Lead-acid battery internal formation and assembly method

Abstract

The present invention discloses a lead-acid battery internal formation and grouping method, which includes a charge and discharge stage, a capacity inspection stage, and a recharge stage. In the capacity inspection stage, the battery is first discharged at a current of 0.5C2 amperes for a fixed time or a fixed voltage, and the end voltage value is recorded as voltage 1. Then, the battery is discharged at a smaller current to an average voltage of 7.2V, and the end voltage value is recorded as voltage 2. Unqualified batteries are eliminated and first graded based on voltage 1, and then graded based on voltage 2, and grouped, and it is necessary to ensure that the open circuit voltage difference of batteries in the same group is not greater than 20mV. Through the grouping method of the present invention, the voltage after low-current discharge is further graded, the similarity of the battery material structure is further subdivided, and defective batteries are eliminated, thereby improving the accuracy and consistency of battery grouping, thereby extending the service life of the battery group.

Description

Technical Field

[0001] The present invention relates to the technical field of lead-acid battery production, in particular to a lead-acid battery internal formation and assembly method. Background Art

[0002] Lead-acid batteries are a widely used chemical power source, offering advantages such as good reversibility, stable voltage characteristics, long service life, wide applicability, abundant raw materials, renewable use, and low cost. In recent years, with increasing environmental awareness and increasingly serious energy issues, lead-acid batteries have played a vital role as a power source in electric vehicle systems.

[0003] The capacity of a battery is primarily determined by the mass of the positive electrode material, the mass of the negative electrode material, and the minimum amount of sulfuric acid. Both the positive and negative electrode materials have porous structures. During the charge and discharge process, sulfuric acid enters the pores of the material through the pore structure to react, thereby achieving charge and discharge. However, from plate manufacturing to formation charging until the battery is offline, the control of each process will affect the weight and structure of the material, especially in plate manufacturing and acid formation. The plate coating process in plate manufacturing affects the amount of paste applied, and curing and drying affect the material composition and structure. Acid formation mainly affects the material structure and acid amount. Studies have shown that the impact of acid formation on the overall performance of batteries is the most critical and the last line of defense. However, the usual practice is still to follow the process route of external formation and weighing, which cannot avoid the uncertain risks brought by internal formation. For example, the control of battery temperature and acid amount during internal formation are the main factors directly affecting battery performance.

[0004] A single lead-acid battery generally has a small capacity. In actual use, multiple lead-acid batteries are generally used in series as a group. The consistency between the batteries in the same group will affect the performance and life of the entire battery group.

[0005] How to improve the matching consistency is one of the keys to improving the consistency of battery packs.

[0006] For example, the invention with publication number CN111416164A discloses a method for internal battery formation and grouping. During capacity check discharge, the battery is discharged to below 10.3V per battery. During grouping, the battery is reviewed for the discharge time required for each battery to reach 10.3V after capacity check discharge. The battery is then grouped according to the discharge time, and several batteries in the same group are grouped. The method for internal battery formation and grouping of the present invention substantially ensures that all batteries are fully discharged to the end of their capacity discharge and are therefore selected, thereby increasing the screening range, the one-time discharge pass rate, and the grouping rate.

[0007] For another example, the invention disclosed in publication number CN106972212A discloses a lead-acid battery internal formation and grouping method, wherein the internal formation is carried out in a capacity check discharge stage, wherein the battery is first discharged at a fixed time or fixed voltage with a current of 1 to 3C amperes, and the end voltage value is recorded as voltage 1; then the battery is discharged at a current of 0.5C amperes to an average voltage of 10.2 to 10.5V, and the end voltage value is recorded as voltage 2. The capacity released in the capacity check discharge stage is controlled at 1.0 to 1.1C ampere-hours; after the internal formation is completed, the battery is taken off the production line, and the open circuit voltage is detected after standing; unqualified batteries are eliminated based on voltage 1 as an indicator, and then the batteries are grouped based on voltage 2, and the difference in open circuit voltage of the batteries in the same group must be ensured to be no greater than 20mV. The lead-acid battery internal formation and grouping method of the present invention can effectively eliminate defective batteries, improve the accuracy and consistency of battery grouping, and thus extend the service life of the battery group.

