JP7629744B2 - Battery System - Google Patents

Description

The present invention relates to a battery system equipped with a rechargeable secondary battery.

Battery systems (battery packs) equipped with rechargeable secondary batteries are known. Due to the multi-functionality of such battery systems, the control unit in the battery system not only controls the charging and discharging of the secondary battery, but also performs various controls, such as protection functions such as overvoltage protection, overcurrent protection, overcharge protection, overdischarge protection, and overtemperature protection, calculation processing of the battery state such as the remaining battery capacity (State of Charge: SOC) and battery deterioration (State of Health: SOH), and a communication function for notifying a higher-level system of the battery state. As a result, the power consumption of the control unit is on the rise. In addition, the control unit consumes power even when charging and discharging are stopped.

In this regard, Patent Document 1 discloses a technology that switches the operating mode of a microcontroller to a power-saving mode (sleep mode) that consumes less power than the normal operating mode when the charging/discharging current value of a battery cell is equal to or lower than a predetermined value.

Japanese Patent Application Publication No. 9-247852

The present invention aims to provide a battery system that can reduce power consumption compared to conventional systems.

The battery system according to the present invention is a battery system equipped with a secondary battery, and includes a detection unit that detects the charge/discharge state of the secondary battery, a main control unit that controls the charge/discharge of the secondary battery and performs calculation processing of the battery state including the remaining battery level and battery deterioration of the secondary battery, the main control unit having a normal operation mode and a power saving mode, and a sub-control unit that controls the start and stop of the main control unit, the sub-control unit consuming less power than the power saving mode of the main control unit. When the charge/discharge state detected by the detection unit indicates the end of charge/discharge, the main control unit transitions from the normal operation mode to the power saving mode, the sub-control unit transitions from a stopped state to an operating state, and cuts off the power supply to the main control unit. When the charge/discharge state detected by the detection unit indicates the start of charge/discharge, the sub-control unit resumes the power supply to the main control unit, transitions from an operating state to a stopped state, and the main control unit operates in the normal operation mode.

The present invention makes it possible to reduce the power consumption of battery systems compared to conventional systems.

1 is a circuit block diagram showing a schematic electrical configuration of a battery pack (battery system) according to an embodiment of the present invention. A diagram showing an example of the timing of the main control unit switching between operating modes in a battery pack according to this embodiment and/or the timing of the sub-control unit cutting off power to the main control unit. 1 is a circuit block diagram showing a schematic electrical configuration of an automated guided vehicle system including a battery pack (battery system) according to an embodiment of the present invention.

Below, an example of an embodiment of the present invention will be described with reference to the attached drawings. Note that the same reference numerals will be used to refer to the same or equivalent parts in each drawing. For convenience, hatching and component reference numerals may be omitted, in which case other drawings should be referenced.

(Battery pack: Battery system)
Fig. 1 is a circuit block diagram showing a schematic electrical configuration of a battery pack (battery system) according to the present embodiment. The battery pack (battery system) 100 shown in Fig. 1 includes a battery module 101, a temperature detection unit 102, a pair of input/output terminals 103 and 104, a connector 105, and a battery management unit (BMU) 200.

The battery pack 100 discharges the battery module 101 to an external load (e.g., a higher-level system, described later) and charges the battery module 101 from an external power source (e.g., a charger, described later) via a pair of input/output terminals 103, 104. The battery pack 100 also communicates with the higher-level system via a connector 105.

The battery module 101 has multiple battery cells connected in parallel and/or series. The battery cells are rechargeable secondary batteries. The battery cells are not particularly limited, but may be, for example, lithium ion batteries. Among lithium ion batteries, lithium ion batteries (hereinafter also referred to as LTO batteries) that use lithium titanate (Lithium Titanate, Lithium Titanium Oxide: LTO) as the material for the negative electrode are preferable. LTO batteries have a small amount of voltage drop due to self-discharge, a long life with repeated charging and discharging, and excellent quick charging capabilities.

