CN112531239B

CN112531239B - Distributed temperature equalization method for battery pack in electric vehicle with good heat dissipation

Info

Publication number: CN112531239B
Application number: CN202011413979.7A
Authority: CN
Inventors: 陈子龙; 鲁新阳; 廖文俊; 李平飞
Original assignee: Xihua University
Current assignee: In A Tianjin Business Information Consulting Co
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2021-11-19
Anticipated expiration: 2040-05-12
Also published as: CN111540983B; CN112531239A; CN112490539B; CN112490539A; CN111540983A

Abstract

The invention particularly relates to a distributed temperature equalization method for a battery pack in an electric vehicle with good heat dissipation, which can realize the rapid auxiliary cooling of one or more single batteries with over-high temperature in the battery pack after temperature equalization is carried out by a temperature equalization device, thereby effectively avoiding the problem of over-high temperature of the single batteries and improving the safety of the battery pack; meanwhile, the heat of the single battery with overhigh temperature can be transferred to the single battery with lower temperature, so that the temperature difference among the single batteries in the battery pack is reduced, and the performance of the battery is improved.

Description

Distributed temperature equalization method for battery pack in electric vehicle with good heat dissipation

The application has the following application numbers: 202010399938.0, filing date: 2020-05-12, entitled "distributed temperature equalization apparatus for battery pack in electric vehicle and temperature equalization method".

Technical Field

The invention relates to the field of temperature control of battery packs of electric vehicles, in particular to a distributed temperature equalization method for battery packs in electric vehicles with good heat dissipation.

Background

Batteries of the new energy automobile are the more key parts of the new energy automobile, the quality of the batteries of the new energy automobile is related to the overall performance of the new energy automobile, once the batteries of the new energy automobile have certain hidden dangers, accidents can be caused, and therefore, corresponding safety design is required to be carried out on some parts of the batteries of the new energy automobile, which may have the hidden dangers.

In recent years, along with the popularization of electric vehicles, many spontaneous combustion accidents of electric vehicles also gradually occur in public vision, for example, many tesla vehicles and automobiles spontaneously combust in this year, generally, a part of an electric vehicle which is most prone to fire is a power battery, and the core of the ignition of the power battery is a local battery pack or a single battery pack, which is out of control in temperature due to failure or external force, so as to cause fire. The excellent power battery design needs to consider that the power battery timely dissipates heat in the rapid heating process or controls the temperature of the power battery within a reasonable range.

From the performance point of view, the starting point of the temperature control of the power battery is to keep the power battery in a good working state all the time. Generally, too low battery temperature affects the charge and discharge capacity of the battery, and too high temperature affects the life and safety of the battery. That is, the electric vehicle is expected to ensure that the power battery works in a temperature range of 20-55 ℃ in normal running, charging and discharging and standby states so as to exert the maximum performance of the power battery and prolong the endurance mileage of the electric vehicle as far as possible.

In order to ensure that the environmental temperature of the power battery is maintained in a proper temperature range, the currently adopted mode is mainly liquid cooling, such as an ES8 automobile, a Tesla model3 automobile; namely, the cooling liquid mode is used for carrying out concentrated heat dissipation on the power battery pack, and the cooling liquid is changed into low-temperature cooling liquid after heat exchange and flows into the power battery to cool the battery. At present, the cooling technology is mature and widely applied, and the cooling principle is shown in figure 1; when the cooling liquid cooling mode is used, the battery packs are generally arranged side by side to form a rectangular or flat plate shape, then the heat dissipation plate is placed below the battery packs, the bottom surfaces of the batteries are in surface contact with the upper surfaces of the heat dissipation plate, the lower surfaces of the heat dissipation plate are in contact with the cooling liquid channels, the battery box is arranged on the automobile chassis, the plurality of battery packs are vertically placed in the battery box, the plurality of cooling liquid channels are formed in the bottom plate of the battery box, when cooling liquid flows through the cooling liquid channels, heat on the bottom plate of the battery box is absorbed, the bottom plate of the battery box is generally made of materials such as copper and aluminum, the heat dissipation performance is good, and the heat of the battery packs placed above the battery box can be quickly taken away.

However, when the temperature of the battery pack is controlled by the cooling liquid cooling method, a plurality of sensors are generally distributed in the battery pack randomly or fixedly, the temperature of the cooling liquid is controlled by averaging the temperatures acquired by the plurality of sensors or by averaging a weighted algorithm, and the like, if the battery pack adopts a single large-volume battery or the number of single batteries in the battery pack is small, the temperature difference of each single battery is small, and the heat of the single battery can be effectively reduced by liquid cooling heat dissipation; however, for a battery pack formed by connecting a plurality of single batteries in series or in parallel, because the number of the single batteries is large, the battery pack is often divided into a plurality of modules according to functions, and then different modules are selected to supply power according to the driving conditions of an automobile under different working conditions, so that the temperature difference of the single batteries at each position in the battery pack is large; for example, about 5000 and 7000 sections of the lithium ion battery 18650 are loosened in Tesla model 3; the cooling liquid channel arranged at the bottom of the lithium ion battery pack divides a plurality of lithium ion batteries into a plurality of modules, so that different heat dissipation efficiencies can be provided for different modules;

