TWI621318B - Electric vehicle range extension system - Google Patents

Abstract

The invention provides an electric vehicle range extension system, which uses an external balanced battery or a power battery pack of the electric vehicle itself as a balancing power source, and uses a regenerative braking energy recovery mechanism to perform each battery cell unit of the power battery pack. Active balancing to achieve the purpose of increasing the mileage of electric vehicles.

Description

Electric vehicle range extension system

The invention relates to the power management technology of an electric vehicle, in particular to an electric vehicle extended range system.

Nowadays, in response to the trend of energy saving, carbon reduction and environmental protection, electric vehicles, electric buses, electric vehicles and other electric vehicles are becoming more and more common. How to increase the mileage (endurance) of electric vehicles has been the main subject in this technical field. In addition to the lead-acid batteries traditionally used in vehicles, lithium-ion batteries have gradually become the mainstream battery type of choice for vehicles powered by pure electricity due to their advantages of high energy and power density. The power battery selected on the electric vehicle needs to be configured in series as a battery pack. When the lithium-ion battery cells are connected in series, the battery management system needs to balance the voltage between the cells because of the inconsistencies between the cells. When the weakest single cell reaches excessive When discharging voltage, the battery management system (BMS) needs to cut the load (electric vehicle motor) for protection. This action of disconnecting protection will directly reduce the effective endurance of the electric vehicle. However, if the system does not immediately protect the weakest battery cells from overdischarge, it will shorten the life of the overall battery pack.

Although lithium-ion batteries have good performance and high safety, they must still avoid overcharging, over-discharging, or over-temperature conditions. In order to extend the battery life and protect the safety of users, a battery management system must be constructed (Battery Management System, BMS) to ensure that the battery operates within a safe range. Basically, the main function of a battery management system is to measure the voltage of a single cell and protect it. In series battery packs, due to different internal resistances or manufacturing processes, inconsistent battery voltages may occur. Such problems will cause series batteries to overcharge or discharge early because of a certain battery cell, which will greatly affect the battery. Group efficiency and life.

In fact, there is a slight difference in the internal resistance and capacity of each battery cell. This difference will gradually increase with the number of charge and discharge cycles. If there is no management, the difference between the battery cells will be expanded to the battery module and the module. So that the battery modules cannot be in a consistent state. The inconsistency between modules will still cause early overcharge and overdischarge of the battery pack. Therefore, the inconsistency between cells and modules must be corrected through a proper management system to fully utilize the performance of lithium iron batteries. To improve this problem, we must add a balance mechanism, which shows the importance of BMS and balance mechanism.

If the size of the battery pack is increased and applied to large-scale power storage applications such as high-voltage energy storage systems or electric buses, the problems caused by the imbalance between cells or modules can no longer be ignored; taking electric vehicles as an example, the most People are criticized for battery price and service life, and the reason is that if the current battery management technology fails to perform the balance between cells or modules, the weakest battery will trigger the management system protection to stop running early. Reduce the use efficiency, or the system does not immediately protect the weakest battery cells from overcharging / overdischarging, and shorten the life of the overall energy storage device.

The use of renewable energy power (such as solar photovoltaic) to directly perform random (because of weather conditions) supplementary power to reach the extended range of the electric vehicle is theoretically feasible, but not practical in practice, because renewable energy power requires a large area To get the required voltage and power. The large-capacity and high series-parallel number battery pack application environment is very different from the 3C hand-held application, but at present the market for high-series, high-voltage battery pack applications, especially for the balancing strategy between modules But there is no complete management system. This phenomenon will not cause much impact in low-voltage or consumer electronics products, but if the battery pack is enlarged and applied to large-scale power storage applications such as energy storage systems and electric buses, this phenomenon can no longer be ignored. Problems that arise.

In order to solve the shortcomings of the prior art, the present invention provides an electric vehicle range extender system, which uses an external balanced battery or the power battery pack of the electric vehicle itself as a balancing power source, with a regenerative braking energy recovery mechanism, to the power battery. Each battery cell unit of the group is actively balanced to achieve the purpose of increasing the mileage of the electric vehicle.

