TW202416625A - Battery parallel connection charging method for electric vehicle separates C-rate of charging current of charger so as to reduce temperature of charging each battery module - Google Patents

Abstract

The invention relates to a battery parallel connection charging method for an electric vehicle, capable of being implemented by utilizing a battery parallel connection charging system. The system is provided to apply on an electric vehicle and comprises a plurality of battery modules and a control unit. When the electric vehicle is connected to a charger to awake the control unit, the control unit is allowed to receive voltage values of each of the battery modules. The control unit determines whether or not voltage differences among a plurality of battery modules is greater than a predetermined voltage value. When the voltage difference is greater than the predetermined voltage, the control unit controls a lower voltage value within the plurality of battery modules to perform charging. When the voltage difference is smaller than the predetermined voltage, the control unit controls the plurality of battery modules to charge together.

Description

Parallel charging method for electric vehicle batteries

The present invention relates to a battery for an electric vehicle, and more particularly to a method for charging the batteries in parallel for an electric vehicle.

Existing electric scooters usually use rechargeable batteries as a power source. In order to improve the capacity problem of a single battery, electric scooters have developed a power supply system using multiple batteries, usually by connecting multiple batteries in series to form a battery pack to increase the endurance of the electric scooter. The battery pack inside the electric scooter can be directly charged through a dedicated charging cable, or the user can take out each battery from the electric scooter for charging. When the user charges the battery pack with the charging cable, because the batteries in the battery pack are connected in series, if the voltages of the batteries are not balanced, one battery may end charging early and the remaining batteries may not be fully charged.

Regarding the shortcomings of battery series charging technology, the Republic of China Patent Application No. 109106621 discloses a multi-cell battery pack charging balance device, system and method. Through a rotation structure, the structure disconnects the series switch in the switching circuit containing a fully charged battery through a controller, and turns on the bypass switch in the switching circuit, so that the fully charged battery leaves the charging circuit, and the remaining batteries can continue to charge stably. The technology may have the following problems: 1.     When the series switch of the switching circuit is suddenly disconnected, the overall charging voltage will drop sharply, affecting the stability of charging. 2.     If the series switch and bypass switch in the switching circuit fail, the battery in the switching circuit is at risk of short circuit and damage.

[The problem the invention is trying to solve]

The batteries in conventional electric vehicles are connected in series. In order to make a fully charged battery leave the charging circuit, the series switch in the switching circuit including the fully charged battery needs to be disconnected, which causes the charging voltage of the charger to drop sharply, affecting the charging stability. In addition, if the switch in the switching circuit fails, the battery in the switching circuit has the risk of short-circuiting and being damaged. In order to solve this technical problem, the present invention proposes a parallel charging method for electric vehicle batteries.

[Technical means to solve the problem]

The present invention provides a battery parallel charging method for an electric vehicle. According to an embodiment of the present invention, the electric vehicle includes a plurality of battery modules and a control unit. The battery module includes a battery core module, a charging switch and a discharging switch, and the plurality of battery modules are connected in parallel. The control unit is electrically connected to the plurality of battery modules. When the electric vehicle is connected to a charger, the control unit receives a trigger wake-up signal transmitted by the charger to execute the battery parallel charging method. The method includes: The control unit receives the voltage values of the plurality of battery modules; The control unit determines whether the voltage difference between the plurality of battery modules is greater than a preset voltage value; When the voltage difference is greater than the preset voltage value, the control unit controls the battery modules with lower voltage values to charge; When the voltage difference is less than the preset voltage value, the control unit controls the battery modules to charge together.

According to another embodiment of the present invention, the electric vehicle includes a first battery module, a second battery module and a control unit, the first battery module includes a first battery core module, a first charging switch and a first discharge switch; the second battery module includes a second battery core module, a second charging switch and a second discharge switch; the first battery module and the second battery module are connected in parallel, and the control unit is electrically connected to the first battery module and the second battery module; when the electric vehicle is connected to a charger, the control unit receives a trigger wake-up signal transmitted by the charger to execute the battery parallel charging method, the method comprising: The control unit receives a first voltage value of the first battery module and a second voltage value of the second battery module; The control unit calculates a voltage difference between the first voltage value and the second voltage value; The control unit determines whether the voltage difference is greater than a preset voltage value; When the voltage difference is greater than the preset voltage value, the control unit controls the first battery module and the second battery module with the lower voltage value to charge; When the voltage difference is less than the preset voltage value, the control unit controls the first battery module and the second battery module to charge together.

