Charging system

Abstract

To appropriately and safely charge a secondary battery by suppressing the influence of communication delays as much as possible, when performing charge control of the secondary battery, using radio communication.SOLUTION: A charge system 10 comprises a secondary battery 11; a charger 12 for charging the secondary battery 11; a radio communication device 13 for wirelessly communicating information about charging between the secondary battery 11 side and the charger 12 side; a control device 14 for controlling a charging condition with the charger 12, based on information about charging acquired via communication by the radio communication device 13; and a delay determination device 15 for determining whether or not a delay is generated in communication of information about charging. The control device 14 changes the charging condition, based on a delay determination result obtained by the delay determination device 15.SELECTED DRAWING: Figure 5

Description

Technical Field

[0004] , , , , ,

[0001] The present invention relates to a charging system, and particularly to a technique for charging a secondary battery using wireless communication.

Background Art

[0002] For example, as a method for charging a secondary battery such as a lithium-ion battery, a constant current constant voltage charging method (also referred to as the CCCV method) is widely known. In this method, first, charging is performed with a constant current until the voltage of the secondary battery reaches a predetermined voltage (specified voltage). After the voltage of the secondary battery reaches the specified voltage, the magnitude of the charging current is controlled so that the voltage of the secondary battery is maintained at a constant voltage (specified voltage). In particular, when the applied voltage slightly exceeds the specified voltage, it tends to be preferably adopted for lithium-ion batteries that are likely to cause not only performance degradation but also problems such as overheating and leakage (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in this type of charging method, feedback control is generally performed to measure the voltage of the secondary battery and control the charging current based on the measured voltage value. Now, if we consider applying the above charging method to a charging system between a secondary battery installed in a vehicle and a charging station, in order to perform the feedback control described above, it becomes necessary to transmit information about the measured voltage of the secondary battery to the control device on the charging station side via wireless communication rather than wired communication. However, when using wireless communication, the problem of communication delay is unavoidable. If a communication delay occurs (for example, if the communication speed drops significantly), a time lag occurs in the transmission and reception of voltage measurement information, which should be in real time. As a result, the feedback control of the charging current cannot keep up, and it becomes difficult to perform proper charging.

[0005] In view of the above circumstances, this specification aims to address the technical problem of properly and safely charging a secondary battery while minimizing the impact of communication delays when controlling the charging of the secondary battery using wireless communication. [Means for solving the problem]

[0006] The aforementioned problems are solved by the charging system according to the present invention. Specifically, this charging system comprises a secondary battery, a charging device for charging the secondary battery, a wireless communication device for wirelessly communicating charging information between the secondary battery and the charging device, and a control device for controlling the charging conditions by the charging device based on the charging information obtained through communication by the wireless communication device. The system further comprises a delay determination device for determining whether or not a delay has occurred in the communication of charging information, and the control device is characterized in that it changes the charging conditions based on the delay determination result by the delay determination device.

[0007] Thus, in this invention, it is determined whether or not there is a delay in the wireless communication of information regarding the charging of the secondary battery by the charging device, and the charging conditions for the secondary battery are changed based on the determination result. For example, if it is determined that a predetermined delay has occurred in the wireless communication, the set value of the charging current at the time of determination can be reduced to reliably avoid voltage overload due to excessive power transmission (a situation in which the voltage of the secondary battery exceeds the specified voltage). Furthermore, if it is determined that the communication delay has been resolved (there is no delay) after a predetermined time has elapsed, the charging conditions can be restored to their original state, or new charging conditions can be set considering the charging conditions during the delay, thereby completing proper charging of the secondary battery.

[0008] Furthermore, in the charging system according to the present invention, if the control device determines that a delay has occurred in the communication of charging-related information, it may reduce the charging current value based on the magnitude of the delay.

[0009] When a delay is detected in the communication, the charging current can be reduced based on the magnitude of the delay. This allows for the current to be suppressed in proportion to the size of the delay, making it possible to more reliably prevent the secondary battery voltage from exceeding the specified voltage if there is a risk of a prolonged delay. Alternatively, if the delay is minor and expected to resolve quickly, the reduction in the current can be kept to a minimum, allowing for a quicker return to normal charging conditions once the delay is resolved.

