Charging control method and electric vehicle

Abstract

This invention provides a charging control method that can appropriately charge each battery when multiple batteries have different output characteristics. [Solution] Assume that the charging time T is shorter than the full charging time Ta which allows the first battery Ba, which has the highest output, to be fully charged. The VCU 30, which functions as a charging control device, allocates a first charging power to the first battery Ba that is greater than the charging power allocated to the second battery Bb from the maximum power of the charger 20, thereby preferentially charging the first battery Ba. Assume that the charging time T is longer than the full charging time Ta, and shorter than the time Tfull which allows all batteries to be fully charged in the shortest time. The VCU 30 controls the charging of the high-voltage energy storage unit 13 so as to allocate charging power such that each battery would be fully charged if the first battery Ba and the second battery Bb were charged for time Tfull, and charges each battery for the charging time T.

Description

Technical Field

[0004] , , ,

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[0001] The present invention relates to a charging control method and an electric vehicle.

Background Art

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The charging control device described in Patent Document 1 is considered to be effective when the output characteristics of a plurality of batteries are substantially the same, but does not consider the case where the output characteristics of a plurality of batteries are different. There is a need for a charging control method and an electric vehicle that can control the appropriate charging of each battery according to the output characteristics of each battery and the charging time of the plurality of batteries when the output characteristics of the plurality of batteries are different.

Means for Solving the Problems

[0005] According to one aspect of the present invention, if the predetermined charging time T is shorter than the full charging time Ta which allows the first battery with the highest output to be fully charged, the first battery is preferentially charged by allocating a first charging power to the first battery that is greater than the charging power allocated to each of the second and subsequent batteries from the maximum power of the charger. If the charging time T is longer than the full charging time Ta and shorter than the time Tfull which allows all of the n batteries to be fully charged in the shortest possible time, the charging of the high-voltage energy storage unit is controlled to charge each of the n batteries for a charging time T such that each battery is charged by allocating charging power such that each battery would be fully charged if all n batteries were charged for a time Tfull. [Effects of the Invention]

[0006] According to the charging control method and electric vehicle of the present invention, when multiple batteries have different output characteristics, it is possible to control the charging of each battery appropriately according to the output characteristics of each battery and the charging time for each battery. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing an electric vehicle that implements a charging control method according to one embodiment. [Figure 2] Figure 2 is a block diagram showing a high-voltage energy storage unit and a charging control device included in an electric vehicle according to one embodiment. [Figure 3A] Figure 3A is a partial flowchart showing a charging control method according to one embodiment. [Figure 3B] Figure 3B is a partial flowchart following Figure 3A, showing a charging control method according to one embodiment. [Figure 4A] Figure 4A shows a state in which multiple batteries are charged by a charging control method according to one embodiment, when the charging time T for charging a high-voltage energy storage unit having multiple batteries is shorter than the full charging time Ta that can fully charge the battery with the highest output. [Figure 4B]Figure 4B is a comparative example with Figure 4A, showing a state in which multiple batteries are charged without employing the charging control method according to one embodiment. [Figure 5A] Figure 5A shows a state in which multiple batteries are charged by a charging control method according to one embodiment, when the charging time T is greater than or equal to the full charging time Ta, and is shorter than the time Tfull which allows all of the multiple batteries to be fully charged in the shortest possible time. [Figure 5B] Figure 5B is a comparative example with Figure 5A, showing a state in which multiple batteries are charged without employing the charging control method according to one embodiment. [Figure 6A] Figure 6A shows a state in which multiple batteries are charged by a charging control method according to one embodiment when the charging time T is equal to or greater than time Tfull. [Figure 6B] Figure 6B is a comparative example with Figure 6A, showing a state in which multiple batteries are charged without employing the charging control method according to one embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, a charging control method and an electric vehicle according to one embodiment will be described with reference to the attached drawings. In Figure 1, the electric vehicle 100 is configured as follows. The output shaft of the motor 2 is connected to the differential gear 4 via the propeller shaft 3. The left and right drive wheels 6 are connected to the differential gear 4 via the drive shaft 5. The motor 2 is connected to the high-voltage energy storage unit 13 via the inverter 10, the junction box 11, and the charging circuit 12. The DC power stored in the high-voltage energy storage unit 13 is converted to AC power by the inverter 10 and supplied to the motor 2. The driving force generated by the motor 2 is transmitted to the drive wheels 6, causing the electric vehicle 100 to move.