[Effects of the invention]

The battery parallel charging method of the electric vehicle of the present invention determines the voltage difference between the battery modules. During the charging process, it is not necessary to make any battery module leave the charging circuit. Therefore, the charging voltage of the charger can be stably output, and each battery module includes a charging switch and a discharging switch. The charging switch and the discharging switch have a one-way conduction function, so that there will be no current mutual injection during the charging process of each battery module. In addition, because charging is performed in parallel, the charge and discharge rate (C-rate) of the charging current of the charger is dispersed, the temperature of each battery module during charging is reduced, and the service life of each battery module is increased.

The present invention is a battery parallel charging method for an electric vehicle, which can be implemented using a battery parallel charging system as shown in FIG1 . The battery parallel charging system is arranged on an electric vehicle. In a first embodiment of the battery parallel charging system of the present invention, it includes a first battery module 10, a second battery module 20 and a control unit 30. The first battery module 10 and the second battery module 20 are connected in parallel and receive power provided by a charger 50 through a charging cable for charging. The control unit 30 has a communication control module 31 and a receiving module 32. The communication control module 31 connects the first battery module 10 and the second battery module 20 for communication. The receiving module 32 can be, but is not limited to, a wake-up circuit and is connected to the charger 50 for communication. When the control unit 30 is awakened by receiving a signal transmitted by the charger 50 through the receiving module 32 , the control unit 30 can receive battery information transmitted by the first battery module 10 and the second battery module 20 through the communication control module 31 , or output instructions to control the first battery module 10 and the second battery module 20 .

The first battery module 10 includes a first battery cell module 11 and a first battery management system (BMS) 12. The first battery cell module 11 may be a single battery cell or a plurality of battery cells. The first battery management system 12 may be implemented on a circuit board as an information management core of the first battery cell module 11 to manage the charging and discharging operations of the first battery cell module 11 and monitor the power information, temperature information, etc. of the first battery cell module 11.

The first battery management system 12 is connected to the charger 50, the first battery cell module 11 and the control unit 30, and includes a first communication interface 13, a first charging switch 14 and a first discharging switch 15. The first communication interface 13 is connected to the communication control module 31, receives control instructions from the control unit 30, or transmits battery information of the first battery module 10 to the control unit 30. Specifically, the first battery management system 12 and the control unit 30 are connected and communicated with the first communication interface 13 through the communication control module 31, wherein the first communication module 13 and the communication control module 31 can support the Controller Area Network (CAN or CAN bus) protocol, or other wired/wireless communication interfaces.

The first charging switch 14 and the first discharging switch 15 are switches with a unidirectional conduction function, such as a metal oxide semi-conductor field effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT). The first charging switch 14 and the first discharging switch 15 are respectively a metal oxide semi-conductor field effect transistor (MOSFET) as an example for explanation. There is a parasitic diode between the source and the drain of the metal oxide semi-conductor field effect transistor. The charger 50, the first charging switch 14, the first discharging switch 15 and the first battery cell module 11 are connected in series, and the first charging switch 14 and the first discharging switch 15 are reversely connected, so that the cathodes of the respective parasitic diodes are connected. The first charging switch 14 and the first discharging switch 15 can be turned on or off according to the control of the control unit 30 , respectively. By changing the states of the first charging switch 14 and the first discharging switch 15 , the charger 50 charges the first battery cell module 11 .

The second battery module 20 also includes a second battery cell module 21 and a second battery management system 22. The second battery management system 22 has a second communication interface 23, a second charging switch 24 and a second discharging switch 25. The second communication interface 23 is also connected to the communication control module 31 of the control unit 30 for communication. Since the circuit structure of the second battery module 20 is the same as that of the first battery module 10, it will not be described in detail.

