CN106253383A - A kind of Li-ion batteries piles auto charge and discharge balancing equipment - Google Patents

Abstract

The invention discloses an automatic charge and discharge equalization device for a lithium ion battery pack. The automatic charge and discharge equalization device for a lithium ion battery pack includes a charge and discharge equalization control interface connected to the two poles of each single battery in the lithium ion battery pack. A battery pack management device that is connected to the ion battery pack and collects the current voltage information of each single battery in the battery pack in real time. The automatic charge and discharge equalization equipment for the lithium ion battery pack also includes a charge and discharge controller, and the charge and discharge controller includes: Central processing unit, communication unit, touch display screen and charge-discharge equalization control unit, the device can automatically charge or discharge each single battery in the lithium battery pack to the same set state according to the preset parameters, the degree of automation of the device High, greatly improved work efficiency, reduced costs, and the balance of high precision, good consistency, but also has the advantages of simple operation, small size, high degree of automation, and good safety.

Description

A lithium-ion battery pack automatic charging and discharging equalization equipment

technical field

The invention relates to the technical field of equalization of power lithium-ion battery packs for new energy electric vehicles, in particular to an automatic charge-discharge equalization device for lithium-ion battery packs.

Background technique

At present, most electric vehicle companies and research institutions use lithium-ion battery packs as their power batteries, and the lithium-ion battery packs used in high-power electric vehicles are composed of multiple single-cell lithium-ion batteries connected in series and parallel to obtain more high output voltage. However, there is a big difference between the use of lithium-ion battery packs and single lithium-ion batteries. In the battery pack, there must be individual differences in the production and manufacture of each single lithium-ion battery, and the degree of aging in use It is also different. With the increase of charging and discharging times and the accumulation of time, this difference will be accumulated or even enlarged, resulting in a greatly reduced performance of the entire battery pack or a serious shortening of the battery pack's life.

The existing charging method generally uses the overall charging of the lithium battery pack. This charging method has a simple structure and can simplify the current sampling circuit, which is convenient for the SOC estimation of the lithium battery pack. However, the disadvantages are also obvious. This charging method cannot guarantee that all the single cells are fully charged, which causes the difference in the capacity of the single cells of the lithium battery pack, resulting in a greatly reduced performance of the entire battery pack. At present, most manufacturers use manual supplementary charging and discharging equalization methods for this kind of battery pack, that is, when the voltage of a certain battery in the battery pack is too low or too high, the charger or discharge device is manually connected to the positive and negative sides of the battery. At both ends of the battery, charge or discharge the battery. After the battery is charged or discharged, it is manually replaced to the next battery that needs to be charged or discharged. This method not only has low efficiency and low safety, but also causes short circuit due to improper operation by operators, and the consistency of the lithium battery pack after charging or discharging is not good, and the equalization effect is poor.

Contents of the invention

The technical problem to be solved by the invention is to provide an automatic charging and discharging equalization device for a lithium-ion battery pack, which can automatically charge each single battery in the lithium-ion battery pack according to preset parameters. Or discharge to the same state as set, compared with manual equalization of the battery pack, it not only has a higher degree of automation, greatly improves work efficiency, reduces costs, but also has high balancing accuracy and good consistency, thereby improving the overall performance of the battery pack. To prolong the service life of the battery pack, the device also has the advantages of simple operation, small size, high degree of automation, and good safety.