The invention is an electric vehicle extended range system, which includes: a power battery pack including a plurality of battery cell units connected in series with each other; a battery active balancing module connected to the power battery pack, which includes a drop A voltage converter, a main switching unit, a cell voltage sensing unit, a plurality of cell switching units, and a control unit are used to balance charge the power battery pack; an external balance battery is connected to the battery to actively balance Module, the external balanced battery system Provide external balancing power to the battery active balancing module; and a regenerative braking power generating unit connected to the external balancing battery. The regenerative braking power generating unit converts the vehicle braking energy into electric power and transmits the power to the external balancing battery.

The present invention uses an external balanced battery or the power battery pack itself as the power source, and the switch circuit corresponding to any single battery cell can be used for active balancing of individual single battery cells. The above power supply can use an external power supply or a flyback power electronic converter to isolate and ground the same charging power source and convert the voltage into a single cell charging voltage. Balanced charging of energy. The battery active balancing module of the present invention can perform balancing when the battery pack is charged, discharged, or left to stand, and can achieve the goal of battery pack balancing in a short time.

In one embodiment of the present invention, the battery active balancing module includes: a step-down converter connected to the power battery pack, which has a first side winding and a second side winding inductive to the first side winding; A main switching unit is connected to the power battery pack and the step-down converter; a cell voltage sensing unit is connected to the power battery pack for sensing individual voltages of the cell units; a plurality of cell switches The unit is connected to the battery cell units and is connected to the second side winding of the step-down converter. A control unit is connected to the main switch unit, the battery cell voltage sensing unit and the battery switches. unit.

In one embodiment of the present invention, it further includes a solar power generation module, and the power generated by the solar power generation module is converted by a maximum power converter and then transmitted to the external balanced battery.

In one embodiment of the present invention, the regenerative braking power generation unit includes an in-wheel generator and a braking energy converter. The regenerative braking power generation unit converts the vehicle braking energy (ie, energy generated during braking) into electricity, and Passed to the external balance battery or the power battery pack.

In one embodiment of the present invention, the cell switching unit is a photo relay.

In one embodiment of the present invention, a positive electrode and a negative electrode of each battery cell unit are connected to a battery cell switching unit.

In an embodiment of the electric vehicle range extender system of the present invention, it has a two-stage charging mode; the first stage is a series charging (series charging) stage. When the power battery pack lacks power, the external balance battery will charge the power battery. The battery pack performs a charging action, that is, the charging current I ₁ flows out of the external balanced battery and enters the entire battery pack. The control unit uses the battery cell voltage sensing unit to measure the voltage of each single battery cell unit and detects the minimum voltage. At the same time, the external balanced battery outputs power to the step-down converter. The step-down converter reduces the voltage of the power to 5V, which is regarded as the external balanced power I ₂ . The voltage difference of the voltage cell unit exceeds a balanced set value (for example, 30mV), the control unit will enable the two cell switch units corresponding to the lowest voltage cell unit, and the step-down converter will inject external balanced power the current I ₂ to the lowest among the unit cell voltage, when the current in the unit of the minimum cell voltages of I ₁ + I _2, the current of the other unit cell was I _1, whereby the pull-fast The minimum amount of the battery cell voltage, until it is the same as the average voltage of the battery power. The end condition of the first stage is that after any single cell in the battery pack exceeds a high voltage set value (such as 3.6V), the series charging is cut off. This cut-off condition setting can prevent any single cell in the battery pack from being overcharged. State, resulting in adverse effects on the health, capacity, and internal resistance of the battery cell. In one embodiment of the present invention, after the first stage (string charging stage) is terminated and charged, the power battery pack usually has more than 80% capacity.

In an embodiment of the electric vehicle range extender system of the present invention, when any cell reaches the high voltage set value (3.6V) during the first stage of series charging, it enters the second stage of the charging stage, which is a separate cell. Balanced charging; when entering the split charging stage, the control unit will sort according to the voltage of each battery cell unit, and perform the individual single battery cell balancing in order from low to high. When the battery cell that is balancedly charged reaches a high voltage The set value (such as 3.6V) will perform the balancing work of the next battery cell unit in descending order, until all the battery cell units of the entire battery pack are completely balanced, which is the end of charging. The control unit judges that the battery pack has completed the two-stage charging method according to the information through the battery cell units, that is, a complete two-stage charging is ended.