[0010] As described above, the charging system according to the present invention enables proper and safe charging of a secondary battery while minimizing the effects of delays, even when delays occur in wireless communication. For example, it is suitable when the control device employs a control method, known as constant voltage constant current (CCCV) charging, in which the control device charges the secondary battery with a constant current value during the first charging period until the voltage value reaches a specified voltage, and then, during the second charging period, reduces the current value during charging in a predetermined manner so that the voltage value of the secondary battery is maintained at the specified voltage.

[0011] Furthermore, as described above, the charging system according to the present invention minimizes the impact of delays and enables proper and safe charging of secondary batteries even when delays occur in wireless communication. For example, it is suitable when the charging device has a transformer having a primary coil and a secondary coil, and a power supply connected to the primary coil, and charges the secondary battery by transmitting current from the power supply to the secondary coil connected to the secondary coil via the transformer, that is, when the charging device and the secondary battery move relative to each other. [Effects of the Invention]

[0012] As described above, the charging system according to the present invention makes it possible to charge a secondary battery properly and safely while minimizing the impact of communication delays when controlling the charging of a secondary battery using wireless communication. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram shows the overall configuration of a charging system according to one embodiment of the present invention. [Figure 2] Figure 1 shows a flowchart illustrating an example of a secondary battery charging method using the charging system shown, specifically the first charging period. [Figure 3] Figure 1 shows a flowchart illustrating an example of a secondary battery charging method using the charging system shown, specifically the second charging period. [Figure 4] Figure 1 shows an example of a voltage-current curve obtained when a secondary battery is charged using the charging system shown in Figure 1, and is an example of a voltage-current curve when no delay occurs in communication. [Figure 5] This is an example of a voltage-current curve obtained when a secondary battery is charged using the charging system shown in Figure 1, and is an example of a voltage-current curve when a communication delay occurs during the first charging period. [Figure 6]Figure 1 shows an example of a voltage-current curve obtained when a secondary battery is charged using the charging system shown in Figure 1, and is an example of a voltage-current curve when a communication delay occurs during the second charging period. [Modes for carrying out the invention]

[0014] The following describes a charging system according to one embodiment of the present invention, and a method for charging a secondary battery using this charging system, based on the drawings.

[0015] Figure 1 shows the overall configuration of a charging system 10 according to one embodiment of the present invention. This charging system 10 is for charging a secondary battery 11 mounted on a vehicle and comprises a secondary battery 11, a charging device 12, a wireless communication device 13, a control device 14, a delay determination device 15, and a BMU 16 as a voltage measuring device for the secondary battery 11. After describing the details of each element, an example of how to use the charging system 10 (i.e., how to charge the secondary battery 11) will be described below.

[0016] The charging device 12 includes, for example, a transformer 17, a primary circuit 18 located on the primary side of the transformer 17, and a secondary circuit 19 located on the secondary side of the transformer 17.

[0017] The transformer 17 has a primary coil 21 and a secondary coil 22 wound around a core 20. In this embodiment, the core 20 is composed of a pair of divided cores 23 and 24 called a UU core, with the primary coil 21 wound around the primary divided core (first divided core 23) and the secondary coil 22 wound around the secondary divided core (second divided core 24). The primary coil 21 is connected to the primary circuit 18, and the secondary coil 22 is connected to the secondary circuit 19.

[0018] In FIG. 1, a form in which coils 21 and 22 corresponding to the bottoms 23a and 24a of the respective divided cores 23 and 24 each having a U shape are wound is illustrated. However, the winding positions of the coils 21 and 22 are not limited to the bottoms 23a and 24a. For example, although not shown in the figure, coils 21 and 22 corresponding to a pair of butting portions 23b and 24b that are bent from both ends of the bottoms 23a and 24a and extend in the same direction may be wound.

[0019] Of course, the form of the core 20 is not limited to the UU core. Not only a form composed of a pair of divided cores, but also any core having a form other than the divided core can be applied.

