Battery management device

Abstract

To provide a battery management device capable of controlling charging and discharging of a battery of a vehicle in a high SOC region while the vehicle is parked.SOLUTION: A battery management device for controlling the capacity of a battery while a vehicle is parked, comprises: an acquisition unit that acquires information on dark current flowing out from the battery every time the prescribed timing comes; a prediction unit that predicts the capacity consumed by the battery until the next timing comes from the current timing on the basis of the information on the dark current acquired by the acquisition unit; an estimation unit that estimates the capacity of the battery at the time when the next timing comes on the basis of the consumption capacity of the battery predicted by the prediction unit; and a request unit that requests battery charging when the capacity of the battery estimated by the estimation unit is equal to or less than a prescribed threshold.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery management device that manages charging and discharging of a battery mounted on a vehicle.

Background Art

[0002] Patent Document 1 discloses a system for managing charging control for an electric vehicle parked in parking facilities. In this system, it is described that the battery of the electric vehicle is charged to full charge at the parking section provided in the parking facilities, the battery capacity of the electric vehicle after full charge is periodically monitored, and the battery is recharged by detecting that the battery capacity has decreased below a predetermined capacity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a lithium iron phosphate ion battery (LFP battery) is used for the battery of a vehicle, it is desirable to perform charging and discharging always in a region where the state of charge is high (high SOC region) in order to prevent cycle degradation. However, in the technology described in Patent Document 1, since the charging control of a plurality of vehicles with different types of batteries mounted is uniformly performed during parking, optimal control may not be performed on the battery. Therefore, there is room for further consideration regarding a method for optimally performing the charging and discharging control of the vehicle battery.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a battery management device capable of performing charging and discharging control of a vehicle battery in a high SOC region while the vehicle is parked.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the disclosed technology is a battery management device that controls the capacity of a battery while the vehicle is parked. The battery management device includes an acquisition unit that acquires information on the leakage current flowing out of the battery each time a predetermined timing arrives, a prediction unit that predicts the capacity consumed by the battery from the current timing to the next timing based on the leakage current information acquired by the acquisition unit, an estimation unit that estimates the capacity of the battery when the next timing arrives based on the predicted capacity consumption of the battery by the prediction unit, and a request unit that requests charging of the battery when the capacity of the battery estimated by the estimation unit is equal to or less than a predetermined threshold value.

Advantages of the Invention

[0007] According to the battery management device of the present disclosure, the necessity of battery charging is determined based on the capacity consumption of the battery predicted from the leakage current during parking in the vehicle unit, so that charge and discharge control of the battery can always be performed in a high SOC region.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] The battery management device of the present disclosure predicts the tendency of the capacity reduction of the auxiliary battery during parking based on the leakage current flowing from the auxiliary battery to the load, and charges the auxiliary battery with the high-voltage battery before the capacity of the auxiliary battery becomes equal to or less than the reference value. As a result, charge and discharge control of the auxiliary battery can always be performed in a high SOC region. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] <Embodiment> [Configuration] FIG. 1 is a functional block diagram of a battery management device 25 and its peripheral parts according to an embodiment of the present disclosure. The functional blocks illustrated in FIG. 1 include a high-voltage battery 10, an auxiliary battery 20, a high-voltage DCDC converter 30, a master ECU 40, and a plurality of loads 50. In FIG. 1, power lines for power transfer are indicated by solid lines, and signal lines through which request instructions flow are indicated by dashed lines.

[0011] The configuration shown in FIG. 1 can be mounted on electric vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs) as an example.

[0012] The high-voltage battery 10 is a secondary battery configured to be chargeable and dischargeable, such as a lithium-ion battery, for example. The high-voltage battery 10 can supply the power it stores to a plurality of loads 50 and the auxiliary battery 20 via the high-voltage DCDC converter 30 and a plurality of switches SW. Further, the high-voltage battery 10 can store the power output from a generator (not shown) such as an alternator. In an electric vehicle, for example, the drive battery corresponds to the high-voltage battery 10.

