated by the heating resistance wire is absorbed by the battery, reducing the loss of heat to the outside of the battery, thereby obtaining the specific heat capacity of the battery more accurately through the temperature rise data of the battery, and reducing the error in the specific heat capacity test process.

[0043] like Figure 1 As shown, a method for measuring the specific heat capacity of a cylindrical power battery of the present invention comprises the following steps:

[0044] Step 1: Drill a hole in the center of the negative electrode of the cylindrical power battery.

[0045] The cylindrical power battery has a hollow battery core shaft, with a slender electrode wire wound on the battery core shaft. Copper sheets are connected to both ends of the electrode wire as positive and negative electrode sheets. The electrode sheets are welded and fixed to the two end surfaces of the battery core shaft to seal the internal cavity of the battery core shaft.

[0046] In this step, a drilling machine can be used to drill a hole in the center of the negative electrode sheet of the battery, thereby penetrating the internal cavity of the battery core shaft.

[0047] Step 2: Insert the heating resistor wire into the battery mandrel through the drilled hole at the negative electrode of the power battery, and connect the heating resistor wire to a DC power supply.

[0048] Step 3: Place the battery in the insulated calorimeter chamber and allow the temperature to stabilize.

[0049] Step 4: Start the DC power supply and turn on the adiabatic mode of the adiabatic calorimeter to record the data.

[0050] Step 5: After the measurement is completed, the specific heat capacity of the battery is calculated using the temperature change data.

[0051] In this embodiment, the cylindrical power battery model is 18650, the positive electrode material is nickel-cobalt-manganese ternary lithium, the diameter is 18.2mm, the height is 65mm, the inner aperture is 2mm, the mass is 48g, the nominal capacity is 2.4Ah, and the current battery power is 50%. The maximum temperature of the cylindrical power battery during the test is not higher than 60°C, the accuracy of the DC power supply is 0.01V and 0.001A, and the room temperature is 18°C. The adiabatic calorimeter used can increase the ambient temperature according to the change of the surface temperature of the power battery, compensate for the heat loss of the power battery, and put the power battery in a nearly adiabatic process without heat loss.

[0052] The specific process of step 1:

[0053] Step S101: Fix the power battery vertically on a drilling machine fixture with the positive electrode facing downward and the negative electrode facing upward;

[0054] Step S102: Install a 1.5 mm drill bit and align it with the center of the negative electrode to drill a hole. A drill bit of this size can drill a hole smoothly but will not penetrate the battery mandrel.

[0055] The specific process of step 2:

[0056] Step S201: Take a heating resistance wire with a length of 120 mm and a diameter of 0.3 mm, measure its resistance R and record it;

[0057] Step S202: Connect the heating resistance wire to a DC power supply through a wire, and set the current of the DC power supply to 0.114A.

[0058] Step S203: Wrap the resistance wire with an insulating layer, add all of it into the power battery mandrel through drilling, and inject thermal conductive silicone grease to make the thermal conductive silicone grease contact the inner wall of the power battery mandrel as well as possible. There may be air in the insulating layer and the inner wall of the mandrel. Air is a poor conductor of heat and will affect the transfer of heat. In particular, the heating wire may be very hot, but the external temperature rise is very small, reducing the experimental accuracy. Therefore, in this embodiment, thermal conductive silicone grease is injected to improve the heat transfer efficiency.

[0059] The specific process of step 3:

[0060] Step S301: Fix the power battery in the cavity of the adiabatic calorimeter using thin wires;

[0061] Step S302: attaching a temperature sensor to the outer surface of the power battery to record the temperature change of the power battery;

[0062] Step S303: Set the starting temperature of the adiabatic calorimeter to 20°C and the ending temperature to 60°C, and start the experiment after the temperature stabilizes.

[0063] The specific process of step 4:

[0064] Step S401: Turn on the DC power supply and set its current value to I=0.114A;

[0065] Step S402: The temperature of the power battery starts to rise. After the adiabatic calorimeter detects the temperature change, it turns on the adiabatic mode, tracks the power battery temperature, ensures that it is in a nearly adiabatic environment without heat loss, and records the temperature change curve, such as Figure 2 shown.

