JP7095659B2 - Charging system - Google Patents

Description

The present invention relates to a charging system.

For example, in a factory, a forklift equipped with a secondary battery is operated to transport a load. The operation of the forklift is carried out according to the operation plan. The operation plan is set, for example, every week, and for each day of the week, the time for the forklift to operate and the time for charging the secondary battery to enable the next operation are set in advance. Has been done.

By the way, the secondary battery deteriorates with the lapse of years of use, and the capacity decreases. Therefore, it is necessary to grasp the current capacity of the secondary battery and grasp the deterioration state of the secondary battery from the capacity of the secondary battery. Then, depending on the deterioration state of the secondary battery, it is necessary to formulate replacement of the secondary battery.

For example, in the battery capacity estimation system disclosed in Patent Document 1, the capacity estimation unit of the secondary battery has a section in which the charge / discharge current continues at a certain value or more from the measurement data stored in the storage unit, and a charge / discharge unit. Extract the stable period before and after the section where the current continues. Then, the charge rate is obtained from the open circuit voltage during the stable period before and after charging and discharging, and the difference between the charging rates before and after charging and discharging and the integrated value of the charging and discharging current flowing during charging and discharging are used to determine the fullness of the secondary battery. Estimates the capacity when charging. By this method, the capacity of the secondary battery can be appropriately estimated.

Japanese Unexamined Patent Publication No. 2016-166817

However, in the case of the battery capacity estimation system disclosed in Patent Document 1, it takes a long period of time to estimate the capacity of the secondary battery. Therefore, if the timing for starting the capacity estimation of the secondary battery is not considered, the secondary battery capacity estimation system must be considered. The timing to discharge the secondary battery comes before the battery capacity estimation is completed, and there is a possibility that an appropriate secondary battery capacity estimation cannot be performed.

An object of the present invention is to provide a charging system capable of reliably estimating the capacity of a secondary battery with high accuracy.

The charging system for solving the above problems includes a charging device for charging the secondary battery of the electric vehicle and an estimation device for estimating the capacity of the secondary battery based on the open circuit voltage of the secondary battery. The charging system has a memory for storing an operation plan in which a plurality of operation periods determined by the operation start time and the operation end time of the electric vehicle are set in advance, and the estimation device has the said from the operation end time. During the period up to the operation start time, the period required from the end of discharging of the secondary battery until the rate of change of the open circuit voltage becomes equal to or less than a predetermined predetermined value, and the period from the end of charging of the secondary battery to the opening. The gist is to estimate the capacity of the secondary battery when it is determined that the period required for the rate of change of the circuit voltage to fall below the predetermined value can be secured before and after charging the secondary battery. ..

According to this, when the period required for the rate of change of the open circuit voltage after charging and discharging to become equal to or less than a predetermined value can be secured in the period from the operation end time to the operation start time, the period is set. Among them, the estimation device estimates the capacity of the secondary battery. Therefore, the timing to discharge the secondary battery does not come before the capacity estimation of the secondary battery is completed, and the capacity of the secondary battery can be estimated using a stable open circuit voltage. It is possible to reliably estimate the capacity of a good secondary battery.

Further, with respect to the charging system, the estimation device may estimate the capacity of the secondary battery when charging until the capacity of the secondary battery is fully charged.
According to this, even when the capacity of the secondary battery is estimated when the capacity of the secondary battery 51 is fully charged, the estimation accuracy of the capacity can be improved.

According to the present invention, it is possible to reliably estimate the capacity of the secondary battery with high accuracy.

A block diagram schematically showing a charging system. The figure which shows the operation plan.

Hereinafter, an embodiment embodying the charging system will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the charging system 10 includes a plurality of charging devices 20 including a control unit 27, a charging control device 30, and a server 40. The control unit 27 and the charge control device 30 are each composed mainly of, for example, a microcomputer. The process executed by the control unit 27 and the charge control device 30 may be performed by the CPU executing the process stored in the memory, or may be performed by the hardware process by the dedicated electronic circuit.