[0020] A control device 14 is connected to the primary side of the primary side circuit 18. In the present embodiment, the control device 14 also serves as the power supply (here, a DC power supply) of the charging device 12. Therefore, as will be described later, DC of a predetermined current value is supplied from the control device 14 to the primary side circuit 18, and the primary side circuit 18 is configured to be able to convert the DC supplied from the control device 14 into AC of a predetermined voltage. In this case, a DC-DC power converter is constituted by the transformer 17, the primary side circuit 18, and the secondary side circuit 19.

[0021] In the present embodiment, the primary side circuit 18 is a so-called bridge circuit and has four switching elements 18a and anti-parallel diodes 18b connected to each switching element 18a. This primary side circuit 18 is configured to be able to convert the DC voltage input from the control device (power supply) 14 into a high-frequency square wave AC voltage.

[0022] The secondary side circuit 19 is configured to be able to control the current supplied from the primary side circuit 18 via the transformer 17 in a predetermined manner. Specifically, it is configured to be able to convert AC into DC of a predetermined voltage.

[0023] In this embodiment, the secondary circuit 19 is a so-called rectifier circuit and has four diodes 19a and smoothing capacitors 19b connected in parallel to each diode 19a. This secondary circuit 19 is configured to convert the square wave AC voltage input from the primary circuit 18 via the transformer 17 into a DC voltage.

[0024] A secondary battery 11 is connected to the secondary side of the secondary circuit 19. As a result, the alternating current input from the primary circuit 18 to the secondary circuit 19 is converted to direct current and then supplied to the secondary battery 11.

[0025] Capacitors 18c and 19c are connected in parallel to the primary circuit 18 and the secondary circuit 19, respectively.

[0026] The BMU16 is connected to the secondary battery 11 and is capable of monitoring the state of the secondary battery 11 (various parameters such as voltage and temperature). In addition, the transmitter 13a of the wireless communication device 13 is connected to the BMU16, and the information regarding the voltage of the secondary battery 11 acquired by the BMU16 can be transmitted to the receiver 13b of the wireless communication device 13 located on the side of the charging device 12.

[0027] The receiving unit 13b of the wireless communication device 13 is connected to the delay determination device 15, and the delay determination device 15 is connected to the control device 14. In other words, information regarding the secondary battery 11 sent to the charging device 12 side via the receiving unit 13b of the wireless communication device 13 is sent to the delay determination device 15. Then, after predetermined processing is performed in the delay determination device 15 based on the information regarding the secondary battery 11, predetermined processing (control of charging current) is performed by the control device 14 based on the result of that processing.

[0028] More specifically, the delay determination device 15 determines whether the information regarding the voltage of the secondary battery 11, among the information sent to the receiving unit 13b, was sent without delay. For example, it determines whether there is a delay in wireless communication based on the communication speed (reception speed) of the most recently received voltage information. In this case, for example, if the communication speed is less than a preset value, it is determined that there is a delay, and if it is equal to or greater than the preset value, it is determined that there is no delay. The determination result is transmitted to the control device 14.

[0029] The control device 14 controls the current supplied to the primary circuit 18. Furthermore, upon receiving a delay determination result from the delay determination device 15, it controls the charging current based on that result. Further details will be described later.

[0030] In this case, the first split core 23 of the transformer 17, the primary coil 21, the primary circuit 18, the control device 14, and the receiving unit 13b of the wireless communication device 13 are provided on the charging station 25 side. The second split core 24 of the transformer 17, the secondary coil 22, the secondary circuit 19, the secondary battery 11, the BMU 16, and the transmitting unit 13a of the wireless communication device 13 are provided on the vehicle 26 side.

[0031] Next, an example of a method for charging a secondary battery 11 using the charging system 10 configured as described above will be explained, mainly based on Figures 2 to 6.

[0032] Herein, the charging method according to this embodiment comprises a voltage measurement step S11, a voltage information transmission step S12, a delay occurrence determination step S13, a current control step S14 (S16) during the first charging period C1a (C1b, C1c), a voltage measurement step S21, a voltage information transmission step S22, a delay occurrence determination step S23, and a current control step S24 (S26, S27) during the second charging period C2a (C2b, ​​C2c). The steps S11 to S16 and S21 to S27 will be described below in chronological order.

[0033] (S11) Voltage measurement step In step S11, before starting to charge the secondary battery 11, the voltage of the secondary battery 11 is first measured as information about the secondary battery 11 (see Figure 2). In this embodiment, the voltage of the secondary battery 11 is measured by a BMU 16 mounted on the vehicle 26.