The temperature detection unit 102 is disposed close to the battery module 101 and detects the temperature of the battery module 101. The temperature detection unit 102 is not particularly limited, but may be, for example, a thermistor.

The battery management unit 200 controls the charging and discharging of the battery module 101, performs protection functions such as overvoltage protection, overcurrent protection, overcharge protection, overdischarge protection, and overtemperature protection for the battery module 101, calculates the battery status such as the remaining battery capacity (State of Charge: SOC) and battery deterioration (State of Health: SOH) of the battery module 101, and communicates with the outside of the battery pack 100 (for example, a higher-level system described below).

The battery management unit 200 includes a main control unit 201, a communication interface device 206, a power supply 207, a current fuse 208, a current detection unit 209, a charge/discharge switch 210, a sub-control unit 211, a power switch 213, and a memory unit 220.

The current fuse 208 is interposed between the battery module 101 and the input/output terminal 103. The current detection unit 209 and the charge/discharge switch 210 are interposed between the battery module 101 and the input/output terminal 104.

The current detection unit 209 detects the charge/discharge current of the battery module 101. As a result, the current detection unit 209 functions as a detector that detects the charge/discharge state of the battery module 101. The current detection unit 209 is not particularly limited, but may be, for example, a shunt resistor. In this case, the current detection unit 209 generates a voltage according to the charge/discharge current of the battery module 101.

The charge/discharge switch 210 is a switching element that controls the charging and discharging of the battery module 101. The charge/discharge switch 210 is not particularly limited, but may be, for example, a field effect transistor (FET).

The communication interface device 206 is interposed between the main control unit 201 and the sub-control unit 211 and the connector 105. The communication interface device 206 is not particularly limited, but may be, for example, a standard interface circuit such as CAN or RS485.

The power switch 213 is interposed between the main control unit 201 and the power supply 207. The power switch 213 is a switching element that controls the supply of power from the power supply 207 to the main control unit 201 or the interruption of the power supply, i.e., the supply of electricity from the power supply 207 to the main control unit 201 or the interruption of the supply of electricity. The power switch 213 is not particularly limited, but may be, for example, a field effect transistor (FET).

The main control unit 201 and the sub-control unit 211 are composed of one or more arithmetic processors, such as a DSP (Digital Signal Processor) or an FPGA (Field-Programmable Gate Array). The various functions of the main control unit 201 and the sub-control unit 211 are realized, for example, by executing predetermined software (programs) stored in the storage unit 220. The various functions of the main control unit 201 and the sub-control unit 211 may be realized by a combination of hardware and software, or may be realized only by hardware (electronic circuits).

The storage unit 220 is a rewritable memory such as an EEPROM. The storage unit 220 stores predetermined software (programs) for executing the various functions of the main control unit 201 and the sub-control unit 211 described above.

The main control unit 201 performs overall control of the battery pack 100. The main control unit 201 includes a main CPU 202, a battery input unit 203, an analog front end (AFE) 204, and a second overvoltage protection IC 205.

The battery input unit 203 inputs the voltage of each battery cell in the battery module 101 and distributes the voltage of each battery cell to the analog front end 204 and the overvoltage second protection IC 205.

The analog front end 204 performs analog-to-digital conversion of the voltage of each battery cell of the battery module 101. The analog front end 204 also performs analog-to-digital conversion of the voltage corresponding to the charge/discharge current of the battery module 101 from the current detection unit 209. The analog front end 204 also performs analog-to-digital conversion of the temperature of the battery module 101 from the temperature detection unit 102.

The main CPU 202 executes protection functions such as overvoltage protection, overcurrent protection, overcharge protection, and overdischarge protection based on the voltage of each battery cell of the battery module 101 converted by the analog front end 204 and the voltage corresponding to the charge/discharge current of the battery module 101. The main CPU 202 also executes the protection function of overtemperature protection based on the temperature of the battery module 101 converted by the analog front end 204.