[0009] During deceleration or regenerative driving on a downhill slope of the electric vehicle 100, the motor 2 acts as a generator due to reverse drive from the drive wheels 6. The negative driving force generated by the motor 2 is transmitted to the drive wheels 6 as braking force, and the AC power generated by the motor 2 is converted to DC power by the inverter 10 and supplied to the high-voltage energy storage unit 13 via the junction box 11 and charging circuit 12 to charge the high-voltage energy storage unit 13. Inside the high-voltage energy storage unit 13, there is a contactor (electromagnetic contactor) that connects or disconnects the electrical circuit. By connecting or disconnecting the electrical circuit with the contactor, the supply and interruption of power to the high-voltage energy storage unit 13 can be controlled.

[0010] The junction box 11 is connected to various electrical devices mounted on the electric vehicle 100. The junction box 11 enables power distribution to these various electrical devices. High-voltage auxiliary equipment 14, such as a cooler compressor or a power steering pump, is connected to the junction box 11. Each of the high-voltage auxiliary equipment 14 operates by receiving power from the high-voltage energy storage unit 13. A low-voltage energy storage unit (not shown) may also be connected to the junction box 11 via a DC-DC converter. This allows for appropriate power supply to devices that operate at low voltage, such as the VCU (vehicle control unit) 30 described later.

[0011] A power receiving port 15 is connected to the junction box 11 via a power supply circuit 16. This allows the junction box 11 to receive a DC current from the charger 20, which is an external power supply device, to charge the high-voltage energy storage unit 13 during rapid charging. In addition, the junction box 11 can receive an AC current from the charger 20 to charge the high-voltage energy storage unit 13 during normal charging. The charger 20 is equipped with a charging plug 21, an AC-DC converter 22, and an AC power supply 23.

[0012] By inserting the charging plug 21 into a power receiving port 15 located at any position on the electric vehicle 100, the alternating current supplied from the AC power source 23 is converted to direct current by the AC-DC converter 22, and the direct current is supplied from the charging plug 21 to the electric vehicle 100. The charger 20 can be, for example, a standard charger, fast charger, or contactless charger using 100V or 200V household power.

[0013] In the case of normal charging, the power supply circuit 16 receives AC current from the charger 20 via the power receiving port 15 and supplies it to the charging circuit 12 via the junction box 11. The power supply circuit 16 may be a circuit with desired characteristics, for example, comprising electronic components such as coils, diodes, transistors, and capacitors, or it may be a circuit that supplies DC current in one direction. The power supply circuit 16 may be located inside the junction box 11.

[0014] A high-voltage energy storage unit 13 is connected to the junction box 11 via a charging circuit 12. The charging circuit 12 receives direct current from the power supply circuit 16 via the junction box 11, supplying direct current to the high-voltage energy storage unit 13. The charging circuit 12 charges the high-voltage energy storage unit 13 with charging power supplied from the charger 20. The charging circuit 12 may be located within the junction box 11. The power stored in the high-voltage energy storage unit 13 is supplied to the junction box 11 via the charging circuit 12. The charging circuit 12 also functions as a discharge circuit. The charging circuit 12 and the discharge circuit may be provided independently of each other.

[0015] The VCU 30 functions as a charge control device and executes a charge control method according to an embodiment. The VCU 30 includes a central processing unit, an input / output device, and a storage device that stores a control program and the like. The VCU 30 controls the charging of the high-voltage power storage unit 13. The VCU 30 acquires charge amount information (SOC (state of charge)) indicating the charge amount of the high-voltage power storage unit 13 and information regarding the battery state such as the battery temperature from the high-voltage power storage unit 13. The VCU 30 can also acquire information regarding the progress status of charging with respect to the high-voltage power storage unit 13. The VCU 30 can also acquire information regarding the presence or absence of connection of the charger 20 from the power receiving port 15.

