A multi-circuit heating system for a forklift battery and control method

Abstract

A kind of multi-circuit heating system and control method for forklift battery, including battery pack and battery management system, the positive pole of battery pack is connected discharge relay, slow charging relay and fast charging relay, the one end of discharge relay, slow charging relay and fast charging relay away from battery pack is also connected with discharge heating relay, slow charging heating relay and fast charging heating relay, discharge heating relay, slow charging heating relay and fast charging heating relay are connected together with the negative pole of battery pack by heating fuse and heating element.The application solves the problems of affecting the performance, quality and cost of battery in the field of electric forklift by battery pack, electric forklift battery electric control system, heating system and control strategy and logic, ensures that electric forklift battery can work normally in low temperature environment, improves the use performance of electric forklift battery, and provides strong guarantee for good work of electric forklift in low temperature working environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric forklift batteries, in particular to a multi-loop heating system for forklift batteries and a control method. BACKGROUND

[0002] With the progress of science and technology and the development of technology, the electrification of industrial vehicles has become an industry trend, especially forklifts, which are widely used in various scenes in life. The traditional forklifts are mostly diesel-driven internal combustion forklifts, and the exhaust gas contains a large amount of harmful substances, which seriously pollutes the environment. In order to protect our living environment from pollution and respond to the call of the state, electric forklifts have emerged and gradually replaced traditional internal combustion forklifts to become the future development trend.

[0003] According to the type of power supply, electric forklifts can be divided into two categories: lead-acid and lithium batteries. Lead-acid batteries have many disadvantages compared to lithium batteries: the effective life of lead-acid batteries is only about 3 years, the battery life is relatively short, and regular maintenance is required, including adding acid and water. Maintenance personnel are also required during use, resulting in increased personnel costs. Lead-acid batteries will electrolyze water into oxygen and hydrogen during discharge, and hydrogen and oxygen are both flammable gases that can explode when exposed to open flames, posing a safety hazard. Therefore, there is an increasing demand for lithium batteries. However, forklifts are used in many scenarios, and the ambient temperature varies in different scenarios. In addition, China is moving from south to north, and the temperature difference gradually increases with changes in geographical location. Low-temperature working environments can cause the battery temperature to be too low, which has a significant negative impact on the battery's life and performance. Low temperatures have a significant impact on vehicles and power batteries. Low temperatures can reduce the battery's discharge capacity, affecting the vehicle's range and power, energy recovery, and other factors. Therefore, a battery heating management system is an important function to ensure that electric forklift batteries can work normally in low-temperature environments. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a multi-loop heating system for forklift batteries and a control method that is simple in architecture and effective.

[0005] The application is implemented by the following technical scheme: a forklift battery multi-loop heating system, comprising a battery pack, the battery pack is connected with a battery management system, the positive electrode of the battery pack is connected with a load positive electrode, a slow charging positive electrode and a fast charging positive electrode through a discharge relay, a slow charging relay and a fast charging relay respectively, the discharge relay, the slow charging relay and the fast charging relay are further connected with a discharge heating relay, a slow charging heating relay and a fast charging heating relay respectively at one end away from the battery pack, the discharge heating relay, the slow charging heating relay and the fast charging heating relay are connected together with the negative electrode of the battery pack through a heating fuse and a heating element, and the negative electrode of the battery pack is connected with a load negative electrode, a fast charging negative electrode and a slow charging negative electrode; the two ends of the discharge relay are connected in parallel with a pre-charging relay and a pre-charging resistor connected together in series; and the control points of the discharge relay, the pre-charging relay, the slow charging relay, the fast charging relay, the fast charging heating relay, the slow charging heating relay and the discharge heating relay are connected together with the battery management system.

[0006] Further, the battery management system is connected with the temperature collection point of the battery pack through a wire to collect the temperature on the battery pack.

