TWI774571B - Lithium battery charging system and method - Google Patents

Abstract

The present invention is a charging system and method for a lithium battery. The charging system includes a charging device and a lithium battery pack. A charging circuit and a communication circuit are established between the charging device and the lithium battery pack, wherein the lithium battery The group includes a battery cell group and a battery management system (BMS), the battery management system receives the state of the battery cell group, and generates a charging command after judging, and sends the charging command to the charging device through the communication loop, so that The charging device outputs the corresponding size of the charging power source according to the charging command, and charges the lithium battery pack through the charging circuit; thereby, the battery management system (BMS) can lead and control the charging operation, and according to the real-time condition of the battery cell pack, Choose the best charging current so that the battery pack can be charged efficiently and safely.

Description

Lithium battery charging system and method

The present invention relates to a charging system for a lithium battery, in particular to a charging system that determines an appropriate charging method based on the current state of the lithium battery.

Please refer to FIG. 7 , which is a schematic diagram of a conventional lithium battery charging system, including a charging device 300 and a rechargeable lithium battery pack 310 . The charging device 300 is, for example, an energy station, a charging pile, a charging stand, a car charger, etc. The lithium battery pack 310 is a battery of an electric vehicle, such as an electric scooter, an electric vehicle, and the like.

The manner of the lithium battery pack 310 completely depends on the design of the charging device 300. Generally speaking, the charging device 300 uses a fixed charging mode to charge the lithium battery pack 310, such as constant current charging (CC) and constant charging. Voltage charging method (CV). The charging device 300 decides to perform constant current charging or constant voltage charging on the lithium battery pack 310 according to the output voltage and output current detected by its own output terminal. After the voltage rises to a preset value, constant voltage charging is performed.

However, if the lithium battery pack 310 is abnormal during the charging process, the charging device 300 using the fixed charging mode usually cannot take appropriate measures. For example, if the temperature of the lithium battery pack 310 is too high, if the charging device 300 still charges the lithium battery pack 300 with a large current, the cells of the lithium battery pack 310 are easily degraded rapidly, thereby reducing the battery life. In addition, since the charging operation of the lithium battery pack 310 is completely determined by the charging device 300 , the lithium battery pack 310 may be affected by errors of the charging device 300 , resulting in failure to fully charge or overcharge.

[Technical problems to be solved by the invention]

The traditional charging method only adopts a fixed charging mode and cannot provide more efficient charging for the lithium battery pack. The present invention proposes a charging system and method for a lithium battery. The current size of the lithium battery pack is charged.

[Technical means to solve problems]

The present invention provides a charging system for a lithium battery, comprising:

A charging device, comprising: a control unit; a charging circuit, connected to the control unit, for outputting a charging power source; a communication unit, connected to the control unit;

A lithium battery pack is connected with the charging device to form a charging circuit, and the lithium battery pack receives the charging power through the charging circuit, wherein the lithium battery pack includes: a battery cell group, including a plurality of battery cells; a battery management system, comprising a communication module, the communication module is connected with the communication unit to form a communication loop;

The battery management system receives the state of the battery cell group, and generates a charging command after judging, and sends the charging command to the charging device via the communication circuit, so that the charging device outputs the corresponding size of the charging power source according to the charging command, via the communication circuit. The charging circuit charges the lithium battery pack.

The present invention provides a charging method for a lithium battery, comprising:

S1: connect the lithium battery pack and the charging device, and form a charging loop and a communication loop between the lithium battery pack and the charging device;

S2: the battery management system receives the state of the battery cell group, and determines a charging command according to the state of the battery cell group;

S3: The battery management system sends the charging command to the charging device through the communication loop, wherein the charging device outputs a charging power to the battery cell pack according to the charging command;

S4: the battery management system judges whether the power of the battery cell group is fully charged, and if not, repeats the step S2;

S5: If the battery management system determines that the power of the battery cell group is fully charged, the battery management system sends an end charging command to the charging device through the communication loop.

[Effect of invention]

In the present invention, the battery management system (BMS) inside the lithium battery pack determines a suitable charging command after judging the current state of the battery cell pack, and sends the charging command to the charging device, requesting the charging device to output the charging command according to the charging command. The battery cell pack is charged with a suitable current. During the charging process, the charging current can be adjusted according to the current state of the battery cell pack, so that the battery pack can efficiently and safely complete the charging operation. It can also play a protective mechanism to stop charging under high temperature conditions, extending battery life.