The main CPU 202 also performs calculations of the battery state, such as the remaining battery charge and battery deterioration, of the battery module 101 based on the voltage of each battery cell of the battery module 101, the voltage according to the charge/discharge current of the battery module 101, and the temperature of the battery module 101. The main CPU 202 also communicates with the outside (for example, a higher-level system, described below) via the communication interface device 206 and the connector 105, and transmits the calculation results of the battery state.

The main CPU 202 also controls the charging and discharging of the battery module 101 by controlling the charging and discharging switch 210 based on commands from the outside (e.g., a higher-level system, described below).

The overvoltage second protection IC 205 is a function independent of the main CPU 202, and performs double overvoltage protection when, for example, an abnormality occurs in the main CPU 202. When the overvoltage second protection IC 205 detects an overvoltage in each battery cell of the battery module 101, it blows the current fuse 208. As a result, the overvoltage second protection IC 205 forcibly stops charging and discharging the battery module 101, ensuring the safety of the battery pack 100.

The main control unit 201 described above has two operation modes: a normal operation mode and a power saving mode. Specifically, the main CPU 202, which is the main processing unit, has two operation modes: a normal operation mode and a power saving mode. On the other hand, the battery input unit 203 and the analog front end (AFE) 204, which are peripheral processing units, only have the normal operation mode. In addition, the second overvoltage protection IC 205, which is used when an abnormality occurs in the main CPU 202, also only has the normal operation mode.

In the normal operation mode, the main CPU 202, i.e., the main control unit 201, performs charge/discharge control of the battery module 101, protection functions such as overvoltage protection, overcurrent protection, overcharge protection, overdischarge protection, and overtemperature protection for the battery module 101, calculation processing of the battery state such as the remaining battery charge and battery deterioration of the battery module 101, and communication with the outside of the battery pack 100. On the other hand, in the power saving mode, the main CPU 202, i.e., the main control unit 201 does not perform all or some of these processes, i.e., stops all or some of these processes.

The sub-controller 211 includes a sub-CPU 212 and controls the start and stop of the main controller 201. The sub-controller 211 is in an operating state when the main controller 201 is stopped, and is in a stopped state when the main controller 201 is started. In an operating state, the sub-controller 211 may control the charging and discharging of the battery module 101 in place of the main controller 201. For example, the sub-controller 211 controls the charging and discharging switch 210 based on a command from the outside (for example, a higher-level system described below).

The sub-controller 211 has only the minimum necessary functions, such as controlling the charging and discharging of the battery module 101, in place of the main controller 201 while the main controller 201 is stopped. As a result, the power consumption of the sub-controller 211 is less than the power consumption of the main controller 201 in the power saving mode.

(Details of the main control unit and sub control unit)
The main control unit 201 and the sub control unit 211 will be described in detail below.

For example, when the battery module 101 is being charged or discharged, when the voltage corresponding to the charging/discharging current of the battery module 101 from the current detection unit 209 drops below a predetermined value and the main CPU 202 determines that charging/discharging has ended (i.e., when the charging/discharging state detected by the current detection unit 209 indicates that charging/discharging has ended), the main CPU 202, i.e., the main control unit 201, transitions from the normal operation mode to the power saving mode.

At this time, the sub-controller 211 goes from a stopped state to an operating state, and cuts off power to the main controller 201. For example, the sub-controller 211 turns off the power switch 213 to stop the power supply to the main controller 201. This stops the main CPU 202, which is the main processing unit, the battery input unit 203 and analog front end (AFE) 204, which are peripheral processing units, and the second overvoltage protection IC 205 in the main controller 201. This reduces the power consumption of the main controller 201 to zero.

On the other hand, for example, when the sub-control unit 211 controls the charge/discharge switch 210 based on a command from the outside (for example, a higher-level system described below), the voltage according to the charge/discharge current of the battery module 101 from the current detection unit 209 rises to or exceeds a predetermined value, and the main CPU 202 determines that charging/discharging has started (i.e., when the charge/discharge state detected by the current detection unit 209 indicates the start of charging/discharging), the sub-control unit 211 resumes power supply to the main control unit 201 and changes from an operating state to a stopped state. For example, the sub-control unit 211 turns on the power switch 213 to resume power supply to the main control unit 201.