The technical solution adopted to solve the technical problem: an automatic charging and discharging equalization device for a lithium-ion battery pack, including a charge-discharging equalization control interface connected to the two poles of each single battery in the lithium-ion battery pack, and a A battery pack management device that collects the current voltage information of each single battery in the battery pack in real time. The automatic charge and discharge equalization equipment for the lithium ion battery pack also includes a charge and discharge controller, and the charge and discharge controller includes: a central processing unit, a communication unit, touch screen and charge-discharge equalization control unit,

The central processing unit receives the current voltage value of each single battery in the lithium battery pack transmitted by the battery pack management device through the communication unit, receives the preset parameters input by the touch screen through the communication unit, and converts the lithium ion battery pack to Compare the current voltage value of each single battery with the set preset parameter value, and output a charge, discharge or end balance command signal to the charge and discharge balance control unit according to the comparison result;

The touch screen displays the current working status and parameters of the system by inputting preset parameters and work instructions to the central processing unit through the communication unit;

The charge-discharge balance control unit receives the charge, discharge or end balance command signal from the central processing unit, and performs charge, discharge or end balance on the corresponding single battery through the charge-discharge balance control interface according to the corresponding command signal.

As an improvement of the present invention: the charge-discharge equalization control unit is composed of a relay switching control circuit, a DC charging circuit and a discharging circuit, and the relay switching control circuit receives the charging/discharging command signal sent by the central processing unit, and drives according to the corresponding command signal The charging control switch or the discharging control switch switches the corresponding single battery to the DC charging circuit, the discharging circuit or ends the equilibrium state.

As a further improvement of the present invention: a current sampling unit is provided between the charge-discharge equalization control interface and the charge-discharge control unit, and the current sampling unit switches the sampling value of the equalization current of each single battery in the lithium battery pack through the relay switching control circuit It is transmitted to the central processing unit, and the central processing unit compares the sampled value with the set protection current upper limit value. When the balanced current value is greater than the set protection current value, the central processing unit outputs a command signal to the relay switching control circuit. Disconnect the battery from the balancing control unit.

Further, the DC charging circuit is a circuit composed of an AC/DC switching power supply, a power diode, a charging control switch and a single battery connected in series.

Further, the discharge circuit is a circuit composed of a high-power resistor, a discharge control switch and a single battery connected in series.

Further, the communication unit includes a 485 communication module, a CAN communication module and a corresponding communication interface, a 485 communication module is used for communication between the central processing unit and the touch display screen, and a CAN communication module is used between the central processing unit and the battery pack management device communication.

As the best solution of the present invention: the lithium-ion battery pack automatic charge-discharge equalization device also includes a charge-discharge controller casing for accommodating a charge-discharge controller, on which a communication interface and a charge-discharge equalization control device are arranged on the charge-discharge controller casing. Interface, cooling fan, power switch.

Beneficial effects: the lithium-ion battery pack automatic charge-discharge equalization device of the present invention adopts the lithium-ion battery pack automatic charge-discharge equalization device including a charge-discharge balance control interface, a battery pack management device, and a charge-discharge controller. The discharge controller includes: a central processing unit, a communication unit, a touch screen, and a technical solution for charge-discharge balance control unit. When performing charge-discharge balance on the battery pack, the central processing unit is based on the preset parameters and the current voltage value of the single battery. Carry out a comparison, control the charge-discharge balance control unit according to the comparison result, and perform charge, discharge or end balance on the corresponding battery. High and greatly improved work efficiency, reduced cost, and high balance accuracy and good consistency, thereby improving the overall performance of the battery pack and prolonging the service life of the battery pack. The device also has the advantages of simple operation, small size, and high degree of automation , good security and so on. Due to the adoption of the technical feature that the charge-discharge balance control unit is composed of a relay switching control circuit, a DC charging circuit and a discharge circuit, the lithium-ion battery pack automatic charge-discharge balance device of the present invention has a simpler structure and more stable and reliable operation. Manufacturing costs are lower. Due to the adoption of the technical feature of a current sampling unit between the charge-discharge balance control interface and the charge-discharge control unit, when the balance current value of a single battery is greater than the set protection current value, the battery will be connected to the battery in time. The balance control unit is disconnected to prevent damage to the equipment or cause danger, further improving the safety and self-protection ability of the equipment, and making the battery balancing operation safer. Due to the adoption of the technical feature that the DC charging circuit is a circuit composed of an AC/DC switching power supply, a power diode, a charging control switch and a single battery in series, the charging of the single battery is more reliable, faster, and more convenient to control . Due to the adoption of the technical feature that the discharge circuit is a circuit composed of a high-power resistor, a discharge control switch and a single battery in series, the discharge of the single battery is easier to control. Due to the adoption of the communication unit including 485 communication module, CAN module communication and corresponding communication interface, the 485 communication module is used for communication between the central processing unit and the touch display screen, and the CAN communication module is used between the central processing unit and the battery pack management device The technical characteristics of communication not only facilitate the connection of each unit, but also make the information transmission speed between each unit fast, and the anti-interference ability is strong, which realizes the real-time communication between the equipment and the battery pack management device, and ensures the voltage of each single battery. And charge and discharge current real-time monitoring, and display on the display. Due to the adoption of the lithium-ion battery pack automatic charge-discharge equalization equipment, it also includes a charge-discharge controller box for accommodating the charge-discharge controller. The charge-discharge controller box is provided with a communication interface, a charge-discharge equalization control interface, and a cooling fan. The technical characteristics of the power switch further optimize the structure of the device, making the device more compact, more convenient to operate, better in heat dissipation, and more stable in work.