In an embodiment of the electric vehicle range extender system of the present invention, the discharge current of the entire series of battery cells of the power battery pack during discharge is I ₃ , and the voltage difference between the highest voltage battery cell and the lowest voltage battery cell is higher than Balance the set value, and the voltage of the lowest voltage cell unit is between the initial balance value and the low voltage set value, so trigger the opening of the balance function. The balanced lowest voltage cell unit is additionally injected with current through the balanced power signal. I ₄ , so the discharge current of the lowest voltage cell unit drops to I ₃ -I ₄ . Because the discharge current of the lowest voltage cell unit is less than that of other cell units, the voltage drop rate will also be slowed down a lot. After the pressure difference between the battery cell being balanced and the battery cell with the lowest battery voltage (the lowest voltage other than the battery cell in the balancing) is greater than the cut-off value, the balancing function is turned off and the conditions are re-evaluated to determine whether Continue to balance, in order to achieve the purpose of slowing the early discharge of the battery cell, and achieve the effect of extended range.

The above summary and the following detailed description and drawings are all for further explaining the methods, means and effects adopted by the present invention to achieve the intended purpose. Other objects and advantages of the present invention will be described in the following description and drawings.

A, B, 32‧‧‧ Power battery pack

B0 ~ B15‧‧‧Battery

11, 23‧‧‧ Buck Converter

12‧‧‧ main switch unit

13, 332‧‧‧ cell voltage sensing unit

14, 22, 333‧‧‧ Cell Switch Unit

15,334‧‧‧Control unit

16, 21, 34‧‧‧ External Balanced Battery

S11 ~ S17, S21 ~ S28‧‧‧Process

31‧‧‧Power Motor

33‧‧‧Battery Active Balance Module

331‧‧‧Buck Switch Unit

35‧‧‧In-wheel generator

351‧‧‧ Energy Converter

36‧‧‧Solar Panel

361‧‧‧Max Power Converter

FIG. 1 is a structural diagram of a battery active balancing module used in the present invention.

FIG. 2 is a structural diagram of another embodiment of a battery active balancing module used in the present invention.

3 is a flowchart of an active balancing mechanism of a power battery pack under a charging state according to an embodiment of the present invention.

FIG. 4 is a flowchart of an active balancing mechanism of a power battery pack in a discharged state according to an embodiment of the present invention.

FIG. 5 is a schematic structural diagram of an embodiment of an electric vehicle range extending system according to the present invention.

The following is a description of specific embodiments of the present invention. Those skilled in the art can easily understand the contents disclosed in this specification. Learn about other advantages and effects of the present invention.

In the following, the functions of each part of the electric vehicle range extending system of the present invention will be described one by one. First, please refer to FIG. 1, which is a structural diagram of a battery active balancing module used in the present invention. As shown in the figure, the battery active balancing module is connected to a power battery pack A of the electric vehicle. The power battery pack includes A plurality of cell units connected in series with each other. The battery active balancing module includes: a step-down converter 11 connected to the power battery pack A, which has a first side winding and a second side winding inductive to the first side winding; a main switching unit 12, Is connected to the power battery pack A and the step-down converter 11; a cell voltage sensing unit 13 is connected to the power battery pack A for sensing individual voltages of the battery cell units; a plurality of battery cell switching units 14, which are correspondingly connected to the battery cell units in the power battery pack A and are connected to the second side winding of the step-down converter 11; a control unit 15, which is connected to the main switching unit 12, the battery cell The voltage sensing unit 13 and the cell switching units 14; an external balanced battery 16 is connected between the power battery pack A and the main switching unit 12.

In one embodiment of the present invention, the step-down converter 11 of the battery active balancing module, the main switching unit 12, the cell voltage sensing unit 13, the cell switching units 14 and the control unit 15 are integrated. It is a BMS circuit board.

In one embodiment of the present invention, the main switch unit 12 is capable of switching on and off states. When the state is "on", it is connected between the positive and negative poles of the external balanced battery and the first side winding of the step-down converter. Positive and negative, when the state is "OFF", it is connected to the positive and negative poles of the power battery pack, The positive and negative poles of the first side winding of the converter.

In an embodiment of the present invention, the positive and negative electrodes of each battery cell unit in the power battery pack A are respectively connected to a battery cell switching unit 14, and the battery cell switching units 14 and the step-down converter 11 The anode of the second winding is connected to the anode.

In one embodiment of the present invention, the control unit 15 controls the switching of the main switching unit 12 and the cell switching units 14 according to the individual voltage of each cell unit measured by the cell voltage sensing unit 13. Action to achieve the effect of balancing the voltage of each battery cell.

