CN101867204B - A battery energy management device and method for an electric vehicle - Google Patents

Abstract

The invention discloses an energy management method for a lithium power battery of an electric vehicle, and provides an electric vehicle lithium battery mounted on a vehicle that can monitor the lithium power battery in real time and can properly control the charging and discharging requirements of the lithium power battery. Power battery energy management system. In the present invention, each integrated lithium power battery is controlled by a dedicated control chip, and the charging process adopts a four-stage method of trickle pre-charging, fast constant current charging, constant voltage charging and pulse supplementary charging. The discharge process adopts balanced discharge control, which is conducive to the stability of the output voltage and makes the electric vehicle run smoothly. The dedicated control chip has a unique address code, and the microprocessor of the system can read and write information on the dedicated chip. According to the collected battery voltage, charge and discharge current, and the voltage change of the energy transmission control module of the temperature information control system, the balance of the charge and discharge process of each group of lithium power batteries is achieved.

Description

A battery energy management device and method for an electric vehicle

technical field

The invention belongs to the field of energy management of electric vehicles, and in particular relates to a management and control method for the charging and discharging process of a lithium power battery pack used in electric vehicles.

Background technique

With the soaring price of international crude oil, the research of various new energy sources has become the focus of public attention. There has been an upsurge in the development of various electric vehicles in China. Lithium power battery has high specific energy density and specific power, which greatly reduces the weight of the on-board battery pack, has no memory effect, can be recharged many times, and has a long service life. It has become the first choice for power electric energy. Batteries are still the bottleneck in the commercialization of electric vehicles. In order to use the battery safely and efficiently, it is very important to develop a battery energy management system that is used in conjunction with the battery.

As a new type of power technology, lithium power batteries must be connected in series to meet the voltage requirements. However, due to the obvious nonlinearity, inconsistency and time-varying nature of lithium batteries, certain management is required during application. In addition, lithium batteries have high requirements for charging and discharging. When overcharging, overdischarging, excessive discharge current or short circuit occur, the temperature of lithium batteries will rise, which will seriously damage the performance of lithium batteries and shorten the battery life. When lithium batteries are used in power equipment in series, due to the inconsistency of the internal characteristics of each single lithium battery, the charging and discharging of each single lithium battery will be inconsistent. When the performance of a single cell deteriorates, the behavior of the entire battery pack will be limited by this cell, reducing the overall performance of the battery pack. In order to maximize the superior performance of the lithium battery pack and prolong its service life, it is necessary to monitor the lithium battery in real time during charging and discharging, provide overvoltage/overcurrent/temperature protection and energy balance between batteries.

Contents of the invention

The technical problem to be solved by the present invention is to provide an electric vehicle lithium power battery energy management system installed on the vehicle that can monitor the lithium power battery in real time and can properly control the lithium power battery according to the charging and discharging requirements of the lithium power battery.

A battery energy management device for an electric vehicle, which includes an electric vehicle power supply system, the electric vehicle power supply system is connected to an interface circuit through a data bus, the interface circuit is sequentially connected to a microcontroller and a communication module, and the microcontroller It is also connected with the display module and the alarm module respectively.

The electric vehicle power supply system includes a plurality of battery packs connected in parallel, and each battery pack includes a plurality of integrated lithium power battery systems connected in series.

The integrated lithium power battery system includes a single-cell lithium power battery and a battery control detection device, wherein the battery control detection device includes a control chip, and the control chip, a drive circuit, a charge and discharge control circuit, and a single-cell lithium power battery are sequentially connected; the control chip is also connected to the single cell lithium power battery through the detection module.

The detection module includes current detection, temperature detection and voltage detection, which are respectively connected with the control chip and the single cell lithium power battery.

A battery energy management method for an electric vehicle, the management method is as follows:

Step1: Initialize the electric vehicle power system and communication module, display module, interface module and alarm module;

Step2: Determine whether the power supply system has an external power supply. If there is an external power supply, it means that the system is charging, and enter step3 to continue execution; otherwise, it means that the system is discharging, and enter step4 to continue execution;

Step3: Detect the voltage and current signals of each single-cell lithium power battery. According to the detected voltage and current signals, the microcontroller controls the input voltage and current signals of each energy transmission module;

Step4: Detect the voltage and current signals of each single cell lithium power battery, and according to the detected voltage and current signals, the microcontroller controls the output voltage and current signals of each energy transmission module;

Step5: The microcontroller judges whether the charging/discharging is complete according to the input/output voltage and current signals;

Step6: If it is charging, the microcontroller will judge whether all the single-cell lithium batteries are fully charged. If it is full, it will turn off the lithium-powered battery pack and the alarm prompt. Otherwise, it will return to step 3 to continue execution; Whether the power battery is fully discharged, if the discharge is complete, turn off the lithium power battery pack and the alarm prompt, otherwise enter step4 and continue to execute.

