JP7353910B2 - Tool battery pack charger, charging method and program - Google Patents

Description

The present invention relates to a charger for a tool battery pack including a plurality of group cells, a charging method, and a program for controlling the charger.

As a high-voltage battery pack, Japanese Patent Laid-Open No. 2003-116226 (Patent Document 1) discloses a battery unit for an electric bicycle. This battery unit contains two assembled batteries. Each assembled battery is provided with a discharge terminal. When the battery unit is attached to the battery mounting part of the electric bicycle body, the two assembled batteries are connected in series by the connection circuit of the battery mounting part, and the total voltage of the two assembled batteries is applied to the electric vehicle. Supplied. This allows high voltage to be supplied. Further, when the battery is removed from the battery mounting section, only the voltage of the divided assembled battery is applied between the discharge terminals of the battery unit. When the battery unit is attached to the charging device, the two charging parts of the charging device are connected to the two assembled batteries, respectively. Each battery pack is charged individually and in parallel by each charging unit. The control unit of the charging device determines that sufficient charging has been performed and ends charging when the voltage of each battery pack exceeds the local maximum value and then decreases by the voltage drop value ΔV.

Furthermore, Japanese Patent Laid-Open No. 2002-313439 (Patent Document 2) discloses a battery pack formed by combining a plurality of battery blocks in parallel. The battery pack includes a plurality of switch elements arranged in respective charging paths of the plurality of battery blocks, a control section that controls the plurality of switch elements, and a thermistor that detects the temperature of each battery block. The control unit performs charging by turning on only a single switch element by periodically turning on and off a plurality of switches in sequence.

Japanese Patent Application Publication No. 2003-116226 Japanese Patent Application Publication No. 2002-313439

In the field of power tools, a wide variety of battery-powered tools have been commercialized as the performance of lithium ion batteries has improved. However, in comparison with AC tools driven by an AC power source and engine tools driven by an engine, battery-powered tools are inferior in terms of output performance such as power and work speed that satisfy users. Therefore, there is a need for battery-powered tools that can be driven at even higher voltages.

The inventors studied a battery pack including a plurality of group cells as a battery pack for a battery-powered tool. The inventors established that when the battery pack is not attached to the tool, the multiple group cells are not directly connected, and when the battery pack is attached to the tool, a circuit within the tool connects each group cell in series. We investigated a configuration in which the devices are connected and used at high voltage (for example, DC 100V). This allows the tool to be used with high voltage. The inventors also considered a configuration in which a plurality of group cells are connected in parallel with a circuit within the tool. By connecting multiple group cells in parallel on the tool side, the usable capacity of the tool can be increased. In this way, battery packs including a plurality of group cells can be used depending on the voltage specifications of the tool body.

A battery pack for a tool is often used at a stage in the middle of a state of charge (SOC) of a plurality of group cells reaching full charge. For example, when a user wants to use a tool, he or she often charges the battery pack for a short period of time. If the SOC of a plurality of group cells is uniform, it becomes possible to use a tool that uses a plurality of group cells connected in series. In a tool that uses a plurality of group cells connected in parallel, if there is a difference in SOC between the plurality of group cells, there is a possibility that a cross flow between the group cells will affect the flow control element or the like.

Therefore, the inventors studied a charging method that would make the SOC of a plurality of group cells uniform even if charging was stopped at any stage during charging. In the above conventional charging control for a plurality of batteries, if charging is stopped before all of the batteries are fully charged, variations may occur in the voltages of the plurality of batteries. For example, if charging is started when the voltages of a plurality of batteries are different from each other and charging is stopped before all the batteries are fully charged, the voltages of the plurality of batteries remain in different states.

This application provides a tool battery pack that can reduce the difference in SOC of multiple group cells even if charging is stopped at any stage until all group cells are fully charged when charging a tool battery pack that includes multiple group cells. A battery pack charger, charging method, and program are disclosed.

A charger according to an embodiment of the present invention is a charger for a tool battery pack including a plurality of group cells. The charger includes a measurement unit that measures at least one of current and voltage of each of the plurality of group cells, and a measurement unit that measures at least one of the current and voltage of each of the plurality of group cells, and a measurement unit that measures each of the plurality of group cells using at least one of the current and voltage measured by the measurement unit. and a charging control section that controls charging. The charging control unit repeats a cycle including charging control for each of the plurality of group cells a plurality of times, and in each cycle, the plurality of group cells measured by the measurement unit The amount of charge of each group cell is controlled based on at least one of the current and voltage of at least one group cell.

According to the present disclosure, when charging a tool battery pack including a plurality of group cells, the difference in SOC of the plurality of group cells can be reduced even if charging is stopped at any stage until all the group cells are fully charged. can.

FIG. 1 is a diagram showing an example of the configuration of a charger according to this embodiment. FIG. 2 is a flowchart showing an example of the operation of the charger shown in FIG. FIG. 3 is a flowchart showing an example of the operation of the charger shown in FIG. FIG. 4 is a graph showing an example of the charging voltage and charging current of the charger shown in FIG. FIG. 5 is a graph showing an example of a change in voltage of each group cell due to the operations shown in FIGS. 2 and 3. FIG. FIG. 6 is a diagram showing a modification of the operation shown in FIGS. 2 and 3. FIG. 7 is a graph showing another example of the charging voltage and charging current of the charger shown in FIG. FIG. 8 is a diagram showing an example of a configuration in which a temperature detection section is added to the charger shown in FIG. 1.

A charger according to an embodiment of the present invention is a charger for a tool battery pack including a plurality of group cells. The charger includes a measurement unit that measures at least one of current and voltage of each of the plurality of group cells, and a measurement unit that measures at least one of the current and voltage of each of the plurality of group cells, and a measurement unit that measures each of the plurality of group cells using at least one of the current and voltage measured by the measurement unit. and a charging control section that controls charging. The charge control unit repeats a cycle including charging control for each of the plurality of group cells a plurality of times, and in each cycle, the plurality of group cells measured by the measurement unit The amount of charge of each group cell is controlled based on at least one of the current and voltage of at least one group cell.