The lithium-ion battery pack automatic charge-discharge equalization device of the present invention can be used not only for the daily maintenance of battery pack balance by new energy electric vehicle users, but also for new energy electric vehicle manufacturers to balance lithium battery packs in batches, and is more suitable for the field of cascade utilization of lithium batteries , Re-balance the charge and discharge of lithium battery packs eliminated in new energy electric vehicles and other fields, and apply these lithium battery packs to grid energy storage or other fields that require lower battery performance.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is the schematic block diagram of the automatic charging and discharging equalization equipment circuit of lithium ion battery pack of the present invention;

Fig. 2 is a charge-discharge equalization control principle diagram in the automatic charge-discharge equalization device of the lithium ion battery pack of the present invention;

Fig. 3 is a schematic diagram of the charge state control of a single battery in the lithium-ion battery pack automatic charge-discharge equalization device of the present invention;

Fig. 4 is a schematic diagram of controlling the discharge state of a single battery in the lithium-ion battery pack automatic charge-discharge equalization device of the present invention;

Fig. 5 is a schematic diagram of the control of the end of the balanced state of a single battery in the lithium-ion battery pack automatic charge-discharge equalization device of the present invention;

Fig. 6 is a schematic diagram of the structure of the charging and discharging controller box in the lithium ion battery pack automatic charging and discharging equalization equipment of the present invention;

Fig. 7 is a connection example diagram of the lithium-ion battery pack automatic charge-discharge equalization device of the present invention;

Fig. 8 is a flow chart of the working principle of the lithium-ion battery pack automatic charging and discharging equalization device of the present invention.

detailed description

In order to further illustrate the technical means adopted by the present invention and its effects, the following describes in detail in conjunction with preferred embodiments of the present invention and accompanying drawings.

As shown in Figure 1, the lithium-ion battery pack automatic charging and discharging equalization equipment of the present invention comprises:

A charge-discharge balance control interface 2 connected to the two poles of each single battery in the lithium-ion battery pack 1;

A battery pack management device 3 that is connected to the lithium-ion battery pack and collects the current voltage information of each single battery in the battery pack in real time;

The charging and discharging controller 4 , the charging and discharging controller includes: a central processing unit 41 , a communication unit 44 , a touch screen 43 , a current sampling unit 45 and a charging and discharging equalization control unit 42 .

The communication unit includes a 485 communication module, a CAN communication module and corresponding communication interfaces.

The charging and discharging equalization control unit includes a relay switching control circuit 421 , a DC charging circuit 422 and a discharging circuit 423 .