In one embodiment of the present invention, the external balanced battery may be a commercial power source, a wind power generation system, a solar power generation system, or another type of renewable energy power generation system. The external balanced battery is used as the external balanced power (balanced power source) of the electric vehicle range extension system to balance the uneven power (voltage, power) between the battery cells. In one embodiment of the present invention, The power battery pack itself can also be used as external balanced power.

The electric vehicle range extension system of the present invention is based on an independent external balanced power (external balanced battery) and a switching circuit method (the buck converter, the main switching unit, the cell voltage sensing unit, and the cell switches). Unit and the control unit) to overcome the shortcomings of the existing balanced charging method. The external balanced battery can use an external power supply or a flyback power electronic converter to isolate and ground the same charging power source, and convert the voltage to a single cell charging voltage to directly lower the voltage (or power). ) Cell unit for larger energy Charge evenly. At the same time, the electric vehicle range extension system of the present invention continuously detects the minimum voltage of the battery cell unit, and pulls up its power to be the same as the battery cell of the second lowest voltage. Because the balance current is large, it can reach the balance in a short time. The effect.

The architecture diagram of another embodiment of the active battery balancing module used in the present invention is shown in FIG. 2. This embodiment is used to explain the active battery balancing module used in the present invention and its active balancing circuit channel (ie, balanced charging). Operating principle. In practical application, taking lithium iron phosphate battery as an example, the maximum balancing current used by the electric vehicle range extender system of the present invention can reach 6A, and the pressure difference of the battery cell after balancing does not exceed 30mV. This embodiment uses an external balanced battery 21, or a power battery pack B itself as a balanced power source. The power battery pack B is composed of 16 groups of cells (B0, B1, ..., B14, B15) connected in series, with 32 The group photo relay is used as the cell switching unit 22, that is, the positive and negative electrodes of each cell are connected to a group of cell switching unit 22. When charging, switch the correct cell switching unit to balance individual single cells. The charging process can be divided into the following two stages:

(1) String charging: When the entire battery pack lacks power, the external balanced battery 21 will perform the charging action of the power battery pack B, that is, the external balanced battery 21 will flow out of the I ₁ current into the entire string of power battery packs B for charging. The controller (not shown) performs individual single-cell voltage measurement at this stage and detects the lowest-voltage cell, and at the same time passes the power of the external balanced battery 21 through a step-down converter 23 to reduce the voltage to 5V. As external balanced power; when the voltage difference between the lowest voltage cell and the highest voltage cell exceeds the balance set value (for example 30mV), the microcontroller (control unit) will enable the two voltages corresponding to the lowest voltage cell Core switching unit, step-down converter 23 and note I ₂ current into the lowest voltage cell, at this time the current on the lowest voltage cell is I ₁ + I ₂ , and the current of other cells is I ₁ , This can quickly pull up the lowest voltage battery cell until its voltage is the same as the average voltage of the battery pack 21.

(II) Split charging: When any cell reaches a high voltage set value (such as 3.6V) during the first stage of charging, the individual cells will enter the second stage for balanced charging. When entering the sub-charging stage, the microcontroller will Sort the voltage according to the voltage of each cell, and perform the individual single cell balancing charging in order from low to high. When the voltage of the balanced cell reaches the high voltage set value (3.6V), the next power is performed according to the order. The balancing of the cores is completed until all the cells of the entire power battery pack are completely balanced, and the charging is terminated. In this embodiment, the system may have a main switching unit (not shown) connected to the buck converter. The invention can ensure that even if the power battery pack has a large difference in capacity or internal resistance, all the series cells can be fully charged without overcharging any one cell, and the balance of the discharge can effectively extend the battery use. With the charge and discharge balancing strategy of the present invention, the effect of increasing the mileage of the electric vehicle can be achieved without adding additional hardware.

FIG. 3 is a flowchart of an active balancing mechanism of a power battery pack under a charging state according to an embodiment of the present invention: during the charging phase, continuously measure the voltage S11 of each battery cell unit and monitor whether the voltage of any battery cell unit is greater than High voltage setting value S12. If the voltage of any battery cell unit is higher than the high voltage setting value, it will be sorted according to the voltage level of each battery cell unit. From low voltage to high voltage, each battery cell unit will be balanced to the high voltage setting value S13 ( (Ie the charging stage mentioned above); before any battery cell voltage is higher than the high voltage set value, if there is any minimum The voltage difference between the battery cell unit with the highest voltage and the battery cell unit with the highest voltage exceeds the balance setting value S14. The system first confirms whether the battery unit with the lowest voltage is accepting the balancing work S15. If not, the balanced charging function S16 is turned on (that is, the aforementioned Phase of charging), until the voltage of the lowest voltage cell unit is the same as the average voltage of each cell unit, then balance charging S17 is turned off, and continue to detect whether any of the lowest voltage cell unit and the highest voltage cell unit The pressure difference between them exceeds the equilibrium setting value.