According to the charger, in each cycle, based on the measured voltage or current of at least one group cell, the amount of charge of each group cell is controlled so that the SOC of all group cells approaches uniformity. For example, when charging is started in a state where there is a difference between the voltages of a plurality of group cells, the SOC of the plurality of group cells can be quickly made uniform by repeating the cycle. When charging a battery pack for a tool, the difference in SOC of a plurality of group cells can be reduced even if charging is stopped at any stage until all group cells are fully charged. Note that the charging control unit does not necessarily need to calculate the SOC in each cycle. For example, based on the current or voltage of the group cells, the SOC of the battery or its change can be determined. Further, for example, by adjusting the relative relationship between the charging times of the plurality of group cells in each cycle, the SOC of the plurality of group cells can be made close to uniform.

The charging control unit may control the amount of charge of other group cells in each cycle based on at least one of the voltage and current after charging of the group cell charged first. Thereby, in each cycle, the SOCs of a plurality of group cells can be made close to uniform with simple processing. Note that the voltage of the group cell can be considered to be equivalent to the capacity of the group cell.

The charging control unit is configured such that in each cycle, at least one of the voltage and current after charging of the other group cells approaches at least one of the voltage and current after charging of the first charged group cell, The amount of charge of the other group cells can be controlled. Thereby, by repeating the cycle, it is possible to reduce the difference in SOC between a plurality of group cells.

The charging control unit may charge the first group of cells to be charged by a predetermined amount in each cycle. Thereby, charging control processing can be simplified in each cycle. For example, the charging control unit can charge the group cells by a predetermined amount by charging the group cells for a predetermined time.

The measurement unit may include a current measurement unit that measures the current of each of the plurality of group cells, and a voltage measurement unit that measures the voltage of each of the plurality of group cells. The charging control unit may be configured to charge the plurality of group cells with a constant current and then with a constant voltage. In this case, during constant current charging, the charging control section controls charging of the other group cells based on the voltage after charging of the first charged group cells in each cycle, and performs constant voltage charging. In this case, in each cycle, charging of the other group cells can be controlled based on the current after charging of the first charged group cell. Thereby, the amount of charge can be controlled more appropriately in order to reduce the difference in voltage between a plurality of group cells.

The charging control unit may determine the order of group cells to be charged in each cycle based on the voltages of the plurality of group cells. This makes it possible to more efficiently perform charging control to reduce variations in the voltages of a plurality of group cells in each cycle. For example, the group cell with the lowest voltage among the plurality of group cells may be determined as the group cell to be charged first. Furthermore, the order of charging the plurality of group cells may be determined based on the voltages of the plurality of group cells.

The charging control unit may charge the plurality of group cells in a predetermined order in each cycle. This makes it possible to simplify the charging control process for each cycle.

In each cycle, the charge control unit may control the amount of charge of other group cells based on a comparison result between the voltage after charging of the group cell charged first and the voltage before charging. This makes it possible to control charging in accordance with the charging characteristics of the group cells. For example, in constant current charging, there may be a region (period) in which almost no voltage change occurs over time until full charging is reached. In such a time domain, based on the above comparison results, appropriate charging control can be performed to make the plurality of group cells close to uniformity.

The charging control unit may correct the charging amount of the other group cell in each cycle based on a relative value of the temperature of the other group cell with respect to the temperature of the first charged group cell. This makes it possible to control the amount of charge of other group cells in accordance with the temperature of the other group cells in each cycle. Therefore, in order to reduce the difference in voltage between a plurality of group cells, it is possible to more appropriately control the amount of charge in consideration of the temperature of each group cell. The relative value is not particularly limited, but may be, for example, the difference between the temperature of the first charged group cell and the temperature of other group cells, or the ratio of the temperature of other group cells to the first charged group cell temperature ( ratio). Further, the charger may include a temperature detection section for detecting the temperature of each group of cells in the battery pack.

A charging method according to an embodiment of the present invention is a method for charging a tool battery pack including a plurality of group cells. The charging method includes a measuring step of measuring at least one of a current and a voltage of each of the plurality of group cells, and a step of measuring at least one of the current and voltage of each of the plurality of group cells, and a step of measuring each of the plurality of group cells using at least one of the current and voltage measured in the measuring step. and a charging control step for controlling charging. The charge control step includes a plurality of cycles including charge control for each of the plurality of group cells, and in each cycle, the plurality of charge control steps measured in the measurement step are performed so that the SOCs of the plurality of group cells approach uniformity. The amount of charge of each group cell is controlled based on at least one of the current and voltage of at least one group cell.

A program in an embodiment of the present invention is a program that causes a charger for a tool battery pack including a plurality of group cells to execute a charging control process. The program includes a measurement process of measuring at least one of current and voltage of each of the plurality of group cells, and charging of each of the plurality of group cells using at least one of the current and voltage measured in the measurement process. The charger is caused to perform a charging control process for controlling the charger. The charging control process includes a plurality of cycles including charging control for each of the plurality of group cells, and in each cycle, the plurality of cells measured in the measurement process are The amount of charge of each group cell is controlled based on at least one of the current and voltage of at least one group cell.

[Embodiment]
Hereinafter, embodiments will be described with reference to the drawings. Identical and corresponding components in the drawings are designated by the same reference numerals, and the same description will not be repeated. Note that, in order to make the explanation easier to understand, in the drawings referred to below, the configuration is shown in a simplified or schematic manner, and some structural members are omitted.