[0034] (S12) Voltage information transmission step In step S12, information regarding the voltage of the secondary battery 11, acquired in the voltage measurement step S11, is transmitted to the charging device 12. In this embodiment, the transmitting unit 13a of the wireless communication device 13, which is connected to the BMU 16, transmits information regarding the voltage of the secondary battery 11 to the receiving unit 13b of the wireless communication device 13. In this case, information regarding some or all of the parameters of the secondary battery 11 that the BMU 16 can monitor, such as the temperature of the secondary battery 11, may be transmitted in addition to the voltage.

[0035] (S13) Delay occurrence determination step Information regarding the voltage of the secondary battery 11 received by the receiving unit 13b is sent to the delay determination device 15. Information regarding the communication delay of the voltage information received by the receiving unit 13b is also sent to the delay determination device 15. The delay determination device 15 determines whether or not a delay has occurred in the communication of the voltage information. In this embodiment, information regarding the communication speed of the voltage information is sent from the receiving unit 13b to the delay determination device 15, and the delay determination device 15 determines whether or not a delay has occurred in the communication of the voltage information based on the value of the communication speed.

[0036] (S14) Constant current charging step (S15) Specified voltage determination step Then, if it is determined in the delay occurrence determination step S13 that no communication delay has occurred, the control device 14 charges the secondary battery 11 with a preset constant current value A1 (see Figure 4). This charging continues until the voltage of the secondary battery 11 reaches a predetermined voltage (specified voltage V1). That is, at predetermined intervals, the voltage of the secondary battery 11 measured in the voltage measurement step S11 is compared with the specified voltage V1 (see Figure 4), and the series of steps S11 to S14 described above are repeated until the voltage of the secondary battery 11 reaches the specified voltage V1. The first charging period C1a ends when the voltage of the secondary battery 11 reaches the specified voltage V1 (see Figure 2).

[0037] (S16) Charging current reduction step Alternatively, during the constant current charging described above (when steps S11 to S15 are repeated), if the delay occurrence determination step S13 determines that a delay has occurred in communication, the control device 14 changes the preset charging current value A1. Specifically, the current value A1 is reduced at or immediately after the delay occurs, depending on the magnitude of the delay (for example, the amount of decrease in communication speed). Then, charging is continued with the reduced current value A2 until the voltage of the secondary battery 11 reaches the specified voltage V1 (see Figure 5). In this case, since the charging current decreases during charging (reduced from current value A1 to current value A2), the first charging period C1b, which is the time from the start of charging until the voltage of the secondary battery 11 reaches the specified voltage V1, becomes longer than the first charging period C1a when no delay occurs (see Figures 4 and 5).

[0038] In addition to the control device 14 as described above, the current value A1 can also be reduced by the single-sided circuit 18. Specifically, although a detailed explanation is left to the specification of Japanese Patent Application Publication No. 2021-83265, for example, when the frequency fs of the high-frequency transformer of the unidirectional isolated DC-DC power conversion circuit is constant, the output power Pout can be reduced by controlling the primary-side circuit 18, which is a primary-side H-bridge circuit, with a predetermined switching pattern. Specifically, by delaying the switching timing of the S-phase switch in the primary-side circuit 18 by a predetermined period Td, a period Td is provided in the square wave waveform of the primary voltage v1 during which the voltage is zero, thereby reducing the effective value of the primary voltage v1. The same applies to the means for changing (reducing) the charging current in the second charging period C2a, which will be described later.

[0039] (S21) Voltage measurement step After the first charging period C1a (C1b) is completed as described above, the second charging period C2a (C2b) is started. Specifically, similar to the first charging period C1a, the voltage of the secondary battery 11 is measured as information regarding the secondary battery 11. In this embodiment, the voltage of the secondary battery 11 is measured by a BMU 16 mounted on the vehicle 26.

[0040] (S22) Voltage information transmission step After measuring the voltage of the secondary battery 11, information regarding the voltage of the secondary battery 11 is transmitted to the charging device 12. In this embodiment, the transmitting unit 13a of the wireless communication device 13, which is connected to the BMU 16, transmits information regarding the voltage of the secondary battery 11 to the receiving unit 13b.

