Charging control device

Abstract

To provide a charging control device capable of controlling charging of a lithium ion battery without exceeding an upper limit current that causes no lithium deposition even when a consumption current on a load side is significantly reduced during charging of the lithium ion battery.SOLUTION: A charging control device includes: a first processing unit configured to estimate an inflow current flowing into a lithium ion battery when a current flowing through a load disappears; a second processing unit configured to derive a protection charging current that is a maximum value of a charging current that causes no lithium deposition in the lithium ion battery; a third processing unit configured to calculate a charging upper limit current that is an upper limit value of a current for charging the lithium ion battery based on the protection charging current and the inflow current; and a fourth processing unit configured to control charging of the lithium ion battery based on limit power calculated from the charging upper limit current and a voltage of the lithium ion battery.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a charge control device for controlling the charging of a lithium-ion battery.

Background Art

[0002] Patent Document 1 discloses a charge-discharge control device capable of improving the controllability of charge-discharge operations while sufficiently protecting the performance of a lithium-ion battery. In this charge-discharge control device, it is described that feed-forward control for performing stable control using an input-output map of the battery and feedback control for performing limitation based on a limit value when feed-forward control is difficult are used in combination.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the charge-discharge control device described in Patent Document 1, in order not to cause lithium precipitation in the lithium-ion battery, feedback control is performed so as not to exceed the upper limit current obtained from the charging current, and the charge and discharge of the lithium-ion battery are controlled.

[0005] However, in a system in which charging from a generator to a lithium-ion battery and power supply to a load can be executed in parallel, the consumption current on the load side may greatly decrease (such as the operation of the load stopping) during the charging of the lithium-ion battery. In this case, the current portion (surplus current) that is no longer consumed by the load flows into the lithium-ion battery. However, if the surplus current is large, the feedback control may not be in time, and there is a possibility of exceeding the upper limit current that does not cause lithium precipitation.

[0006] The present disclosure has been made in view of the above problems, and even when the charging current increases due to a decrease in the consumption current on the load side during the charging of a lithium-ion battery, it is possible to control the charging of the lithium-ion battery without exceeding the upper limit current that does not cause lithium precipitation. The purpose is to provide a charge control device.

Means for Solving the Problems

[0007] In order to solve the above problems, one aspect of the present disclosure technology is a charge control device for controlling the charging of a lithium-ion battery, including a first processing unit that estimates the inflow current flowing into the lithium-ion battery when the current flowing through the load becomes zero, and a second processing unit that derives a protection charging current that is the maximum value of the charging current that does not cause lithium precipitation in the lithium-ion battery, and a third processing unit that calculates a charging upper limit current that is the upper limit value of the current for charging the lithium-ion battery based on the protection charging current and the inflow current, and a fourth processing unit that controls the charging of the lithium-ion battery based on the limiting power calculated from the charging upper limit current and the voltage of the lithium-ion battery. It is a charge control device.

Effects of the Invention

[0008] According to the charge control device of the present disclosure, even when the current consumption of the load disappears and the charging current of the lithium-ion battery increases during the charging of the lithium-ion battery, it is possible to control the charging of the lithium-ion battery without exceeding the upper limit current that does not cause lithium precipitation.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0010] When the charging control device of the present disclosure performs charging of a lithium-ion battery and power supply to a load using a power source, it assumes a scenario where the current flowing into the lithium-ion battery increases as the current consumption of the load stops, and controls the charging of the lithium-ion battery after obtaining in advance the charging upper limit current in such a scenario. Thereby, the occurrence of lithium precipitation in the lithium-ion battery can be avoided. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] <Embodiment> [Configuration] FIG. 1 is a functional block diagram of a charging control device 100 according to an embodiment of the present disclosure and its peripheral parts. This FIG. 1 shows an example in which a lithium-ion battery 41 mounted on a vehicle is controlled by the charging control device 100. The functional blocks illustrated in FIG. 1 include an engine 10, a motor generator (MG) 20, an electronic load 30, an Li battery module 40, an auxiliary battery 50, and a charging control device 100.

[0012] The engine 10 is an internal combustion engine that serves as a power source of the vehicle. This engine 10 is started by a motor generator (MG) 20 or the like.

[0013] The motor generator (MG) 20 is an electric generator having both an electric motor function for starting the engine 10 and a generator function for generating power by being driven by the power of the engine 10 or a regenerative operation. This motor generator (MG) 20 exhibits the electric motor function by the power supplied from the Li battery module 40.

[0014] The electronic load 30 is various devices and systems that consume the electric power mounted on the vehicle. This electronic load 30 is configured to operate with at least any one of the electric power generated by the motor generator (MG) 20, the electric power supplied from the Li battery module 40 via the charge control device 100, and the electric power stored in the auxiliary battery 50. As the electronic load 30, auxiliary devices (such as air conditioning devices and lighting devices) other than those for driving the vehicle can be exemplified.