The communication unit and the relay switching control circuit are respectively connected to the central processing unit; the touch display screen and the battery pack management device are respectively connected to the communication unit through the communication interface; the current sampling unit is connected to the relay switching control circuit, and the lithium battery pack is connected through the charge and discharge equalization control interface The current sampling unit is connected with the DC charging circuit or discharging circuit.

Wherein: the central processing unit receives the current voltage value of each battery in the lithium battery pack transmitted by the battery pack management device through the communication unit. At the same time, after the central processing unit receives the preset value input by the touch screen, it compares the voltage value of each battery in the lithium battery pack with the set parameter value in turn. If the set balanced voltage value is greater than that of the single battery The current voltage value, the central processing unit controls the relay to switch the control circuit, so that the single battery is connected to the DC charging circuit and disconnected from the discharging circuit, and the battery is charged; if the set balanced voltage value is less than the current voltage value of the battery, The central processing unit controls the relay to switch the control circuit so that the single battery is connected to the discharge circuit and disconnected from the charging circuit to discharge the battery.

The touch display screen inputs preset parameters and work instructions to the central processing unit through the communication unit, and displays the current working status and parameters of the system;

The charge-discharge balance control unit receives the charge, discharge or end balance command signal from the central processing unit, and performs charge, discharge or end balance on the corresponding single battery through the charge-discharge balance control interface according to the corresponding command signal.

The current sampling unit will transmit the sampled value of the balanced current of each battery in the lithium battery pack to the central processing unit through the relay switching control circuit after the charging and discharging equalization starts. After the central processing unit obtains the current sampling value through A/D conversion, Compare the sampling value with the set protection current upper limit value, if the balance current value is greater than the set protection current value, the central processing unit will control the relay to switch the control circuit, and disconnect the battery from the corresponding charging circuit and discharging circuit. Open, stop the balance of the battery, and display the alarm information on the balance status display interface of the touch screen.

Taking a battery pack composed of eight single lithium-ion batteries connected in series as an example, the automatic charge-discharge equalization device for a lithium-ion battery pack of the present invention will be further described in detail.

As shown in Figure 2, eight lithium batteries BT1-BT8 are connected in series to form a lithium battery pack, P1 is the charging and discharging equalization control interface, the positive pole of BT1-BT8 is connected to pins 1-8 of P1, and the negative pole of BT1 is connected to pin 9 of P1 connected.

K1-K8 is a relay for controlling charging balance, and its corresponding single-pole double-throw switch is a charging control switch. The 4-pin of K1 is connected to the 8-pin of P1, the 4-pin of K2 is connected to the 7-pin of P1, and the 4-pin of K3 is connected to P1 The 6 pins of K4 are connected with the 5 pins of P1, the 4 pins of K5 are connected with the 4 pins of P1, the 4 pins of K6 are connected with the 3 pins of P1, the 4 pins of K7 are connected with the 2 pins of P1, the K8 The 4 feet of the P1 are connected with the 1 feet of the P1.

K9-K16 is a relay for controlling discharge balance, and its corresponding SPDT switch is a discharge control switch. The 4 pins of K9 are connected with the 8 pins of P1, the 4 pins of K10 are connected with the 7 pins of P1, and the 4 pins of K11 are connected with P1 The 6 pins of K12 are connected with the 5 pins of P1, the 4 pins of K13 are connected with the 4 pins of P1, the 4 pins of K14 are connected with the 3 pins of P1, the 4 pins of K15 are connected with the 2 pins of P1, the K16 The 4 feet of the P1 are connected with the 1 feet of the P1.

It needs to be specially explained that the connection method of the lithium battery pack and the relay above can ensure that the charge and discharge balance of each battery in the lithium battery pack is completely independent, and the balance of each battery will not be affected by the balance state of other batteries. influences.