however, if one of the single batteries in one module is in failure, or has an excessive load or has an excessive charging current, the average temperature of the batteries collected by the plurality of temperature sensors in the module does not change significantly, and at this time, the cooling system does not increase the heat dissipation effect, which may cause the temperature of the single batteries to continue to rise;

when the temperature of a plurality of batteries in a module is too high, the Battery Management System (BMS) generally increases the heat dissipation power of a radiator, reduces the temperature of cooling liquid and improves the flow rate of the cooling liquid, but because the cooling is performed on all the single batteries in the whole module instead of on a plurality of single batteries with too high temperature, the cooling effect of the single batteries with too high temperature is not obvious, and the temperature of other single batteries in a normal state in the module is lower than a normal value, the problems of deterioration of the working environment of the battery pack, increase of energy consumption and the like are caused, and even the spontaneous combustion phenomenon is caused because the single battery can not be rapidly cooled.

That is to say, the existing cooling method is to cool the whole battery pack, or divide the battery pack into several modules, and cool down the average value obtained after the temperature of a plurality of batteries in the modules is collected, if the heat dissipation capacity of a plurality of single batteries in the battery pack is the same, it can be ensured that the temperatures of the plurality of single batteries are close to each other, but if the heat dissipation capacity of a certain single battery is increased due to a fault, the temperature control of a single battery by a coolant system is difficult, or there is no effective method for performing balanced control on the heat dissipation capacity of the plurality of single batteries. If the heat dissipation control of the single batteries is to be realized, the cooling channel needs to be made into a plurality of independent circulation channel type cooling systems, and the structure of the cooling system is too complex, so that no manufacturer adopts the mode at present, the single circulation type cooling channel is still used, or the cooling system is divided into a plurality of modules for partition control, the battery pack with less single batteries can be well temperature controlled, and the battery pack with more batteries can not be effectively temperature controlled or temperature balanced, so that great potential safety hazards are left for battery temperature management.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a distributed temperature equalization method for a battery pack in an electric vehicle, which has high safety and good heat dissipation.

In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: the balancing device used in the balancing method and an original cooling liquid type cooling system of the battery pack are jointly installed on a battery pack support of the electric automobile, the battery pack support is of a box type framework structure formed by welding or connecting a plurality of steel pipes with one another through bolts, the battery pack support is internally provided with the battery pack formed by a plurality of vertically placed cylindrical single batteries, the battery pack is placed on a cooling plate with a cooling liquid channel, the cooling plate is welded or connected with the battery pack support through bolts, and the battery pack support is connected with a cross beam or a longitudinal beam of a body framework of the electric automobile through the bolts; a box-shaped upper cover with an opening is sleeved above the battery pack, and flanges are arranged on the periphery of the upper cover and connected with the battery pack bracket through bolts;

the cooling plate (a plurality of cooling liquid holes are arranged along the transverse direction or the longitudinal direction of the cooling plate, cooling liquid flows in the cooling liquid holes, the inlets of the cooling liquid holes are connected with one end of a cooling liquid inlet pipe, the other end of the cooling liquid inlet pipe is connected with the outlet of a cooling water pump, and a water pipe connected with the inlet of the cooling water pump extends into the bottom of the cooling water tank;

the cooling plate, the cooling liquid hole, the cooling water pump, the cooling water tank, the cooling liquid inlet pipe, the radiator and the cooling liquid outlet pipe form a cooling liquid type heat dissipation device of the electric automobile;

the balancing device comprises a plurality of Peltier elements arranged between the battery pack and the upper cover, the number of the Peltier elements is consistent with that of the single batteries, and the cold end face of each Peltier element is in contact with the upper surface of the single battery arranged below the Peltier element and leaves the positive lead of the upper surface of the single battery; the hot end face of the Peltier element is tightly attached to the lower surface of the heat conducting frame in a sticking or buckling connection or clamping manner; the heat conducting frame is a # -shaped flat frame consisting of a plurality of metal heat conducting strips which are arranged in a staggered manner transversely and longitudinally, each Peltier element is positioned right below a # -shaped grid intersection point, and flange flanges arranged on the periphery of the heat conducting frame are connected with the upper cover through bolts;

the power supply lead of the Peltier element is led out from the side surface of the Peltier element and then is connected with the power supply line of the auxiliary battery through the relay switch; a temperature sensor is stuck on the outer side surface or the lower bottom surface of the upper part of the single battery, the signal output end of the temperature sensor is connected with the signal input port of the microcomputer, and the signal control end of the relay switch is connected with the signal output port of the microcomputer; the power cord of the microcomputer is connected with the auxiliary battery, and the auxiliary battery and the microcomputer are installed on the battery pack bracket or the heat dissipation plate through bolts or buckles.