[0015] The Li battery module 40 is a unit including a secondary battery configured to be chargeable and dischargeable. This Li battery module 40 includes a lithium ion battery 41 and a sensor 42. The lithium ion battery 41 is a secondary battery and takes, for example, a stack configuration in which a plurality of lithium ion battery cells are connected in series. The sensor 42 is a configuration for detecting the state of the lithium ion battery 41. Various sensors such as a voltage sensor for monitoring the voltage of the lithium ion battery 41, a current sensor for monitoring the current flowing in and out of the lithium ion battery 41, and a temperature sensor for monitoring the temperature of the lithium ion battery 41 are used for this sensor 42.

[0016] This Li battery module 40 stores the electric power output by the motor generator (MG) 20 or outputs the electric power it stores to the charge control device 100. As this Li battery module 40, a battery module with a rated voltage of 48V used in a so-called mild hybrid system can be exemplified.

[0017] The auxiliary battery 50 is a secondary battery configured to be chargeable and dischargeable, such as a lead-acid battery or a lithium ion battery. This auxiliary battery 50 stores the electric power output from the charge control device 100 or supplies the electric power it stores to the electronic load 30. As this auxiliary battery 50, a battery with a rated voltage of 12V can be exemplified.

[0018] The charging control device 100 is configured to control the charging of the lithium-ion battery 41 of the Li battery module 40. This charging control device 100 includes a DDC circuit 101 and a control processing unit 102.

[0019] The DDC circuit 101 is a step-down DCDC converter that converts the input power into a predetermined voltage and outputs it. This DDC circuit 101 is arranged between the motor generator (MG) 20 and the Li battery module 40 and the electronic load 30 and the auxiliary battery 50, and steps down the 48V system power input from the motor generator (MG) 20 and the Li battery module 40 to 12V system power and outputs it to the electronic load 30 and the auxiliary battery 50. The operation of the DDC circuit 101 is controlled by the control processing unit 102.

[0020] The control processing unit 102 acquires the state (voltage, current, temperature) of the lithium-ion battery 41 from the sensor 42 of the Li battery module 40. Also, the control processing unit 102 acquires the value of the current flowing from the DDC circuit 101 to the electronic load 30 (and the auxiliary battery 50) (hereinafter referred to as "12V current"). This 12V current can be acquired using a current sensor (not shown) provided at the output stage of the DDC circuit 101. Then, the control processing unit 102 controls the charging of the lithium-ion battery 41 based on the state of the lithium-ion battery 41 and the 12V current. The charging control of this lithium-ion battery 41 will be described later.

[0021] Note that part or all of the above-described charging control device 100 can typically be configured by an electronic control unit (ECU) including a processor such as a microcomputer, a memory, and an input / output interface. This electronic control device can realize part or all of the above-described functions by the processor reading and executing the program stored in the memory.

[0022] [Control] Next, with further reference to FIG. 2, the control performed by the charging control device 100 according to the present embodiment will be described. FIG. 2 is a flowchart for explaining the charging control processing procedure of the lithium-ion battery 41 executed by the control processing unit 102 of the charging control device 100.

[0023] The charging control of the lithium-ion battery 41 illustrated in FIG. 2 is started, for example, when the vehicle system is started, and is repeatedly performed at a predetermined timing (such as a constant cycle) until the vehicle system stops.

[0024] (Step S201) Based on the 12V current output from the DDC circuit 101, the control processing unit 102 of the charging control device 100 estimates the inflow current to the lithium-ion battery 41 that is expected to increase when the electronic load 30 stops (first process). This inflow current (hereinafter referred to as "estimated inflow current") can be estimated by the following formula [1] using a current conversion coefficient and a DDC efficiency coefficient. Estimated inflow current = 12V current × current conversion coefficient × DDC efficiency coefficient... [1]

[0025] Here, the current conversion coefficient is a coefficient (48V / 12V) for converting the value of the 12V current into the value of the current flowing from the motor generator (MG) 20 to the DDC circuit 101 (hereinafter referred to as "48V current"). The DDC efficiency coefficient is a coefficient corresponding to the conversion efficiency in the DDC circuit 101. When the system is such that the DDC circuit 101 does not perform a step-down operation, the current conversion coefficient may be omitted.

[0026] When the inflow current to the lithium-ion battery 41 is estimated by the control processing unit 102, the process proceeds to step S202.

