WO2005076430A1

WO2005076430A1 - Combined battery and battery pack

Info

Publication number: WO2005076430A1
Application number: PCT/JP2005/001616
Authority: WO
Inventors: Kazuyuki Sakakibara; Masaaki Fukumoto
Original assignee: Makita Corporation
Priority date: 2004-02-05
Filing date: 2005-02-03
Publication date: 2005-08-18
Also published as: JP2005224024A

Abstract

It is an object of the invention to prevent the difference in charge efficiency between battery cells from adversely affecting the combined battery. According to the invention, in a combined battery including a plurality of battery cells, based on the difference in charge efficiency between first battery cells (lithium-ion battery cells 111-113) and a second battery cell (nickel metal hydride battery cell 121) that constitute the combined battery, the charging current for charging the first battery cells is diverted.

Description

Specification

Battery pack and battery pack

Technical field

The present invention relates to a technique for effectively dealing with an adverse effect caused by a difference in charging efficiency between battery cells in an assembled battery and a battery pack including a plurality of battery cells. Background art

[0002] One example of a charging device for charging an assembled battery in which a plurality of lithium-ion battery cells are connected in series is disclosed in Japanese Patent Application Laid-Open No. 6-165399. In this charging device, a bypass circuit and a voltage detector connected in parallel to the lithium-ion battery cell are provided. When a voltage detector detects that a predetermined lithium ion battery cell has reached a charge stop voltage (full charge), a no-pass circuit provided in the lithium ion battery cell is connected in parallel with the battery cell. The battery cell is prevented from being overcharged by supplying a charging current to the binos circuit thereafter.

Disclosure of the invention

Problems to be solved by the invention

[0003] With this charging device, it is possible to prevent each battery cell from being overcharged when charging is performed until charging is completed. By the way, if charging is stopped during charging, the remaining capacity of each battery cell is likely to differ! When the battery pack is discharged in a state where the remaining capacity difference occurs between the battery cells! /, The remaining capacity of the battery cell with the lowest remaining capacity becomes zero first, so the remaining capacity of the other battery cells becomes zero. Despite the presence, the battery cannot be used as an assembled battery, and the performance of each battery cell cannot be fully utilized.

An object of the present invention is to prevent a difference in charging efficiency between battery cells from affecting a battery pack.

Means for solving the problem

[0004] The object is to provide an assembled battery having a plurality of battery cells, based on a difference in charging efficiency between a first battery cell and a second battery cell constituting the assembled battery! The charging current for charging the first battery cell is shunted, and the charging current is divided by the assembled battery according to the present invention. Is decided.

According to the present invention, an assembled battery having a plurality of battery cells is configured. As the battery cell, typically, a lithium ion battery cell, a nickel hydride battery cell, or a nickel cadmium battery cell is used. A battery pack can be composed of the same type of battery cells (for example, lithium-ion battery cells only) or different types of battery cells (for example, lithium-ion battery cells and nickel-metal hydride battery cells). Good. Also, each battery cell in the assembled battery may be connected in series with each other, or may be connected in parallel.

[0005] The specification of the output voltage of the assembled battery is generally called a nominal voltage, and is determined by the type, number, connection mode, and the like of the battery cells constituting the assembled battery. Typically, the nominal voltage of an assembled battery in which a plurality of battery cells are connected in series can be set as a value obtained by adding the nominal voltage of each battery cell. Among assembled batteries, assembled batteries having a nominal voltage of approximately 9.6V, 12V, 14.4V, 18V, 24V, etc. are frequently used in devices such as electric tools. Particularly in battery packs for power tools, in addition to momentary high power, continuous high power is often required, and it is necessary to maintain the performance of the battery as high as possible. In addition, battery packs for power tools are often used in situations where they consume a large amount of battery, so they are used while being repeatedly charged with a charger, so high durability is easily required! /.

[0006] In a plurality of battery cells, the charging efficiency may differ depending on the type of the battery cell, the remaining capacity, the temperature, the magnitude of the charging current and the like. The charging efficiency is referred to as ampere-hour efficiency, and is represented by a ratio (%) of the amount of discharged electricity (Ah) of the battery cell to the amount of charged electricity (Ah). The amount of discharged electricity (Ah) of the battery cell, that is, the amount of electricity (Ah) that can be taken out when the battery cell is discharged, indicates the amount of electricity (Ah) actually charged to the battery cell. For example, lithium-ion battery cells and nickel-metal hydride battery cells have smaller charge loss than lithium-ion battery cells, and therefore have the same effect factors such as remaining battery cell capacity, temperature, and charging current. If so, the lithium ion battery cell has higher charging efficiency. If the remaining capacity difference occurs between the battery cells due to the difference in the charging efficiency of the battery cells, it may be difficult to sufficiently extract the performance of each battery cell, as described in the above-described conventional technology.