[0016] Using FIG. 2, the detailed configurations of the high-voltage power storage unit 13 and the VCU 30 and the specific operations regarding the charging of the high-voltage power storage unit 13 will be described. In FIG. 2, the illustration of the configuration between the charger 20 and the charging circuit 12 is omitted. The high-voltage power storage unit 13 has a first battery pack 13a and a second battery pack 13b connected in parallel with each other. The high-voltage power storage unit 13 may have three or more battery packs connected in parallel.

[0017] The first battery pack 13a has a first contact Ca and a first battery Ba connected in series via an internal resistance R. The second battery pack 13b has a second contact Cb and a second battery Bb connected in series via an internal resistance R. The configurations of the third and subsequent battery packs when the high-voltage power storage unit 13 has three or more battery packs are the same as those of the first battery pack 13a and the second battery pack 13b. The first battery Ba and the second battery Bb are batteries having different output characteristics from each other.

[0018] The types of the first battery Ba and the second battery Bb are not limited. As an example, the first battery Ba is a quasi-solid battery and the second battery Bb is a liquid-based lithium-ion battery. Both the first battery Ba and the second battery Bb may be liquid-based lithium-ion batteries having different capacities from each other.

[0019] The first contactor Ca electrically connects the first battery pack 13a to the charging circuit 12 when closed, and disconnects the connection between the first battery pack 13a and the charging circuit 12 when open. The second contactor Cb electrically connects the second battery pack 13b to the charging circuit 12 when closed, and disconnects the connection between the second battery pack 13b and the charging circuit 12 when open.

[0020] The VCU30 includes a charge control unit 31 that individually controls the opening and closing of the first contactor Ca and the second contactor Cb, a full charge time calculation unit 32 that calculates the full charge time by acquiring the SOC1, which is the state of charge (SOC) of the first battery Ba, and the SOC2, which is the state of charge (SOC) of the second battery Bb, and a charge time acquisition unit 33. Users such as the driver can set the charge time T for the first battery Ba and the second battery Bb from the in-vehicle touch panel, charger 20, mobile phone, etc. The charge time acquisition unit 33 acquires the charge time T set by the user.

[0021] The charging time T can be set by the user, determined by constraints imposed by the charger 20, or calculated backward from the required charging capacity. The required charging capacity can be obtained, for example, by dividing the distance to the destination by the estimated energy consumption and multiplying by a safety factor. If the charging time set by the user, the charging time determined by constraints imposed by the charger 20, and the charging time calculated backward from the required charging capacity differ, the shortest of these charging times should be set as the charging time T. In this way, it is possible to achieve a high level of balance between the total charge amount and the output of the first battery Ba and the second battery Bb within the time range in which the first battery Ba and the second battery Bb can be charged.

[0022] The charging control method for the first battery Ba and the second battery Bb (or the third and subsequent batteries) performed by the VCU30 will be explained using the flowcharts shown in Figures 3A and 3B. In Figure 3A, the charging time acquisition unit 33 of the VCU30 acquires the charging time T in step S1. In step S2, the VCU30 calculates the maximum output Pa, Pb, ... for each battery (first battery Ba, second battery Bb, ...). Alternatively, the charger 20 may calculate the maximum output Pa, Pb, ... for each battery and the VCU30 may acquire it. The first battery Ba, the second battery Bb, ... are assumed to have larger maximum outputs Pa, Pb, ... in this order.

[0023] In step S3, the VCU30's full charge time calculation unit 32 calculates the full charge times Ta, Tb, ... for each battery at its maximum output Pa, Pb, .... In step S4, the VCU30 calculates the time Tfull required to fully charge all batteries (first battery Ba, second battery Bb, ...) in the shortest possible time using the charger 20's maximum power Pmax. In step S5, the VCU30 sets the battery Bx to which the charging power Px setting is to be applied to the first battery Ba, which has the highest maximum output. The battery Bx to which the charging power Px setting is to be applied to the battery that will be charged with a charging power Px [kW].

[0024] In Figure 3B, in step S6, the VCU30 determines whether the predetermined charging time T is shorter than the full charging time Tx (here, Ta) of battery Bx (here, the first battery Ba). If the charging time T is shorter than the full charging time Tx (YES), in step S7, the VCU30 sets the charging power of battery Bx to Px. If Px > Pmax, in step S7, the VCU30 sets the charging power of battery Bx to Pmax. In step S8, the VCU30 determines whether battery Bx has the smallest maximum output among all batteries.