FIG. 4 is a flowchart of an active balancing mechanism of a battery pack under a discharging state according to an embodiment of the present invention: during the discharging phase, the voltage S21 of each cell unit is continuously measured to determine (find) the highest voltage cell unit and the lowest Voltage cell unit S22; determine whether the voltage difference between the highest voltage cell unit and the lowest voltage cell unit is higher than the balance setting value S23; if so, determine whether the voltage of the lowest voltage cell unit is lower than the equilibrium starting value S24 (That is, the system setting must give a balanced voltage starting value); if so, determine whether the voltage of the lowest voltage battery cell unit is lower than the low voltage setting value S25, and lower than the low voltage setting value indicates that the battery cell unit may be degraded , So it is no longer balanced charging; if the voltage of the lowest voltage cell unit is between the initial balance value and the low voltage set value, the balance function (balanced charging function) S26 is turned on, and the lowest voltage cell The unit performs balance charging until the pressure difference between the battery cell unit in the balance and the battery cell unit with the lowest battery voltage (the lowest voltage other than the battery cell unit in the balance) is greater than the balance cut-off value S After 27, the balance function S28 is turned off.

The active balancing mechanism of the electric vehicle range extension system of the present invention can take into account the full period of vehicle operation (charging, discharging, standing) and the full battery pack (can be targeted at Any series cell unit for active balancing). The electric vehicle range extender system of the present invention has the following operation modes: when there is an external balance battery and the power battery pack is charged: when the battery pack is charged by the external balance battery, the battery active balance module (built-in buck converter) of the present invention , Main switch unit, cell voltage sensing unit, multiple cell switch unit and control unit) convert the high voltage external balance battery to a low voltage power source and balance the discrete lowest piezoelectric core (at this time, the state of the main switch unit is "on" ); If any battery cell reaches the high voltage set value, it will stop series charging, but the balance mechanism continues to operate, and the balance logic turns to each battery cell according to the voltage level in order to charge, until the power battery pack reaches the set protection voltage (High voltage setting).

When externally balanced batteries and battery packs are discharged: The present invention can perform a balancing mechanism for delaying the over-discharge of the battery cells. When the voltage status of each battery cell is excessively discrete (the individual voltage difference is too large), and the battery cell voltage is lower than the set balance, At the initial value, the battery pack active balancing mechanism of the present invention is activated to externally balance the battery cells that need assistance and delay the battery over-discharge (at this time, the state of the main switch unit is "on") to achieve the series battery cells at the same time. Reaching the over-discharge state, that is, delaying the weakest cell to over-discharge early.

When there is an externally balanced battery and the battery pack is at rest: When the battery pack is at rest and when the voltage status of each cell is excessively discrete (individual pressure difference is too large), the present invention can start the active balancing mechanism of the battery pack (at this time the state of the main switch unit "On"), the discrete low-voltage cells are balanced from the external balance battery to the average voltage of the battery pack.

In one embodiment of the present invention, even if the electric vehicle is not equipped with an external balancing battery, the active balancing mechanism of the battery active balancing module of the present invention can be used to achieve the balance compensation action of each battery cell unit of the power battery pack. 2. Increase the mileage of the electric vehicle. When the electric vehicle does not have an external balance battery and the power battery pack is discharged: The present invention can perform a balancing mechanism for delaying the over-discharge of the battery cells. When it is lower than the preset balance starting value, the active balancing mechanism of the battery pack of the present invention is activated (at this time, the state of the main switch unit is "off"), and the weakest battery is supplemented with the entire battery pack to delay the battery over. Discharge in order to achieve a series of cells at the same time reached the over-discharge state (that is, the weakest complementary delay of the cell, the cell is over-discharged early).