The charging and discharging control method of each single-cell lithium power battery is as follows:

Step1: The control chip detects the voltage, current and temperature signals of the lithium power battery;

Step2: The control chip communicates with the microcontroller to obtain the voltage and current signals that control the single-cell lithium power battery;

Step3: According to the obtained voltage and current signals, the control chip judges whether the lithium power battery is in a charging state;

Step4: If it is in the charging state, judge whether it is in the trickle pre-charging state. If it is in the trickle pre-charging state, perform trickle pre-charging for a certain period of time and return to step1; if it is not in the trickle pre-charging state, judge whether it is in the constant-current charging state , if yes, perform constant current charging for a certain period of time and return to step1; if it is not in the constant current charging state, then judge whether it is in the constant voltage charging state; if so, perform constant voltage charging for a certain period of time and return to step1; It is the state of pulse supplementary charging, if so, return to step1 after pulse supplementary charging for a certain period of time, otherwise end the charging process of this single cell battery;

Step5: If it is not in the charging state, judge whether it is in the forced discharge state, if not, return to step1; if it is, judge whether the voltage exceeds the limit value, if it does not exceed the set limit value, discharge for a certain period of time and return to step1; if it exceeds the set limit value value, stop discharging and end the discharge process of this single cell. the

The electric vehicle power management management system of the present invention has the following advantages:

1. The battery monitoring and control circuit can monitor the voltage, temperature, charging current, discharging current and other parameters of the battery and battery pack in real time, and properly control the charging and discharging circuit to prevent overcharging and overdischarging and ensure the safety of the battery. Effectively improve battery life.

2. The charging and discharging circuit adopts the independent charging method of single cells, precisely controls the charging and discharging process of single cells, and prevents the inconsistency of the internal characteristics of each single cell lithium power battery after multiple charging and discharging, resulting in inconsistent charging and discharging of each lithium power battery. When the performance of a single cell deteriorates, the behavior of the entire battery pack will be limited by this cell, reducing overall battery pack performance.

3. Each dedicated control chip integrated with a lithium power battery has a unique address code, and the microprocessor can read and write information on it to collect information and control the drive circuit.

4. For each lithium power battery, the battery charge and discharge control circuit can be used to isolate it to prevent its current from being too large, overcharged or overdischarged during charging and discharging. When it is isolated, the voltage of this group of batteries will inevitably be inconsistent with the voltage of other battery groups. . The control command can be issued by the microprocessor, and according to the detected voltage and temperature signals in each group, the corresponding number of poor lithium power batteries in other groups are actively isolated, so that the terminal voltage of the lithium power battery pack is kept the same, and no Circulation consumes energy.

5. When one or k batteries are isolated, the back-end voltage will decrease, and the impact on the battery pack will be small during the discharge process, but the charging voltage needs to be reduced during charging to prevent irreversible damage to the lithium battery caused by excessive charging current . The energy transmission control module can be controlled according to the detected signal, and variable voltage/current control can be performed.

6. The battery monitoring/control circuit has a communication function, which can transmit the battery status parameters to the main control ECU in time, and display the corresponding power, current, voltage and temperature information on the display panel. When the charging or discharging is completed, an alarm can be given to charge or disconnect the power supply in time. The internal storage unit can store the state information of each lithium power battery for maintenance of the battery.

Description of drawings

Fig. 1 is the schematic diagram of the principle of the lithium power battery energy management system of the electric vehicle of the present invention;

Figure 2 Schematic diagram of a single-cell lithium power battery system;

Figure 3 The timing diagram of conventional charging method for lithium power battery;

Figure 4 Lithium battery control system charging sequence diagram;

Figure 5. Discharge characteristic curves of lithium power batteries under different discharge currents

Fig. 6 Flow chart of the control program of the micro-controller of the electric vehicle power supply control system;

Figure 7 The control flow chart of a single cell lithium power battery;

Among them, 1. Lithium power battery control and detection device, 2. Single cell lithium power battery, 3. Energy transmission control module, 4. Data bus, 5. Interface circuit, 6. Display module, 7. Microcontroller, 8. Communication Module, 9. Alarm module, 10. Energy transmission line, 11. Control chip, 12. Current detection circuit, 13. Temperature detection circuit, 14. Voltage detection circuit, 15. Drive circuit, 16. Charge and discharge control circuit.