As a result, the main CPU 202, which is the main processing unit in the main control unit 201, the battery input unit 203 and analog front end (AFE) 204, which are peripheral processing units, and the second overvoltage protection IC 205 resume operation. At this time, the main CPU 202, i.e., the main control unit 201, resumes operation in the normal operation mode.

When the sub-control unit 211 returns the main control unit 201 from the power saving mode before cutting off the power supply to the main control unit 201, it is possible to return the main CPU 202 to the normal operation mode by inputting an interrupt signal.

As described above, according to the battery pack (battery system) 100 of this embodiment, when the battery module 101 is not being charged or discharged, the main control unit 201 transitions from the normal operation mode to the power saving mode. This allows the power consumption of the battery pack 100 to be reduced.

Furthermore, according to the battery pack 100 of this embodiment, when the battery module 101 is not being charged or discharged, the sub-controller 211 goes from a stopped state to an operating state and cuts off power to the main controller 201. As a result, the power consumption of the main controller 201 becomes zero. Also, the power consumption of the sub-controller 211 is smaller than the power consumption of the main controller 201 in the power saving mode. This allows the power consumption of the battery pack 100 to be further reduced.

Incidentally, in the battery pack 100 of this embodiment, the main CPU 202, i.e., the main control unit 201, may notify the upper system of the operating state of the battery pack 100 and the battery state of the battery module 101 via the communication interface device 206 and the connector 105 before transitioning from the normal operating mode to the power saving mode.

The upper system may periodically inquire of the battery pack 100 about the battery status, such as the remaining battery charge (SOC) and battery degradation (SOH) of the battery module 101. In such a case, the upper system can recognize that the main control unit 201 is going to switch to a power saving mode, and can obtain the battery status of the battery module 101 immediately before the main control unit 201 switches to the power saving mode. This allows the upper system to stop the periodic inquiries and reduce power consumption.

In addition, in the battery pack 100 of this embodiment, the main control unit 201 may change the timing of transition from the normal operation mode to the power saving mode depending on the remaining battery charge of the battery module 101. Specifically, the main control unit 201 increases the delay in transition from the normal operation mode to the power saving mode as the remaining battery charge of the battery module 101 increases.

The sub-control unit 211 may also change the timing of cutting off power to the main control unit 201 depending on the remaining battery charge of the battery module 101. Specifically, the greater the remaining battery charge of the battery module 101, the greater the delay in cutting off power to the main control unit 201.

Figure 2 is a diagram showing an example of the timing of the main control unit to switch between operating modes and/or the timing of the sub-control unit to cut off power to the main control unit in a battery pack according to this embodiment. In Figure 2, the vertical axis shows the remaining battery power, and the horizontal axis shows the timing of the main control unit 201 to switch between operating modes and/or the timing of the sub-control unit 211 to cut off power to the main control unit 201.

For example, the main control unit 201 manages the calculated remaining battery power in increments of, for example, 10%. For example, when the remaining battery power is extremely low, such as 10% or less, the main control unit 201 transitions to a power saving mode after a short waiting time of about 5 seconds, prioritizing reduction in power consumption of the battery cells. Similarly, when the remaining battery power is extremely low, such as 10% or less, the sub-control unit 211 cuts off power to the main control unit 201 after a short waiting time of about 5 seconds, prioritizing reduction in power consumption of the battery cells.

On the other hand, when the battery level is high, such as 70% or more, the main control unit 201 transitions to power saving mode after a long waiting period of about 60 seconds. Similarly, when the battery level is high, such as 70% or more, the sub-control unit 211 cuts off power to the main control unit 201 after a long waiting period of about 60 seconds.