Preferably, the heat conducting frame is made of a copper plate, the peltier element is a cylinder, the lower bottom surface of the cylinder is a cold end surface, the cold end surface is in contact with the upper end surface of the single battery, a first annular groove is formed in the lower bottom surface of the cylinder and is matched with the outer diameter of the single battery, an inverted L-shaped lead hole is formed in the bottom of the first annular groove, the other end of the lead hole penetrates out of the side wall of the cylinder, a lead penetrates into the lead hole, and the lead penetrates out of the lead hole and is sequentially connected with the relay switch and the auxiliary battery; the upper end surface of the cylinder is a hot end surface, and the hot end surface is contacted with the bottom surface of the ring groove arranged at the corresponding position on the lower bottom surface of the heat conduction frame.

According to the method for performing temperature equalization in the distributed temperature equalization device for the battery pack in the electric vehicle, after the battery pack starts to operate, the cooling liquid type heat dissipation system starts to operate, and the microcomputer performs temperature equalization of the battery pack according to the following steps:

step a: marking the Peltier element above each single battery according to the position of the Peltier element in the grid of the heat conduction frame, then acquiring the respective temperature of all the single batteries in the battery pack in real time through a temperature sensor, and sequentially marking as T1 and T2.. Tn; finding out the maximum value and the minimum value in T1-Tn, and marking as T _ max and T _ min; the microcomputer also stores a temperature upper limit value T _ H and a temperature lower limit value T _ D when the battery works normally; then the method comprises the following steps:

step b: the value of T _ max is determined as follows:

if T _ max is within the first temperature range T01, indicating that the battery pack is working normally, returning to step a;

if T _ max exceeds the first temperature range T01 and is within the second temperature range T02, go to step c;

if T _ max exceeds the second temperature range T02 and is within the third temperature range T03, go to step d;

if T _ max exceeds the third temperature range T03 and is less than T _ H, go to step e;

if T _ max is larger than T _ H, entering step f;

step c: the method comprises the steps that a microcomputer controls a Peltier element at a node position where T _ max is located to be electrified and cooled, the single battery corresponding to T _ max is cooled, heat of the single battery is transferred to adjacent single batteries at the periphery through a heat conducting frame, after a certain time, if T _ max is located within a first temperature range T01, the step a is returned, and otherwise, the step d is returned;

step d: taking a position node where a single battery corresponding to T _ max is located as a central node, recording nodes, the peripheries of which are directly connected with the central point through a # -shaped grid, as first nodes, recording nodes, the peripheries of which are directly connected with the first nodes through the # -shaped grid, as second nodes, and if the nodes are marked as the central node or the first nodes, not marking the second nodes; electrifying and cooling the plurality of Peltier elements corresponding to the central node, the first node and the second node, and after a certain time, if T _ max is within a second temperature range T02, returning to the step c, otherwise, entering the step e;

step e: d, marking the node position where the single battery with the lowest temperature in all the residual unmarked nodes marked in the step d is located as an end point, wherein the temperature of the end point is T _ min in the residual unmarked nodes, calculating a shortest path from the start point to the end point by taking the central node as the start point, then marking all the unmarked nodes corresponding to the shortest paths as third nodes, and electrifying and cooling the central node, the first node, the second node, the third nodes and the Peltier elements at the end point; monitoring T1 and T2.. Tn after a certain time, if T _ max does not exceed the third temperature range T03, returning to the step d, otherwise, entering the step f;

step f: finding out all nodes with temperature ranges of [ T _ min, T _ min + T _00] in all the remaining unmarked nodes, and marking the nodes meeting the requirements as an auxiliary end point 1 and an auxiliary end point 2.. the auxiliary end point n;

calculating a plurality of ring shortest paths from the central node to all auxiliary end points and end points, marking one ring shortest path with the largest number of unmarked nodes in the plurality of ring shortest paths as an optimal path, and marking all unmarked nodes in the optimal path as fourth nodes; electrifying and cooling the Peltier elements at the central node, the first node, the second node, the third node and the fourth node;

monitoring T1 and T2.. Tn after a certain time, if T _ max is in a third temperature range T03, returning to the step e, otherwise, entering the step g;

step g: and powering off the central node and the plurality of single batteries corresponding to the first node, recording the position of the central node by the microcomputer, generating an alarm signal, and displaying the alarm signal and the position of the central node by a display screen in communication connection with the microcomputer.

Preferably, in the step e, if there is more than one shortest path, the average temperature of all the third nodes in each shortest path in the plurality of shortest paths is calculated, the path with the lowest average temperature is selected as the shortest path, and the peltier elements at all the nodes corresponding to the shortest path are powered on and cooled down.

The invention has the following beneficial effects: after the temperature equalization is carried out by the temperature equalization device, one or more single batteries with overhigh temperature in the battery pack can be quickly cooled in an auxiliary manner, so that the problem of overhigh temperature of the single batteries is effectively avoided, and the safety of the battery pack is improved; meanwhile, the heat of the single battery with overhigh temperature can be transferred to the single battery with lower temperature, so that the temperature difference among the single batteries in the battery pack is reduced, and the performance of the battery is improved.