[0013] The auxiliary battery 20 is a secondary battery configured to be chargeable and dischargeable, such as an LFP battery, for example. The auxiliary battery 20 stores the power output from the high-voltage battery 10 via the high-voltage DCDC converter 30, or supplies the power it stores to the loads 50 via a plurality of switches SW. This auxiliary battery 20 includes, in addition to the battery cells connected in series, a battery management device 25 and a switch SW whose electrical connection state can be switched under the control of the battery management device 25. This auxiliary battery 20 alternately transitions between a wake-up state in which all functions are activated and a sleep state in which some functions are stopped at a certain cycle in order to reduce power consumption during parking.

[0014] As shown in FIG. 2, for this auxiliary battery 20, a “usable area”, which is the amount of power of the battery allowed to be used by discharge, is predetermined as the lower limit of the battery capacity [Ah] or the state of charge (SOC) [%] of the battery. This lower limit value is set to a value that can suppress, for example, the deterioration of the auxiliary battery 20 due to charge and discharge processing to the content required for the electric vehicle.

[0015] The battery management device 25 is a configuration for managing the state of the auxiliary battery 20 including charge and discharge control of the auxiliary battery 20, and is typically a microcomputer. This battery management device 25 can acquire information on the leakage current flowing from the auxiliary battery 20 to a plurality of loads 50 (acquisition unit), predict the capacity consumed by the auxiliary battery 20 based on the acquired leakage current information (prediction unit), estimate the capacity (remaining capacity) or state of charge of the auxiliary battery 20 based on the predicted consumed capacity of the auxiliary battery 20 (estimation unit), and request charging of the auxiliary battery 20 based on the estimated capacity or state of charge of the auxiliary battery 20 (request unit). The acquisition of the leakage current information and the prediction of the capacity (state of charge) of the auxiliary battery 20 can be performed using the detection values of detection devices (voltage sensors, current sensors, temperature sensors, etc.) provided in the auxiliary battery 20.

[0016] The high-voltage DCDC converter 30 is provided between the high-voltage battery 10 and the integrated ECU 40, and is a voltage converter that converts the input voltage of the high-voltage battery 10 into the voltage required for the auxiliary battery 20 and the load 50 and outputs it to each component via the integrated ECU 40. For this high-voltage DCDC converter 30, for example, a step-down type DCDC converter that steps down the voltage of the high-voltage battery 10 and outputs it to the auxiliary battery 20 and the load 50 can be used.

[0017] The overall ECU 40 is a configuration (Electronic Control Unit) for controlling the power transfer between the high-voltage battery 10, the auxiliary battery 20, and the plurality of loads 50. This overall ECU 40 includes a microcomputer 45 and a plurality of switches SW whose electrical connection states can be switched under the control of the microcomputer 45.

[0018] The microcomputer 45 is communicably connected to the battery management device 25 of the auxiliary battery 20 and a network such as CAN. In response to a charging request (described later) output from the battery management device 25, this microcomputer 45 performs control to charge the auxiliary battery 20 with the power of the high-voltage battery 10.

[0019] The plurality of loads 50 are in-vehicle devices that operate with the power supplied from the high-voltage battery 10 or the power supplied from the auxiliary battery 20 via the high-voltage DCDC converter 30. Note that the number of loads mounted on the vehicle is not limited to the number shown in FIG. 1.

[0020] [Control] Next, with further reference to FIG. 3, the control performed by the battery management device 25 according to the present embodiment will be described. FIG. 3 is a flowchart for explaining the processing procedure of the charge and discharge control of the auxiliary battery 20 executed by the battery management device 25.

[0021] The charge and discharge control of the auxiliary battery 20 illustrated in FIG. 3 is started when the electric vehicle is in the parked state (IG-OFF) and is repeatedly performed until the electric vehicle becomes the starting state (IG-ON).

[0022] (Step S301) The battery management device 25 determines whether it is the timing to activate a predetermined function for performing the charge and discharge control of the auxiliary battery 20. This activation timing can be arbitrarily set, such as at a fixed cycle. When the battery management device 25 determines that it is the activation timing (Step S301, Yes), after activating the predetermined function, the process proceeds to Step S202.