(Charger configuration example)
FIG. 1 is a diagram showing an example of the configuration of a charger in this embodiment. Charger 1 shown in FIG. 1 can be connected to external power source 100 and battery pack 2. Charger 1 shown in FIG. Charger 1 charges battery pack 2 with power supplied from power source 100 . The battery pack 2 is a tool battery pack. Battery pack 2 is connectable to charger 1 . The battery pack 2 includes a plurality of group cells 2a to 2c. Each of group cells 2a-2c includes a plurality of batteries connected in series. Each of the group cells 2a-2c has positive terminals 3a-3c connected to the positive electrode of the battery, and negative terminals 4a-4c connected to the negative electrode of the battery.

The charger 1 includes a plurality of positive terminals 5a to 5c, a plurality of negative terminals 6a to 6c, a plurality of switch elements 7a to 7c, and a control section 10. The control section 10 includes a charging control section 11 , a voltage measurement section 12 , a current measurement section 13 , and a connection detection section 14 . The positive terminals 5a to 5c can be connected to the positive terminals 3a to 3c of the plurality of group cells 2a to 2c of the battery pack 2, respectively. The negative terminals 6a to 6c can be connected to the negative terminals 4a to 4c of the plurality of group cells 2a to 2c, respectively. A voltage for charging each group cell 2a to 2c is applied between each of the positive terminals 5a to 5c and each of the negative terminals 6a to 6c, respectively. The switch elements 7a to 7c switch which of the plurality of sets of positive and negative terminals (5a to 6a, 5b to 6b, and 5c to 6c) to apply the voltage for charging. Switch elements 7a to 7c are controlled by charging control section 11. The voltage measurement unit 12 detects the respective voltages between the plurality of sets of plus and minus terminals (5a-6a, 5b-6b, 5c-6c). The current measurement unit 13 detects the current flowing between each of the plurality of sets of plus and minus terminals (5a-6a, 5b-6b, 5c-6c).

In the example shown in FIG. 1, the positive terminals 5a to 5c are connected to a common positive wiring K1, and the negative terminals 6a to 6c are connected to a common negative wiring K2. A voltage for charging is applied between the common positive wiring K1 and the common negative wiring K2. Switch elements 7a to 7c are provided between each of positive terminals 5a to 5c and common positive wiring K1. That is, each of the switch elements 7a to 7c switches conduction/nonconduction of the charging path connected to each of the positive terminals 5a to 5c. As an example, the switch elements 7a to 7c are configured with FETs. In this case, the source and drain of the FET are connected in series to the charging path. The gate of the FET is connected to the charging control section 11.

The charging control unit 11 controls on/off of the switch elements 7a to 7c by supplying control signals to the switch elements 7a to 7c. The charging control unit 11 switches the group of cells to be charged by controlling on/off of the switch elements 7a to 7c. For example, the group cell 2a can be charged by turning on the switch element 7a and turning off the switch elements 7b and 7c. The charging control unit 11 controls charging of each group of cells 2a to 2c.

The voltage measurement unit 12 detects the voltage of the common positive wiring K1. The common positive wiring K1 is electrically connected to any of the positive terminals 5a to 5c, that is, to any of the group cells 2a to 2c, depending on whether the switch elements 7a to 7c are turned on or off. The voltage measurement unit 12 detects the charging voltage of one of the group cells 2a to 2c by detecting the voltage of the common positive wiring K1 electrically connected to one of the group cells 2a to 2c. .

The current measurement unit 13 detects the current by measuring the voltage of the current detection resistor 8 provided in the common negative wiring K2. The current measuring unit 13 detects the current while one of the group cells 2a to 2c is being charged. In this case, the charging current of one of the group cells 2a to 2c is detected. Note that the current measurement is not limited to the case where the current detection resistor of the above embodiment is used, and for example, a current transformer or an internal resistance of an FET, etc. may be used.

The connection detection unit 14 detects the connection between the charger 1 and the battery pack 2 by detecting the connection between the connection detector 92 of the charger 1 and the connection detector 91 of the battery pack 2. The connection between the connection detectors 91 and 92 to be detected may be a mechanical connection or an electrical connection, and is not limited to a specific form. Note that the connection detection unit 14 and connection detectors 91 and 92 may be omitted. In this case, for example, the connection between the battery pack 2 and the charger 1 is detected by detecting the connection between the positive terminals 5a to 5c and the negative terminals 6a to 6c, and the positive terminals 3a to 3c and the negative terminals 4a to 4c. can do.

The control unit 10 is configured by, for example, a circuit. For example, the control section 10 includes a circuit that constitutes the charging control section 11, a voltage measurement circuit that constitutes the voltage measurement section 12, a current measurement circuit that constitutes the current measurement section 13, and a connection detection circuit that constitutes the connection detection section 14. May include. Further, the control unit 10 may include a computer including a processor and a memory. For example, at least part of the functions of the charging control unit 11 may be realized by a processor executing a program. Such programs and non-transitory recording media on which the programs are recorded are also included in the embodiments of the present invention.

Note that the configuration of the charger 1 is not limited to the example shown in FIG. 1. In the example shown in FIG. 1, the configuration is such that a switch element switches charging of a plurality of group cells. As a modification, a plurality of charge control sections may be provided corresponding to each of a plurality of group cells. In this case, each charging control section can control charging of each group of cells.

[Charging control section]
The charging control unit 11 controls charging of each of the plurality of group cells 2a to 2c. The charging control unit 11 sequentially charges the plurality of group cells 2a to 2c. The charging control unit 11 controls charging of the group cells 2a to 2c using at least one of the voltage measured by the voltage measurement unit 12 and the current measured by the current measurement unit 13. The charging control unit 11 repeats a cycle including charging control for each of the plurality of group cells multiple times. The operation of the charging control unit 11 in one cycle includes, for example, determining charging control for each of the plurality of group cells and charging at least one of the plurality of group cells. In one cycle, it is not necessary to charge all of the plurality of group cells. The charging control unit 11 controls the plurality of group cells to be sequentially charged in each cycle.