Drawings

FIG. 1 is a schematic diagram of a coolant cooling system for an electric vehicle battery pack;

FIG. 2 is a schematic diagram of heat dissipation from a Peltier element;

FIG. 3 is a schematic diagram of a liquid cooling system;

FIG. 4 is a schematic view of a battery pack bracket and a heat sink plate;

FIG. 5 is a schematic diagram of the connection of a single cell to a Peltier element;

FIG. 6 is a schematic diagram of a microcomputer control circuit;

FIG. 7 is a diagram of a thermal frame bottom mounting 8x8 Peltier elements;

FIG. 8 is a schematic diagram of a 74HC595 chip expansion control bit circuit;

FIG. 9 is a schematic view of a heat-conducting frame;

FIG. 10 is a flow chart of a method of temperature equalization;

fig. 11 is a schematic diagram of marking a center node and a first node in step c of the temperature equalization method;

FIG. 12 is a schematic diagram of the method for temperature equalization with a second node labeled in step d;

fig. 13 is a schematic diagram illustrating the shortest path from the central node to the destination in step e of the temperature equalization method;

FIG. 14 is a schematic diagram of the third node according to FIG. 13;

fig. 15 is a schematic diagram of marking the fourth node in step f of the temperature equalization method.

Detailed Description

As shown in fig. 4-9, the balancing device used in the balancing method and the original coolant-type heat dissipation system of the power battery pack of the electric vehicle are installed on the battery pack bracket of the electric vehicle or the bottom plate of the vehicle chassis together, the structure of the coolant-type heat dissipation system can refer to the single-cycle structure provided in fig. 1, the heat dissipation plate 1 is provided with a plurality of coolant holes 2 along the transverse or longitudinal direction thereof, coolant flows through the coolant holes 2, the inlets of the coolant holes 2 are connected with one end of a coolant inlet pipe 5, the other end of the coolant inlet pipe 5 is connected with the outlet of a coolant pump 3, and the water pipe connected with the inlet of the coolant pump 3 extends into the bottom of the coolant tank 4; a water return hole arranged on the upper surface of the cooling water tank 4 is connected with an outlet of the finned radiator 6 through a water pipe, an inlet of the radiator 6 is connected with one end of a cooling liquid outlet pipe, and the other end of the cooling liquid outlet pipe is communicated with an outlet of the cooling liquid hole 2; the radiator 6 is arranged at the position of an air inlet grille at the front part of the automobile body through a bolt; the cooling water pump 3 and the cooling water tank 4 are arranged in an engine room at the front part of the vehicle body or in front of the lower part of a vehicle body chassis in a bolt connection or welding mode;

the cooling plate 1, the cooling liquid hole 2, the cooling water pump 3, the cooling water tank 4, the cooling liquid inlet pipe 5, the radiator 6 and the cooling liquid outlet pipe form a cooling liquid type heat dissipation device of the electric automobile; a zoned cooling structure or a common electric vehicle coolant type heat dissipation system, such as tesla model3 or yulai ES6 or other electric vehicle existing coolant type heat dissipation systems, may also be used, as well as coolant type heat dissipation devices of other structures.

The battery pack bracket is a hollow box type framework structure formed by welding or bolting a plurality of steel pipes, and can also be formed by splicing a plurality of rectangular steel pipes; the battery pack support is internally provided with a plurality of vertically-arranged cylindrical single batteries, the plurality of single batteries are arranged side by side to form a rectangular, square or polygonal shape to form a battery pack, the battery pack is arranged on a heat dissipation plate 1 with a cooling liquid channel, the heat dissipation plate 1 is welded or bolted with a bottom frame of the battery pack support, and the battery pack support is connected with a cross beam or a longitudinal beam of a body framework of an electric automobile through bolts; the upper surface of the heat dissipation plate 1 can be provided with a groove which is adaptive to the shape of the battery pack, the battery pack is clamped in the groove, or the upper surface of the heat dissipation plate 1 is welded or bolted with a plurality of flange plates with flange holes, and the battery pack is placed in the flange plates; or the peripheries of a plurality of single batteries are bound into a row by using metal strips, and the metal strips are connected with corresponding clamping grooves arranged on the upper surface of the heat dissipation plate 1 through buckles, so that the battery pack is fixed on the heat dissipation plate;

the heat dissipation plate 1 is a rectangular or square flat plate with a certain thickness, a box-shaped upper cover 21 with an opening is sleeved above the battery pack, and flange plates are arranged on the periphery of the upper cover 21 and are connected with the battery pack bracket or the heat dissipation plate 1 through bolts; an annular groove is arranged on the lower end face of the upper cover 21, a sealing ring is clamped in the groove, and the lower part of the sealing ring is in contact with a sealing groove arranged at a corresponding position on the heat dissipation plate 1, so that the upper cover 21 and the heat dissipation plate 1 can form a closed space, and the waterproof and dustproof effects are achieved;