The charging system 10 is supplied with electric power from a power supplier such as an electric power company. The charging system 10 is provided in, for example, a factory, a public facility, or a commercial facility. The charging system 10 is a system for charging the secondary battery 51 mounted on the electric vehicle 50.

The electric vehicle 50 includes a secondary battery 51, a battery control unit 52, and a communication unit 53. The electric vehicle 50 is a vehicle that travels using a rechargeable secondary battery 51 as an electric power source. The electric vehicle 50 may be of any kind, such as a passenger car such as an electric vehicle or a plug-in hybrid vehicle, or an industrial vehicle such as a forklift. In this embodiment, the electric vehicle 50 is a forklift.

As the secondary battery 51, any kind of secondary battery such as a lithium ion secondary battery, a nickel hydrogen secondary battery, a lead battery and the like may be used.
The battery control unit 52 has a voltage sensor that measures OCV: Open circuit voltage, which is the open circuit voltage of the secondary battery 51, and a current sensor that measures the charge / discharge current flowing through the secondary battery 51. Information on the secondary battery 51 such as the OCV of the 51 and the charge / discharge current flowing through the secondary battery 51 is acquired, and the state of the secondary battery 51 is monitored.

Further, the battery control unit 52 has a detection unit (not shown) for detecting that the charging plug 24 described later is connected to the electric vehicle 50, and the charging plug 24 is connected to the electric vehicle 50. When detected, the information indicating that the charging plug 24 is connected to the electric vehicle 50 from the communication unit 53 to the first communication unit 25 described later of the charging device 20, and the secondary battery 51 such as the open circuit voltage and the charge / discharge current are related. Send information.

The detection unit may be any as long as it can detect that the charging plug 24 is connected to the electric vehicle 50, and examples thereof include a sensor.
Further, the battery control unit 52 may periodically transmit information about the secondary battery 51 after recognizing that the charging plug 24 is connected to the electric vehicle 50, or may transmit information about the secondary battery 51 periodically, or when there is a transmission request, the battery control unit 52 may transmit information. Information about the battery 51 may be transmitted.

The charging device 20 supplies electric power from the system power source 11 to the secondary battery 51 of the electric vehicle 50. That is, the charging device 20 charges the secondary battery 51 of the electric vehicle 50. Further, the charging device 20 includes a conversion unit 23 that converts AC power supplied from the system power supply 11 into DC power, a charging plug 24 connected to the electric vehicle 50, a first communication unit 25, and a second communication unit. 26 and a control unit 27 are provided.

The first communication unit 25 is a member for transmitting / receiving information to / from the communication unit 53 of the electric vehicle 50. The second communication unit 26 is a member for transmitting / receiving information to / from the charge control device 30.
The control unit 27 controls the charging device 20.

When the control unit 27 receives the information indicating that the charging plug 24 is connected to the electric vehicle 50 and the information regarding the secondary battery 51, the first communication unit 25 receives information about the secondary battery 51 from the second communication unit 26, which will be described later. The second communication unit 26 is controlled so as to transmit information indicating that the charging plug 24 is connected to the electric vehicle 50 and information regarding the secondary battery 51 to the communication unit 32.

Further, when the control unit 27 is instructed to start charging from the charge control device 30 through the second communication unit 26, the control unit 27 controls the conversion unit 23 and powers the secondary battery 51 of the electric vehicle 50 from the system power supply 11. Supply.

The charge control device 30 has a communication unit 32 for communicating with a plurality of charge devices 20, and is connected to the server 40.
The server 40 has a memory 41, and the operation plan of the electric vehicle 50 is stored in the memory 41. In the operation plan, a plurality of operation periods of the electric vehicle 50 are set in advance.