After the main control unit 201 transitions to the power saving mode or stops, it takes time to return to the normal operation mode due to software processing, etc. Therefore, if charging or discharging is performed during the waiting time, the main control unit 201 has not yet stopped, so smooth system operation can be performed without requiring recovery time because the main control unit 201 has not yet stopped. In this way, when the battery level is high, smooth system operation that does not require recovery time due to stopping is prioritized over reducing power consumption of the battery cells.

In this way, by changing the timing of the operation mode transition by the main control unit 201 and the timing of the power cut-off by the sub-control unit 211 to the main control unit 201 according to the remaining battery power, it is possible to achieve a balance between reducing power consumption of the battery cells and smooth system operation without requiring recovery time due to shutdown.

In particular, for battery packs that are installed in a system with a battery capacity that is kept as low as possible, optimizing the remaining battery capacity and the timing of switching between operating modes and cutting off power is effective. For example, in the case of a battery with relatively poor quick-charging capabilities, the battery capacity is set to be large. In contrast, the LTO battery mentioned above is capable of quick charging, so the battery capacity can be made small.

In addition, as the battery capacity decreases, it is expected that there will be a demand for further reduction in the power consumption of the control unit of the battery pack. The battery pack 100 of this embodiment is suitable for use in battery packs using LTO batteries, for which it is expected that there will be a demand for further reduction in the power consumption of the control unit.

(Automated guided vehicle system)
An example of an automated guided vehicle system to which the battery pack 100 of the above-described embodiment can be suitably applied will be given below.

Figure 3 is a circuit block diagram showing the general electrical configuration of an automated guided vehicle system equipped with a battery pack according to this embodiment. The automated guided vehicle system shown in Figure 2 includes one or more automated guided vehicles (AGVs) 300, an AGV controller 301, and an AGV charger 302.

The AGV 300 includes the battery pack 100 described above and a control unit 400. The control unit 400 is connected to the input/output terminals 103, 104 and connector 105 of the battery pack 100 via a cable. The control unit 400 receives power from the battery pack 100 and controls the operation of the AGV 300 by communicating with the BMU 200 of the battery pack 100. The control unit 400 mainly includes a CPU 401, a memory 402, and a wireless module 403.

The CPU 401 communicates with the main control unit 201 of the BMU 200 of the battery pack 100, and monitors information such as the operating state of the battery pack 100 and the battery state such as the remaining battery power and battery deterioration of the battery module 101 of the battery pack 100. When the remaining battery power of the battery module 101 of the battery pack 100 falls below a predetermined level, the CPU 401 controls the AGV 300 to move toward the charging station where the AGV charger 302 is located, and charges the battery module 101 of the battery pack 300. For example, when the AGV 300 approaches the AGV charger 302, the AGV charger 302 extends its electrodes and contacts the charging contact unit 405 of the AGV 300. At this time, the main control unit 201 of the BMU 200 of the battery pack 300 controls the charge/discharge switch 210 based on a command from the CPU 401.

The AGV controller 301 centrally manages one or more AGVs 300. The AGV controller 301 wirelessly communicates with each AGV 300 to send and receive information. For example, if an error occurs in an AGV 300, the AGV controller 301 receives a notification of this from the AGV 300. The AGV controller 301 also performs operational management to prevent charging congestion at the AGV charger 302.

Here, when the AGV 300 is in standby mode due to a command from the AGV controller 301, if the discharge current of the battery module 101 of the battery pack 100 falls below a predetermined value, the main control unit 201 of the BMU 200 determines that charging and discharging has ended, the main control unit 201 transitions from normal operation mode to power saving mode, and the sub-control unit 211 may cut off power to the main control unit 201. At this time, the AGV controller 301 manages information on the operating state of the battery pack 100 via the CPU 401 of the control unit 400 of the AGV 300, and can return the BMU 200 of the battery pack 100 to the normal operation mode and control the AGV 300. At this time, the sub-control unit 211 of the BMU 200 of the battery pack 300 resumes power supply to the main control unit 201 based on a command from the CPU 401, and the main control unit 201 returns to the normal operation mode.