When the electric vehicle has no external balance battery and the power battery pack is standing still: When the power battery pack is standing still and when the voltage states of the battery cells are excessively discrete, the battery pack active balancing mechanism of the present invention is started The unit status is "Off"), the weakest battery is recharged with the entire power battery pack, and balanced to an equal voltage condition.

The schematic diagram of the embodiment of the electric vehicle extended range system of the present invention is shown in FIG. 5. The electric vehicle of this embodiment has a driving power motor 31 and a power battery pack 32. The electric vehicle extended range system includes: The battery active balancing module 33 is connected to the power battery pack 32, and includes a step-down switching unit 331 (that is, the step-down converter and the main switching unit of the present invention are combined into a single component), and a cell voltage sensing unit 332. The battery cell switching unit 333 and the control unit 334; an external balanced battery 34 connected to the battery active balancing module 33, the The external balance battery 34 provides external balance power to the battery active balance module 33; a round of internal generator 35 is used to transfer the braking energy of the electric vehicle (that is, the energy generated during braking) to an energy converter 351, and then Passed to the external balanced battery for use as external balanced power. In this embodiment, a solar panel 36 may be further included. The power generated by the solar panel 36 is converted by a maximum power converter 361 and then transmitted to the external balanced battery 34 for use as external balanced power.

In an embodiment of the electric vehicle range extending system of the present invention, the power source of the external balance battery may be regenerative braking energy, solar cells, city power, shock system recovery energy, or other types of regenerative energy commonly used in general electric vehicles. Since the current electric vehicle is used for driving, it is often equipped with another battery with a smaller capacity for use by other peripheral devices on the vehicle (such as meters, lights, etc.). Balanced batteries can also be used to achieve the active balancing effect of the battery of the present invention.

An experimental comparison table of the range extension effect of an embodiment of the electric vehicle range extension system of the present invention is shown in Table 1. This experiment uses an electric vehicle using a 96V power battery pack as a test platform, and uses the electric vehicle to supply peripheral power. The lithium iron battery pack is used as an external balanced battery (its rated voltage is 24V and its rated capacity is 30Ah). This external balanced battery can be charged by external power (solar panel). When the electric vehicle is in the running state, the power battery pack will continuously supply the power required by the motor, and the 24V external balanced battery provides the surrounding electric power for the electric vehicle. It is not necessary to rely on the power of the 96 power main battery pack, so that the 96V main battery pack Able to fully supply the motor. When the voltage of a single cell in a 96V power battery pack is lower than When the voltage difference between the maximum cell voltage and the minimum cell voltage of the 96V power battery pack is higher than 0.1V at 3.0V (balanced initial value), the balancing function is activated. At this time, the electric vehicle range increasing system of the present invention It will use 24V to 5V step-down switching elements to use the power of the external balanced battery as the active balanced power source, and increase the voltage of the weakest cell with 5V / 6A / 30W power. When the voltage difference between the voltage of the battery cell unit and the voltage of the other weakest battery cell is greater than the cutoff value of the balance, the balance function is stopped and the balance conditions are re-determined to extend the endurance and efficiency of the 96V power battery pack.

Table 1 shows that the electric vehicle range extender system of the present invention can effectively increase the battery life of the power battery pack. The earlier the range extension control method is started, the greater the range extension effect will be. Table 1 The maximum range extension distance occurs at the equilibrium starting value. 3.10V, relatively no Starting the extended range control method increases the range by approximately 6.9 kilometers or 10%, and the amount of power transferred by the external balance battery is proportional to the range of the range. At the maximum range of 3.10V, the maximum amount of transferred power is It is 17.8Wh, which is only 2.5% of the external balance battery (24V / 30Ah / 720Wh), but it can achieve the effect of 10% range extension of the electric vehicle. This shows that the electric vehicle range extension system of the present invention has a very high Conversion efficiency and range extension effect.

In summary, the present invention provides an electric vehicle range extender system. The present invention uses an external balanced battery or the power battery pack itself as the power source, and performs switching individually with a switch circuit corresponding to any single battery cell. Single cell active balancing. The above power supply can use an external power supply or a flyback power electronic converter to isolate and ground the same charging power source and convert the voltage into a single cell charging voltage. Balanced charging of energy. The electric vehicle range extender system of the present invention can perform active battery balancing when the battery pack is charged, discharged, or left to stand, and can achieve the goal of battery pack balancing in a short time. The invention can ensure that even if the battery has a large difference in capacity or internal resistance, all series cells can be fully charged without overcharging any one cell, and the balance of discharge can effectively extend the battery use time. With the electric vehicle range extending system and the charging and discharging balancing strategy of the present invention, the effects of increasing the mileage of the electric vehicle and improving the battery life can be achieved without adding any additional hardware.