The "operating period" is a period during which the electric vehicle 50 is used continuously or intermittently without charging the secondary battery 51 on the way, and specifically, the manager or the electric vehicle 50 is used. It is a period determined by the operation start time and the operation end time of the electric vehicle 50 reserved in advance by the person.

Here, a period other than the operating period is defined as a non-operating period. The "non-operating period" is specifically a period in which the electric vehicle 50 is placed in a position where it can be charged by the charging device 20 in a state where the ignition is off.

As shown in FIG. 2, in the present embodiment, the server 40 stores the operation plan for one week in the memory 41. The weekly operation plan includes the operation plan for each day of the week.
In the operation plan of the present embodiment, from Monday to Friday, there are non-operation periods during each of the three operation periods. It is a non-operating period from after the operating period on Saturday morning to midnight on Monday. Therefore, the non-working period that exists from Monday to Friday is shorter than the non-working period that exists on Saturday and Sunday, and the non-working period on Sunday is the longest.

The plurality of operating periods are set at intervals so that the electric vehicle 50 can be charged enough to operate during the non-operating period and during the next operating period.
Here, the secondary battery 51 deteriorates with the lapse of years of use, and its capacity decreases. Therefore, the charge control device 30 needs to periodically estimate the capacity of the secondary battery 51 and grasp the deterioration state of the secondary battery 51 from the capacity of the secondary battery 51. Then, depending on the deterioration state of the secondary battery 51, it is necessary to formulate replacement of the secondary battery 51.

The capacity estimation of the secondary battery 51 performed by the charge control device 30 will be described.
The capacity estimation of the secondary battery 51 is performed by the charge control device 30. That is, the charge control device 30 corresponds to an estimation device.

The charge control device 30 estimates the capacity of the secondary battery 51 based on the open circuit voltage.
In the present embodiment, the capacity of the secondary battery 51 is estimated from the charge rate (SOC :: State Of Charge) corresponding to the open circuit voltage and the integrated current value which is the integrated value of the current flowing through the secondary battery 51 during charging. do.

More specifically, the current integrated value is the charging rate corresponding to the open circuit voltage of the secondary battery 51 during the period from the operation end time to the time when the charging of the secondary battery 51 is started, and the charging of the secondary battery 51. The capacity of the secondary battery 51 is estimated by dividing by the charge rate difference value, which is the difference from the charge rate corresponding to the open circuit voltage of the secondary battery 51 during the period from the end time to the operation start time.

By the way, the value of the open circuit voltage changes greatly until the polarization of the secondary battery 51 is eliminated to some extent, and the correct open circuit voltage cannot be detected. Therefore, it is not preferable to estimate the capacity of the secondary battery 51 based on the value of the open circuit voltage before the polarization is eliminated to some extent.

Polarization caused by charging / discharging of the secondary battery 51 is eliminated by leaving the secondary battery 51 without charging / discharging over time. Therefore, in order to accurately estimate the capacity of the secondary battery 51, charging / discharging is performed. It is necessary to wait for a predetermined period before and after.

Therefore, in the present invention, the open circuit voltage after the change rate of the open circuit voltage becomes equal to or less than a predetermined predetermined value after a predetermined period elapses after the discharge of the secondary battery 51 is completed, and the secondary battery 51 The capacity of the secondary battery 51 is estimated based on the open circuit voltage after the rate of change of the open circuit voltage becomes equal to or less than a predetermined predetermined value after a predetermined period has elapsed from the end of charging.

The rate of change of the open circuit voltage is the ratio of the change of the open circuit voltage in a period shorter than the period required for the polarization to be eliminated to some extent.
Further, the predetermined value to be compared with the rate of change is a value appropriately determined by the user or designer of the charging system 10 or the electric vehicle 50, and the capacity estimation desired by the user or designer when using the electric vehicle 50 is performed. It is decided based on the accuracy. When a more accurate capacity estimation is required, the predetermined value becomes a smaller value. The term "end of discharge of the secondary battery" in the present invention does not include spontaneous discharge.