[0025] If, in step S8, battery Bx does not have the lowest maximum output among all batteries (NO), then in step S12, VCU30 replaces the maximum power Pmax of charger 20 with the power obtained by subtracting the charging power Px of battery Bx from the maximum power Pmax. In step S13, VCU30 sets the battery Bx to which the charging power Px setting is to be applied to the battery Bx with the next highest maximum output, and returns to step S6.

[0026] If, in step S6, the charging time T is not shorter than the full charging time Tx (NO), then in step S9, the VCU30 determines whether the predetermined charging time T is shorter than the time Tfull required to fully charge all batteries in the shortest possible time. If the charging time T is shorter than time Tfull (YES), then in step S10, the VCU30 sets the charging power of battery Bx to an output that will fully charge it in charging time T, and proceeds to step S8. If, in step S9, the charging time T is not shorter than time Tfull (NO), then in step S11, the VCU30 sets the charging power of each battery to an output that will fully charge it in time Tfull, and proceeds to step S14.

[0027] In step S14, the VCU30 charges each battery to full charge with the set charging power and then terminates the process.

[0028] Using Figures 4A to 6B, we will specifically explain how the VCU 30 controls the charging of each battery in the high-voltage energy storage unit 13, which has multiple batteries with different output characteristics, according to the output characteristics and charging time T.

[0029] The high-voltage energy storage unit 13 consists of a first battery to the nth battery, each having different output characteristics, where n is an integer of 2 or more. The first battery has the highest output, and the output decreases as the value of n increases. The VCU 30 controls the charging of this high-voltage energy storage unit 13. If n is 2, the high-voltage energy storage unit 13 has a first battery Ba and a second battery Bb, and the maximum output of the first battery Ba is greater than the maximum output of the second battery Bb.

[0030] Figure 4A shows a charging control method according to one embodiment when the charging time T is shorter than the full charging time Ta. As shown in Figure 4A(a), the VCU 30 allocates a first charging power to the first battery Ba that is greater than the charging power allocated to the second battery Bb from the maximum power of the charger 20. As a result, as shown in Figure 4A(b), the VCU 30 preferentially charges the first battery Ba. If the high-voltage energy storage unit 13 has n batteries, the VCU 30 preferentially charges the first battery by allocating a first charging power to the first battery that is greater than the charging power allocated to each battery from the second battery onward from the maximum power of the charger 20.

[0031] Figure 4B is a comparative example with Figure 4A. As shown in Figure 4B(a), the VCU 30 allocates more charging power to the second battery Bb than the charging power allocated to the first battery Ba from the maximum power of the charger 20. In the comparative example shown in Figure 4B, the first battery Ba, which has a larger maximum output, is charged with less capacity than the second battery Bb, thus limiting the time during which it can exert output after charging.

[0032] In contrast, in Figure 4A, since the first battery Ba, which has a larger maximum output, is charged with a larger capacity, the time during which it can exert output after charging can be extended. When a high output request is made while the electric vehicle 100 is running, it becomes possible to meet the request at a high level. Therefore, it is preferable for the VCU 30 to control the charging of the first battery Ba and the second battery Bb as shown in Figure 4A.

[0033] The VCU 30 charges the second battery Bb by allocating power to it obtained by subtracting the first charging power from the maximum power of the charger 20. If the high-voltage energy storage unit 13 has a third or subsequent battery, the VCU 30 charges the batteries from the second battery Bb onward by allocating power obtained by subtracting the first charging power from the maximum power to each of the subsequent batteries. In this way, the output characteristics of the charger 20 can be maximized.

[0034] In detail, let m be an integer greater than or equal to 3, and assume that there are batteries from the mth battery onward. For the (m-1)th battery, the VCU30 charges the (m-1)th battery by allocating a power that is greater than the power allocated to each battery from the mth battery onward, which is obtained by subtracting the first charging power from the maximum power. For the batteries from the mth battery onward, the VCU30 charges them by allocating a power that is obtained by subtracting the charging power up to the (m-1)th battery from the power obtained by subtracting the first charging power from the maximum power. In this way, the output after charging and the total charge amount can be satisfied at a high level.