POWER1-POWER8 is the AC/DC switching power supply, D1-D8 is the power diode to prevent the reverse current of the AC/DC switching power supply, POWER1-POWER8 is powered by AC 220 volts, the positive pole of the DC output of POWER1 passes through the diode D1 and the 5 pin of the relay K1 Connected, the negative pole of the DC output of POWER1 is connected with the 9th pin of P1, the positive pole of the DC output of POWER2 is connected with the 5th pin of the relay K2 through the diode D2, the negative pole of the DC output of POWER2 is connected with the 8th pin of P1, the positive pole of the DC output of POWER3 is connected through the diode D3 It is connected to pin 5 of relay K3, the negative pole of DC output of POWER3 is connected to pin 7 of P1, the positive pole of DC output of POWER4 is connected to pin 5 of relay K4 through diode D4, the negative pole of DC output of POWER4 is connected to pin 6 of P1, and the positive pole of POWER5 is connected to pin 5 of relay K4. The positive pole of the DC output is connected to the 5-pin of the relay K5 through the diode D5, the negative pole of the DC output of POWER5 is connected to the 5-pin of the P1, the positive pole of the DC output of the POWER6 is connected to the 5-pin of the relay K6 through the diode D6, and the negative pole of the DC output of the POWER6 is connected to the pin 5 of the relay K6. The 4 pins are connected, the positive pole of the DC output of POWER7 is connected with the 5 pin of the relay K7 through the diode D7, the negative pole of the DC output of the POWER7 is connected with the 3 pin of P1, the positive pole of the DC output of the POWER8 is connected with the 5 pin of the relay K8 through the diode D8, the POWER8 The DC output negative pole is connected to pin 2 of P1.

R1-R8 are high-power resistors, the 5th pin of the relay K9 is connected with the 9th pin of P1 through R1, the 5th pin of the relay K10 is connected with the 8th pin of P1 through R2, the 5th pin of the relay K11 is connected with the 7th pin of P1 through R3, Pin 5 of relay K12 is connected to pin 6 of P1 through R4, pin 5 of relay K13 is connected to pin 5 of P1 through R5, pin 5 of relay K14 is connected to pin 4 of P1 through R6, pin 5 of relay K15 is connected to pin 5 of relay K15 through R7 Pin 3 of P1 is connected, and pin 5 of relay K16 is connected with pin 2 of P1 through R8.

The control ends of pins 1 and 2 of the relays K1-K16 are connected with the central processing unit.

It needs to be specifically explained that the central processing unit can control several groups of relay switching control circuits, and each relay switching control circuit can control a battery pack composed of 1-8 single batteries to perform charge and discharge equalization.

Taking one of the batteries in the lithium battery pack as an example, the working process of the charge and discharge equalization control unit in the automatic charge and discharge equalization device for lithium ion battery packs of the present invention will be described in detail below.

As shown in Figure 3, when performing charge equalization, the central control unit controls the relays K8 and K16 to make the normally open contacts 4 and 5 of the charge control switch of K8 close, and the normally open contacts 4 and 5 of the discharge control switch of K16 remain open. Open, at this time the current direction is shown in the charging state as shown in the figure, and the lithium battery is charged through the switching power supply;

As shown in Figure 4, when performing discharge equalization, the central control unit controls the relays K8 and K16 to keep the normally open contacts 4 and 5 of the charge control switch of K8 off, and the normally open contacts 4 and 5 of the discharge control switch of K16 Closed, at this time the current direction is shown in the discharge state in the figure, and the lithium battery is discharged through a high-power resistor.

As shown in Figure 5, when the charging and discharging equalization ends, the central control unit controls the relays K8 and K16 to keep the normally open contacts 4 and 5 of the charging control switch of K8 disconnected, and the normally open contacts 4 and 5 of the K16 discharging control switch 5 stay disconnected.

The central processing unit performs the above operations on each battery of each lithium battery pack in sequence from 1-N (wherein N is a positive integer of 1-16), so that all selected lithium battery packs start charging and discharging equalization.