Detailed ways

Below in conjunction with accompanying drawing and example the present invention is described in further detail:

As shown in Figure 1, the electric vehicle power source management system of the present invention includes: a lithium power battery control detection device 1, a single cell lithium power battery 2, an interface circuit 5, a microcontroller 7, a display module 6, an alarm module 9 and a communication module 8, etc. .

Among them, the lithium power battery control and detection device 1 can monitor parameters such as the voltage, charge and discharge current, and temperature of the single cell lithium power battery 2 in real time, and input the signal to the microcontroller 7 through the data bus 4 and the interface circuit 5, and the microcontroller 7 Controlling the energy transmission control module 3 to adjust the voltage and current transmitted through the energy transmission line 10 .

N integrated lithium power battery systems are connected in series to form a group of batteries. The number of batteries connected in series is selected according to the voltage of the system. M battery groups are connected in parallel to form an M×N electric vehicle power system. Each integrated lithium power battery system is connected through the data bus. 4 and the interface circuit 5 input information to the microcontroller 7 of the electric vehicle power supply control system.

Lithium power battery control detection device 1 and single cell lithium power battery 2 form an integrated lithium power battery system. The principle block diagram of the system is shown in Figure 2. The detection circuit 14, the driving circuit 15, the charging and discharging control circuit 16 and the single-cell lithium power battery 2 are composed, and it can be connected with the microcontroller 7 of the power control system through the data bus 4 and the interface circuit 5. Among them, the dedicated control chip can be DS2784 or DS2786 of Maxim Company or AN1260 of Microchip Company. The dedicated control chip integrates voltage detection and temperature detection circuits, and only needs to add a shunt for current detection.

The current detection circuit 12 detects the charging and discharging current of the battery and provides a signal to the dedicated control chip 11 .

The temperature detecting circuit 13 detects the temperature of the battery, automatically stops charging when the temperature is too high during the charging process, and limits the magnitude of the current when the temperature is too high during the discharging process.

The voltage detection circuit 14 detects the voltage of the battery, and according to the voltage of the lithium power battery, it is determined that the charging phases are the pre-charge state, constant current charging and constant voltage charging phases.

The charging and discharging control circuit 16 is driven by the driving circuit 15 to complete the bidirectional transmission control of electric energy. the

The status information of the lithium battery collected by the dedicated control chip 11 is transmitted to the microcontroller 7 of the power control system through the bus and the interface circuit 5 for processing, controls the charging and discharging process of the entire battery pack, and displays the information during the entire process.

Since the dedicated control chip 11 is monitored in real time during the charging and discharging process of the lithium power battery, it also has the following functions:

1. Battery Capacity Prediction

According to the monitoring of battery capacity, the remaining capacity of a single battery can be obtained in real time and sent to the microcontroller for display. According to the recorded data, the combination of batteries can be adjusted. During the charging process of the battery, each single battery can be recorded and displayed. The charging time and discharging time of the battery pack can be optimized to prevent the overall characteristics of the battery pack from rapidly deteriorating and the accelerated damage of some batteries due to the inconsistent characteristics of the individual cells used in the same pack or the inconsistent initial state when combined and packaged. For this reason, when multiple batteries are used in series and parallel, they must be effectively matched. Make the battery pack play the best efficiency, and at the same time, it can also display the reminder that the bottom of the capacity needs to be charged;

2. Battery self-test function

Through data parameters such as voltage, current, temperature, etc., it can analyze whether the battery is working normally, and can automatically perform system self-inspection. If there is a fault, it will send a fault signal to the microcontroller and cut off the power switch.

3. Fault warning

During the use of the battery, record the battery use parameters at any time to judge the effectiveness of the battery. If any battery in the system is found to be invalid or will fail or the inconsistency with other batteries increases, it will be transmitted to the microcontroller through the bus and displayed. Fault.

4. External circuit fault protection

When a serious failure or failure occurs in the external circuit, the system can generate safety protection so that the battery will not be over-discharged, over-charged, short-circuited, etc.

According to the requirements of the charging process of the lithium power battery pack, the conventional charging method is carried out in three stages: pre-charging, constant current charging, and constant voltage charging, as shown in Figure 3. The figure only qualitatively describes the change curve of charging current and voltage of lithium power battery with the charging process in the conventional charging method. The solid line represents the current change curve during the charging process; the dotted line represents the terminal voltage change curve during the charging process.