In the present embodiment, the electric vehicle 50 takes a period required for the rate of change of the open circuit voltage to be equal to or less than a predetermined value after charging / discharging the secondary battery 51 of the electric vehicle 50 when the charging system 10 is used for the first time. (Hereafter, unstable time) is calculated, and the calculated unstable period is stored in a memory (not shown). When the charging plug 24 of the charging system 10 is connected to the electric vehicle 50 for the first time, the electric vehicle 50 transmits an unstable time to the charging device 20, and the charging device 20 transfers the received unstable time to the charging control device 30. Send.

When estimating the capacity of the secondary battery 51 using the open circuit voltage after the polarization is eliminated to some extent as in the charging system 10 of the present invention, it takes a lot of time to estimate the capacity of the secondary battery 51. Since it will be hung up, it is necessary to consider when to estimate the capacity of the secondary battery 51.

Therefore, in the present invention, the charge control device 30 is from the operation start time and the operation end time of the electric vehicle 50 stored in the memory 41 of the server 40 to the time from the operation end time to the time to start charging the secondary battery 51. During the period of 1), the period required from the end of discharging the secondary battery 51 until the rate of change of the open circuit voltage becomes equal to or less than a predetermined predetermined value, and the rate of change of the open circuit voltage from the end of charging of the secondary battery 51. However, it is determined whether the period required for the value to be equal to or less than the predetermined value can be secured before and after charging the secondary battery 51, and if it is determined that the period can be secured, the capacity of the secondary battery 51 is estimated. ..

In the present invention, when the charging control device 30 receives the information indicating that the charging plug 24 is connected to the electric vehicle 50 in the communication unit 32, the operation plan stored in the memory 41 of the server 40 and the charging device 20 are used. With reference to the received unstable time, the total period of the period required for the electric vehicle 50 to be charged enough to operate (hereinafter referred to as the charging period) and the two unstable periods in the next operating period. Is calculated, and it is determined whether or not the calculated total period is shorter than the period from the present to the next operation start time. The charging period is calculated by the charge control device 30 from the length of the next operating period.

When the charge control device 30 determines that the calculated total period is shorter than the period from the present to the next operation start time, the charge control device 30 transmits the open circuit voltage to the charge device 20 after the lapse of unstable time from the present. Request. Upon receiving the request, the charging device 20 requests the electric vehicle 50 to transmit the open circuit voltage, and transmits the latest received open circuit voltage (hereinafter referred to as the pre-charging open circuit voltage) to the charge control device 30.

The charge control device 30 that has received the pre-charge open circuit voltage from the charging device 20 instructs the charging device 20 to charge only during the charging period. When the charging is completed, the charging device 20 informs the charging control device 30 that the charging is completed, and the charging control device 30 informs the charging device 20 of the open circuit voltage after an unstable time has elapsed since the charging is completed. And request the transmission of the current integrated value.

Upon receiving the request, the charging device 20 requests the electric vehicle 50 to transmit the open circuit voltage and the integrated current value, and receives the latest open circuit voltage (hereinafter referred to as the open circuit voltage after charging) and the integrated current value. Is transmitted to the charge control device 30.

Then, the charge control device 30 estimates the capacity of the secondary battery 51 based on the pre-charge open circuit voltage, the post-charge open circuit voltage, and the integrated current value.
When the charge control device 30 grasps the deterioration state of the secondary battery 51 from the capacity of the secondary battery 51, the charge control device 30 has the capacity of the secondary battery 51 estimated as described above and the secondary battery stored in advance in the server 40. The deterioration state of the secondary battery 51 is diagnosed by comparing with the capacity of 51.