[0008] However, the grading method in the above-mentioned prior art is still relatively rough, and the differences between different batteries in the same group are still relatively large. Summary of the Invention

[0009] The present invention addresses the deficiencies in the prior art and provides a lead-acid battery internal formation and assembly method, which further divides the voltage after low-current deep discharge into smaller grades to subdivide the similarity of the battery material structure, thereby extending the service life of the battery pack.

[0010] A lead-acid battery internal formation and assembly method includes a charge and discharge stage, a capacity check discharge stage, a residual acid treatment stage, and a recharge stage. In the capacity check discharge stage, multiple batteries are connected in series, first discharged at a current of 0.5C2 amperes for a fixed time or a fixed voltage, and the termination voltage value of each battery is recorded as V1. Then, the batteries are discharged at a current of 0.1C2 to 0.3C2 amperes to an average voltage of 7.2V, and the termination voltage value of each battery is recorded as V2. In the capacity check discharge stage, the discharged capacity is controlled at 1.1C2 to 1.3C2 ampere-hours.

[0011] The pairing comprises the following steps:

[0012] (1) Calculate the average value of V1 of the batteries to be assembled and eliminate batteries whose V1 is less than 0.97 times the average value;

[0013] (2) First, perform the first grading based on the battery V1, and then perform the second grading based on the V2 value. The voltage difference in the same grading level should not exceed 100mV.

[0014] (3) Measure the open circuit voltage of the battery after it has been left to stand for a period of time after internal formation is completed;

[0015] (4) Group batteries with a maximum open circuit voltage difference of no more than 20mV within the same range.

[0016] During the first grading, the lead-acid batteries are divided into 4 to 6 grades according to the termination voltage value V1. The difference in the termination voltage values ​​of the lead-acid batteries in the same grade is 0.1 to 0.21V.

[0017] The lead-acid battery internal formation and assembly method can discharge 100% to 110% of its rated capacity when discharged for a fixed time at a current of 0.5C2 ampere.

[0018] The rated capacity is the nominal capacity of a lead-acid battery. It sets the expected discharge value when discharged to 10.5V. During a deep discharge (for example, to 7.2V), the actual discharge capacity of a lead-acid battery may exceed the rated capacity. C2 represents the battery's two-hour rate rated capacity. When the charge and discharge current is expressed as a multiple of C2 in amperes, C2 is used only as a numerical value, and the current is expressed in amperes.

[0019] The lead-acid battery internal formation and assembly method is to discharge at a constant voltage with a current of 0.5C2 ampere until the voltage of a single battery is 7.2V to 9.6V.

[0020] The battery is first discharged with 0.5C2 to 100% to 110% of the rated capacity or to a single battery voltage of 7.2V to 9.6V, and then discharged with a current of 0.1C2 to 0.3C2 amperes to an average voltage of 7.2V. It is obvious that the battery is deeply discharged to fully release the battery capacity and over-discharge is performed with a small current. At this time, what is reflected is whether the positive and negative electrode material structures and the transmission of sulfuric acid in the pore structure of the separator are smooth or consistent, thereby reflecting whether the materials of each battery are similar after formation, which is directly reflected in the discharge voltage of over-discharge. Therefore, secondary grading with this voltage has a significant effect on improving the life of the battery pack.

[0021] The lead-acid battery internal formation and assembly method, wherein the internal formation charge and discharge stage comprises the following steps:

[0022] (1) Circuit inspection stage: charge at a constant current of 0.01C2 to 0.015C2 amperes for 2 to 5 minutes;

[0023] (2) Static stage: 0.5 to 1.5 hours;

[0024] (3) First charging stage: charging at a current of 0.15C2 to 0.18C2 amperes for 22 to 27 hours. The charging capacity in this stage is controlled at 3.8C2 to 4.9C2 ampere-hours.

[0025] (4) First discharge stage: discharge at a current of 0.5C2 ampere for 1 h, releasing a capacity of 0.5C2 ampere-hour;

[0026] (5) Second charging stage: charge at a current of 0.2C2 to 0.25C2 amperes for 2 to 3 hours, and then charge at a current of 0.15C2 to 0.18C2 amperes for 18 to 22 hours. The charging capacity in this stage is controlled at 3.2C2 to 4C2 ampere-hours.

[0027] Preferably, the recharging stage includes the following steps: charging at a current of 0.2C2 to 0.25C2 amperes for 2 to 3 hours, and then charging at a current of 0.15C2 to 0.18C2 amperes for 10 to 12 hours. The charging capacity in this stage is controlled at 2.2C2 to 2.7C2 ampere-hours.