[0007] The battery management system and an external charger are connected through fast charging communication and slow charging communication to perform LAN communication, and the battery management system confirms fast charging connection or slow charging connection through the reception of a wake-up signal.

[0008] The main positive contact of the discharge relay is connected with the positive electrode of the battery pack, the main negative contact of the discharge relay is connected with the load positive electrode, the negative electrode of the battery pack is connected with the load negative electrode to form a discharge loop; the main positive contact of the discharge heating relay is connected with the main negative contact of the discharge relay, and the main negative contact of the discharge heating relay is connected with the front end of the heating fuse.

[0009] The main negative contact of the slow charging relay is connected with the positive electrode of the battery pack, the main positive contact of the slow charging relay is connected with the slow charging positive electrode, the negative electrode of the battery pack is connected with the slow charging negative electrode to form a slow charging loop; the main positive contact of the slow charging heating relay is connected with the slow charging positive electrode, and the main negative contact of the slow charging heating relay is connected with the front end of the heating fuse.

[0010] The main negative contact of the fast charging relay is connected with the positive electrode of the battery pack, the main positive contact of the fast charging relay is connected with the fast charging positive electrode, the negative electrode of the battery pack is connected with the fast charging negative electrode to form a fast charging loop; the main positive contact of the fast charging heating relay is connected with the fast charging positive electrode, and the main negative contact of the fast charging heating relay is connected with the front end of the heating fuse.

[0011] Also include the mounting plate, positive copper bar, negative copper bar, heating parallel copper bar, slow charging copper bar, large insulating column and small insulating column, the battery management system, discharge relay, pre-charge relay, pre-charge resistor, slow charging relay, fast charging relay, fast charging heating relay, slow charging heating relay, discharge heating relay, large insulating column and small insulating column are fixed on the mounting plate, the positive copper bar is connected together with the main contact of the discharge relay and the fast charging relay, the negative copper bar is fixed on the large insulating column by the screw, the heating parallel copper bar connects the main contact of the fast charging heating relay, the slow charging heating relay and the discharge heating relay together in parallel.

[0012] The control method of the multi-loop heating system for the forklift battery includes a heating management method in a discharging state and a heating management method in a charging state,

[0013] The heating management method in the discharging state includes the following steps:

[0014] S1, when the battery pack is powered on, the battery management system receives a discharging wake-up signal, closes the discharge relay, and the battery management system detects the temperature of the battery pack:

[0015] S2, when the lowest temperature T of the battery pack is less than or equal to a set value 1, the discharge relay is opened, and at this time, heating and discharging are prohibited;

[0016] S3, when the lowest temperature of the battery pack is greater than the set value 1 and less than or equal to a set value 2, the discharge heating relay is closed, and a heating and discharging mode is entered; after a period of heating, the temperature of the battery pack rises, and when the lowest temperature is greater than a set value 3, the discharge heating relay is opened to stop heating, and a pure discharging mode is entered;

[0017] S4, when the lowest temperature T of the battery pack is greater than the set value 2, a pure discharging mode is directly entered;

[0018] S5, after entering the pure discharging mode, if the switch is closed, the discharge relay is opened, and the battery pack is powered off;

[0019] The heating management method in the charging state includes the following steps:

[0020] T1, when the battery pack is connected to a charger, and the wake-up signal is detected to be fast charging wake-up, the fast charging relay is closed, and the battery management system detects the temperature of the battery pack;

[0021] T2, when the lowest temperature T of the battery pack is less than or equal to a set value 1, the fast charging heating relay is closed, and after detecting that the end voltage of the heating relay is normal, the fast charging relay is opened, at this time, a pure heating mode is entered with continuous heating; after a period of heating, the lowest temperature of the battery pack rises, and when the set value 1 is less than T and less than or equal to a set value 2, the fast charging relay is closed, and a heating and charging mode is entered;

[0022] T3, when the battery pack minimum temperature setting value 1 < T ≤ setting value 2, the fast charging heating relay is closed, and the heating and charging mode is entered, after a period of heating, the battery pack minimum temperature rises to T > setting value 2, the fast charging heating relay is disconnected to stop heating, and the pure charging mode is entered;

[0023] T4, when the battery pack minimum temperature T > setting value 2, the pure charging mode is directly entered, the SOC is calibrated after charging to 100%, the fast charging relay is disconnected, and the charging is completed after the charging connection is disconnected;

[0024] The heating management principle in the slow charging state is the same as that in the fast charging state.