The charging control unit 11 controls the charging amount of each group cell so that the SOC of the plurality of group cells 2a to 2c approaches uniformity in each cycle. The charging control unit 11 controls the amount of charge of each group cell using at least one of the voltage and current of at least one of the plurality of group cells 2a to 2c measured in each cycle. In each cycle, the charging control unit 11 determines that the degree of uniformity of the SOC of the plurality of group cells 2a to 2c after the start of the cycle is the same as or higher than the degree of uniformity of the SOC of the plurality of group cells 2a to 2c before the end of the cycle. In this manner, the amount of charge of the plurality of group cells 2a to 2c can be controlled. For example, the amount of charge of the plurality of group cells 2a to 2c is controlled so that the difference between the SOC of one group cell and the SOC of another group cell among the plurality of group cells 2a to 2c is the same or smaller.

In the present embodiment, as an example, the charging control unit 11 determines, in each cycle, based on at least one of the voltage and current after charging of the group cells charged first (hereinafter also referred to as first group cells). , controls the amount of charge of other group cells. The charging control unit 11 may include a storage device (for example, a memory, etc.) for storing at least one of the voltage and current of the first group of cells. In each cycle, the charging control unit 11 compares the stored voltage of the first group cell with the measured voltage of the other group cells, and compares the stored current of the first group cell with the measured voltage of the other group cell. Charging of the other group cells may be controlled based on at least one of the results of comparison with the current of the group cells.

The charging control unit 11 controls, in each cycle, so that at least one of the voltage and current after charging of the other group cells other than the first group cells approaches at least one of the voltage and current after charging of the first group cells. , the amount of charge of other group cells can be controlled. For example, in each cycle, if the voltage of another group cell is lower than the voltage of the first group cell after charging, the charging control unit 11 charges the other group cell, and the voltage of the other group cell is If the voltage is the same as or higher than the voltage of the first group cells after charging, it may be determined not to charge the other group cells. Alternatively, in each cycle, the charging control unit 11 determines the charging amount (for example, charging time) of the other group cells based on the difference between the voltage after charging of the first group cells and the voltage of the other group cells. You may. Alternatively, the charging control unit 11 may charge other group cells in each cycle until the voltage reaches the voltage after charging of the first group cells. In this way, the charging control unit 11 sets the target value based on the voltage after charging of the first group cells, and sets the target value based on the voltage of the other group cells (in this example, the second group cells and the third group cells) (SOC ) can approach the target value by controlling the amount of charge of other group cells. Similarly, the charging control unit 11 sets a target value based on the current after charging of the first group cells, and controls the charging amount of the other group cells so that the current of the other group cells approaches the target value. be able to.

The order of charging control of the plurality of group cells in each cycle may be determined in advance, or may be determined based on the voltages of the plurality of group cells. For example, the charging control unit 11 can determine which group cell to charge first in each cycle based on the voltages of a plurality of group cells. For example, the charging control unit 11 can determine the group cell with the lowest voltage among the plurality of group cells as the group cell to be charged first. This causes the lower voltage group cells to be charged first in each cycle.

The charging control unit 11 may charge the first group cells by a predetermined amount in each cycle. For example, the charging control unit 11 may charge the first group of cells for a predetermined time. Alternatively, the charging control unit 11 may monitor the amount of change in voltage or current during charging, and perform charging until the amount of change in voltage or current of the first group cells reaches a predetermined amount. Note that in each cycle, the charging control unit 11 may determine the amount of charge of the first group cells based on the voltage of the first group cells.

The charging control unit 11 may set an upper limit for the charging time of the cells in groups other than the first group cells in each cycle. In each cycle, the upper limit of the charging time of the other group cells may be set to be the same as or longer than the charging time of the first group cells. As a result, for example, if charging is started when the voltage of the other group cells is lower than the first group cell, each cycle of charging will cause the voltage of the other group cells to reach the voltage of the first group cell. It becomes easier to catch up.

In each cycle, the charging control unit 11 may control the amount of charge of the other group cells based on the comparison result between the voltage before charging and the voltage after charging of the first group cells. For example, if it is determined that the voltage of the first group cells after charging does not change compared to the voltage before charging, the other group cells can be charged for a predetermined constant time.

The charging control unit 11 can also control charging of each of the plurality of group cells 2a to 2c using the current measured by the current measurement unit 13. For example, the charging control unit 11 can perform constant voltage charging (CV charging) on the plurality of group cells 2a to 2c after performing constant current charging (CC charging). In this case, the charging control unit 11 controls charging of other group cells using the voltage after charging of the first group cells in each cycle during constant current charging, and controls charging of other group cells during constant voltage charging in each cycle. In this case, the current of the first group cell may be used to control charging of the other group cells. During constant voltage charging, the charging control unit 11 may control charging of the other group cells so that the current of the other group cells approaches the current after charging of the first group cells in each cycle. can.

[Operation example]
2 and 3 are flowcharts showing an example of the operation of the charger 1 in this embodiment. Referring to FIG. 2, when the connection detection unit 14 detects the connection of the battery pack 2 to the charger 1 (YES in step S1), the charging control unit 11 reads the voltage of each of the group cells 2a to 2c, The charging order is determined (step S2). The charging control unit 11 sequentially turns on the switch elements 7a to 7c, thereby sequentially connecting the group cells 2a to 2c to the common positive wiring K1. Thereby, the charging control section 11 can sequentially detect the voltages of the group cells 2a to 2c. The detected voltages of the group cells 2a to 2c are recorded in a recording device such as a memory, and read by the charging control section 11.