Here, the control unit 400 of the AGV 300 and the AGV controller 301 are the upper system (external load) 406, and the AGV charger 302 is the external power source.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment and various modifications and variations are possible.

100 Battery pack (battery system)
101 Battery module (secondary battery)
102 Temperature detection unit 103, 104 Input/output terminal 105 Connector 200 Battery management unit (BMU)
201 Main control unit 202 Main CPU (main calculation unit)
203 Battery input unit (peripheral calculation unit)
204 Analog Front End (AFE) (peripheral calculation unit)
205 Overvoltage Secondary Protection IC
206 Communication interface device 207 Power supply 208 Current fuse 209 Current detection unit (detection unit)
210 Charge/discharge switch 211 Sub-control unit 212 Power switch 300 Automatic guided vehicle (AGV)
301 AGV controller 302 AGV charger 400 Control unit 401 CPU
402 memory 403 wireless module 405 charging contact section 406 upper system

Claims (8)

A battery system including a secondary battery,
A detection unit that detects a charge/discharge state of the secondary battery;
a main control unit that controls charging and discharging of the secondary battery and performs calculation processing of a battery state including a remaining battery capacity and battery deterioration of the secondary battery, the main control unit having a normal operation mode and a power saving mode;
a sub-controller that controls activation and shutdown of the main control unit and consumes less power than the main control unit in the power saving mode;
Equipped with
the detection unit is a current detection unit that detects a charge/discharge current of the secondary battery,
When the voltage corresponding to the charge/discharge current detected by the detection unit falls to a predetermined value or less, and the charge/discharge state detected by the detection unit indicates the end of charge/discharge,
The main control unit transitions from the normal operation mode to the power saving mode,
The sub-controller goes from a stopped state to an operating state and cuts off power to the main control unit,
When the voltage corresponding to the charge/discharge current detected by the detection unit rises to or exceeds a predetermined value, and the charge/discharge state detected by the detection unit indicates the start of charge/discharge,
The sub-controller resumes power supply to the main controller, and goes from an operating state to a stopped state.
The main control unit operates in the normal operation mode.
Battery system. the main control unit includes a main processing unit that controls charging and discharging of the secondary battery and performs calculation processing of the battery state of the secondary battery, and a peripheral processing unit therefor;
In the power saving mode, all or a part of the processing of the main processing unit is stopped,
When the sub-controller cuts off power to the main control unit, the main processing unit and the peripheral processing unit stop.
The battery system according to claim 1 . In the normal operation mode, the main control unit performs charge/discharge control of the secondary battery and performs calculation processing of the battery state of the secondary battery,
In the power saving mode, the main control unit does not perform all or a part of charge/discharge control of the secondary battery and calculation processing of the battery state of the secondary battery.
The battery system according to claim 1 or 2. The battery system according to any one of claims 1 to 3, wherein the main control unit notifies a host system of the battery system of the operating state of the battery system and the battery state of the secondary battery before transitioning from the normal operating mode to the power saving mode. The battery system according to any one of claims 1 to 4, wherein the sub-controller controls charging and discharging of the secondary battery in an operating state. the main control unit changes a timing of transition from the normal operation mode to the power saving mode in accordance with a remaining battery charge of the secondary battery;
the sub-controller changes a timing for cutting off power to the main controller in accordance with a remaining battery charge of the secondary battery.
The battery system according to any one of claims 1 to 5. the main control unit increases a delay in timing of transition from the normal operation mode to the power saving mode as the remaining battery level of the secondary battery increases;
the sub-controller increases a delay in timing for cutting off power to the main control unit as the remaining battery charge of the secondary battery increases.
The battery system according to claim 6 . The battery system according to any one of claims 1 to 7, wherein the secondary battery is a lithium ion battery using lithium titanate as the negative electrode material.

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