[0027] (Step S202) The control processing unit 102 of the charging control device 100 derives the Li precipitation protection charging current of the lithium-ion battery 41 (second process). This Li precipitation protection charging current is the maximum value of the charging current that can charge the lithium-ion battery 41 without generating lithium precipitation. The Li precipitation protection charging current is derived based on the voltage, current, and temperature of the lithium-ion battery 41 at the time of derivation, and further based on the state of charge (SOC) calculated from this information. Note that various well-known methods can be used to derive the Li precipitation protection charging current.

[0028] When the control processing unit 102 derives the Li precipitation protection charging current of the lithium-ion battery 41, the process proceeds to step S203.

[0029] (Step S203) The control processing unit 102 of the charging control device 100 derives the charging upper limit current of the lithium-ion battery 41 (third process). This charging upper limit current is the upper limit value of the charging current that can charge the lithium-ion battery 41 without generating lithium precipitation, taking into account the current increase toward the lithium-ion battery 41 when the operation of the electronic load 30 stops and current consumption disappears. The charging upper limit current is derived by the following formula [2] based on the estimated inflow current estimated in step S201 and the Li precipitation protection charging current derived in step S202. Charging upper limit current = Li precipitation protection charging current - estimated inflow current …[2]

[0030] When the control processing unit 102 derives the charging upper limit current of the lithium-ion battery 41, the process proceeds to step S204.

[0031] (Step S204) The control processing unit 102 of the charging control device 100 derives the limited power of the lithium-ion battery 41 (fourth process). This limited power indicates the charging power with which the lithium-ion battery 41 can be charged without causing lithium precipitation in consideration of the operation stop of the electronic load 30 and the like. The limited power is derived by the following formula [3] based on the charging upper limit current derived in step S203 and the voltage of the lithium-ion battery 41 (battery voltage). Limited power = Charging upper limit current × Battery voltage …[3]

[0032] When the control processing unit 102 derives the limited power of the lithium-ion battery 41, the process proceeds to step S205.

[0033] (Step S205) The control processing unit 102 of the charging control device 100 controls the charging of the lithium-ion battery 41 based on the limited power derived in step S204 (fourth process). When the control processing unit 102 performs the charging control of the lithium-ion battery 41 based on the limited power, the process proceeds to step S201.

[0034] <Operation and effect> As described above, according to the charging control device 100 according to an embodiment of the present disclosure, based on the charging current assuming that the current consumed by the electronic load 30 flows into the lithium-ion battery 41, the charging of the lithium-ion battery 41 is controlled using the preset charging power within the range where lithium precipitation does not occur in the lithium-ion battery 41 (feedforward control).

[0035] By this control, for example, in a state where the charging of the lithium-ion battery 41 and the power supply to the electronic load 30 are performed by the power generation power of the motor generator (MG) 20, even when the current consumption of the electronic load 30 disappears or significantly decreases and the inflow current to the lithium-ion battery 41 suddenly increases, the charging of the lithium-ion battery 41 can be continued without causing lithium precipitation.

[0036] As described above, one embodiment of the present disclosure has been explained. However, the present disclosure can be regarded not only as a charging control device, but also as a method executed by a charging control device including a processor, a memory, etc., a program for executing this method, a computer-readable non-transitory storage medium storing the program, and a vehicle equipped with the charging control device.

Industrial Applicability

[0037] The charging control device of the present disclosure can be used when it is desired to control the charging of a lithium-ion battery without generating lithium precipitation.

Explanation of Signs

[0038] 10 Engine 20 Motor Generator (MG) 30 Electronic Load 40 Li Battery Module 41 Lithium-Ion Battery 42 Sensor 50 Auxiliary Battery 100 Charging Control Device 101 DDC Circuit 102 Control Processing Unit

Claims

1. A charge control device for controlling the charging of a lithium-ion battery, comprising: a first processing unit that estimates an inflow current flowing into the lithium-ion battery when the current flowing through the load becomes zero; a second processing unit that derives a protection charging current, which is the maximum value of the charging current that does not cause lithium precipitation in the lithium-ion battery; a third processing unit that calculates a charging upper limit current, which is the upper limit value of the current for charging the lithium-ion battery, based on the protection charging current and the inflow current; a fourth processing unit that controls the charging of the lithium-ion battery based on a limit power calculated from the charging upper limit current and the voltage of the lithium-ion battery.

2. The charge control device according to claim 1, wherein the second processing unit derives the protection charging current based on at least one of the voltage, current, temperature, and state of charge of the lithium-ion battery.

3. The lithium-ion battery and the load are connected by a DC-DC converter, The charge control device according to claim 1 or 2, wherein the first processing unit estimates the inflow current based on the current flowing through the load and the conversion efficiency of the DC-DC converter.

4. The DC-DC converter is a step-down type, The charge control device according to claim 3, wherein the first processing unit further estimates the inflow current based on a current conversion coefficient.

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