In this example, the charging control unit 11 determines the charging order of the group cells 2a to 2c in descending order of voltage. Below, among the group cells 2a to 2c, the group cell with the lowest voltage will be referred to as the first group cell, the group cell with the second lowest voltage will be referred to as the second group cell, and the group cell with the third lowest voltage will be referred to as the first group cell. are called the third group of cells. The charging order in each cycle is the first group cells, the second group cells, and the third group cells. The processing shown in steps S3 to S21 in FIG. 2 constitutes one cycle of processing. This cycle is repeated multiple times.

In each cycle, first, the first group of cells is charged (steps S3 to S5). Charging of the first group of cells (step S3) is continued until it is determined that the cells are fully charged (YES in step S4) or a predetermined time (30 seconds) has elapsed (YES in step S5). . In addition, in step 4, as an example, when the current during charging measured by the current measurement unit 13 is equal to or less than a preset full charge current, it is determined that the battery is fully charged. When it is determined that the first group cells are fully charged, in subsequent cycles, charging control is performed for the second group cells and the third group cells, excluding the first group cells (FIG. 3).

If the first group cells end charging after 30 seconds without reaching full charge (YES in step S4), the charging control unit 11 stores the voltage V1min and the charging current I1 at the end of charging of the first group cells. (Step S6).

Subsequently, the charging control unit 11 performs charging control of the second group cells and the third group cells. Charging control for the second group cells and the third group cells differs depending on whether CC charging or CV charging is performed. Specifically, if CC charging is determined in step S7, charging control in steps S8 to S13 is executed, and if CV charging is determined, charging control in steps S14 to S21 is executed.

Note that in this example, the charging control unit 11 starts charging by CC charging. When the first group cells reach the set voltage Vs, CC charging is switched to CV charging. FIG. 4 is a graph showing an example of charging voltage and charging current for one group of cells when CV charging is performed after CC charging. The horizontal axis of the graph in FIG. 4 indicates time (charging time), and the vertical axis indicates voltage or current. Line Lv indicates charging voltage, and line Li indicates charging current. In the example shown in FIG. 4, CC charging is performed from the start of charging at t0 until the charging voltage reaches the set voltage Vs at t1. At t1, CC charging is switched to CV charging. Thereafter, CV charging continues, and when the charging current reaches a preset full charging current Is at t2, charging ends. In such a case, multiple cycles are repeated during the CC charging period, and multiple cycles are also repeated during the CV charging period.

Referring again to FIG. 2, in the case of CC charging, charging of the second group cells (step S8) is performed when the voltage of the second group cells becomes V1min or more (YES at step S9) or when the second group cells are charged (step S8). The charging continues until a predetermined time (60 seconds) has elapsed from the start of charging (YES in step S10). After that, the third group of cells is charged (step S11). The charging of the third group cells also starts when the voltage of the third group cells becomes V1min or more (YES in step S12), or a predetermined time (60 seconds) has elapsed from the start of charging the third group cells ( The process continues until step S13 (YES). Note that, if the voltage of the second group cells is already equal to or higher than V1min, the charging control unit 11 determines not to charge the second group cells. Similarly, if the voltage of the third group cells is already equal to or higher than V1min, the third group cells are not charged.

In the case of CV charging, charging of the second group cells (step S14) determines whether the current of the second group cells becomes less than the full charge current (YES in step S15) or the current of the second group cells becomes less than I1. Alternatively, the charging continues until a predetermined time (60 seconds) has elapsed from the start of charging the second group of cells (YES in step S17). After that, the third group cells are charged (step S18). Regarding charging of the third group cells, either the current of the third group cells becomes less than or equal to the full charge current (YES in step S19), or the current of the third group cells becomes less than or equal to I1 (YES in step S20), or , continues until a predetermined time (60 seconds) has elapsed from the start of charging of the third group cells (YES in step S21).

As described above, the charging of the first group cells, the second group cells, and the third group cells is sequentially controlled, and one cycle ends. This cycle is repeated.

Steps S22 to S32 shown in FIG. 3 are an example of a cycle after the first group of cells is determined to be fully charged. In this cycle, charging of the second group cells and the third group cells is sequentially controlled. The charging of the second group cells (step S22) is determined to be fully charged (YES in step S23), or a predetermined time (30 seconds) has elapsed since the start of charging the second group cells (step S24). The process continues until YES).

If the second group cells end charging after 30 seconds without reaching full charge (YES in step S24), the charging control unit 11 stores the voltage V2min and charging current I2 at the end of charging of the second group cells. (Step S25).

Thereafter, the third group of cells is charged. In the case of CC charging (CC charging in step S26), charging of the third group cells (step S27) is performed until the voltage of the third group cells becomes V2min or more (YES in step S28) or when the voltage of the third group cells is The charging continues until a predetermined time (60 seconds) has elapsed from the start of charging (YES in step S29). In the case of CV charging (CV charging in step S26), charging of the third group cells (step S30) is performed when the current of the third group cells becomes I2 or less (YES in step S31), or when the third group cells are charged The process continues from the start until a predetermined time (60 seconds) has elapsed (YES in step S32).

The cycle of charging control of the second group cells and the third group cells (steps S22 to S32) is repeated until the second group cells are determined to be fully charged. If it is determined that the second group cells are fully charged (YES in step S23), then the third group cells are charged (step S33) until it is determined that they are fully charged (YES in step S34).

In the example shown in FIGS. 2 and 3 above, a cycle including charging control for each of the plurality of group cells 2a to 2c is repeated. In each cycle during CC charging, the first group of cells is charged first. When the voltage of the second group cell and the third group cell is lower than the voltage after charging of the first group cell, the voltage of the second group cell and the third group cell is lowered until the voltage after charging of the first group cell is reached or the charging time reaches the upper limit. will be charged up to. Furthermore, in each cycle during CV charging, the first group of cells is charged first. When the charging current of the second group cells and the third group cells is larger than the charging current of the first group cells, the cells of the second group and the third group are charged until the charging current reaches the charging current of the first group cells or until the charging time reaches the upper limit. Ru. This makes it possible to reduce the difference in voltage between the plurality of group cells 2a to 2c in each cycle through CC charging and CV charging. The more the cycle is repeated, the smaller the difference in voltage between the plurality of group cells 2a to 2c becomes. Therefore, for example, even if charging is stopped before reaching full charge, the difference in voltage between the plurality of group cells 2a to 2c is smaller than when charging starts.