the balancing device comprises a plurality of Peltier elements 30 arranged between the battery pack and the upper cover 21, the working principle of the Peltier elements 30 is shown in figure 2, the Peltier elements are generally in a flat plate shape, two surfaces of the Peltier elements are respectively a cold end or a hot end, an N pole/P pole and a connecting lead are arranged in an interlayer in the middle of the flat plate, when the lead is electrified, the cold end absorbs heat, the hot end releases heat, and when current in the lead reversely flows, the positions of the cold end and the hot end are interchanged; the peltier element adopted in the application can be a type TEC1-12712, a type TEC1-12707, a type DA-12-110-01, or other common peltier element types.

The number of the peltier elements 30 is the same as the number of the single cells, and as shown in fig. 5, the cold end surface of the peltier element 30 contacts the upper surface of the single cell placed therebelow and leaves the positive lead of the upper surface of the single cell; the hot end face of the Peltier element 30 is tightly attached to the lower surface of the heat conducting frame 34 in a sticking or buckling connection or clamping manner;

as shown in fig. 9, the heat conducting frame 34 is a cross-shaped flat frame composed of a plurality of metal heat conducting strips arranged in a staggered manner in the horizontal and vertical directions, each peltier element 30 is located right below the intersection point of the cross-shaped grid, and flange flanges arranged around the heat conducting frame 34 are connected with the upper cover 21 by bolts;

the heat conducting frame 34 is made of a copper plate, a magnesium-copper alloy plate or a magnesium-aluminum alloy plate, the peltier element 30 is a cylinder, the lower bottom surface of the cylinder is a cold end surface, the cold end surface is in contact with the upper end surface of the single battery 12, a first annular groove is formed in the lower bottom surface of the cylinder and is matched with the outer diameter of the single battery 12, an inverted-L-shaped lead hole is formed in the bottom of the first annular groove, the other end of the lead hole penetrates out of the side wall of the cylinder, a lead penetrates into the lead hole, and the lead penetrates out of the lead hole and is sequentially connected with the relay switch and the auxiliary battery 11; the upper end surface of the cylinder is a hot end surface, and the hot end surface is contacted with the bottom surface of the ring groove arranged at the corresponding position on the lower bottom surface of the heat conducting frame 34;

the power supply lead of the peltier element 30 is led out from the side thereof and then connected to the power supply line of the auxiliary battery 11 through the relay switch 31; the auxiliary battery 11 can be independently arranged in the battery pack bracket, or can be formed by directly connecting a plurality of single batteries in the battery pack in series or in parallel; a temperature sensor 32 is stuck on the outer side surface or the lower bottom surface of the upper part of the single battery, the signal output end of the temperature sensor 32 is connected with the signal input port of the microcomputer 33, and the signal control end of the relay switch 31 is connected with the signal output port of the microcomputer 33; the power cord of the microcomputer 33 is connected to the auxiliary battery 11, and the auxiliary battery 11 and the microcomputer 33 are mounted on the battery pack holder or the heat radiating plate 1 by bolts or snaps.

The temperature sensor can be a naked paster PT1000 temperature sensor, an imported paster DS18b20 digital temperature sensor probe, or paster temperature sensors of other types or buckle temperature sensors;

the microcomputer 33 can be STM32F100ZC 112GPIO singlechip or AT89C52 singlechip or other singlechips, or can be PLC industrial control machine of Mitsubishi corporation, or can be other microcomputers with complete control function; when the number of the single batteries is large, a single chip microcomputer with matched number of I/O ports can be used, or a serial-to-parallel mode can be used to increase control pins, as shown in FIG. 7, a groove is arranged on the lower bottom surface of the heat conduction frame, Peltier elements are placed in the groove, 64 Peltier elements with 8x8 in total are arranged, three 74HC595 chips can be used to control corresponding to 64 single batteries, as shown in FIG. 8, three 74HC595 chips are connected in series, serial DATA is input through a DATA pin of U45, a SQH pin of U45 is connected to a DATA pin of U46, a SQH pin of U46 is connected to a DATA pin of U47, so that 24-bit serial DATA is input through U45 and then latched, the 3-byte values can be respectively output through U45, U46 and U47, expansion of the pins is realized, and only a circuit of the single chip microcomputer which can be used when a plurality of Peltier elements are controlled is taken as an example, other common expansion methods can also be used, and the expansion method of the circuit pins is not limited herein.