[0035] Figure 5A shows a charging control method according to one embodiment, where the charging time T is greater than or equal to the full charging time Ta, but shorter than time Tfull. The VCU 30 controls the charging of the high-voltage energy storage unit 13 by allocating charging power such that the first battery Ba and the second battery Bb would be fully charged if they were charged for time Tfull. Figure 5A(a) shows the allocation of charging power such that the first battery Ba and the second battery Bb are fully charged. Since the charging time T is shorter than time Tfull, the VCU 30 charges the first battery Ba and the second battery Bb for charging time T while under such control, as shown in Figure 5A(b).

[0036] If the high-voltage energy storage unit 13 has n batteries, the VCU 30 controls the charging of the high-voltage energy storage unit 13 by allocating charging power to each of the n batteries such that each battery would be fully charged if all n batteries were charged for a total time T. The VCU 30 charges each battery for a charging time T under these controlled conditions. By controlling each battery for a charging time T under these conditions, the maximum power of the charger 20 can be fully utilized.

[0037] Figure 5B is a comparative example with Figure 5A. As shown in Figure 5B(a), the charger 20 allocates more charging power to the first battery Ba than to the second battery Bb, so that the first battery Ba is fully charged in the full charging time Ta. In this case, as shown in Figure 5B(b), the first battery Ba is fully charged before the charging time T, but the charger 20's maximum power cannot be fully utilized. Therefore, it is preferable for the VCU 30 to control the charging of the first battery Ba and the second battery Bb as shown in Figure 5A.

[0038] Figure 6A shows a charging control method according to one embodiment when the charging time T is equal to or greater than time Tfull. Time Tfull is the time required to fully charge the first battery Ba and the second battery Bb with the maximum power of the charger 20. As shown in Figures 6A(a) and (b), the VCU 30 controls the charging of the high-voltage energy storage unit 13 by allocating charging power such that the first battery Ba and the second battery Bb would be fully charged if they were charged for time Tfull. Therefore, the charging time required to fully charge the first battery Ba and the second battery Bb can be minimized.

[0039] Figure 6B is a comparative example with Figure 6A. As shown in Figures 6B(a) and (b), the VCU 30 does not allocate charging power such that the first battery Ba and the second battery Bb will be fully charged if they are charged for a full time T. If the second battery Bb is not fully charged, the charging speed decreases and the second battery Bb cannot be fully charged. Therefore, it is preferable for the VCU 30 to control the charging of the first battery Ba and the second battery Bb as shown in Figure 6A.

[0040] As described above, according to the charging control method and electric vehicle 100 of one embodiment, when the output characteristics of multiple batteries are different, it is possible to control the charging of each battery appropriately according to the output characteristics of each battery and the charging time for each battery.

[0041] Incidentally, the high-voltage energy storage unit 13 may be charged without (or without) pre-determining the charging time T. In such cases, it is desirable that the VCU 30 be configured to allow the user to freely select between the charging control mode for the high-voltage energy storage unit 13 shown in Figure 4A and the charging control mode for the high-voltage energy storage unit 13 shown in Figure 5A, regardless of the charging time T. The control mode shown in Figure 4A is the control mode that the VCU 30 executes when the charging time T is shorter than the full charging time Ta. The control mode shown in Figure 5A is the control mode that the VCU 30 executes when the charging time T is greater than or equal to the full charging time Ta and shorter than time Tfull. Allowing the user to freely select the control mode improves usability.

[0042] Furthermore, the VCU 30 may be configured as follows: It may be configured to allow the user to change the charging time of the high-voltage energy storage unit 13 after charging has started. For example, the VCU 30 may communicate with the user's smartphone to shorten the charging time when the user approaches the electric vehicle 100 and lengthen the charging time when the user moves away from the electric vehicle 100. The user or the electric vehicle 100 may be notified when the charging time of the charger 20 is changed. The user can obtain the information that the charging time has been changed by having the smartphone application program communicate with the charger 20 or the electric vehicle 100.

[0043] The VCU 30 may determine whether to prioritize output or capacity based on the traffic congestion conditions of the surrounding roads where the electric vehicle 100 is traveling. For example, the charger 20 or the electric vehicle 100 may communicate with a server via the internet or acquire probe traffic information to determine which to prioritize.