[0025] Before the discharge relay is closed, the pre-charging relay is closed first, and then the discharge relay is closed after the negative voltage of the main contact of the discharge relay is raised.

[0026] In the discharge state, the setting value 1 is-30 DEG C, the setting value 2 is 0 DEG C, and the setting value 3 is 5 DEG C; in the charging state, the setting value 1 is 0 DEG C, the setting value 2 is 10 DEG C.

[0027] The forklift battery multi-loop heating system and the control method have the following advantages: through the battery pack, the forklift battery electric control system, the heating system and the control strategy and logic, the problems of the performance, the quality and the cost of the battery in the electric forklift field caused by the low temperature environment are solved, the normal work of the electric forklift battery in the low temperature environment is ensured, the use performance of the electric forklift battery is improved, and the good work of the electric forklift in the low temperature working environment is provided with strong guarantee. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application, the schematic embodiments of the present application and the description thereof serve to explain the present application, but do not constitute an improper limitation on the present application. Obviously, the accompanying drawings in the following description are only some embodiments, and other drawings can be obtained from these drawings without creative labor for those skilled in the art.

[0029] In the drawings:

[0030] Figure 1 is a structural schematic diagram of the present application;

[0031] Figure 2 is a topology diagram of the heating system of the present application;

[0032] Figure 3 is a topology diagram of the heating management system in the discharge state of the present application;

[0033] Figure 4 is a topology diagram of the heating management system in the charging state of the present application.

[0034] In the figure: 1, battery management system, 2, heating element, 3, battery pack, 4, discharge relay, 5, pre-charge relay, 6, pre-charge resistor, 7, slow charge relay, 8, fast charge relay, 9, heating fuse, 10, fast charge heating relay, 11, slow charge heating relay, 12, discharge heating relay, 13, mounting plate, 14, wire I, 15, wire II, 16, wire III, 17, positive copper bar, 18, negative copper bar, 19, heating parallel copper bar, 20, slow charge copper bar, 21, large insulating column, 22, small insulating column.

[0035] It should be noted that these drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application.

[0037] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0038] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] As Figures 1 to 4The fork truck battery multi-circuit heating system shown in the application comprises a battery pack 3, a battery management system 1 connected to the battery pack 3, a positive electrode of the battery pack 3 connected to a load positive electrode, a slow charging positive electrode and a fast charging positive electrode through a discharge relay 4, a slow charging relay 7 and a fast charging relay 8 respectively, and the discharge relay 4, the slow charging relay 7 and the fast charging relay 8 are further connected to a discharge heating relay 12, a slow charging heating relay 11 and a fast charging heating relay 10 respectively at the end away from the battery pack 3, the discharge heating relay 12, the slow charging heating relay 11 and the fast charging heating relay 10 are connected together with the negative electrode of the battery pack 3 through a heating fuse 9 and a heating element 2, and the negative electrode of the battery pack 3 is connected to a load negative electrode, a fast charging negative electrode and a slow charging negative electrode; the discharge relay 4 is connected in parallel with a pre-charging relay 5 and a pre-charging resistor 6 connected in series at both ends of the discharge relay 4; and the control points of the discharge relay 4, the pre-charging relay 5, the slow charging relay 7, the fast charging relay 8, the fast charging heating relay 10, the slow charging heating relay 11 and the discharge heating relay 12 are connected together with the battery management system 1.