In order to improve the charging speed of the lithium power battery, and avoid overcharging and overheating during the charging process, causing the active material of the plate to fall off and damage, the lithium power battery in the present invention adopts a four-stage charging method: trickle pre-charging, fast constant current charging , constant voltage charging, and pulse supplementary electricity, as shown in Figure 4. The shaded part in the figure represents the change of charging energy; the solid line represents the change curve of the charging voltage during the charging process; the dotted line represents the change curve of the charging current during the charging process. In the figure, it is only a qualitative expression of the voltage and current variation trend of the lithium power battery with the charging time in different charging stages.

1. trickle precharge phase

If the lithium power battery is already in a state of deep discharge at the initial stage of charging, in order to avoid excessive charging current to the battery and cause thermal runaway, the microprocessor monitors the voltage of the battery and implements a stable low-current trickle charge to the battery. In the trickle charging stage, the battery voltage begins to rise, and when the battery voltage rises to the threshold that can accept high current charging, it will enter the fast charging stage.

2. Fast constant current charge phase

This stage is high-current constant-current charging. The charging current varies depending on the battery capacity, generally 0.1C (C is the capacity of the battery pack). When the voltage rises to the constant-voltage threshold, it will enter the constant-voltage stage.

3. Constant voltage charging

This stage is constant voltage charging, and the voltage value depends on the number of battery cells and the temperature of the battery. At this time, the charging current gradually decreases, and when the current drops to a certain threshold, it will automatically switch to pulse supplementary charging.

4. Pulse supplementary electricity

This stage is mainly used to replenish the energy consumed by the self-discharge of the battery. When the charging voltage reaches the set maximum value, it marks the end of the charging process.

Comparing the two charging methods, it can be seen that the method used in the present invention is more in line with the charging process principle of the lithium power battery to achieve fast and safe charging, which can better protect the lithium battery, bring into play the superior performance of the lithium power battery, and prolong the service life.

The discharge process of lithium power battery is a complex electrochemical change process. The discharge process is affected by various factors such as battery temperature, discharge rate, self-discharge, charge-discharge cycle times, etc., making it very difficult to control the discharge process.

Figure 5 is the discharge characteristic curve of the lithium power battery under different discharge currents. The characteristics of this curve are:

(1) The lithium power battery has a good load capacity and can safely provide a maximum discharge current of 3C.

(2) Different discharge currents have different effects on voltage and power, and the effective power that can be output also varies greatly.

(3) Discharge to about 3V, the battery power has basically been output.

According to the discharge characteristics, appropriate discharge management and protection technologies will be adopted in this design to manage the discharge process.

Figure 6 shows the control program flow chart of the microcontroller of the electric vehicle power supply control system. The control steps of the microcontroller of the power supply control system are as follows:

Step1: Carry out initialization, complete the initialization of the microcontroller 7 of the power supply control system, carry out the initialization of the communication module 8, the display module 6, the interface module 5, and the alarm module 9, and detect the status of each system;

Step2: Collect the voltage, current, and temperature signals of each single cell lithium power battery 2, display the current state of the battery, and set the direction of the voltage and current of each group of energy transmission control modules 3 during charging (or discharging) according to the collected information;

Step3: Carry out charging state or discharging state;

If it is charging, the microcontroller will judge whether all the single-cell lithium power batteries are full. If it is full, the lithium power battery pack and the alarm prompt will be turned off. Otherwise, it will return to step 2 to continue execution; if it is discharging, the microcontroller will judge all the single-cell lithium power batteries. Whether the discharge is complete, if the discharge is complete, turn off the lithium power battery pack and the alarm prompt, otherwise enter step2 to continue execution.

The special control chip program flow chart 7 of the lithium power battery control and detection device realizes the control of the charge and discharge process of each single cell lithium power battery 2 .

Step1: Power-on initialization, communication setting with the microcontroller of the system, receiving the control signal sent by the microcontroller, and initializing the control and detection device 1 of each lithium battery;

Step2: Detect the voltage, current, temperature, etc. of the lithium power battery and transmit it to the lithium power battery control and detection device 1. According to the state setting of the lithium power battery control and detection device 1 through the interface circuit 5 of the microcontroller 7 of the electric vehicle power supply control system, Judgment is charging and discharging;

Step3: If it is in the charging state, judge whether it is in the trickle pre-charging state. If it is in the trickle pre-charging state, perform trickle pre-charging for a certain period of time, such as 5 seconds, and then return to step2; if it is not in the trickle pre-charging state, judge whether it is in the constant state. Current charging state, if it is, carry out constant current charging for a certain period of time, such as 10 seconds, and then return to step2; if it is not in constant current charging state, judge whether it is in constant voltage charging state, if so, perform constant voltage charging for a certain period of time, such as 5 seconds, and then return to step2; If it is not in the constant voltage charging state, then judge whether it is in the state of pulse supplementary charging, if so, return to step2 after the pulse supplementary charging is completed for a certain period of time, such as 3 seconds, otherwise end the charging process of this single cell battery;