[0044] The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0045] 2 motors 3 Propeller shafts 4 Differential device 5 Drive shaft 6 drive wheels 10 Inverters 11 Junction Box 12 Charging circuit 13. High-voltage energy storage unit 13a First Battery Pack 13b Second battery pack 14. High-voltage auxiliary equipment 15 Power receiving port 16 Power supply circuit 20 charger 21 Charging plug 22 AC-DC Converters 30 VCU (Charging Control Unit) 31 Charging Control Unit 32 Full charge time calculation unit 33 Charging time acquisition section 100 Electric Vehicles Ba, the first battery Bb Second Battery Ca First Contactor Cb Second Contactor R internal resistance

Claims

1. A charge control device for a high-voltage energy storage unit having n batteries, where n is an integer of 2 or more, and each battery has different output characteristics from the first battery to the nth battery, with the first battery having the highest output and the output decreasing as the value of n increases, is provided. If the default charging time T is shorter than the full charging time Ta that can fully charge the first battery, The first battery is charged preferentially by allocating a first charging power, which is greater than the charging power allocated to each of the second and subsequent batteries, from the maximum power of the charger. For the batteries from the second battery onward, the power obtained by subtracting the first charging power from the maximum power is allocated to charge the batteries from the second battery onward. When there are batteries beyond the m-th battery, where m is an integer of 3 or more, the (m-1) battery is charged by allocating a charging power to the (m-1) battery that is greater than the charging power allocated to each battery beyond the m-th battery, which is obtained by subtracting the first charging power from the maximum power. For batteries from battery m onward, the power obtained by subtracting the first charging power from the maximum power, and then further subtracting the charging power up to (m-1), is allocated to charge the batteries from battery m onward. If the charging time T is longer than the full charging time Ta, and shorter than the time Tfull required to fully charge all of the n batteries in the shortest possible time, The high-voltage energy storage unit controls the charging of each of the n batteries in such a way that the charging power allocated to each battery would result in a full charge if all n batteries were charged for the time T. Charging control method.

2. The charging control method according to claim 1, wherein the charging time T is set by the user, determined by constraints imposed by the charger, or calculated backward from the required charging capacity.

3. The charging control method according to claim 2, wherein the charging time T is the shortest of the charging time set by the user, the charging time determined by the constraints of the charger, and the charging time calculated backward from the required charging capacity.

4. The charging control method according to claim 1, wherein the user can freely select a charging control mode for the high-voltage energy storage unit to be executed when the charging time T is shorter than the full charging time Ta, and a charging control mode for the high-voltage energy storage unit to be executed when the charging time T is longer than the full charging time Ta and shorter than the time Tfull, regardless of the charging time T.

5. A high-voltage energy storage unit having n batteries, where n is an integer of 2 or more, and each battery has different output characteristics, from the first battery to the nth battery, with the first battery having the highest output and the output decreasing as the value of n increases. A charging control device that controls the charging of the n batteries, Equipped with, The charging control device is If the default charging time T is shorter than the full charging time Ta that can fully charge the first battery, The first battery is charged preferentially by allocating a first charging power, which is greater than the charging power allocated to each of the second and subsequent batteries, from the maximum power of the charger. For the batteries from the second battery onward, the power obtained by subtracting the first charging power from the maximum power is allocated to charge the batteries from the second battery onward. When there are batteries beyond the m-th battery, where m is an integer of 3 or more, the (m-1) battery is charged by allocating a power to the (m-1) battery that is greater than the power allocated to the batteries beyond the m-th battery, which is obtained by subtracting the first charging power from the maximum power. For each battery from battery m onward, the power obtained by subtracting the first charging power from the maximum power, and then further subtracting the charging power up to (m-1), is allocated to charge the batteries from battery m onward. If the charging time T is longer than the full charging time Ta, and shorter than the time Tfull required to fully charge all of the n batteries in the shortest possible time, The high-voltage energy storage unit controls the charging of each of the n batteries in such a way that the charging power allocated to each battery would result in a full charge if all n batteries were charged for the time T. Electric vehicle.

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