Referring to FIG. 1 , the lithium battery charging system of the present invention includes a charging device 10 and a lithium battery pack 20 . The charging device 10 can be a charging device such as an energy station for exchanging batteries, a charging pile, a charging stand, a car charger, etc., and includes a control unit 11 , a charging circuit 12 and a communication unit 13 inside. Wherein, the control unit 11 is responsible for controlling the operation of the charging device 10; the charging circuit 12 is connected to the control unit 11 for externally outputting a charging power; the communication unit 13 is connected to the control unit 11 for connecting with the lithium battery pack 20 are connected to each other for communication to establish a communication circuit B, and receive a charging command from the lithium battery pack 20 .

The lithium battery pack 20 is connected to the charging device 10 to establish a charging circuit A, through which the charging circuit A receives the charging power output from the charging device 10 . The lithium battery pack 20 includes a battery cell pack 21 and a battery management system (BMS) 22 . The battery cell pack 21 is composed of a plurality of battery cells, and the battery management system 22 is used for monitoring and managing the battery cell pack 21 , wherein the battery management system 22 includes a communication module 221 and a temperature sensing module 222 , a voltage sensing module 223 , and a current sensing module 224 . The communication module 221 is correspondingly connected with the communication unit 13 of the charging device 10; the temperature sensing module 222, the voltage sensing module 223 and the current sensing module 224 respectively detect the temperature of the battery cell pack , voltage and current.

In the present invention, after the lithium battery pack 20 is connected to the charging device 10 , the charging circuit A and the communication circuit B are established between the two, and the battery management system 22 senses the battery cell pack 21 according to the sensing In the test state, a charging command is output to the charging device 10, and the charging device 10 is required to output a charging power source according to the charging command. The detailed method flow is shown in FIG. 2 and includes the following steps S21-S25.

S21: Connect the lithium battery pack 20 and the charging device 10, wherein the charging circuit A between the lithium battery pack 20 and the charging device 10 can be connected through a wire (such as a charging cable), or contact each other with conductive contacts In order to transmit power, the communication circuit B can be wired connection or wireless connection, as long as both parties can transmit data.

S22: The battery management system 22 receives the state of the battery cell pack 21, and determines a charging command according to the state, wherein the state of the battery cell pack 21 may include its temperature and state of charge (SOC), The calculation of the battery power can be obtained according to the current and voltage of the battery cell group 21 , since the calculation method is not a feature of this case, and will not be repeated here. The generation method of the charging command is determined by looking up the charging command curve built into the table of the battery management system 22 . Please refer to FIGS. 3A to 3F , wherein the horizontal axis of each figure represents the battery cell group 21 The percentage of battery power (SOC) of the battery, the vertical axis represents the amount of charging current to be output, expressed in the unit of charge-discharge rate (C-rate), the charge-discharge rate is related to the rated capacity of the battery, for example, for a 100Ah If the battery is charged at 1C, it means that the battery is charged with a current of 100A, and 0.5C means that the battery is charged with a current of 50A.

3A represents the corresponding charging commands when the temperature of the battery cell group 21 is at three temperature values of -5°C, 0°C, and 55°C. The charging command curves of these three temperatures are the same, that is, the current of the charging power source is all 0. The charging device 10 will not output charging current to the lithium battery pack 20 regardless of the amount of battery power. If the battery management system 22 determines that the current temperature of the battery cell pack 21 is greater than or equal to 0°C and less than 5°C (ie, 0°C≦t<5°C ), the charging current will not be output to the lithium battery pack 20 either.

Taking FIG. 3B as an example again, if the battery management system 22 determines that the current temperature of the battery cell pack 21 is greater than or equal to 5°C and less than 10°C (ie, 5°C≦t<10°C), the curve in FIG. 3B will be selected to refer to the current temperature. The battery capacity of the battery determines the charging current. For example, when the current battery capacity of the battery pack 21 is 40%, a charging command with a charging current of 0.4C (ie, C-rate is 40%) will be output; if the temperature of the battery pack 21 is still If maintained in the same range (ie, 5°C≦t < 10°C), but the battery power has increased to 70%, the charging command will be changed to require the charging device 10 to output a charging current of 0.2C (ie, C-rate is 20%).

Similarly, the curve in Figure 3C is the charging command used when the temperature is between 10°C ≦ t < 15°C; the curve in Figure 3D is the charging command when the temperature is between 15°C ≦ t < 40°C; The curve is the charging command when the temperature is between 15℃≦t < 40℃; the curve in Figure 3E is the charging command when the temperature is between 40℃≦t < 50℃; and the curve in Figure 3F is the charging command when the temperature is between The charging command used when 50°C ≦ t < 55°C, where the curves of Figure 3F and Figure 3E are consistent.