Step4: If it is not in the charging state, judge whether it is in the forced discharge state, if not, return to step2; if it is, judge whether the voltage exceeds the limit value, if it does not exceed the set limit value, discharge for a certain period of time, such as 10 seconds, and then return to step2; If the set threshold is exceeded, the discharge will be stopped and the discharge process of this cell will end. the

Four different charging processes are controlled according to the detected voltage, current and temperature during charging;

During discharge, the discharge process is controlled according to the detected voltage, current, and temperature to protect the battery and prevent over-discharge or short-circuit faults.

The above-mentioned examples are only preferred solutions embodying the technical solutions of the present invention, and some changes that may be made by those skilled in the art to some parts thereof reflect the principles of the present invention and fall within the protection scope of the present invention.

Claims (3)

1. A battery energy management device for an electric vehicle, characterized in that: it includes an electric vehicle power supply system, the electric vehicle power supply system is connected with an interface circuit through a data bus, and the interface circuit is connected with a microcontroller and a communication module in sequence , the microcontroller is also connected to the display module and the alarm module respectively; the electric vehicle power system includes a plurality of parallel battery packs, each battery pack includes a plurality of integrated lithium power battery systems in series; the integrated lithium power The battery system includes a single-cell lithium power battery and a battery control detection device, wherein the battery control detection device includes a control chip, and the control chip, a drive circuit, a charging and discharging control circuit and a single-cell lithium power battery are connected in sequence; the control The chip is also connected to the single-cell lithium power battery through the detection module; The battery energy management method using the battery energy management device is as follows: Step1: Initialize the electric vehicle power system and communication module, display module, interface module and alarm module; Step2: Determine whether the power supply system has an external power supply. If there is an external power supply, it means that the system is charging, and enter step3 to continue execution; otherwise, it means that the system is discharging, and enter step4 to continue execution; Step3: Detect the voltage and current signals of each single-cell lithium power battery. According to the detected voltage and current signals, the microcontroller controls the input voltage and current signals of each energy transmission module; Step4: Detect the voltage and current signals of each single cell lithium power battery, and according to the detected voltage and current signals, the microcontroller controls the output voltage and current signals of each energy transmission module; Step5: The microcontroller judges whether the charging/discharging is complete according to the input/output voltage and current signals; Step6: If it is charging, the microcontroller will judge whether all the single-cell lithium batteries are fully charged. If it is full, it will turn off the lithium-powered battery pack and the alarm prompt. Otherwise, it will return to step 3 to continue execution; Whether the power battery is fully discharged, if the discharge is complete, turn off the lithium power battery pack and the alarm prompt, otherwise enter step4 and continue to execute. 2. A battery energy management device for an electric vehicle according to claim 1, wherein the detection module includes current detection, temperature detection and voltage detection, which are respectively connected to the control chip and the single-cell lithium power battery . 3. Adopt the battery energy management method of the battery energy management device of a kind of electric vehicle described in claim 1, it is characterized in that, the charging and discharging control method of each single cell lithium power battery is as follows: Step1: The control chip detects the voltage, current and temperature signals of the lithium power battery; Step2: The control chip communicates with the microcontroller to obtain the voltage and current signals that control the single-cell lithium power battery; Step3: According to the obtained voltage and current signals, the control chip judges whether the lithium power battery is in a charging state; Step4: If it is in the charging state, judge whether it is in the trickle pre-charging state. If it is in the trickle pre-charging state, perform trickle pre-charging for a certain period of time and return to step1; if it is not in the trickle pre-charging state, judge whether it is in the constant-current charging state , if yes, perform constant current charging for a certain period of time and return to step1; if it is not in the constant current charging state, then judge whether it is in the constant voltage charging state; if so, perform constant voltage charging for a certain period of time and return to step1; It is the state of pulse supplementary charging, if so, return to step1 after pulse supplementary charging for a certain period of time, otherwise end the charging process of this single cell battery; Step5: If it is not in the charging state, judge whether it is in the forced discharge state, if not, return to step1; if it is, judge whether the voltage exceeds the limit value, if it does not exceed the set limit value, discharge for a certain period of time and return to step1; if it exceeds the set limit value value, stop discharging and end the discharge process of this single cell.

Images