[0066] The specific process of step 5:

[0067] Step S501: When the power battery temperature reaches 60°C, the experiment stops, the DC power supply and the adiabatic calorimeter are turned off, and the temperature data is read. Figure 2 As shown;

[0068] Step S502: randomly select two points of temperature data between 20 and 60°C and record them as (T1, t1) and (T2, t2); wherein T1 is the battery measured temperature at time t1, and T2 is the battery measured temperature at time t2.

[0069] Step S503: The temperature rise of the power battery in this stage can be considered to be entirely caused by the heat generated by the heating resistor wire, so the heat capacity calculation expression of the power battery is:

[0070]

[0071] Where C is the heat capacity of the power battery, P is the heating power of the heating resistor, I is the constant current value given by the DC power supply, and R is the resistance value of the heating resistor;

[0072] Step S504: Calculate the specific heat capacity of the power battery according to the mass of the power battery, and the calculation formula is:

[0073]

[0074] Where c is the specific heat capacity of the power battery, m is the mass of the power battery, and C is the heat capacity of the power battery, which is calculated by formula (1).

[0075] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A method for measuring the specific heat capacity of a cylindrical power battery, characterized in that: include: Step 1: Drill a hole in the center of the negative electrode of the cylindrical power battery; Step 2: Insert the heating resistor wire into the battery mandrel through the drill hole and connect the DC power supply; Step 3: Place the cylindrical power battery into the adiabatic calorimeter cavity; Step 4: Start the DC power supply, turn on the adiabatic calorimeter to work in adiabatic mode, and record the temperature change data; Step 5: After the measurement is completed, use the temperature change data to calculate the specific heat capacity of the battery.

2. The method according to claim 1, characterized in that The step 2 is: Step S201: Take a heating resistance wire with a length of 120 mm and a diameter of 0.3 mm and measure the resistance value R; Step S202: Connect the heating resistance wire to a DC power supply through a wire, and set the current of the DC power supply to 0.114A; Step S203: Wrap the resistance wire with an insulating layer and insert it into the power battery core shaft through drilling.

3. The method according to claim 1 or 2, characterized in that In the step 2, after inserting the heating resistance wire into the battery core shaft through the negative electrode drilling hole, further: injecting thermal conductive silicone grease into the battery core shaft, and the thermal conductive silicone grease fills the inside of the power battery core shaft.

4. The method according to claim 1, characterized in that The step 3 is: Step S301: Fix the power battery in the cavity of the adiabatic calorimeter using thin wires; Step S302: attaching a temperature sensor to the outer surface of the power battery to record the temperature change of the power battery; Step S303: Set the starting temperature of the adiabatic calorimeter to 20°C and the ending temperature to 60°C, and start the experiment after the temperature stabilizes.

5. The method according to claim 1, characterized in that The step 4 is: Step S401: Turn on the DC power supply and set the current value to I=0.114A; Step S402: The temperature of the power battery starts to rise. After the adiabatic calorimeter detects the temperature change, it turns on the adiabatic mode, tracks the temperature of the power battery, ensures that it is in a nearly adiabatic environment without heat loss, and records the temperature change curve.

6. The method according to claim 1, characterized in that The step 5 is: Step S501: When the temperature of the power battery reaches the termination temperature, the experiment stops, the DC power supply and the adiabatic calorimeter are turned off, and the temperature data of the adiabatic calorimeter is read; Step S502: randomly select two points within the range from the starting temperature to the ending temperature and record them as (T1, t1) and (T2, t2); T1 is the battery measurement temperature at time t1, and T2 is the battery measurement temperature at time t2; Step S503: Calculate the thermal capacity of the power battery: Wherein, C is the heat capacity of the power battery, P is the heating power of the heating resistor, I is the constant current value given by the DC power supply, and R is the resistance value of the heating resistor; Step S504: Calculate the specific heat capacity of the power battery according to the mass of the power battery, and the calculation formula is: Among them, c is the specific heat capacity of the power battery, and m is the mass of the power battery.

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