FIG. 5 is a graph showing an example of changes in the voltage and capacity of the group cells 2a to 2c when the charging control shown in FIGS. 2 and 3 is executed. In the graph of FIG. 5, the vertical axis shows voltage and the horizontal axis shows time. A diagram showing changes in the capacitance of the group cells 2a to 2c is inserted into the graph. In the example shown in FIG. 5, at the start of charging (t0), the capacity and voltage of group cell 2b are smaller than those of group cell 2a and group cell 2c. Therefore, in the period T1 from t0 to t1, only the group cell 2b is charged in each cycle, and the group cells 2a and 2c are not charged, until the voltage of the group cell 2b becomes substantially the same as that of the group cell 2a. During period T2 from t1 to t2 when the voltages of group cells 2b and 2a become substantially the same as the voltage of group cell 2c, group cell 2b and group cell 2a are charged in each cycle, and group cell 2c is not charged. After t2, group cells 2b, 2a, and 2c are charged in each cycle. In each cycle, the charge amount of group cells 2b, 2a, and 2c is approximately the same. In this example, at any stage after the start of charging t0, the difference in voltage, that is, the difference in capacity, between the group cells 2a to 2c is smaller than at the start of charging.

Note that the operation example of the charger 1 is not limited to the example shown in FIGS. 2 and 3. For example, in the above example, CV charging is performed after CC charging, but for example, only CC charging may be performed. Further, in the above example, the order of charging the group cells 2a to 2c in a plurality of cycles is the same, but the order may be different depending on the cycle. Further, in the above example, the order of charging the group cells 2a to 2c in each cycle is determined based on the voltage of the group cells 2a to 2c, but the order of charging in each cycle may be determined in advance. good. Further, in the above example, the upper limit of the charging time of each of the group cells 2a to 2c in each cycle is a predetermined time, but the charging time of each of the group cells 2a to 2c in each cycle, for example, It may be determined based on the cell voltage or the like. In the example shown in FIG. 5, the SOCs of the group cells 2a to 2c are approximately equal after a plurality of cycles. On the other hand, charging may be controlled so that the SOCs of the group cells 2a to 2c become approximately equal in one cycle.

FIG. 6 is a diagram showing a modification of the operation of the charger 1. In the example shown in FIG. 6, the order of the group cells in each cycle is predetermined as 2c, 2a, and 2b. The capacities (ie, voltages) of the group cells 2a to 2c at the start of charging are 2b<2a<2c. In this case, in each cycle, the group cell 2c is charged first and then the group cells 2a, 2c are charged until the voltage reaches the voltage of the group cell 2c or the charging time reaches an upper limit. Therefore, in one cycle, the charging time of the group cells 2a and 2b is longer than the charging time of the group cell 2c. When this cycle is repeated, the difference in capacitance (voltage) between the group cell 2c and the group cells 2a and 2b becomes smaller, and eventually the capacitances (voltages) of the group cell 2c and the group cells 2a become approximately the same.

When the capacities (voltages) of the group cells 2a to 2c are 2b<2a≈2c, the charging time of the group cell 2b is longer than the charging time of the group cells 2c and 2a in one cycle. In this case, in each cycle, the group cell 2c is charged first, the group cell 2a is charged by approximately the same amount, and the group cell 2b is charged until the voltage reaches the voltage of the group cell 2c or the charging time reaches the upper limit. will be charged until it reaches . When this cycle is repeated, the capacities (voltages) of the group cells 2a, 2b, and 2c eventually become the same.

When the capacities (voltages) of the group cells 2a, 2b, and 2c are the same (2b≈2a≈2c), the group cells 2a, 2b, and 2c are charged by the same amount in each cycle. As a result, at the end of each cycle, the capacitances (voltages) of the group cells 2a, 2b, and 2c become approximately the same.

In the example shown in FIG. 6, in each cycle, the charging time of the first group cell to be charged is determined according to the voltages of the group cells 2a to 2c. In this example, the charging time is such that the pre-charge voltage of the first group cell to be charged is higher than at least one of the other group cells. The charging time is shorter than the same or lower than the group cell. This makes it possible to further reduce the difference in voltage between the plurality of group cells 2a to 2c in each cycle.

Depending on the type of battery in the group cell and the charging current value, there may be a region (period) in which the voltage hardly changes even during CC charging. FIG. 7 is a graph showing changes in voltage and current with respect to charging time in such a case. In the example shown in FIG. 7, there is a period (i.e., a period from t1 to t2) in which the voltage does not change as the charging time elapses, in a part of the period from the start of charging t0 to the time t3 when the set voltage Vs is reached. .

The charging control unit 11 controls only the charging time of the plurality of group cells 2a to 2c in each cycle when at least one of the group cells 2a to 2c is in a state where the voltage does not change as the charging time elapses. can do. For example, in a certain cycle, when the voltage of the second group cell and the third group cell is equal to or higher than the voltage V1min at the end of charging of the first group cell, the first group cell is charged for 30 seconds in the next cycle. If it can be determined that the voltage V1min of the first group cells after charging does not change from the value before charging, the second group cells and the third group cells are also charged for the same 30 seconds. That is, all of the first group cells, the second group cells, and the third group cells are controlled so that the charging time is a preset time. If the state in which it is determined that the voltage before and after charging of the first group cells does not change continues, a cycle of charging each group cell for a predetermined period of time is repeated.