During the charging process of the battery cell pack 21, the battery management system 22 will judge the temperature of the battery cell pack 21 at any time and select a corresponding charging command curve. The temperature endpoint values shown in FIGS. Description of the preferred embodiment; the temperature endpoint value can be increased or decreased according to the actual situation. In the present invention, 0°C is used as the lower limit of low temperature. When the temperature of the battery cell group 21 is lower than or equal to 0°C, the charging current is controlled to be 0, which can avoid the damage of the battery cell material due to the high current received by the battery cell in the low temperature environment. The problem. On the other hand, in the present invention, 55° C. is used as the upper limit of high temperature. When the temperature of the battery cell group 21 is higher than or equal to 55° C., the charging current is controlled to be 0, which can prevent the battery cells from overheating due to the increase in capacity in a high-temperature environment. charging situation.

S23: The battery management system 22 sends the charging command to the charging device 10 through the communication circuit B, wherein after the charging device 10 receives the charging command, it outputs charging power to the battery cell pack 21 according to the charging command.

S24: The battery management system 22 judges whether the power of the battery cell group 21 is fully charged, if not, the process returns to step S22; if yes, the next step S25 is performed.

S25 : The battery management system 22 sends a charging end command to the charging device 10 through the communication circuit B. After the charging device 10 receives the end charging command, it stops outputting the charging current.

Please refer to FIG. 4 , which is another embodiment of the method of the present invention. The difference from the embodiment in FIG. 2 is that after step S21, a device confirmation process is further performed, and the device confirmation process includes the following steps:

S41: The battery management system 22 sends a connection request to the charging device 10, wherein the connection request is used to request the charging device 10 to return a device identification code thereof.

S42: The battery management system 22 determines whether the device identification code is valid. If the received device identification code is valid, proceed to the next step S22; if it is invalid or the device identification code is not received, the charging operation is ended. Among them, the battery management system 22 can distinguish different types of charging devices according to the device identification code, such as one of an energy station, a charging pile, a charging stand or a car charger; if the device identification code returned cannot be identified If it is in the format, it is judged that the charging device 10 is invalid and the charging operation is stopped.

Please refer to FIG. 5 , which is another embodiment of the method of the present invention. The difference from the embodiment in FIG. 2 is that before step S22, a pre-charging process is further included, and the pre-charging process includes the following steps:

S51 : The battery management system 22 sends a precharge command to the charging device 10 to request the charging device 10 to output a precharge current for a preset time, wherein the precharge current is lower than the normal charging current, such as the The pre-charging current is only 1A, and the preset time is only enough for the battery management system 22 to determine whether the two parties are working normally, for example, 30 seconds.

S52: During the pre-charging process, the battery management system 22 determines whether the communication, line connection, status of the two parties, etc. between the charging device 10 and the lithium battery pack 20 are normally connected; if the two parties are normally connected, proceed to the next step S22; If there is an abnormality, stop charging. The purpose of pre-charging with a small current in the present invention is to ensure that both the charging device 10 and the lithium battery pack 20 can operate normally, so as to avoid damage to the lithium battery pack 20 by directly outputting a large current if one of them is abnormal.

In another embodiment of the method of the present invention, the embodiment of FIG. 4 and FIG. 5 can also be combined to perform the pre-charging process after the confirmation device process is performed first.

In the foregoing embodiments, the battery management system 22 will monitor the status of the battery cell pack 21 at any time. When it is found that the battery cell pack 21 suddenly has an abnormal state or needs to perform maintenance operations, the battery management system 22 will send a zero current. The charging command is given to the charging device 10, so that the charging device 10 suspends charging; after the battery state is restored or the maintenance operation is completed, the original charging operation is resumed. The maintenance operation may be that the voltages of the battery cells in the battery cell group 21 are unbalanced, and the battery management system 22 manages the voltage difference balance of the battery cell group 21 .

When the output voltage of the charging device 10 cannot satisfy the charging command, the charging device 10 will enter a certain voltage mode (CV mode), and the current output by the charging device 10 will be less than the current required by the charging command. If there is no forced charging device 10 Stop, it will cause the charging work to not end. Therefore, if the battery management system 22 determines that the charging device 10 has entered the constant voltage mode, the battery management system 22 will issue an end charging command to the charging device 10 to terminate the operation of the charging device 10 and avoid inefficient charging operations.