[0040] As shown in the fork truck battery multi-circuit heating system, the battery management system 1 is connected to the temperature acquisition point of the battery pack 3 by a wire for acquiring the temperature on the battery pack. Figures 1 to 2 The battery pack temperature acquisition of the application is realized by the battery management system connection wire, which is convenient for subsequent control system action according to the temperature of the battery pack, so that the fork truck battery can work well in different working environments.

[0041] As shown in the fork truck battery multi-circuit heating system, the battery management system 1 is connected to the temperature acquisition point of the battery pack 3 by a wire for acquiring the temperature on the battery pack. Figures 1 to 2The battery management system 1 and the external charger are connected through LAN communication, and the battery management system 1 confirms the fast charging connection or the slow charging connection through the receiving of the wake-up signal.

[0042] As shown in Figures 1 to 2 The main contact positive pole of the discharging relay 4 is connected with the positive pole of the battery pack 3, the main contact negative pole of the discharging relay 4 is connected with the positive pole of the load, the negative pole of the battery pack 3 is connected with the negative pole of the load, and the discharging circuit is formed; the main contact positive pole of the discharging heating relay 12 is connected with the main contact negative pole of the discharging relay 4, and the main contact negative pole of the discharging heating relay 12 is connected with the front end of the heating fuse 9.

[0043] As shown in Figures 1 to 2 The main contact negative pole of the slow charging relay 7 is connected with the positive pole of the battery pack 3, the main contact positive pole of the slow charging relay 7 is connected with the positive pole of the slow charging, the negative pole of the battery pack 3 is connected with the negative pole of the slow charging, and the slow charging circuit is formed; the main contact positive pole of the slow charging heating relay 11 is connected with the positive pole of the slow charging, and the main contact negative pole of the slow charging heating relay 11 is connected with the front end of the heating fuse 9.

[0044] As shown in Figures 1 to 2 The main contact negative pole of the fast charging relay 8 is connected with the positive pole of the battery pack 3, the main contact positive pole of the fast charging relay 8 is connected with the positive pole of the fast charging, the negative pole of the battery pack 3 is connected with the negative pole of the fast charging, and the fast charging circuit is formed; the main contact positive pole of the fast charging heating relay 10 is connected with the positive pole of the fast charging, and the main contact negative pole of the fast charging heating relay 10 is connected with the front end of the heating fuse 9.

[0045] As shown in Figure 1The forklift battery multi-circuit heating system shown also includes a mounting plate 13, a positive copper bar 17, a negative copper bar 18, a heating parallel copper bar 19, a slow charging copper bar 20, a large insulating column 21 and a small insulating column 22, the battery management system 1, the discharge relay 4, the pre-charging relay 5, the pre-charging resistor 6, the slow charging relay 7, the fast charging relay 8, the fast charging heating relay 10, the slow charging heating relay 11, the discharge heating relay 12, the large insulating column 21 and the small insulating column 22 are fixed on the mounting plate 13, the positive copper bar 17 is connected together with the main contact positive of the discharge relay 4 and the main contact negative of the fast charging relay 8, the negative copper bar 18 is fixed on the large insulating column 21 through a screw, the heating parallel copper bar 19 connects together the main contact positive of the fast charging heating relay 10, the slow charging heating relay 11 and the discharge heating relay 12, the slow charging copper bar 20 connects together the main contact negative of the slow charging relay 7 and the main contact negative of the fast charging relay 8, the wire I 14 connects in series the main contact negative of the discharge relay 4 and the positive of the discharge heating relay 12, the wire II 15 connects together the main contact positive of the fast charging relay 8 and the main contact positive of the fast charging heating relay 10, and the wire III 16 connects together the main contact positive of the slow charging relay 7 and the main contact positive of the slow charging heating relay 11. In the electric heating system of the application, the battery management system, the discharge relay, the pre-charging relay, the pre-charging resistor, the slow charging relay, the fast charging relay, the fast charging heating relay, the slow charging heating relay, the discharge heating relay and the mounting plate are fixedly connected through screws, the large insulating column and the small insulating column are tightly fixed on the mounting plate, after the whole device is installed, it is used as a module, when multiple modules are connected together for use, the negative of the Nth module is connected with the positive of the previous module, after series connection, the negative of the module 1 is the total negative of the battery pack, and the positive of the module N is the total positive of the battery pack; at the same time, the battery pack for electric forklifts can be composed of any number of modules, and is adapted according to the demand of the forklift system for voltage and electric quantity, and a matching heating element is selected according to the total voltage of the battery pack.