[0023] (Step S302) While the electric vehicle is parked, the auxiliary battery management device 25 acquires information on the leakage current flowing from the auxiliary battery 20 to the plurality of loads 50. The leakage current is the current consumed by functions related to the authentication of the electronic key and the like. The acquired leakage current information is sequentially stored in a storage unit or the like (not shown), and necessary learning is performed. When the auxiliary battery management device 25 acquires the leakage current information of the auxiliary battery 20, the process proceeds to step S303.

[0024] (Step S303) The auxiliary battery management device 25 acquires the current capacity (or state of charge) of the current auxiliary battery 20. This capacity (or state of charge) can be derived from the detection value of a detection device provided in the auxiliary battery 20. When the auxiliary battery management device 25 acquires the capacity (or state of charge) of the auxiliary battery 20, the process proceeds to step S304.

[0025] (Step S304) Based on the leakage current information of the auxiliary battery 20 acquired in step S302 above, the auxiliary battery management device 25 predicts the capacity consumed by the auxiliary battery 20 during the startup timing intervals. The startup timing intervals refer to the period from the current startup timing when the latest leakage current information of the auxiliary battery 20 is acquired to the next startup timing. When the startup timing arrives at a fixed cycle, the time interval of this cycle is the startup timing interval.

[0026] As an example, the consumption capacity Cc [Ah] of the auxiliary battery 20 during the startup timing intervals of time T [h] can be predicted by the following formula (1) using the leakage current I [A] of the current auxiliary battery 20. Alternatively, in order to improve the prediction accuracy, instead of the leakage current I, the average value AVE_I [A] of the leakage currents of the plurality of auxiliary batteries 20 that have been acquired so far can be used to predict by the following formula (2). Consumption capacity Cc = leakage current I × time T …(1) Consumption capacity Cc = average leakage current AVE_I × time T …(2)

[0027] When the battery management device 25 predicts the consumption capacity of the auxiliary battery 20 during the startup timings, the process proceeds to step S305.

[0028] (Step S305) The battery management device 25 determines whether the capacity (or state of charge) of the auxiliary battery 20 estimated at the next startup timing is equal to or lower than a predetermined threshold value. This determination is to determine whether there is a possibility that the auxiliary battery 20 will exhaust the capacity in an unfavorable usage area regarding deterioration before the next startup timing arrives. Therefore, as the predetermined threshold value, the lower limit value of the capacity of the auxiliary battery 20 or the lower limit value of the state of charge (SOC) described above is used.

[0029] The estimated capacity Ce (or estimated state of charge) of the auxiliary battery 20 can be obtained by subtracting the capacity Cc [Ah] (or state of charge [%]) that the auxiliary battery 20 consumes from the current capacity Cp [Ah] (or state of charge [%]) of the auxiliary battery 20 acquired in step S303 above, as shown in the following formula (3), until the next startup timing predicted in step S304 above. Estimated capacity Ce = Current capacity Cp - Consumption capacity Cc...(3)

[0030] Also, in order to improve the estimation accuracy, instead of the consumption capacity Cc, the average value AVE_Cc [Ah] of the consumption capacities of a plurality of auxiliary batteries 20 predicted so far may be used (the following formula (4)). Alternatively, the total value TOTAL_Cc [Ah] of the consumption capacities of a plurality of auxiliary batteries 20 predicted after the auxiliary battery 20 reaches the full charge capacity Cmax may be obtained by subtracting it from the full charge capacity Cmax (the following formula (5)). Estimated capacity Ce = Current capacity Cp - Average consumption capacity AVE_Cc...(4) Estimated capacity Ce = Full charge capacity Cmax - Total consumption capacity TOTAL_Cc...(5)

[0031] When the battery management device 25 determines that the estimated capacity (or estimated state of charge) of the auxiliary battery 20 at the next startup timing is equal to or lower than a predetermined threshold (step S305, yes), the process proceeds to step S306. On the other hand, when the battery management device 25 determines that the estimated capacity (or estimated state of charge) of the auxiliary battery 20 at the next startup timing does not become equal to or lower than the predetermined threshold (step S305, no), the process returns to step S301.