A first embodiment of the battery parallel charging method of the electric vehicle of the present invention can be executed by connecting the above-mentioned battery parallel charging system to the charger 50. Specifically, the charger 50 has a charging communication module 51 and a wake-up module 52. When the battery parallel charging system is connected to the charger 50, the charging communication module 51 is connected to the communication control module 31 for communication, and the wake-up module 52 is connected to the receiving module 32 for communication, so that the charger 50 transmits a trigger wake-up signal T1 to the receiving module 32 through the wake-up module 52, and the receiving module 32 receives the trigger wake-up signal T1. Thus, the control unit 30 triggers wake-up and executes the battery parallel charging method, wherein the trigger wake-up signal T1 can be a power signal. Please refer to FIG. 2, the battery parallel charging method includes:

S10: The control unit 30 receives a first voltage value of the first battery module 10 and a second voltage value of the second battery module 20. The control unit 30 triggers and wakes up the first battery module 10 and the second battery module 20 through the communication control module 31, so that the first battery module 10 transmits the first voltage value to the communication control module 31 through the first communication interface 13, and the second battery module 20 transmits the second voltage value to the communication control module 31 through the second communication interface 23.

S11: The control unit 30 calculates a voltage difference according to the first voltage value and the second voltage value.

S12: Determine whether the voltage difference is greater than a preset voltage value.

S13: When the voltage difference is greater than the preset voltage value, the first battery module 10 and the second battery module 20 are controlled to charge the one with the lower voltage value. For example, as shown in FIG3 , the second battery module 20 is the one with the lower voltage value, and the control unit 30 controls the first battery management system 12 and the second battery management system 22 through the communication control module 31 to turn on the first charging switch 14, the second charging switch 24 and the second discharge switch 25, so that the charger 50 outputs a larger second charging current I2 to first charge the second battery module. 20 is charged. Since only the first charging switch 14 is turned on, only a small first charging current I1 is input into the first battery module 10. The first charging current I1 is input into the first battery module 10 through the parasitic diode of the first discharge switch 15. The total charging current output by the charger 50 is the sum of the first charging current I1 and the second charging current I2.

As the second battery module 20 is gradually charged, the voltage value of the second battery module 20 will gradually increase, making the second charging current I2 gradually decrease, while the first charging current I1 input to the first battery module 10 will gradually increase. When the first charging current I1 will exceed the maximum current value that the parasitic diode can withstand, it means that the voltage difference between the first battery module 10 and the second battery module 20 will be less than the preset voltage value. It is particularly noted that in the above-mentioned charging process, since the first discharge switch 15 is kept interrupted, it can be prevented that the current of the first battery module 10 with a higher voltage is injected into the second battery module 20 with a lower voltage, thereby preventing the second battery module 20 from being damaged.

S14: When the voltage difference is less than the preset voltage value, the first battery module 10 and the second battery module 20 are controlled to be charged together. As shown in FIG4 , the control unit 30 controls the first battery management system 12 and the second battery management system 22 through the communication control module 31, so that the first charging switch 14, the first discharging switch 15, the second charging switch 24 and the second discharging switch 25 are turned on, so that the first battery module 10 and the second battery module 20 receive the first charging current I1 and the second charging current I2 respectively and are charged together, wherein the first charging current I1 and the second charging current I2 will change as the voltage values of the first battery module 10 and the second battery module 20 increase. When the voltage values of the first battery module 10 and the second battery module 20 are equal, the first charging current I1 is equal to the second charging current I2. In one embodiment of the present invention, when the first battery module 10 and the second battery module 20 are charged together, the control unit 30 can communicate with the charging communication module 51 through the communication control module 31 to enable the charger 50 to increase the total charging current output.

A second embodiment of the battery parallel charging method of the electric vehicle of the present invention can be implemented using a second embodiment of the battery parallel charging system. In this embodiment of the system, based on the circuit architecture in the first embodiment of the system, a plurality of battery modules are added, each of which has a charging switch and a discharging switch. The following description is made using the battery parallel charging system having three battery modules as an example.