If the changes in voltage and current with respect to the charging time during charging of each group cell are as shown in the example shown in FIG. can be controlled. For example, the amount of charge of each group of cells can be controlled in the same manner as in FIG. During the period from t1 to t2, a cycle is repeated in which the first group of cells, the second group of cells, and the third group of cells are all charged for a predetermined period of time. If a voltage change occurs again after t2, the control is returned to such that the voltages of the second group cells and the third group cells reach the target values, similar to the control from t0 to t1, and a plurality of cycles are repeated. Note that in CV charging after t3, control is switched from voltage-based control to current-based control, and a plurality of cycles are repeated. That is, after t3, a cycle is repeated in which the current of at least one of the second group cell and the third group cell is controlled to reach the target value.

In the example shown in FIG. 7, during the periods t0 to t1 and t2 to t3, the voltage of at least one group cell is controlled to reach the target value in each cycle. During the period from t1 to t2, the charging time of each group cell (first to third group cells) is controlled to reach a target value in each cycle. After t3, the current of at least one group cell is controlled to reach the target value in each cycle. In this way, control that combines voltage-based control, time-based control, and current-based control is possible. Note that a combination of control based on voltage and control based on time, or control based on current and control based on time is also possible.

Note that, in each cycle, the mode of controlling the charging of each group cell based on at least one of the voltage and current of at least one of the plurality of group cells is such that the charging of each group cell is controlled based on at least one of the voltage and current of at least one of the plurality of group cells. The present invention is not limited to controlling the charging of each group cell in a cycle based on at least one of the voltage and current of at least one group cell. The cycle leading to full charge may include a cycle in which charging of each group cell is controlled not based on either the voltage or current of the group cell.

The charging characteristics of batteries change depending on the temperature. Furthermore, the temperature range for charging may be limited depending on the temperature profile of the battery. The charger may include a T terminal and a temperature detection section (detection circuit) for detecting the temperature of each group of cells in the battery pack.

FIG. 8 is a diagram showing an example of a configuration in which a T terminal and a temperature detection section are added to the charger shown in FIG. 1. In the example shown in FIG. 8, each group of cells 2a to 2c of the battery pack 2 is provided with thermistors 16a to 16c and T terminals 17a to 17c. Thermistors 16a to 16c are connected between T terminals 17a to 17c and negative terminal 4a. A charger 1A shown in FIG. 8 includes T terminals 18a to 18c and a temperature detection section 15 in addition to the configuration shown in FIG. The T terminals 18a to 18c are provided at positions corresponding to the plurality of negative terminals 6a to 6c, respectively. T terminals 18a to 18c of charger 1A can be connected to T terminals 17a to 17c of battery pack 2, respectively. T terminals 18a to 18c are connected to temperature detection section 15. The temperature detection unit 15 is, for example, a temperature detection circuit. The temperature detection unit 15 can measure the temperature of each of the group cells 2a to 2c, for example, by detecting the resistance of the thermistors 16a to 16c connected to the T terminals 18a to 18c, respectively.

The charging control unit 11 can further use the temperature of each group cell 2a to 2c measured by the temperature detection unit 15 to control charging of each group cell 2a to 2c. For example, the charging control unit 11 can control the amount of charge of each group of cells 2a to 2c in each cycle by further using the temperature of each group of cells 2a to 2c.

As an example, the charging control unit 11 may perform control so as not to charge group cells whose temperature satisfies the charging prohibition condition in each cycle. In this case, the charging control unit 11 detects the temperature of each group cell in each cycle, skips the group cells whose temperature prohibits charging, and charges only the other group cells. When a group cell whose charging was prohibited becomes chargeable, this group cell is charged preferentially over other group cells. For example, the target group cell is preferentially charged so that the target group cell is supplemented with the charging amount of other group cells during the period when the target group cell was at a temperature that prohibited charging. The amount of charge of other group cells during the period when the target group cell was at a temperature that prohibits charging can be determined from, for example, at least one of the length of the period, voltage, and current.

In each cycle, the charging control unit 11 may control the amount of charge of other group cells based on the temperature of the first charged group cell and the voltage after charging is completed. For example, a value obtained by correcting the voltage of the first charged group cell after charging is completed based on the temperature of this group cell may be set as the target value of the voltage of the other group cells. In this case, the charging control unit 11 can charge the other group cells until the voltage of the other group cells reaches the target value or the charging time reaches a predetermined time. Note that the target value may be corrected, for example, based on the difference between the temperature of the first charged group cell and the temperature of another group cell to be charged. Thereby, the SOCs of the plurality of group cells can be made more uniform in one cycle.

In each cycle, the charging control unit 11 may control the amount of charge of other group cells based on the temperature of the first charged group cell and the current after charging is completed. For example, a value obtained by correcting the current after charging of the first charged group cell based on the temperature of this group cell may be set as the target value of the current of the other group cells. In this case, the charging control unit 11 can charge the other group cells until the current of the other group cells reaches the target value or the charging time reaches a predetermined time. The target value may be corrected, for example, based on the difference between the temperature of the first charged group cell and the temperature of other group cells to be charged. Thereby, the SOCs of the plurality of group cells can be made more uniform in one cycle.

The charger of this embodiment is used as a charger for a battery pack of a power tool. That is, the present invention is a charger for a battery pack for a power tool, which has a plurality of group cells and a charge/discharge terminal is provided for each group cell. The charger sequentially charges each group of cells. By charging with a charger, the state of charge (SOC) of each group of cells becomes substantially uniform at any stage of charging up to full charge.

