A parallel charging and discharging device and method during the manufacture of a button cell

Abstract

The present invention relates to the field of rechargeable batteries, and particularly to a battery parallel charging and discharging device and a charging and discharging method during the manufacturing process of button batteries. The parallel charging and discharging device is that a power management system is connected in series with a plurality of groups of parallel charging and discharging branches. Each group of charging and discharging branches includes a battery, a matching resistor R, and a current limiting resistor R connected in series f . The method of the present invention ingeniously finds a balance among solving the problems of parallel charging and discharging consistency and discharge circulating current, manufacturing cost, and the allowable range of battery pack system deviation. The provided circuit changes the single-point control of charging and discharging into multi-point unified control. The designed system is simple, safe, and efficient, greatly reducing the control system cost.

Description

Technical Field

[0001] The present invention relates to the field of rechargeable batteries, and particularly to a parallel charge-discharge device and a charge-discharge method in the manufacture of button batteries. Background Art

[0002] During the battery manufacturing process, after the battery assembly is completed, a charge-discharge process of formation and grading is required. In the traditional battery manufacturing process, the battery charge-discharge adopts a single-loop control method. For large-scale manufacturing enterprises, this charge-discharge mode with one loop for each battery brings huge cost burdens to the enterprises. The parallel charge-discharge method can upgrade the single-point single-loop control to single-point multi-loop control, thereby reducing the equipment investment cost, floor space cost, and management cost during the battery manufacturing process. However, for small-capacity batteries including button batteries, due to the difference in battery internal resistance, a simple parallel charge-discharge method will result in a large difference in the current passing through the parallel branches, and further cause a large difference in the voltage of each charge-discharge battery. And it takes a long time to achieve the battery consistency required for factory shipment, and the time cost is too high.

[0003] For the parallel charging of multiple battery groups of small batteries, how to maintain the charging consistency; during discharging, since the internal resistance of the battery is very small, when there is a relatively large voltage difference between the battery groups, a large circulating current will be formed between the battery groups, and this large circulating current between the battery groups will have an adverse effect on the battery groups and even damage them. How to reduce the influence of the circulating current of parallel discharging on the battery; theoretically, for a single battery, it is itself a parallel body. Therefore, how to find an optimal balance among the above problems, manufacturing costs, and the allowable range of battery group system deviation is the basis of the solution of the present invention. Summary of the Invention

[0004] To solve the above problems, the present invention provides a multi-battery parallel charge-discharge device and a charge-discharge method in the manufacture of button batteries. The TAPER charging mode is adopted, and series resistance is configured in the parallel branches to control the balance and consistency of the current flowing through the batteries in each parallel branch during charging; and the configured series resistance can also play a role in shunting in case of an accidental short circuit, and can also effectively reduce the influence of the circulating current generated in the parallel branch circuit during discharging; the method of the present invention also configures a current-limiting resistance to ensure that the parallel branches are blocked when the current in the system line exceeds the limit; the circuit provided by the method of the present invention changes the single-point control of charge-discharge into multi-point unified control, and the designed system is simple, safe, and efficient, greatly reducing the control system cost.

[0005] To achieve the above object, the technical solution of the present invention is as follows. A battery parallel charge-discharge device during the manufacture of button batteries includes a power management system and several groups of parallel charge-discharge branches.

[0006] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the power management system is connected in series with several groups of parallel charging and discharging branches.

[0007] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, each group of charging and discharging branches includes a battery, a matching resistor R, and a current-limiting resistor R connected in series. f 。

[0008] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the resistance values of the matching resistors R in each group of charging and discharging branches are the same.

[0009] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the resistance value of the matching resistor R is K times the average internal resistance of the batteries in each charging and discharging branch, and K ranges from 2 to 10.

[0010] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the current-limiting resistors R in each charging and discharging branch f have the same resistance value.

[0011] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the current-limiting resistor R f allows a maximum passing current that is 1 to 10 times the maximum discharge current marked on the battery.

[0012] In the above battery parallel charging and discharging device during the manufacturing process of a button cell, the current-limiting resistor R f allows a maximum passing current that is 3 to 8 times the maximum discharge current marked on the battery.

[0013] In the charging method of the above battery parallel charging and discharging device during the manufacturing process of a button cell, the power management system starts charging in a constant current manner, switches to constant voltage charging after the battery is charged to a certain voltage, and stops charging when the charging current drops to the cut-off current.

[0014] In the discharging method of the above battery parallel charging and discharging device during the manufacturing process of a button cell, the power management system starts discharging in a constant current manner, switches to constant current discharging after the discharged battery capacity drops to 10% SOC, and stops discharging when the circuit voltage drops to the cut-off voltage.

[0015] The principle of the method provided by the present invention for balancing the internal resistance of the battery is as follows:

[0016] Suppose that n batteries with an internal resistance deviation of ±20% are charged using the method provided by the present invention. Let the matching resistor R in the parallel branch be 5 times the average resistance value, and its resistance deviation is ±1%. Then:

[0017]

[0018] That is, by charging with the method provided by the present invention, the deviation of a battery pack with an original internal resistance deviation of ±20% can be reduced to ±4.2% of the actual deviation, thereby meeting the system deviation requirements.