[0028] Preferably, the temperature of the battery electrolyte is controlled at 30-45°C during the internal formation process.

[0029] Preferably, the standing time before detecting the open circuit voltage is 24 hours.

[0030] The battery pack matching method of the present invention further divides the voltage after low-current deep discharge into different grades, further subdivides the similarity of the battery material structure, further eliminates defective batteries, improves the accuracy and consistency of battery matching, and thus extends the service life of the battery pack. DETAILED DESCRIPTION

[0031] Example 1

[0032] The same batch of semi-finished 6-DZF-20 batteries (with the same plate batch process) was subjected to the internal formation process of the present invention, with a total of 54 three-circuit batteries formed in one process, with a total formation capacity of 211Ah. After a 0.5C2A current discharge inspection to remove abnormal batteries, the first binning was performed, followed by a 0.1C2 capacitance inspection voltage. A comparative test was also conducted with the 0.5C2 capacitance inspection voltage alone.

[0033] The formation process is shown in Table 1.

[0034] Table 1

[0035]

[0036]

[0037] The capacitance test voltage is as follows:

[0038] Voltage 1: The voltage when the current is 0.5C2A and the average voltage is 10.1V or the discharge time is 120 minutes;

[0039] Voltage 2: 0.1C2A current discharge to an average voltage of 7.2V or the voltage after discharging for 160 minutes.

[0040] The values ​​of voltage 1 and voltage 2 of the 54 batteries are shown in Table 2.

[0041] Table 2

[0042]

[0043] The average voltage of voltage 1 is calculated to be 10.106V, and its lower limit is set to 9.803V with a deviation of 3%. There are 8 batteries with voltage 1 lower than 9.803V (deleted and bolded). After eliminating these 8 batteries, the first grading is performed using voltage 1, and then the subsequent grouping process is carried out using voltage 2. At the same time, the results of grouping using voltage 1 as the condition alone are compared and tested.

[0044] When voltage 1 is used alone as the pairing condition, the batteries are divided into 6 groups according to the final voltage value V1. The final voltage difference of lead-acid batteries in the same group is 0.099 to 0.195V. The voltage difference of the groups gradually decreases from low to high. The voltage difference of groups 1 to 5 is 0.099V, and the voltage difference of group 6 (low voltage group) is the largest at 0.195V. The grouping results are shown in Table 3.

[0045] Table 3

[0046]

[0047]

[0048] According to the above grading conditions, taking grading 2 as an example, there are 12 batteries in this grading position (italic bold). It can be seen that the lowest voltage of these 12 batteries is 6.190V and the highest is 7.850V, with a difference of 1660mV. The difference is obvious. If secondary grading is not carried out, the battery consistency will be poor.

[0049] Select 2nd and 3rd grade batteries for group testing respectively. After the batteries are formed and left to stand for 24 hours, they are grouped based on the open circuit voltage (OCV) (within 20mV).

[0050] Group identification: Voltage 1+2 means that voltage 1 is first divided into groups and then grouped with voltage 2; Voltage 1 means that voltage 1 is used for grouping only. Each grouping method has 2 groups, and each group has 4 batteries, as shown in Table 4.

[0051] Table 4

[0052]

[0053] The two battery groups were subjected to cycle life testing. The results, shown in Table 5, show that the 1+2 voltage pairing method offers significant advantages over the conventional 1 voltage pairing method. During battery cycling, the discharge voltage consistency of each battery pack was significantly improved, resulting in a higher capacity plateau. The battery life of the entire pack was improved by over 15% using this pairing method.

[0054] Table 5

[0055]

[0056] Example 2

[0057] The same batch of semi-finished 6-DZF-20 batteries (with the same plate batch process) was subjected to the internal formation process of the present invention. A total of 54 three-circuit batteries (with a total formation capacity of 218 Ah) were formed using one process. First, a 0.5C2A discharge current was used to inspect and remove abnormal batteries, followed by a first binning. Binning was then performed using a 0.2C2 capacitance test voltage. A comparative test was also conducted using only the 0.5C2 capacitance test voltage.

[0058] The formation process is shown in Table 6.