After the charging and discharging equalization starts, the central processing unit communicates with the battery pack management device in real time. If the communication is abnormal, after a certain period of time, the touch screen will display abnormal alarm information on the main interface, and the central processing unit will control the relay switching control circuit, disconnect all charging circuits and discharging circuits, and stop charging and discharging equalization.

During the charging and discharging equalization process, the central processing unit communicates with the battery pack management device in real time to obtain the voltage value of the single battery in real time, and compares it with the set parameters. If the actual voltage value of the single battery reaches the set balanced voltage value, the central processing unit will control the corresponding relay switching control circuit, disconnect the corresponding charging circuit and discharging circuit, and display the balanced state on the touch screen. Indicates that the balance is completed.

In the process of charging and discharging equalization, if the actual voltage value of the single battery exceeds the set upper and lower limits of the protection voltage, the central processing unit will control the corresponding relay to switch the control circuit, and connect the single battery with the corresponding charging circuit or discharge The circuit is disconnected, and an alarm message is displayed on the main interface of the touch screen.

It should be noted that after a certain lithium battery pack completes charge-discharge equalization, it can be immediately replaced with a new unbalanced battery pack for equalization, which will not have any impact on other battery packs that are being balanced.

It should be noted that during the charging and discharging equalization process, the AC/DC switching power supply and high-power resistors will generate relatively high heat, and the cooling fan can quickly and effectively discharge the heat to ensure stable operation of the device.

As shown in Figure 6, the lithium-ion battery pack automatic charge-discharge equalization device also includes a charge-discharge controller box 46 for accommodating the charge-discharge controller, on which a communication interface 441, a charge-discharge equalization control Interface 2, cooling fan 47, power switch 48, 220V mains interface 49.

Fig. 7 shows the connection method between the lithium-ion battery pack automatic charge-discharge equalization device and the battery pack of the present invention. In this embodiment, the automatic charge-discharge equalization of the lithium-ion battery pack of the present invention is performed by taking two battery packs to perform charge-discharge equalization at the same time as an example. The connection method between the equipment and the battery pack will be described. Two battery packs are connected in series through cables. In the figure, 11 is the total positive pole of the battery pack, and 12 is the total negative pole of the battery pack. The charging and discharging controller communicates with the battery pack through CAN communication bus 442. The device is connected to the touch screen, the charge-discharge balance control interface is connected to the battery pack interface 13 through the cable 21, the battery pack management device is connected to the battery pack, and the charge-discharge controller is connected to the 220V mains 5.

As shown in Figure 8, the working process of the lithium-ion battery pack automatic charge-discharge equalization device of the present invention is as follows: first, connect the battery pack management device with the lithium battery pack to be balanced, and then connect the automatic charge-discharge balance device with the battery pack management device communications are connected. Start the battery pack management device, start the automatic charge-discharge equalization equipment, check the abnormal situation if the communication is abnormal, and connect the automatic charge-discharge equalization equipment and the lithium battery pack to be balanced if the communication is normal. Enter the parameter setting interface by touching the display screen to set the equalization parameters, return to the main interface, select the number of the lithium battery pack that needs to be balanced, and start the automatic charge and discharge equalization of the lithium battery pack. At this time, the charge-discharge equalization process is carried out automatically. If any abnormal situation occurs during this process, the automatic charge-discharge equalization device will immediately stop the equalization operation and send out an abnormal alarm message. After the operator eliminates the abnormal situation, the charge-discharge equalization can be restarted. When the lithium battery pack reaches the set equilibrium state, the automatic charge and discharge equalization device will stop the equalization and send out a prompt message that the equalization is completed. If there are new lithium battery packs to be balanced that need to be balanced, the operator will replace the lithium battery packs that have been balanced, and start to automatically charge and discharge the new lithium battery packs to be balanced. When all lithium battery packs to be balanced have been balanced, the operation is completed.