[0046] As Figures 3 to 4 The control method of the forklift battery multi-circuit heating system shown, including a heating management method in the discharging state and a heating management method in the charging state,

[0047] As Figure 3 The discharging state heating management system topology shown, the heating management method in the discharging state is as follows:

[0048] S1, when the battery pack 3 is powered on, the battery management system 1 receives the discharging wake-up signal, closes the discharge relay 4, and the battery management system 1 detects the temperature of the battery pack 3:

[0049] S2, when the battery pack 3 minimum temperature T≤ set value 1, open the discharge relay 4, at this time, heating and discharging are prohibited;

[0050] S3, when the battery pack 3 minimum temperature set value 1 < T≤ set value 2, close the discharge heating relay 12, enter the heating and discharging mode; after a period of heating, the temperature of the battery pack 3 rises, and when the minimum temperature rises to T> set value 3, open the discharge heating relay 12 to stop heating, and enter the pure discharge mode;

[0051] S4, when the battery pack 3 minimum temperature T> set value 2, directly enter the pure discharge mode;

[0052] S5, after entering the pure discharge mode, if the switch is closed, the discharge relay 4 is opened, and the battery pack 3 is powered off;

[0053] As shown in the charging state heating management system topology diagram, the heating management method in the charging state is as follows: Figure 4

[0054] T1, when the battery pack 3 is connected to the charger, the wake-up signal is detected to be fast charging wake-up, the fast charging relay 8 is closed (when the wake-up signal is detected to be slow charging wake-up, the slow charging relay 7 is closed), and the battery management system 1 detects the temperature of the battery pack 3;

[0055] T2, when the minimum temperature T of the battery pack 3≤ set value 1, the fast charging heating relay 10 (or the slow charging heating relay 11) is closed, after detecting that the voltage at the end of the heating relay is normal, the fast charging relay 8 (or the slow charging relay 7) is opened, at this time, continuous heating enters the pure heating mode, after a period of heating, the minimum temperature of the battery pack 3 rises, reaches set value 1 < T≤ set value 2, the fast charging relay 8 (or the slow charging relay 7) is closed, and the heating and charging mode is entered;

[0056] T3, when the minimum temperature of the battery pack 3 set value 1 < T≤ set value 2, the fast charging heating relay 10 (or the slow charging heating relay 11) is closed, the heating and charging mode is entered, after a period of heating, when the minimum temperature of the battery pack 3 rises to T> set value 2, the fast charging heating relay 10 (or the slow charging heating relay 11) is opened to stop heating, and the pure charging mode is entered;

[0057] T4, when the minimum temperature of the battery pack 3 T> set value 2, directly enter the pure charging mode, calibrate the SOC after charging to 100%, and stop charging, open the fast charging relay 8 (or open the slow charging relay 7), and disconnect the charging connection after completing the charging;

[0058] The heating management principle in the slow charging state is the same as that in the fast charging state.