[0032] (Step S306) The battery management device 25 executes charging of the auxiliary battery 20 using the power of the high-voltage battery 10. This charging is performed by the battery management device 25 transmitting a charging request from the high-voltage battery 10 to the auxiliary battery 20 to the integrated ECU 40. The integrated ECU 40 that has received the charging request controls (instructs) the high-voltage DCDC converter 30 to perform power transfer between the high-voltage battery 10 and the auxiliary battery 20. When the battery management device 25 executes charging of the auxiliary battery 20 using the power of the high-voltage battery 10, the process returns to step S301.

[0033] <Operation and Effect> According to the battery management device 25 according to the above-described embodiment of the present disclosure, the capacity consumed by the auxiliary battery 20 during a predetermined period is predicted based on the quiescent current flowing out of the auxiliary battery 20 while parked, the change in the battery capacity is estimated based on the predicted consumption capacity of the auxiliary battery 20, and it is determined whether the capacity of the auxiliary battery 20 will become equal to or lower than a threshold value that affects battery capacity degradation in the near future. Then, when it is determined that the capacity of the auxiliary battery 20 is likely to become equal to or lower than the threshold value in the near future, the auxiliary battery 20 is charged.

[0034] By this control, since the auxiliary battery 20 is charged in advance so as not to become equal to or lower than the threshold value, it is possible to always perform charge / discharge control of the auxiliary battery 20 in a high SOC region. Therefore, it is possible to suppress the progress of degradation of the auxiliary battery 20.

[0035] Also, according to the battery management device 25 according to the present embodiment, by predicting the consumption capacity of the auxiliary battery 20 based on the average value (learning) of the dark current, the prediction accuracy can be improved even when the dark current can be obtained only at the start timing. Further, the estimation accuracy can be improved by estimating the capacity of the auxiliary battery 20 based on the average value of the consumption capacity of the auxiliary battery 20.

[0036] Also, according to the battery management device 25 according to the present embodiment, since the charging determination is made using the consumption capacity of the auxiliary battery 20, it can be applied to a battery in which it is difficult to specify the state of charge SOC by voltage, such as an LFP battery having a flat region (section) in the SOC-OCV characteristic.

[0037] Note that, among the services provided during parking, there may be a service that consumes a large amount of dark current even when the auxiliary battery 20 is in the sleep state. In such a case, if a dark current equal to or greater than a certain value is flowing, the auxiliary battery 20 may be activated without waiting for the activation timing (wake-up state). At this time, the consumption capacity of the auxiliary battery 20 may be predicted and the capacity may be estimated from the elapsed time since the previous activation timing and the current dark current.

[0038] As described above, one embodiment of the present disclosure has been described. However, the present disclosure can be regarded not only as the above-described battery management device, but also as a method executed by a battery management device including a processor and a memory, a program of the method, a computer-readable non-transitory recording medium storing the program, or a vehicle equipped with the battery management device.

Industrial Applicability

[0039] The battery management device of the present disclosure can be used in a vehicle including a high-voltage battery and an auxiliary battery.

Explanation of Reference Numerals

[0040] 10 High-voltage battery Auxiliary battery Battery management device High-voltage DCDC converter Integrated ECU Microcomputer Load

Claims

1. A battery management device that controls a capacity of a battery while a vehicle is parked, an acquisition unit that acquires information on a dark current flowing out of the battery at each predetermined timing; a prediction unit that predicts a capacity consumed by the battery from a current timing to a next timing based on the information on the dark current acquired by the acquisition unit; an estimation unit that estimates a capacity of the battery at the next timing based on the consumption capacity of the battery predicted by the prediction unit; a request unit that requests charging of the battery when the capacity of the battery estimated by the estimation unit is equal to or smaller than a predetermined threshold.

2. The battery management device according to claim 1 , wherein the prediction unit predicts a consumed capacity of the battery from the current timing to the next timing based on an average value of a plurality of the dark currents previously acquired by the acquisition unit.

3. The battery management device according to claim 1 , wherein the estimation unit estimates the capacity of the battery at the next timing based on an average value of a plurality of consumed capacities of the battery predicted in the past by the prediction unit.

4. 4. The battery management device according to claim 1, wherein the predetermined timing is determined by a constant cycle.

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