According to the above embodiment, the following effects can be obtained.
(1) In the capacity estimation of the secondary battery 51, the rate of change in the open circuit voltage after discharging and charging the secondary battery 51 is predetermined during the period from the operation end time to the time when the secondary battery 51 starts charging. This is performed when the period required for the value to be below the value can be secured before and after charging the secondary battery 51. Therefore, the timing of discharging the secondary battery 51 does not come before the capacity estimation of the secondary battery 51 is completed, and the capacity estimation of the secondary battery is surely performed using a stable open circuit voltage to some extent. It can be carried out.

(2) Even when the capacity of the secondary battery 51 is estimated when the capacity of the secondary battery 51 is fully charged, the estimation accuracy of the capacity can be improved.
The embodiment can be modified and implemented as follows. The embodiments and the following modifications can be implemented in combination with each other within a technically consistent range.

○ In the embodiment, the detection unit of the battery control unit 52 detects that the charging plug 24 is connected to the electric vehicle 50, but the charging device 20 is provided with a detection unit that detects that the charging plug 24 is connected. The charging device 20 itself may detect that the charging plug 24 is connected to the electric vehicle 50.

○ In the charging device 20, the first communication unit 25 and the second communication unit 26 may be configured as one communication unit.
○ The operation plan may be stored in the memory of the charge control device 30 or the memory of the charge device 20 instead of the memory of the server 40.

○ The charging period required for the operating period is not calculated by the charging control device 30, but may be stored in the memory 41 of the server 40 according to the operating period.
○ In the embodiment, when the electric vehicle 50 first uses the charging system 10, the unstable time is calculated and stored in the memory of the electric vehicle 50, and thereafter, the electric vehicle 50 uses the charging system 10. When estimating the capacity, the unstable time stored in the memory of the electric vehicle 50 is used, but the unstable time may be calculated each time the capacity is estimated.

For example, the charge control device 30 periodically receives the open circuit voltage of the secondary battery 51 via the charging device 20, and changes the ratio of the open circuit voltage received this time to the open circuit voltage received last time. The calculated change rate is compared with the predetermined value stored in the memory in advance, and it is repeated whether the calculated change rate is equal to or less than the predetermined value, and the period required for the change rate to be equal to or less than the predetermined value. Is calculated as the unstable time.

○ In the embodiment, the charging control device 30 calculates the charging time each time the communication unit 32 receives information indicating that the charging plug 24 is connected to the electric vehicle 50, but the charging time is not limited to this. For example, the required charging time may be calculated for each operating time set in the operating plan and stored in the memory of the charging control device 30.

○ The operation plan may be set for a length other than one week, and may be changed as appropriate, such as one month, two months, or three months.
○ After estimating the capacity of the secondary battery 51 when it is fully charged, it is not necessary to diagnose the state of the secondary battery 51. Alternatively, other determinations may be made using the estimated capacity of the secondary battery 51.

○ The charging device 20 may be a single unit, or the electric vehicle 50 may be a single unit.

10 ... Charging system, 20 ... Charging device, 30 ... Charging control device as an estimation device, 41 ... Memory, 50 ... Electric vehicle, 51 ... Secondary battery.

Claims (2)

A charging device that charges the secondary battery of an electric vehicle,
A charging system comprising an estimation device that estimates the capacity of the secondary battery based on the open circuit voltage of the secondary battery.
It has a memory for storing an operation plan in which a plurality of operation periods determined by the operation start time and the operation end time of the electric vehicle are set in advance.
The estimation device includes a period from the end time of operation to the start time of operation, and a period required from the end of discharge of the secondary battery until the rate of change of the open circuit voltage becomes equal to or less than a predetermined value.
When it is determined that the period required from the end of charging of the secondary battery to the change rate of the open circuit voltage becoming equal to or less than the predetermined value can be secured before and after charging the secondary battery, the secondary battery is used. A charging system characterized by estimating the capacity of a battery. The charging system according to claim 1, wherein the estimation device estimates the capacity of the secondary battery when the capacity of the secondary battery is fully charged.

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