[0059] Table 6

[0060]

[0061]

[0062] The capacitance test voltage is as follows:

[0063] Voltage 1: The voltage when the current is 0.5C2A and the average voltage is 10.1V or the discharge time is 120 minutes;

[0064] Voltage 2: 0.2C2A current discharge to an average voltage of 7.2V or the voltage after discharging for 35 minutes.

[0065] The values ​​of voltage 1 and voltage 2 of the 54 batteries are shown in Table 7.

[0066] Table 7

[0067]

[0068] The average voltage of voltage 1 is calculated to be 10.098V, and its lower limit is set to 9.795V with a deviation of 3%. There are 7 batteries with voltage 1 lower than 9.795V (deleted and bolded). After eliminating these 7 batteries, the first grading is performed using voltage 1, and then the subsequent grouping process is carried out using voltage 2. At the same time, the results of grouping using voltage 1 as the condition alone are compared and tested.

[0069] When voltage 1 is used alone as the pairing condition, the batteries are divided into 5 groups according to the termination voltage value V1. The termination voltage difference of lead-acid batteries in the same group is 0.099 to 0.203V. The voltage difference of the groups gradually decreases from low to high. The voltage difference of groups 1 to 2 is 0.099V, the voltage difference of groups 3 to 4 is 0.149V, and the voltage difference of group 5 (low voltage group) is the largest at 0.203V. The results of the grouping are shown in Table 8.

[0070] Table 8

[0071]

[0072] According to the above grading conditions, taking grading 4 as an example, there are 21 batteries in this grading position (italic bold). It can be seen that the lowest voltage of these 21 batteries is 6.176V and the highest is 7.956V, with a difference of 1780mV. The difference is obvious. If secondary grading is not carried out, the battery consistency will be poor.

[0073] Four grades of batteries were selected for group testing. After the batteries were formed and left to rest for 24 hours, they were grouped based on the open circuit voltage (OCV) (within 20mV).

[0074] Group identification: Voltage 1+2 means voltage 1 is first divided into groups and then grouped with voltage 2; Voltage 1 means grouping with voltage 1 only. Each grouping method has 2 groups, and each group has 4 batteries, as shown in Table 9.

[0075] Table 9

[0076]

[0077]

[0078] The two battery groups were subjected to cycle life testing. The results, shown in Table 10, demonstrate that the 1+2 voltage pairing method offers significant advantages over the conventional 1 voltage pairing method. During battery cycling, the discharge voltage consistency of each battery pack was significantly improved, resulting in a higher capacity plateau. The battery life of the entire pack was improved by over 15% using this pairing method.

[0079] Table 10

[0080]

[0081] Example 3

[0082] The same batch of semi-finished 6-DZF-20 batteries (using the same plate batch process) was subjected to the internal formation process of the present invention, with a total of 54 three-circuit batteries formed in one process, with a total formation capacity of 206Ah. After a 0.5C2A discharge current inspection to remove abnormal batteries, the first binning was performed, followed by a 0.3C2 capacitance inspection voltage. A comparative test was also conducted with binning using only the 0.5C2 capacitance inspection voltage.

[0083] The formation process is shown in Table 11.

[0084] Table 11

[0085]

[0086] The capacitance test voltage is as follows:

[0087] Voltage 1: The voltage when the current is 0.5C2A and the average voltage is 10.1V or the discharge time is 120 minutes;

[0088] Voltage 2: 0.3C2A current discharge to an average voltage of 7.2V or the voltage after discharging for 18 minutes.

[0089] The values ​​of voltage 1 and voltage 2 of the 54 batteries are shown in Table 12.

[0090] Table 12

[0091]

[0092] The average voltage of voltage 1 is calculated to be 10.102V, and its lower limit is set to 9.8V with a deviation of 3%. There are 6 batteries with voltage 1 lower than 9.8V (deleted and bolded). After these 6 batteries are eliminated, the first grading is performed with voltage 1, and then the subsequent grouping process is carried out with voltage 2. At the same time, the results of grouping with voltage 1 as the only condition are compared and tested.

[0093] When voltage 1 is used alone as the pairing condition, the batteries are divided into four groups according to the final voltage value V1. The final voltage difference of lead-acid batteries in the same group is 0.149 to 0.189V. The voltage difference of the groups gradually decreases from low to high. The voltage difference of group 1 is 0.149V, the voltage difference of group 2 is 0.169V, the voltage difference of group 3 is 0.179V, and the voltage difference of group 4 (low voltage group) is 0.189V. The grouping results are shown in Table 13.