When charging a lithium battery pack 20 according to the method of the present invention, the waveform changes of voltage, current and battery power (SOC) of the lithium battery pack 20 can be measured as shown in FIG. 6A , FIG. 6B and FIG. 6C , respectively. The charging device 10 can output a maximum constant current of 17A. The lithium battery pack 20 starts charging when the battery power is 4%. During the charging process, the battery management system 22 changes the charging command according to the charging command curve in FIGS. 3A to 3F. and sent to the charging device 10, so the waveform of the current change can be seen in FIG. 6B. When the last fully charged battery is 100%, the battery voltage is 57.4V.

The present invention utilizes the battery management system (BMS) in the lithium battery pack to control the charging operation. After judging the state of the battery pack, it sends a charging command to the charging device, so that the battery pack receives an appropriate charging current and is gradually charged. It can play a protective mechanism to stop charging in the state of too low temperature or too high temperature, and prolong the battery life.

10: Charging device 11: Control unit 12: Charging circuit 13: Communication unit 20: Lithium battery pack 21: Battery cell pack 22: Battery Management System 221: Communication module 222: Temperature sensing module 223: Voltage sensing module 224: Current Sensing Module 300: Charging device 310: Lithium battery pack A: Charging circuit B: Communication loop

Fig. 1: The circuit block diagram of the charging system of the lithium battery of the present invention. FIG. 2 is a flow chart of the first embodiment of the charging method of the lithium battery of the present invention. FIG. 3A : the charging command curve diagram of the present invention at -5°C, 0°C, and 55°C. 3B : a charging command curve diagram of the present invention when the battery temperature is between 5°C≦t<10°C. 3C : a charging command curve diagram of the present invention when the battery temperature is between 10°C≦t<15°C. FIG. 3D : the charging command curve diagram of the present invention when the battery temperature is between 15°C≦t＜40°C. FIG. 3E : the charging command curve diagram of the present invention when the battery temperature is between 40°C≦t＜50°C. FIG. 3F : a charging command curve diagram of the present invention when the battery temperature is between 50°C≦t＜55°C. FIG. 4 is a flow chart of the second embodiment of the charging method of the lithium battery of the present invention. FIG. 5 is a flow chart of the third embodiment of the charging method of the lithium battery of the present invention. FIG. 6A is a waveform diagram of the voltage change measured by charging the lithium battery pack using the method of the present invention. FIG. 6B is a waveform diagram of current change measured by charging a lithium battery pack using the method of the present invention. FIG. 6C is a waveform diagram of the battery power (SOC) change in the actual measurement of the charging of the lithium battery pack using the method of the present invention. Figure 7: Block diagram of a conventional lithium battery charging system.

10: Charging device

11: Control unit

12: Charging circuit

13: Communication unit

20: Lithium battery pack

21: Battery cell pack

22: Battery Management System

221: Communication module

222: Temperature sensing module

223: Voltage sensing module

224: Current Sensing Module

A: Charging circuit

B: Communication loop

Claims (19)