[0041] (S23) Delay occurrence determination step The voltage information of the secondary battery 11 received by the receiving unit 13b is sent to the delay determination device 15. In addition, information regarding the communication delay of the voltage information received by the receiving unit 13b, in this case the communication speed, is also sent to the delay determination device 15. The delay determination device 15 determines, based on the value of the communication speed, whether or not a delay has occurred in the communication of the voltage information.

[0042] (S24) Constant voltage charging step (S25) Full charge determination step Then, if it is determined in the delay occurrence determination step S23 that no delay has occurred, the control device 14 controls the charging current so that the voltage of the secondary battery 11 is maintained at the specified voltage V1 (constant voltage charging step S24). In this case, constant voltage charging is performed by rapidly decreasing the charging current from the current value A1 at the time of the first charging period C1a, and then gradually decreasing the gradient as time progresses (see Figure 4).

[0043] Then, at predetermined intervals, the charge state of the secondary battery 11 is evaluated, and the series of steps S21 to S24 described above are repeated until it is determined that the secondary battery 11 is fully charged. The second charging period C2a ends when the secondary battery 11 reaches a fully charged state.

[0044] (S26) Charging current reduction step Alternatively, if the delay occurrence determination step S23 determines that a delay has occurred while steps S21 to S25 described above are repeatedly performed during the second charging period C2a, the control device 14 changes the charging current during the second charging period C2a. Specifically, depending on the magnitude of the delay (for example, the amount of decrease in communication speed), the current value at the time of the delay t2 or immediately thereafter is reduced steeply, and then the charging current is reduced so that the slope gradually becomes gentler (see Figure 6). As shown in Figure 6, if it is anticipated that the voltage of the secondary battery 11 will temporarily drop due to the current drop immediately after the delay, it is preferable to control the charging current so that the voltage of the secondary battery 11 converges to the specified voltage V1 after a predetermined time while satisfying the above conditions (voltage convergence control step S27). In this case as well, charging is continued until the secondary battery 11 is fully charged.

[0045] The current value (end current value) at the point when the secondary battery 11 reaches a fully charged state is not particularly limited. For example, as shown in Figure 5, if the first charging period C1b becomes longer than the first charging period C1a when there is no delay due to a delay in communication during the constant current charging period, the charging current may be controlled so that the total charging time (sum of the first charging period C1a and the second charging period C2a) is the same as the total charging time when there was no delay. In this case, the end current value A4 will be higher than the end current value A3 when there was no delay.

[0046] On the other hand, even if a delay occurs in communication during the first charging period C1a or the second charging period C2a, the charging current may be controlled with the utmost importance given to ensuring that the final charge amount of the secondary battery 11 is equal to the charge amount of the secondary battery 11 if there had been no delay. In this case, for example, as shown in Figure 6, the termination current value A5 when a delay occurs in communication during the second charging period C2c will be smaller than the termination current value A3 when there was no delay in communication.

[0047] As described above, in the charging system 10 according to this embodiment, it is determined whether or not a delay has occurred in the wireless communication between the charging device 12 and the secondary battery 11, and the charging conditions (charging current) for the secondary battery 11 are changed based on the determination result. For example, if it is determined that a predetermined delay has occurred in the wireless communication, the set value A1 of the charging current at the time t1 when the delay occurs can be reduced to reliably avoid voltage overload due to excessive power transmission (a situation in which the voltage of the secondary battery 11 exceeds the specified voltage V1). Furthermore, if it is determined that the communication delay has been resolved (there is no delay) after a predetermined time has elapsed, the charging conditions can be restored to their original state, or new charging conditions can be set considering the charging conditions at the time of the delay, thereby completing proper charging of the secondary battery. Thus, according to the charging system 10 according to this embodiment, it is possible to safely and properly charge the secondary battery 11.

[0048] Although one embodiment of the present invention has been described above, the charging system and charging method according to the present invention may also adopt configurations other than those described above, without departing from the spirit of the invention.