According to the distributed temperature equalization device for the battery pack in the electric vehicle, the method for performing temperature equalization comprises the following steps: after the battery pack starts to operate, the coolant-type heat dissipation system starts to operate, and the microcomputer 33 performs battery pack temperature equalization according to the following steps:

the first embodiment is as follows: using the heat conducting frame with 8 × 8 peltier elements shown in fig. 7, 64 loose 18650 lithium battery cells are placed in corresponding positions below the heat conducting frame to form a battery pack, and common temperatures of the lithium battery include charging temperature: 0-45 ℃, discharge temperature: -20 ℃ to 60 ℃, temperature protection: 70 +/-5 ℃, wherein the normal working temperature area of the single battery is-20-60 ℃, the high-load working temperature area is 60-65 ℃, the warning temperature area is 65-75 ℃, and the highest temperature critical value which can be borne by the battery is 75 ℃.

Step a: the peltier elements 30 above each single battery 12 are labeled according to the positions of the peltier elements in the grid of the heat conduction frame 34, and then the respective temperatures of all the single batteries 12 in the battery pack are collected in real time through the temperature sensors 32 and are sequentially marked as T1, T2.. Tn; finding out the maximum value and the minimum value in T1-Tn, and marking as T _ max and T _ min; the microcomputer 33 also stores a temperature upper limit value T _ H and a temperature lower limit value T _ D when the battery normally operates; where T _ H is 75 ℃ and T _ D is-20 ℃, and then the following steps are followed:

step b: the value of T _ max is determined as follows:

if T _ max is within the first temperature range T01, indicating that the battery pack is working normally, returning to step a; t01 is here set to-20 deg.c, 60 deg.c,

the temperature of each single battery in the battery pack is less than 60 ℃, the battery pack can be considered to be in a normal state, and when the average temperature of a plurality of single batteries is more than 40 ℃ or 50 ℃, a cooling liquid type heat dissipation system can be started to carry out conventional heat dissipation, so that the temperature stability of the single batteries in the battery pack is ensured;

if T _ max exceeds the first temperature range T01 and is within the second temperature range T02, go to step c; here T02 is set to [60 ℃, 65 ℃ ]

If T _ max exceeds the second temperature range T02 and is within the third temperature range T03, go to step d; here T03 was set at 65 ℃, 70 ℃

If T _ max exceeds the third temperature range T03 and is less than T _ H, i.e. at 70 ℃, 75 ℃ entering step e;

if T _ max is larger than T _ H, entering step f;

step c: as shown in fig. 11, as can be seen from the operating temperature range of the loose battery, at this time, the temperature of the single battery corresponding to T _ max is between [60 ℃ and 65 ℃), which indicates that the battery is in a large working load state, and may exceed the normal operating temperature range, and enters the alert temperature range, so that in addition to the conventional overall cooling of the battery pack by the liquid cooling heat dissipation device, the microcomputer 33 also controls the peltier element 30 at the node position of T _ max to be powered on and cooled, cools the single battery 12 corresponding to T _ max, and quickly transfers the heat of the single battery 12 to the adjacent single batteries 12 with lower temperatures around through the heat conduction frame 34, and after a certain time, if T _ max is within the first temperature range T01, that is, less than 65 ℃, the step a is returned, otherwise, step d is entered;

step d: as shown in fig. 12, as can be seen from the operating temperature range of the loose battery, when the temperature of the single battery corresponding to T _ max is between 65 ℃ and 70 ℃, the temperature of the single battery exceeds the normal operating temperature, which may be too high load, or poor heat dissipation, or battery failure, and therefore, a better auxiliary heat dissipation measure needs to be performed on the single battery; taking a position node where the single battery 12 corresponding to the T _ max is located as a central node, recording nodes corresponding to nodes directly connected with the central point at the periphery through a # -shaped grid as first nodes, recording nodes directly connected with the first nodes at the periphery of the first nodes through the # -shaped grid as second nodes, and if the nodes are marked as the central node or the first nodes, not marking the second nodes; electrifying the plurality of Peltier elements 30 corresponding to the central node, the first node and the second node for cooling, so that the plurality of Peltier elements around T _ max can be started, and heat generated by the single battery corresponding to T _ max can be rapidly transmitted to the periphery to achieve the effect of rapid cooling, after a certain time, if T _ max is located within T02, namely less than or equal to 65 ℃, it is indicated that the cooling measure is effective, and the temperature of the single battery is reduced to be below a warning region, returning to the step c, so that the starting number of the Peltier elements can be reduced, and electric energy can be saved; if the temperature of T _ max is not obviously reduced, which indicates that the temperature of the single battery is still too high, and a more powerful cooling measure needs to be taken, then step e is carried out;

step e: as shown in fig. 13 and 14, the node position where the unit cell 12 with the lowest temperature is located in all the remaining unmarked nodes marked in step d is marked as an end point, the temperature of the end point is T _ min in the remaining unmarked nodes, the shortest path from the start point to the end point is calculated by taking the center node as the start point, then all the unmarked nodes corresponding to the shortest path are marked as a third node, and the peltier elements 30 at the center node, the first node, the second node, the third node and the end point are electrified and cooled; therefore, when more Peltier elements are controlled to perform auxiliary heat dissipation, the single batteries with the highest temperature and the lower temperature are used as heat dissipation paths, the temperature difference among the single batteries can be adjusted, the temperature of each single battery is closer, the temperature consistency of each single battery in the battery pack can be greatly improved, and the positive influence on the voltage stability, the discharge efficiency of the battery, the cycle life and the like is realized;