As shown in FIG5 , the third battery module 40 also includes a third battery cell module 41 and a third battery management system 42. The third battery management system 42 has a third communication interface 43, a third charging switch 44 and a third discharging switch 45. The third communication interface 43 is also connected to the communication control module 31 of the control unit 30 for communication. Since the circuit structure of the third battery module 30 is the same as that of the first battery module 10, it will not be repeated. When the second embodiment of the battery parallel charging system is connected to the charger 50, the control unit 30 triggers the wake-up and executes the second embodiment of the battery parallel charging method. Please refer to FIG6 . The method includes:

S20: The control unit 30 receives the voltage values of the first battery module 10, the second battery module 20 and the third battery module 40. Since the receiving method is the same as step S10 in the first embodiment of the method, it will not be repeated.

S21: The control unit 30 determines whether the voltage difference between the plurality of battery modules is greater than a preset voltage value. Specifically, the control unit 30 can determine that the battery module with the smallest voltage value among the first battery module 10, the second battery module 20 and the third battery module 40 is a reference battery module, for example, the third battery module 40 is the reference battery module. The control unit 30 then calculates a voltage difference between the reference battery module and each of the other battery modules, and determines whether the voltage differences are greater than the preset voltage value, wherein the voltage difference between the reference battery module and the first battery module 10 is a first voltage difference, and the voltage difference between the reference battery module and the second battery module 20 is a second voltage difference. The preset voltage value is related to the maximum current value that each of the parasitic diodes can withstand, as in the first embodiment of the method.

S22: When the voltage difference is greater than the preset voltage value, the control unit 30 controls the battery modules with lower voltage values to charge. As described above, when the first voltage difference and the second voltage difference are respectively greater than the preset voltage values, the control unit 30 controls the reference battery module to charge. Because the charging method is the same as step S14 in the first embodiment of the method, it will not be described in detail.

S23: When the voltage difference is less than the preset voltage value, the control unit 30 controls the plurality of battery modules to be charged together. In conjunction with the above example, for example, when at least one of the first voltage difference and the second voltage difference is less than the preset voltage value, the control unit 30 controls the battery module whose voltage difference is less than the preset voltage value to be charged together with the reference battery module. For example, when the second voltage difference is less than the preset voltage value, the control unit 30 controls the second battery management system 22 and the third battery management system 42 through the communication control module 31, so that the second battery module 20 and the third battery module 40 are charged together.

The battery parallel charging method of an electric vehicle of the present invention is directed to a method for connecting an electric vehicle to a charger via a charging cable, wherein a plurality of battery modules with different voltages in the electric vehicle are identified, wherein a battery module with a minimum voltage value is used as a reference battery module, and a voltage difference between the reference battery module and each of the other battery modules is calculated respectively. When it is determined that the voltage differences are all greater than a preset voltage value, the reference battery module is charged alone, and the charging switch and the discharging switch of the reference battery module are controlled to be turned on, and the charging switches of the other battery modules are turned on first to limit the current of the other battery modules from being poured into the reference battery module; when it is determined that at least one of the voltage differences is less than the preset voltage value, the battery module with the voltage difference less than the preset voltage value is charged together with the reference battery module, and the charging switch and the discharging switch of the reference battery module are controlled to be turned on, and the charging switch and the discharging switch of the battery module with at least one voltage difference less than the preset voltage value are turned on. Because the present invention charges in parallel, the voltage values of the battery modules can be charged simultaneously even if they are different, thereby averaging the voltage values of the battery modules.

In summary, the above only records the implementation methods or examples of the technical means adopted by the present invention to solve the problem, and is not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications that are consistent with the scope of the patent application of the present invention or made according to the scope of the patent of the present invention are covered by the scope of the patent of the present invention.