[0059] As​Figures 1 to 4 The control method of the forklift battery multi-circuit heating system closes the pre-charging relay 5 before closing the discharge relay 4, and then closes the discharge relay 4 after the negative voltage of the main contact of the discharge relay 4 is raised. In the control method of the forklift battery multi-circuit heating system, the pre-charging resistor and the pre-charging relay are connected in series and then connected in parallel across the main contact of the discharge relay, and the pre-charging relay is closed before the discharge relay is closed, which can effectively prevent the damage of the discharge relay caused by the excessive voltage difference across the main contact at the moment of closing the main contact, and improves the service life of the equipment,

[0060] As shown in Figures 3 to 4 The control method of the forklift battery multi-circuit heating system sets the set value 1 to -30℃, the set value 2 to 0℃, and the set value 3 to 5℃ in the discharge state, and sets the set value 1 to 0℃ and the set value 2 to 10℃ in the charging state. Table 1 is the heating opening and closing temperature threshold table provided by the first embodiment of the present application. When the battery pack is in the discharge state, the heating is prohibited when Tmin≤-30℃, the discharge heating is started when -30℃

[0061]

[0062] Table 1

[0063] In the description provided herein, a large number of specific details are illustrated. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure the understanding of the present description.

[0064] In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not others, the combination of features of different embodiments is also meant to be within the protection scope of the present application and forms different embodiments. For example, in the above embodiments, those skilled in the art can use the features in a combined manner according to the known technical solutions and the technical problems to be solved by the present application.

[0065] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application, and any skilled person in the art can make some changes or modifications to the above-mentioned technical content with the above-mentioned prompt without departing from the technical solution of the present application, and any simple modification, equivalent change and modification of the above-mentioned embodiments made according to the technical essence of the present application without departing from the technical solution of the present application still belong to the scope of the present application.

Claims

1. A multi-circuit heating system for a forklift battery, characterized by: The application relates to a battery management system (1) connected with a battery pack (3), wherein the positive pole of the battery pack (3) is connected with a load positive pole, a slow charging positive pole and a fast charging positive pole through a discharging relay (4), a slow charging relay (7) and a fast charging relay (8) respectively; the ends of the discharging relay (4), the slow charging relay (7) and the fast charging relay (8) away from the battery pack (3) are further connected with a discharging heating relay (12), a slow charging heating relay (11) and a fast charging heating relay (10) respectively; the discharging heating relay (12), the slow charging heating relay (11) and the fast charging heating relay (10) are connected together with the negative pole of the battery pack (3) through a heating fuse (9) and a heating element (2); the negative pole of the battery pack (3) is connected with a load negative pole, a fast charging negative pole and a slow charging negative pole; the two ends of the discharging relay (4) are connected in parallel with a pre-charging relay (5) and a pre-charging resistor (6) connected together; the control points of the discharging relay (4), the pre-charging relay (5), the slow charging relay (7), the fast charging relay (8), the fast charging heating relay (10), the slow charging heating relay (11) and the discharging heating relay (12) are connected together with the battery management system (1). The system is used for heating management of the battery pack in the charging and discharging state, In the discharging state: S1, when the battery pack (3) is powered on, the battery management system (1) receives a discharging wake-up signal, the discharging relay (4) is closed, the battery management system (1) detects the temperature of the battery pack (3): the pre-charging relay (5) is closed before the discharging relay (4) is closed, and the discharging relay (4) is closed again after the negative pole voltage of the main contact point of the discharging relay (4) is raised; S2, when the minimum temperature T of the battery pack (3) is less than or equal to a set value 1, the discharging relay (4) is opened, and heating and discharging are prohibited at this time; S3, when the minimum temperature of the battery pack (3) is greater than the set value 1 and less than or equal to a set value 2, the discharging heating relay (12) is closed, and a heating and discharging mode is entered; after heating for a period of time, the temperature of the battery pack (3) is raised, the minimum temperature is raised to T greater than the set value 3, the discharging heating relay (12) is opened to stop heating, and a pure discharging mode is entered; S4, when the minimum temperature T of the battery pack (3) is greater than the set value 2, a pure discharging mode is directly entered; S5, after entering the pure discharging mode, if the switch is closed, the discharging relay (4) is opened, and the battery pack (3) is powered off; In the charging state: T1, when the battery pack (3) is connected with a charger, the wake-up signal is detected to be a fast charging wake-up signal, the fast charging relay (8) is closed, and the battery management system (1) detects the temperature of the battery pack (3); T2, when the minimum temperature T of the battery pack (3) is less than or equal to a set value 1, the fast charging heating relay (10) is closed, the end voltage of the heating relay is detected to be normal, the fast charging relay (8) is opened, a pure heating mode is entered, and the fast charging relay (8) is closed after heating for a period of time, and a heating and charging mode is entered; T3, when the battery pack (3) minimum temperature set value 1 < T ≤ set value 2, close the fast charging heating relay (10), enter the heating and charging mode, after a period of heating, the battery pack (3) minimum temperature rises to T > set value 2, disconnect the fast charging heating relay (10) to stop heating, enter the pure charging mode; T4, when the battery pack (3) minimum temperature T > set value 2, directly enter the pure charging mode, calibrate SOC and stop charging after charging to 100%, disconnect the fast charging relay (8), and disconnect the charging connection after completing charging; The heating management principle in the slow charging state is the same as that in the fast charging state. Among them, the set value 1 is-30℃, the set value 2 is 0℃, and the set value 3 is 5℃ in the discharging state; the set value 1 is 0℃, the set value 2 is 10℃ in the charging state.

2. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: The battery management system (1) is connected to the temperature collection point of the battery pack (3) by a wire for collecting the temperature on the battery pack.

3. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: The battery management system (1) and the external charger are in local area network communication through fast charging communication and slow charging communication, and the battery management system (1) confirms fast charging connection or slow charging connection through the reception of the wake-up signal.

4. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: The main contact positive of the discharging relay (4) is connected to the positive of the battery pack (3), the main contact negative of the discharging relay (4) is connected to the positive of the load, the negative of the battery pack (3) is connected to the negative of the load, forming a discharging loop; the main contact positive of the discharging heating relay (12) is connected to the main contact negative of the discharging relay (4), and the main contact negative of the discharging heating relay (12) is connected to the front end of the heating fuse (9).

5. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: The main contact negative of the slow charging relay (7) is connected to the positive of the battery pack (3), the main contact positive of the slow charging relay (7) is connected to the slow charging positive, the negative of the battery pack (3) is connected to the slow charging negative, forming a slow charging loop; the main contact positive of the slow charging heating relay (11) is connected to the slow charging positive, and the main contact negative of the slow charging heating relay (11) is connected to the front end of the heating fuse (9).

6. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: The main contact negative of the fast charging relay (8) is connected to the positive of the battery pack (3), the main contact positive of the fast charging relay (8) is connected to the fast charging positive, the negative of the battery pack (3) is connected to the fast charging negative, forming a fast charging loop; the main contact positive of the fast charging heating relay (10) is connected to the fast charging positive, and the main contact negative of the fast charging heating relay (10) is connected to the front end of the heating fuse (9).

7. A multi-circuit heating system for a forklift battery as defined in claim 1, wherein: Also include the installation plate (13), positive copper bar (17), negative copper bar (18), heating parallel copper bar (19), slow charging copper bar (20), big insulating column (21) and small insulating column (22), the battery management system (1), discharge relay (4), pre-charging relay (5), pre-charging resistance (6), slow charging relay (7), fast charging relay (8), fast charging heating relay (10), slow charging heating relay (11), discharge heating relay (12), big insulating column (21) and small insulating column (22) are fixed on (13) installation plate, the positive copper bar (17) and the main contact of discharge relay (4) and fast charging relay (8) are connected together, the negative copper bar (18) is fixed on big insulating column (21) through screw, the heating parallel copper bar (19) parallelly connects the main contact of fast charging heating relay (10), slow charging heating relay (11) and discharge heating relay (12) together.

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