[0049] For example, in the above embodiment, if a communication delay occurs during the first charging period C1b, the charging current value is changed (reduced), and charging is continued with the changed current value A2 until the end of the first charging period C1b (see Figure 5). However, the charging system or charging method according to the present invention can also adopt other control modes. For example, if the degree of delay (degree of decrease in communication speed) is minor and the communication delay is resolved quickly, the charging conditions may be returned to their original state. In the example shown in Figure 5, the charging current value A1 may be changed to the reduced current value A2 at t1 when the delay occurs or immediately thereafter, and then, when it is determined that the delay has been resolved, the current value may be returned to the original A1 to raise the voltage of the secondary battery 11 to the specified voltage V1. Alternatively, in the example shown in Figure 6, the charging current may be changed to follow a new downward curve that causes a steep decrease in the charging current at t2 when the delay occurs or immediately thereafter, and then, when it is determined that the delay has been resolved, the charging current may be changed so that it can return to the original downward curve (the downward curve of the charging current in the second charging period C2a in Figure 4).

[0050] Alternatively, if a delay is detected, the delay detection device 15 may obtain the duration of the delay and transmit it to the control device 14. In this case, the control device 14 may determine whether or not to stop charging based on the delay time. For example, a threshold may be set in advance for the delay time, and if the delay time exceeds the threshold, the control device 14 may set the charging current to zero.

[0051] Furthermore, in the above embodiment, the control device 14 is shown as changing the charging current based on the magnitude of the delay, but of course, other control methods may also be used. For example, when transmitting information about the voltage of the secondary battery 11 from the transmitting unit 13a of the wireless communication device 13 to the receiving unit 13b, information about conditions other than the voltage of the secondary battery 11 (such as temperature) may be transmitted, and if it is determined that a delay has occurred in communication, the amount of reduction in the charging current may be set by taking into account the temperature of the secondary battery 11 at the time of the delay, in addition to the communication speed.

[0052] Furthermore, while the above description has illustrated the application of the present invention to a system or method for performing constant current constant voltage charging, it is of course not limited to this. The present invention may be applied to any charging system or charging method, as long as it is a system or method for charging the secondary battery 11 using wireless communication to transmit and receive charging-related information between the secondary battery 11 and the charging device 12.

[0053] Furthermore, from the perspective of applications, the above description has provided an example of applying the present invention to the charging of a secondary battery for motor drive in a motor-driven vehicle 26, such as an electric vehicle, but of course, it is not limited to this. For example, the present invention may be applied to an on-board secondary battery that supplies power to a power load other than the drive motor. Alternatively, the charging system or charging method according to the present invention may be applied to secondary battery applications in general where continuous and stable operation of the secondary battery is required, not limited to on-board applications. [Explanation of Symbols]

[0054] 10 Charging Systems 11 Secondary battery 12 Charging device 13 Wireless communication equipment 13a Transmitter 13b Receiver 14 Control device 15 Delay detection device 16 BMU 17 Transformers 18 Primary circuit 19 Secondary circuit 20 cores 21,22 coils 23,24 split cores 25 Charging Stations 26 vehicles A1, A2 Current values ​​(constant current) A3, A4, A5 Termination Current Values C1a,C1b,C1c First charging period C2a,C2b,C2c Second charging period S11, S21 Voltage measurement step S12, S22 Voltage information transmission step S13, S23 Delay occurrence determination step S14 Constant current charging step S15 Specified voltage determination step S16, S26 Charging current reduction step S24 Constant Voltage Charging Step S25 Full Charge Determination Step S27 Voltage convergence control step V1 Nominal Voltage

Claims

1. Rechargeable batteries and A charging device for charging the secondary battery, A wireless communication device for wirelessly communicating charging information between the secondary battery and the charging device, A charging system comprising a control device that controls the charging conditions of the charging device based on the charging information obtained by communication via the wireless communication device, The system further includes a delay determination device that determines whether or not a delay occurs in the communication of the charging information. A charging system in which, if the control device determines that a delay has occurred in the communication of information regarding charging, the current value during charging is reduced based on the magnitude of the delay.

2. The charging system according to claim 1, wherein the control device charges the secondary battery with a constant current value during a first charging period until the voltage value of the secondary battery reaches a specified voltage, and then during a second charging period, reduces the current value during charging in a predetermined manner so that the voltage value of the secondary battery is maintained at the specified voltage.

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