[0094] Table 13

[0095]

[0096] According to the above grading conditions, taking grading 3 as an example, there are 25 batteries in this grading position (italic bold). It can be seen that the lowest voltage of these 25 batteries is 6.144V and the highest is 7.585V, with a difference of 1441mV. The difference is obvious. If secondary grading is not carried out, the battery consistency will be poor.

[0097] Three grades of batteries were selected for group testing. After the batteries were formed and left to rest for 24 hours, they were grouped based on the open circuit voltage (OCV) (within 20mV).

[0098] Group identification: Voltage 1+2 means that voltage 1 is first divided into groups and then grouped with voltage 2; Voltage 1 means that voltage 1 is used for grouping only. Each grouping method has 2 groups, and each group has 4 batteries, as shown in Table 14.

[0099] Table 14

[0100]

[0101]

[0102] Table 15

[0103]

[0104] The two battery groups were subjected to cycle life testing. The results, shown in Table 15, demonstrate that the 1+2 voltage pairing method offers significant advantages over the conventional 1 voltage pairing method. During battery cycling, the discharge voltage consistency of each battery pack was significantly improved, resulting in a higher capacity plateau. The battery life of the entire pack was improved by over 15% using this pairing method.

Claims

1. A lead-acid battery internal formation and assembly method, comprising a charge and discharge stage, a capacity check discharge stage, and a recharge stage, characterized in that: During the capacity check discharge phase, multiple batteries are connected in series and first discharged at a current of 0.5C2 amperes for a fixed time, discharging 100% to 110% of their rated capacity, and recording the final voltage value of each battery as V1. Then, they are discharged at a current of 0.1C2 to 0.3C2 amperes to an average voltage of 7.2V, and recording the final voltage value of each battery as V2. The discharged capacity during the capacity check discharge phase is controlled at 1.1C2 to 1.3C2 ampere-hours. The pairing comprises the following steps: (1) Calculate the average value of V1 of the batteries to be assembled and eliminate batteries whose V1 is less than 0.97 times the average value; (2) First, perform the first grading based on the battery V1, and then perform the second grading based on the V2 value. The voltage difference of the same grading level during the second grading should not exceed 100mV. (3) Measure the open circuit voltage of the battery after it has been left standing for a period of time after internal formation is completed; (4) Group batteries with a maximum open circuit voltage difference of no more than 20mV within the same range; During the first grading, the batteries are divided into 4 to 6 grades according to the termination voltage value V1. The termination voltage difference of lead-acid batteries in the same grade is 0.1 to 0.21V.

2. The lead-acid battery internal formation and assembly method according to claim 1, wherein: When the constant voltage discharge is performed at a current of 0.5C2 amperes, the constant voltage discharge is performed to a single battery voltage of 7.2V~9.6V.

3. The lead-acid battery internal formation and assembly method according to claim 1, wherein: The charge and discharge stage includes the following steps: (1) Circuit inspection stage: charge at a constant current of 0.01C2~0.015C2 amperes for 2~5 minutes; (2) Standing stage: standing for 0.5~1.5h; (3) First charging stage: charging at a current of 0.15C2~0.18C2 amperes for 22~27 hours. The charging capacity in this stage is controlled at 3.8C2~4.9C ampere-hours; (4) First discharge stage: discharge at a current of 0.5C2 ampere for 1 hour, releasing a capacity of 0.5C2 ampere-hour; (5) Second charging stage: charge at a current of 0.2C2~0.25C2 amperes for 2~3 hours, and then charge at a current of 0.15C2~0.18C2 amperes for 18~22 hours. The charging capacity in this stage is controlled at 3.2C2~4C2 ampere-hours.

4. The lead-acid battery internal formation and assembly method according to claim 1, wherein: The recharging stage includes the following steps: charging at a current of 0.2C2 to 0.25C2 amperes for 2 to 3 hours, and then charging at a current of 0.15C2 to 0.18C2 amperes for 10 to 12 hours. The charging capacity in this stage is controlled at 2.2C2 to 2.7C2 ampere-hours.

5. The lead-acid battery internal formation and assembly method according to claim 1, characterized in that: The battery electrolyte temperature is controlled at 30-45°C during the internal formation process.

6. The lead-acid battery internal formation and assembly method according to claim 1, characterized in that: The standing time before testing the open circuit voltage is 24 hours.

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