A charging system for lithium batteries, comprising a charging device, comprising: a control unit; a charging circuit connected to the control unit for outputting a charging power source; a communication unit connected to the control unit; a lithium battery pack connected to the control unit The charging device is connected to form a charging circuit, and the lithium battery pack receives the charging power through the charging circuit, wherein the lithium battery pack includes: a battery cell pack, including a plurality of battery cells; a battery management system, including a a communication module, the communication module is connected with the communication unit to form a communication loop; wherein, the battery management system receives the state of the battery cell group, and generates a charging command after judgment, which is sent to the charging device through the communication loop The charging command makes the charging device output the corresponding size of the charging power source according to the charging command, and charges the lithium battery pack through the charging circuit; when the lithium battery pack is connected to the charging device, the battery management system outputs A connection request is sent to the charging device, and the charging device is required to return a device identification code. The charging system for lithium batteries according to claim 1, wherein the battery management system further comprises: a temperature sensing module for sensing the temperature of the battery cell group; a voltage sensing module for sensing measuring the voltage of the battery cell group; a current sensing module for sensing the current of the battery cell group. The charging system for a lithium battery according to claim 2, wherein when the battery management system determines that the temperature of the battery cell group is lower than or equal to a temperature lower limit value, the battery management system outputs a charging command representing zero current to the battery The charging device stops the charging of the charging device. The charging system for lithium batteries according to claim 2, wherein when the battery management system determines that the temperature of the battery cell group is higher than or equal to a temperature upper limit, the battery management system outputs a charging command representing zero current to the battery The charging device stops the charging of the charging device. The charging system for a lithium battery according to claim 2, wherein the battery management system adjusts the charging command to change the size of the charging power source according to the current temperature of the battery cell pack and the battery level (SOC). The charging system for a lithium battery according to claim 5, wherein a plurality of sets of charging command curves corresponding to different temperature ranges are preset in the battery management system, and the battery management system finds out a table according to the current temperature of the battery cell group. The corresponding charging command curve is determined, and the charging command to be output is determined from the corresponding charging command curve according to the current battery power of the battery cell group. The charging system for a lithium battery as claimed in claim 1, wherein after the lithium battery pack is connected to the charging device, the battery management system outputs a pre-charging command to the charging device. The charging system for a lithium battery according to claim 1, wherein when the battery management system determines that the lithium battery pack is currently in an abnormal state or needs to be maintained, the battery management system sends a charging command representing zero current to the battery The charging device makes the charging device suspend charging. The charging system for lithium batteries according to claim 1, wherein when the battery management system determines that the charging device has entered a certain voltage mode, the battery management system sends an end charging command to the charging device to stop the charging device Charge. A charging method for a lithium battery, which is suitable for a connected charging device and a lithium battery pack, wherein the lithium battery pack has a battery cell pack and a battery management system, and the charging method for the lithium battery comprises: S1: connecting The lithium battery pack and the charging device form a charging loop and a communication loop between the lithium battery pack and the charging device. The battery management system sends a connection request to the charging device, requesting the charging device to return a device identification code; S2: The battery management system receives the state of the battery cell pack, and determines a charging command according to the state of the battery cell pack; S3: The battery management system sends the charging command to the charging device through the communication loop, wherein the charging The device outputs a charging power source to the battery pack according to the charging command; S4: The battery management system judges whether the power of the battery pack is fully charged, if not, repeats the step S2; S5: If the battery management system judges The battery cell group is fully charged, and the battery management system sends an end charging command to the charging device through the communication loop. The charging method for a lithium battery according to claim 10, wherein after the step S1, a device confirmation process is further executed, and the device confirmation process includes: the battery management system determines whether the device identification code is valid, and if it determines whether the device identification code is valid If the device identification code is valid, proceed to step S2; if it is determined that the device identification code is invalid or the device identification code is not received, the charging is ended. The charging method for a lithium battery according to claim 10, wherein, before the step S2, a pre-charging process is further performed, and the pre-charging process includes: the battery management system sends a pre-charging command to the charging device, requesting The charging device outputs a pre-charging current for a preset time; the battery management system determines whether the charging device and the lithium battery pack are normally connected, if so, proceed to step S2; if not, end charging. The charging method for a lithium battery according to claim 10, wherein after the step S1 and before the step S2, a device confirmation process and a pre-charging process are sequentially performed, wherein the device confirmation process includes: the battery The management system sends a connection request to the charging device, requesting the charging device to return a device identification code; The battery management system determines whether the device identification code is valid, and if the device identification code is determined to be valid, the pre-charging process is continued; if the device identification code is determined to be invalid or the device identification code is not received, the charging is ended; The charging process includes: the battery management system sends a pre-charging command to the charging device, requesting the charging device to output a pre-charging current for a preset time; the battery management system determines whether there is a connection between the charging device and the lithium battery pack If the connection is normal, if yes, proceed to step S2; if no, end the charging. The charging method for a lithium battery according to claim 10, wherein when the battery management system determines that the temperature of the battery cell group is lower than or equal to a lower temperature limit, the battery management system outputs a charging command representing zero current to the battery The charging device stops charging the charging device. The charging method for a lithium battery according to claim 10, wherein when the battery management system determines that the temperature of the battery cell group is higher than or equal to a temperature upper limit value, the battery management system outputs a charging command representing zero current to the battery management system. The charging device stops charging the charging device. The charging method for a lithium battery according to claim 10, wherein the battery management system adjusts the charging command to change the size of the charging power source according to the current temperature of the battery cell pack and the battery level (SOC). The charging method for a lithium battery as claimed in claim 16, wherein a plurality of sets of charging command curves corresponding to different temperature ranges are preset in the battery management system, and the battery management system finds out a table according to the current temperature of the battery cell group. The corresponding charging command curve is determined, and the charging command to be output is determined from the corresponding charging command curve according to the current battery power of the battery cell group. The charging method for a lithium battery as claimed in claim 10, wherein when the battery management system determines that the lithium battery pack is currently in an abnormal state or needs to be maintained, the battery management system sends a charging command representing zero current to the battery The charging device makes the charging device suspend charging. The charging method for a lithium battery as claimed in claim 10, wherein when the battery management system determines that the charging device has entered a certain voltage mode, the battery management system sends an end charging command to the charging device to stop the charging device Charge.

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