10: First battery module 11: First battery core module 12: First battery management system 13: First communication interface 14: First charging switch 15: First discharge switch 20: Second battery module 21: Second battery core module 22: Second battery management system 23: Second communication interface 24: Second charging switch 25: Second discharge switch 30: Control unit 31: Communication control module 32: Receiving module 40: Third battery module 41: Third battery core module 42: Third battery management system 43: Third communication interface 44: Third charging switch 45: Third discharge switch 50: Charger 51: Charging communication module 52: Wake-up module I1: First charging current I2: Second charging current T1: Trigger wake-up signal

Figure 1: A circuit block diagram of a battery parallel charging system for implementing a first embodiment of the present invention. Figure 2: A flow chart of a first embodiment of a battery parallel charging method for an electric vehicle of the present invention. Figure 3: A circuit block diagram of a second battery module in a first embodiment of the present invention when charging. Figure 4: A circuit block diagram of a first battery module and a second battery module in a first embodiment of the present invention when charging simultaneously. Figure 5: A circuit block diagram of a battery parallel charging system for implementing a second embodiment of the present invention. Figure 6: A flow chart of a second embodiment of a battery parallel charging method for an electric vehicle of the present invention.

Claims (9)

A battery parallel charging method for an electric vehicle, the electric vehicle includes a plurality of battery modules and a control unit, the battery module includes a battery core module, a charging switch and a discharging switch, and the plurality of battery modules are connected in parallel, and the control unit is electrically connected to the plurality of battery modules; when the electric vehicle is connected to a charger, the control unit receives a trigger wake-up signal transmitted by the charger to execute the battery parallel charging method, the method comprising: The control unit receives the voltage values of the plurality of battery modules; The control unit determines whether the voltage difference between the plurality of battery modules is greater than a preset voltage value; When the voltage difference is greater than the preset voltage value, the control unit controls the battery modules with lower voltage values to charge; When the voltage difference is less than the preset voltage value, the control unit controls the battery modules to charge together. A battery parallel charging method for an electric vehicle, the electric vehicle comprises a first battery module, a second battery module and a control unit, the first battery module comprises a first battery core module, a first charging switch and a first discharge switch; the second battery module comprises a second battery core module, a second charging switch and a second discharge switch; the first battery module and the second battery module are connected in parallel, the control unit is electrically connected to the first battery module and the second battery module; when the electric vehicle is connected to a charger, the control unit receives a trigger wake-up signal transmitted by the charger to execute the battery parallel charging method, the method comprising: The control unit receives a first voltage value of the first battery module and a second voltage value of the second battery module; The control unit calculates a voltage difference between the first voltage value and the second voltage value; The control unit determines whether the voltage difference is greater than a preset voltage value; When the voltage difference is greater than the preset voltage value, the control unit controls the first battery module and the second battery module with the lower voltage value to charge; When the voltage difference is less than the preset voltage value, the control unit controls the first battery module and the second battery module to charge together. A parallel charging method for electric vehicle batteries as described in claim 1 or 2, wherein the control unit includes a receiving module, the charger includes a wake-up module, and the charger transmits the trigger wake-up signal to the receiving module via the wake-up module, and the trigger wake-up signal is a power signal. As described in claim 3, the parallel charging method for electric vehicle batteries, wherein the receiving module is a wake-up circuit, and the wake-up circuit wakes up the control unit according to the trigger wake-up signal. A method for parallel charging batteries of an electric vehicle as described in claim 2, wherein the first battery module includes a first battery management system, the second battery module includes a second battery management system, and the control unit includes a communication control module, wherein the control unit communicates with the first battery management system and the second battery management system respectively through the communication control module to receive the first voltage value and the second voltage value. A method for parallel charging batteries of an electric vehicle as described in claim 5, wherein the charger further comprises a charging communication module, and the charging communication module communicates with the communication control module. A method for parallel charging batteries of an electric vehicle as described in claim 6, wherein when the first battery module and the second battery module are charged together, the control unit causes the charger to increase the total charging current output through the charging communication module. A method for parallel charging batteries of an electric vehicle as described in claim 2, wherein, when the voltage difference is greater than the preset voltage value, the control unit turns on the charging switch and the discharging switch of the first battery module and the second battery module having the lower voltage value, and turns on the charging switch of the first battery module and the second battery module having the higher voltage value. A method for parallel charging batteries of an electric vehicle as described in claim 2, wherein when the voltage difference is less than the preset voltage value, the control unit turns on the second charging switch and the second discharging switch, and turns on the first charging switch and the first discharging switch for joint charging.

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