The invention is controlled by a micro-control chip, and the device can automatically charge and discharge each single cell of the lithium battery pack independently, and has abnormal alarm and protection functions, thereby avoiding the danger caused by manual operation and ensuring the safety of each single cell. Finally, a completely consistent state is reached, which effectively improves the performance of the battery pack and prolongs the service life of the battery pack. At the same time, the device can work with multiple machines at the same time, and multiple sets of lithium battery packs can be charged or discharged at the same time, which greatly improves the equalization efficiency.

As explained above, the automatic charging and discharging equalization equipment for lithium-ion battery packs is easy to operate, has a high degree of automation, can greatly improve the work efficiency of operators, and avoids the danger caused by manual operation.

Claims (7)

1. A lithium-ion battery pack automatic charge-discharge equalization device, including a charge-discharge equalization control interface connected to the two poles of each single battery in the lithium-ion battery pack, and a real-time acquisition interface connected to the lithium-ion battery pack for each single cell in the battery pack. The battery pack management device for the current voltage information of the single battery is characterized in that: the lithium-ion battery pack automatic charge and discharge equalization equipment also includes a charge and discharge controller, and the charge and discharge controller includes: a central processing unit, a communication unit, a touch Display screen and charge-discharge equalization control unit, The central processing unit receives the current voltage value of each single battery in the lithium battery pack transmitted by the battery pack management device through the communication unit, receives the preset parameters input by the touch screen through the communication unit, and converts the lithium ion battery pack to Compare the current voltage value of each single battery with the set preset parameter value, and output a charge, discharge or end balance command signal to the charge and discharge balance control unit according to the comparison result; The touch screen displays the current working status and parameters of the system by inputting preset parameters and work instructions to the central processing unit through the communication unit; The charge-discharge balance control unit receives the charge, discharge or end balance command signal from the central processing unit, and performs charge, discharge or end balance on the corresponding single battery through the charge-discharge balance control interface according to the corresponding command signal. 2. The lithium-ion battery pack automatic charge-discharge equalization device according to claim 1, characterized in that: the charge-discharge equalization control unit is composed of a relay switching control circuit, a DC charging circuit and a discharging circuit, and the relay switching control circuit receives a central The charging/discharging instruction signal sent by the processing unit drives the charging control switch or the discharging control switch according to the corresponding instruction signal, and switches the corresponding single battery to the DC charging circuit, discharging circuit or ends the equilibrium state. 3. The lithium-ion battery pack automatic charge-discharge equalization device according to claim 2, characterized in that: a current sampling unit is arranged between the charge-discharge equalization control interface and the charge-discharge control unit, and the current sampling unit connects the lithium-ion battery pack The sampling value of the balanced current of each single battery is transmitted to the central processing unit through the relay switching control circuit, and the central processing unit compares the sampling value with the set upper limit value of the protection current. value, the central processing unit outputs an instruction signal to the relay switching control circuit to disconnect the battery from the balance control unit. 4. The lithium-ion battery pack automatic charging and discharging equalization device according to claim 3, characterized in that: the DC charging circuit is a circuit composed of an AC/DC switching power supply, a power diode, a charging control switch and a single battery connected in series . 5. The lithium-ion battery pack automatic charge-discharge equalization device according to claim 4, characterized in that: the discharge circuit is a circuit composed of a high-power resistor, a discharge control switch and a single battery connected in series. 6. The lithium-ion battery pack automatic charging and discharging equalization device according to any one of claims 1 to 5, characterized in that: the communication unit includes a 485 communication module, a CAN communication module and corresponding communication interfaces, and the central processing unit and The 485 communication module is used for communication between the touch screens, and the CAN communication module is used for communication between the central processing unit and the battery pack management device. 7. The automatic charging and discharging equalization device for lithium-ion battery pack according to claim 6, characterized in that: the automatic charging and discharging equalizing device for lithium-ion battery pack also includes a charge-discharge controller box for accommodating the charge-discharge controller. The discharge controller box is provided with a communication interface, a charge-discharge equalization control interface, a cooling fan, and a power switch.