The above-mentioned embodiments are merely illustrative for describing the features and effects of the present invention, and are not intended to limit the scope of the essential technical content of the present invention. any Those skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention should be listed in the scope of patent application described later.

Claims (6)

An electric vehicle range extension system includes: a power battery pack including a plurality of battery cell units connected in series; a battery active balancing module connected to the power battery pack, which includes a step-down converter, A main switching unit, a cell voltage sensing unit, a plurality of cell switching units and a control unit are used to balance charge the power battery pack; an external balanced battery is connected to the battery active balancing module. The external balancing battery provides external balancing power to the battery active balancing module; and a regenerative braking power generation unit is connected to the external balancing battery. The regenerative braking power generation unit converts the vehicle braking energy into electricity and transmits the power to the vehicle. External balance battery; when the power battery pack lacks power, the charging current I ₁ flows from the external balance battery into the power battery pack, and the control unit detects the lowest voltage battery cell unit through the battery cell voltage sensing unit. At the same time, the external balanced battery outputs power to the step-down converter, and the step-down converter reduces the voltage of the power to 5V as an external Power I _2, the battery cell when the battery cell pressure minimum voltage and maximum voltage exceeds an equilibrium set value, the control unit activates the switching unit cell can be the minimum unit cell voltage corresponding to the buck converter The device injects the current of the external balanced power I ₂ into the cell unit of the lowest voltage. At this time, the current on the cell unit of the lowest voltage is I ₁ + I ₂ , and the current of other cell units is I ₁ . When any of the battery cells in the power battery pack exceeds a high voltage setting value, the charging is stopped. The electric vehicle range extender system according to claim 1, wherein the source of electric power of the external balance battery is regenerative braking energy, solar cells, utility power, regenerative energy of the suspension system or other types of regenerative energy. The electric vehicle range extending system according to claim 1, wherein the battery cell switching unit is a photorelay. The electric vehicle range extension system described in claim 1, wherein the battery pack active balancing mechanism flow of the electric vehicle range extension system under charging is: during the charging phase, continuously measuring the voltage of each battery cell unit And monitor whether the voltage of any battery cell unit is higher than the high voltage set value. If the voltage of any battery cell unit is higher than the high voltage set value, the voltage of each battery cell unit is sorted from low to high voltage in order. Balance each cell unit to the high voltage set value; before the voltage of any cell unit is higher than the high voltage set value, if the voltage difference between any one of the lowest voltage cell unit and the highest voltage cell unit exceeds the balanced set value, First confirm whether the lowest voltage cell unit is receiving balancing work. If not, turn on the balance charging function until the voltage of the lowest voltage cell unit is the same as the average voltage of each cell unit. Then turn off the balanced charging and continue to detect Whether the voltage difference between any of the lowest voltage cell units and the highest voltage cell unit exceeds the balance set value. The electric vehicle range extension system according to claim 1, wherein the battery pack active balancing mechanism flow of the electric vehicle range extension system in a discharged state is: During the discharge phase, continuously measure the voltage of each cell unit to determine the highest voltage cell unit and the lowest voltage cell unit; determine whether the voltage difference between the highest voltage cell unit and the lowest voltage cell unit is higher than the balance set value; If yes, judge whether the voltage of the lowest voltage battery cell unit is lower than the equilibrium starting value; if so, judge whether the voltage of the lowest voltage battery cell unit is lower than the low voltage set value; if the voltage of the lowest voltage battery cell unit is lower Between the initial balance value and the low voltage set value, the balance charging function is turned on, and the lowest voltage battery cell is balancedly charged until the battery cell in the balance and the lowest voltage battery cell unit (the balance After the voltage difference between the battery cells is the lowest), the balance charging function is turned off. According to the electric vehicle range extender system described in claim 1, when any battery cell unit reaches the high voltage set value, the control unit will sort according to the voltage level of each battery cell unit, and perform individual orders in order from low to high. Balanced charging of battery cells. When the battery cell being charged balance reaches the high voltage setting value, the next battery cell balancing work is performed in descending order until all battery cells of the entire battery pack are completely balanced. , Which is the end of charging.