[0019] The beneficial effects of the present invention are as follows:

[0020] For small batteries, due to the difference in battery internal resistance, when charging in parallel, the current difference flowing through each parallel branch is relatively large. The series resistors configured in each parallel branch designed by the present invention can effectively balance the current flowing through each parallel branch and ensure the consistency of the charge and discharge current. When one or several parallel branches are short-circuited, the current-limiting resistors configured in each parallel branch can ensure that the other parallel branches can charge and discharge normally without being affected. The method of the present invention cleverly finds a balance among feasible solutions, manufacturing costs, and the allowable range of battery pack system deviation. The provided circuit changes the single-point control of charge and discharge into multi-point unified control. The designed system is simple, safe, and efficient, greatly reducing the control system cost. Description of the Drawings

[0021] Figure 1 Block diagram of the battery parallel charge and discharge device. Detailed Embodiments

[0022] In order to make the technical problems, technical solutions, and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Figure 1 It is a structural block diagram of an embodiment provided for the battery pack parallel charging device of the present invention. Refer to Figure 1 , the power management system is connected in series with several groups of parallel charge and discharge branches. The parallel charge and discharge branches include n groups of charge and discharge branches, and the n groups of charge and discharge branches are connected in parallel by the first charge and discharge branch, the second charge and discharge branch, the third charge and discharge branch,..., the nth charge and discharge branch. Where n is a natural number and n≥1, that is, n is also the number of charging branches.

[0024] Among them, the first charge and discharge branch includes a series-connected resistance-matching resistor R, a current-limiting resistor R f and a battery C1, the second charge and discharge branch includes a series-connected resistance-matching resistor R, a current-limiting resistor R f and a battery C2, the third charge and discharge branch includes a series-connected resistance-matching resistor R, a current-limiting resistor R f and a battery C3,..., the nth charge and discharge branch includes a series-connected resistance-matching resistor R, a current-limiting resistor R f and a battery Cn.

[0025] The power management system controls the charging and discharging methods, startup, and termination. The matching resistor R is used to balance the charging and discharging currents of each branch and balance the discharging voltages at both ends of each branch. The current-limiting resistor R f is used to limit the maximum current that each branch can withstand.

[0026] Example 1

[0027] The battery parallel charging and discharging device during the manufacturing process of the button battery is that the power management system and 20 groups of parallel charging and discharging branches are connected in series. 20 single cells with a capacity of 70 mAh are connected in parallel. The internal resistance values of the 20 cells are in the range of 200 mΩ ± 20%. Each parallel charging and discharging branch is connected in series with a matching resistor R with a resistance of 1 Ω and a current-limiting resistor R f with a current limit of 0.5 A. The power management system starts charging in a constant current mode of 1C (0.07 A). After the battery charge reaches 90% of the battery charge index (hereinafter referred to as SOC), it changes to constant voltage (4.2 V) charging. After charging for 10 minutes, the charging stops, and the current passing through each branch is tested and recorded. During discharging, the power management system starts discharging in a constant current mode of 1C (0.07 A). When the discharged battery capacity drops to 10% SOC, it changes to constant current discharging at 0.2C (0.0014 A). When the circuit voltage drops to the cut-off voltage (2.75 V), the discharging stops, and the battery capacity released by each branch of the battery is recorded (see Table 1).

[0028] Example 2

[0029] The battery parallel charging and discharging device during the manufacturing process of the button battery is that the power management system and 20 groups of parallel charging and discharging branches are connected in series. 20 single cells with a capacity of 70 mAh are connected in parallel. The internal resistance values of the 20 cells are in the range of 200 mΩ ± 20%. The power management system starts charging in a constant current mode of 1C (0.07 A). After the battery charge reaches 90% SOC, it changes to constant voltage (4.2 V) charging. After charging for 10 minutes, the charging stops, and the current passing through each branch is tested and recorded. During discharging, the power management system starts discharging in a constant current mode of 1C (0.07 A). When the discharged battery capacity drops to 10% SOC, it changes to constant current discharging at 0.2C (0.0014 A). When the circuit voltage drops to the cut-off voltage (2.75 V), the discharging stops, and the battery capacity released by each branch of the battery is recorded.

[0030] As can be seen from Table 1, compared with Example 2, after the resistors are connected in series in the branch of Example 1, the current balance of each branch is very good, and the deviation of charge and discharge capacity is also small. The charging time of the entire device is 83 minutes, and the discharging time is 69 minutes; in Example 2, the charging time of the entire device is 102 minutes, and the discharging time is 74 minutes. Example 1 using the method provided by the present invention can complete charge and discharge in a shorter time. Compared with simple parallel charging, the charging time can be reduced by 18%.

[0031] Table 1

[0032]

Claims

1. A battery parallel charging and discharging device during the manufacturing process of a button battery, characterized in that, the power management system is connected in series with several groups of parallel charging and discharging branches; Each charge-discharge branch includes a battery, a matching resistor R, and a current-limiting resistor R connected in series f ; the resistance values of the shunt resistors R in each group of charging and discharging branches are the same; the resistance value of the shunt resistor R is К times the average internal resistance of the batteries in each charging and discharging branch, and К is between 2 and 10; The current-limiting resistors R in each charge and discharge branch f have the same resistance value; Current-limiting resistor R f The maximum allowable current passing through it is 3 to 8 times the maximum discharge current marked on the battery.

2. The charging method of a battery parallel charging and discharging device during the manufacturing process of a button battery according to claim 1, characterized in that, the power management system starts charging in a constant current manner, and changes to constant voltage charging after the battery is charged to a certain voltage. When the charging current drops to the cut-off current, the charging stops.

3. The discharging method of a battery parallel charging and discharging device during the manufacturing process of a button battery according to claim 1, characterized in that, the power management system starts discharging in a constant current manner. After the discharged battery capacity drops to 10% SOC, it changes to constant current discharging. When the circuit voltage drops to the cut-off voltage, the discharging stops.

Images