if the temperature T _ max is reduced to a third temperature range T03 after a certain time, the heat dissipation measures reach the preset effect, the step d is returned, the temperature reduction measures are reduced to save energy, if the temperature still exceeds T03, the current temperature reduction measures still cannot effectively reduce the temperature of the single battery, and the step f is entered;

step f: as shown in fig. 15, among all the remaining unmarked nodes, finding out all nodes with temperature ranges [ T _ min, T _ min + T _00], and marking the nodes meeting the requirements as an auxiliary end point 1 and an auxiliary end point 2.. auxiliary end point n;

calculating a plurality of ring shortest paths from the central node to all auxiliary end points and end points, marking one ring shortest path with the largest number of unmarked nodes in the plurality of ring shortest paths as an optimal path, and marking all unmarked nodes in the optimal path as fourth nodes; the Peltier elements 30 at the central node, the first node, the second node, the third node and the fourth node are electrified and cooled;

if the temperature of the single battery is reduced to the third temperature range T03 after a certain time, returning to step e, otherwise, indicating that the temperature of the single battery cannot be adjusted by the temperature equalizing device, if the battery is damaged or burnt due to continuous operation, entering step g to prevent the condition;

step g: the power of a plurality of single batteries corresponding to the central node and the first node is cut off, other single batteries are used for continuing working, the position of the central node is recorded by the microcomputer 33 and an alarm signal is generated, the alarm signal and the position of the central node are displayed by a display screen in communication connection with the microcomputer 33, the single batteries with overhigh temperature in the battery pack of a driver are reminded, and therefore the overall temperature stability and safety of the battery pack are effectively protected.

After the temperature equalization is carried out by the temperature equalization device, one or more single batteries with overhigh temperature in the battery pack can be quickly cooled in an auxiliary manner, so that the problem of overhigh temperature of the single batteries is effectively avoided, and the safety of the battery pack is improved; meanwhile, the heat of the single battery with overhigh temperature can be transferred to the single battery with lower temperature, so that the temperature difference among the single batteries in the battery pack is reduced, and the performance of the battery is improved.

Example two: as shown in fig. 13, in step e, if there is more than one shortest path, calculating the average temperature of all the third nodes in each shortest path in the plurality of shortest paths, selecting the path with the lowest average temperature as the shortest path, and powering on and cooling the peltier elements 30 at all the nodes corresponding to the shortest path; this may achieve a faster cooling effect.

Example three: and when the battery pack has the single batteries isolated by power failure, the remaining single batteries can continue to repeat the steps from the step a to the step g, and when the shortest path is searched in the steps from the step e and the step f, the isolated single batteries are used as obstacles, and a labyrinth treasure searching type calculation mode is carried out from the starting point to the end point to calculate the shortest path, wherein the search can be carried out by adopting an algorithm A, the algorithm A + can also be adopted, and other common two-dimensional plane labyrinth treasure searching type algorithms can also be adopted for calculation.

Claims

1. The distributed temperature equalization method for the battery pack in the electric automobile with good heat dissipation is characterized in that an equalization device used in the equalization method and an original cooling liquid type heat dissipation system of the battery pack are jointly installed on a battery pack support of the electric automobile, the battery pack support is of a box type framework structure formed by welding or connecting a plurality of steel pipes with one another through bolts, the battery pack support is internally provided with the battery pack formed by a plurality of vertically placed cylindrical single batteries, the battery pack is placed on a heat dissipation plate (1) with a cooling liquid channel, the heat dissipation plate (1) is welded or connected with the battery pack support through bolts, and the battery pack support is connected with a cross beam or a longitudinal beam of a body framework of the electric automobile through the bolts; a box-shaped upper cover (21) with an opening is sleeved above the battery pack, and flange plates are arranged on the periphery of the upper cover (21) and connected with the battery pack bracket through bolts;

the heat dissipation plate (1) is provided with a plurality of cooling liquid holes (2) along the transverse direction or the longitudinal direction, cooling liquid flows in the cooling liquid holes (2), the inlet of each cooling liquid hole (2) is connected with one end of a cooling liquid inlet pipe (5), the other end of each cooling liquid inlet pipe (5) is connected with the outlet of a cooling water pump (3), and a water pipe connected with the inlet of the cooling water pump (3) extends into the bottom of a cooling water tank (4); a water return hole arranged on the upper surface of the cooling water tank (4) is connected with an outlet of the finned radiator (6) through a water pipe, an inlet of the radiator (6) is connected with one end of a cooling liquid outlet pipe, and the other end of the cooling liquid outlet pipe is communicated with an outlet of the cooling liquid hole (2); the radiator (6) is arranged at the position of an air inlet grille at the front part of the automobile body through a bolt; the cooling water pump (3) and the cooling water tank (4) are arranged in an engine room at the front part of the vehicle body or in front of the lower part of a vehicle body chassis in a bolt connection or welding mode;