Power tools may require a high voltage power source. The circuit of the power tool can be configured such that a plurality of group cells are connected in series with each other when the battery pack is attached to the power tool. In this way, when multiple cells in a battery pack are connected in series in a tool's circuit, no matter where charging is stopped during charging of the battery pack, the amount of charge in each group of cells is uniform. This makes it possible to perform certain operations using tools. It is thought that users of power tools often charge the battery pack for a short period of time when they want to use it. Therefore, the charger of this embodiment, which can make the SOC of a plurality of group cells substantially uniform at any stage of charging, is preferably used.

Further, the circuit of the power tool can be configured such that a plurality of group cells are connected in parallel with each other while the battery pack is attached to the power tool. In this way, when multiple group cells of a battery pack are connected in parallel and used, if the SOCs of the multiple group cells are significantly different, a large cross current may flow between the group cells and affect the control element. There is. According to the charger of this embodiment, the SOCs of the plurality of group cells are substantially uniform at any stage of charging. This makes it possible to suppress cross currents in the group cells.

Note that by charging each cell at the same time, it is possible to make the SOC of a plurality of group cells close to uniform at any stage of charging. However, a charger configured to charge a plurality of group cells simultaneously is larger and more expensive to manufacture than a charger configured to sequentially charge a plurality of group cells. In this embodiment, since a plurality of group cells are sequentially charged, the charger can be made smaller and lower in cost.

Moreover, since the charger of this embodiment sequentially charges a plurality of group cells, the charging voltage, that is, the output voltage can be kept low. For example, the charging voltage of the charger can be set to DC60V or less. By setting the charging voltage of the charger to DC60V or less, it is advantageous in terms of cost and size. One of the reasons for this is that, in classification based on the Electrical Appliance and Material Safety Law, the standards required for design change depending on whether the output voltage exceeds DC 60V.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

1: Charger, 2: Battery pack, 2a to 2c: Group cell, 11: Charging control section, 12: Voltage measurement section, 13: Current measurement section, 14: Connection detection section

Claims (10)

A charger for a tool battery pack including a plurality of group cells,
a measurement unit that measures at least one of the current and voltage of each of the plurality of group cells;
a charging control unit that controls charging of each of the plurality of group cells using at least one of the current and voltage measured by the measurement unit,
The charging control unit repeats a cycle of sequentially controlling charging for each of the plurality of group cells multiple times, and in each cycle, the measurement unit measures the SOC of the plurality of group cells so that they approach uniformity. A charger for a battery pack for a tool, which sequentially controls the amount of charge of each group cell based on at least one of the current and voltage of at least one of the plurality of group cells. The charger according to claim 1,
A charger for a battery pack for a tool, wherein the charge control section controls the amount of charge of other group cells in each cycle based on at least one of the voltage and current after charging of the group cell charged first. The charger according to claim 2,
The charging control unit is configured such that in each cycle, at least one of the voltage and current after charging of the other group cells approaches at least one of the voltage and current after charging of the first charged group cell, A charger for a battery pack for a tool, which controls the amount of charge of the other group cells. The charger according to any one of claims 1 to 3,
The charge control unit is a charger for a battery pack for a tool that charges a group of cells to be charged first in each cycle by a predetermined amount. The charger according to any one of claims 1 to 4,
In the battery pack charger for a tool, the charging control unit determines the order of group cells to be charged in each cycle based on the voltages of the plurality of group cells. The charger according to any one of claims 1 to 4,
The charging control unit is a charger for a battery pack for a tool, and the charging control unit charges the plurality of group cells in a predetermined order in each cycle. A charger for a tool battery pack including a plurality of group cells,
a measurement unit that measures at least one of the current and voltage of each of the plurality of group cells;
a charging control unit that controls charging of each of the plurality of group cells using at least one of the current and voltage measured by the measurement unit,
The charge control unit repeats a cycle including charging control for each of the plurality of group cells a plurality of times, and in each cycle, the plurality of group cells measured by the measurement unit controlling the amount of charge of each group cell based on at least one of the current and voltage of at least one group cell;
The charge control section controls the charging amount of other group cells in each cycle based on the comparison result between the voltage of the group cell charged first and the voltage before charging. charger. A charger for a tool battery pack including a plurality of group cells,
a measurement unit that measures at least one of the current and voltage of each of the plurality of group cells;
a charging control unit that controls charging of each of the plurality of group cells using at least one of the current and voltage measured by the measurement unit,
The charge control unit repeats a cycle including charging control for each of the plurality of group cells a plurality of times, and in each cycle, the plurality of group cells measured by the measurement unit controlling the amount of charge of each group cell based on at least one of the current and voltage of at least one group cell;
The charge control unit corrects the charge amount of the other group cell in each cycle based on the relative value of the temperature of the other group cell with respect to the temperature of the first charged group cell. . A method for charging a tool battery pack including a plurality of group cells, the method comprising:
a measuring step of measuring at least one of the current and voltage of each of the plurality of group cells;
a charging control step of controlling charging of each of the plurality of group cells using at least one of the current and voltage measured in the measuring step,
The charging control step includes a plurality of cycles in which charging is controlled in order for each of the plurality of group cells, and in each cycle, the SOC of the plurality of group cells is measured in the measurement step so that the SOC approaches uniformity. A method of charging a battery pack for a tool, wherein the amount of charge of each group cell is sequentially controlled based on at least one of the current and voltage of at least one of the plurality of group cells. A program that causes a charger for a tool battery pack including a plurality of group cells to execute charging control processing,
a measurement process of measuring at least one of the current and voltage of each of the plurality of group cells;
causing the charger to perform a charging control process of controlling charging of each of the plurality of group cells using at least one of the current and voltage measured in the measurement process;
The charging control process includes a plurality of cycles in which charging is controlled in order for each of the plurality of group cells, and in each cycle, the SOC of the plurality of group cells is measured in the measurement process so that it approaches uniformity. A program that sequentially controls the amount of charge of each group cell based on at least one of a current and a voltage of at least one of the plurality of group cells.

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