the cooling plate (1), the cooling liquid hole (2), the cooling water pump (3), the cooling water tank (4), the cooling liquid inlet pipe (5), the radiator (6) and the cooling liquid outlet pipe form a cooling liquid type heat dissipation device of the electric automobile;

the balancing device comprises a plurality of Peltier elements (30) arranged between the battery pack and an upper cover (21), the number of the Peltier elements (30) is the same as that of the single batteries, and the cold end face of each Peltier element (30) is in contact with the upper surface of the single battery arranged below the Peltier element and leaves the upper surface of the single battery from a positive lead; the hot end face of the Peltier element (30) is clung to the lower surface of the heat conduction frame (34) in a sticking or buckling connection or clamping manner; the heat conduction frame (34) is a # -shaped flat frame consisting of a plurality of metal heat conduction strips which are arranged in a staggered mode in the transverse and longitudinal directions, each Peltier element (30) is located right below a # -shaped grid intersection point, and flange flanges arranged on the periphery of the heat conduction frame (34) are connected with the upper cover (21) through bolts;

the power supply lead of the Peltier element (30) is led out from the side surface and then is connected with the power supply line of the auxiliary battery (11) through a relay switch (31); a temperature sensor (32) is stuck on the outer side surface or the lower bottom surface of the upper part of the single battery, the signal output end of the temperature sensor (32) is connected with the signal input port of the microcomputer (33), and the signal control end of the relay switch (31) is connected with the signal output port of the microcomputer (33); a power line of the microcomputer (33) is connected with the auxiliary battery (11), and the auxiliary battery (11) and the microcomputer (33) are arranged on the battery pack bracket or the heat dissipation plate (1) through bolts or buckles;

the method is characterized in that: after the battery pack starts to operate, the cooling liquid type heat dissipation system starts to operate, and the microcomputer (33) performs battery pack temperature equalization according to the following steps:

step a: marking the Peltier element (30) above each single battery (12) according to the position of the Peltier element in the grid of the heat conduction frame (34), and then acquiring the respective temperatures of all the single batteries (12) in the battery pack in real time through a temperature sensor (32), and sequentially marking as T1, T2. Finding out the maximum value and the minimum value in T1-Tn, and marking as T _ max and T _ min; the microcomputer (33) also stores a temperature upper limit value T _ H and a temperature lower limit value T _ D when the battery works normally; then the method comprises the following steps:

step b: the value of T _ max is determined as follows:

if T _ max is larger than T _ H, entering step f;

step c: the microcomputer (33) controls the Peltier element (30) at the node position of T _ max to be electrified and cooled, the single battery (12) corresponding to the T _ max is cooled, the heat of the single battery (12) is transferred to the adjacent single batteries (12) at the periphery through the heat conducting frame (34), and if the T _ max is located in a first temperature range T01 after a certain time, the step a is returned, otherwise, the step d is returned;

step d: taking a position node where a single battery (12) corresponding to T _ max is located as a central node, recording nodes corresponding to nodes which are directly connected with the central point at the periphery through a # -shaped grid as first nodes, recording nodes which are directly connected with the first nodes at the periphery of the first nodes through the # -shaped grid as second nodes, and if the nodes are marked as the central node or the first nodes, not marking the second nodes; electrifying and cooling a plurality of Peltier elements (30) corresponding to the central node, the first node and the second node, and returning to the step c if T _ max is within a second temperature range T02 after a certain time, otherwise, entering the step e;

step e: marking the node position where the single battery (12) with the lowest temperature is located in all the residual unmarked nodes marked in the step d as an end point, wherein the temperature of the end point is the minimum value in the residual unmarked nodes, calculating the shortest path from the start point to the end point by taking the central node as the start point, then marking all the unmarked nodes corresponding to the shortest paths as third nodes, and electrifying and cooling the central node, the first node, the second node, the third node and the Peltier elements (30) at the end point; if the shortest path is not more than one, calculating the average temperature of all third nodes in each shortest path in the shortest paths, selecting the path with the lowest average temperature as the shortest path, and electrifying and cooling the Peltier elements (30) at all the nodes corresponding to the shortest path;

monitoring T1 and T2.. Tn after a certain time, if T _ max does not exceed the third temperature range T03, returning to the step d, otherwise, entering the step f;

calculating a plurality of ring shortest paths from the central node to all auxiliary end points and end points, marking one ring shortest path with the largest number of unmarked nodes in the plurality of ring shortest paths as an optimal path, and marking all unmarked nodes in the optimal path as fourth nodes; energizing and cooling Peltier elements (30) at the central node, the first node, the second node, the third node and the fourth node;

step g: the central node and the plurality of single batteries corresponding to the first node are powered off, the microcomputer (33) records the position of the central node and generates an alarm signal, and a display screen in communication connection with the microcomputer (33) displays the alarm signal and the position of the central node.