[0007] In the battery pack according to the present invention, charging for charging the first battery cell is performed based on a difference in charging efficiency between the first battery cell and the second battery cell constituting the battery pack. The current is shunted. The “first battery cell” may be the same type of battery cell as the “second battery cell” or a different type of battery cell! /.

The path through which the charging current of the first battery cell is diverted is provided separately for one or more first battery cells in the battery group, and provided in common for the plurality of first battery cells. Therefore, the present invention encompasses all of the embodiments described above, and the cases in which these embodiments are mixed.

[0008] The charging current for charging the first battery cell may have a charging efficiency corresponding to each battery cell set in advance, and may be divided based on the difference in charging efficiency. Alternatively, an index related to the difference in charging efficiency may be detected, and the flow may be divided based on the detected index related to the difference in charging efficiency. Alternatively, both may be used in combination. When detecting an index related to a difference in charging efficiency, at least one of the remaining capacity index (typically, a voltage value, etc.), a temperature index, and a magnitude of a charging current of the battery cell is appropriately selected as the index. Preferably.

[0009] The phrase "charging current is diverted" broadly includes a case where all or a part of the charge electricity (Ah) of the charging current for charging the battery cell is diverted. This charge amount (Ah) is indicated by the integrated value of the charge current value (A) and time (h), so when determining the charge amount (Ah) to be divided, the divided current value (Ah) A mode for determining the time (h) for shunting while fixing A), a mode for determining the current value (A) for shunting while fixing the time (h) for shunting, the current value (A) for shunting and the shunting All embodiments for determining the time (h) are included. Typically, the battery pack is charged while a part of the charging current of the first battery cell having a higher charging efficiency than the second battery cell is shunted at a predetermined timing. In addition, the difference between the charging efficiencies of the first battery cell and the second battery cell is so large that the amount of charge electricity (Ah) shunted from the charging current of the first battery cell increases. Preferably. The mode in which the charging current is shunted includes the mode in which the charging current is bypassed.

[0010] Further, the battery pack of the present invention is configured such that the charging current for charging the second battery cell is divided as long as the charging current for charging at least the first battery cell is divided. Such a case is preferably included.

[0011] Further, a path (circuit) through which the charging current of the first battery cell is shunted may be incorporated in the configuration of the assembled battery, or may be provided outside the configuration of the assembled battery. . For example, it may be provided on the side of the battery pack into which the assembled battery is incorporated. [0012] According to the battery pack of the present invention, based on a difference in charging efficiency between the first battery cell and the second battery cell, a typical charging current for charging the first battery cell is shunted while shunting. Therefore, each battery cell can be charged in a well-balanced manner while preventing a difference in remaining capacity between the first battery cell and the second battery cell due to a difference in charging efficiency. Further, when a remaining capacity difference has already occurred between the battery cells, the remaining capacity difference can be reduced. This makes it difficult for battery cells with high charging efficiency to overdischarge during charging, and hardly causes battery cells with low charging efficiency to overdischarge during discharging. Further, even when the battery pack is stopped in the middle and discharged, the possibility of the problems described in the prior art described above is reduced, thereby making full use of the performance of each battery cell. It became possible to do.

Further, as described above, the assembled battery of the present invention is also suitably applied to an assembled battery of an electric tool that requires the performance of the assembled battery to be as high as possible and requires high durability. . BEST MODE FOR CARRYING OUT THE INVENTION

[0013] (First embodiment)

FIG. 1 shows a battery pack 100 as a first embodiment. FIG. 1 also shows a configuration of an example of a charger 200 for charging the battery pack 100.

Battery pack 100 has an assembled battery in which a lithium-ion battery group and a nickel-metal hydride battery group are connected in series, and a shunt circuit for shunting the charging current of the lithium-ion battery group is provided. Further, the battery pack 100 has a circuit configuration in which the battery pack is charged using an external device such as the charger 200, a circuit configuration in which the battery pack is discharged when a device such as a power tool is connected, and a battery charger. It has a printed circuit board on which terminals TE1 to TE6 that can be connected to the terminals of devices such as 200 and power tools are mounted. Although not shown, the battery pack 100 includes a housing for accommodating the battery pack printed board, and is configured to be detachable from devices such as the charger 200 and the power tool. When the battery pack 100 is mounted on the charger 200, the terminals TE1 and TE6 of the battery pack 100 are connected to the corresponding terminals TE11 and TE16 of the charger 200, and the battery pack 100 is assembled using the charger 200. The battery can be charged. On the other hand, although not shown, when the battery pack 100 is attached to a device such as a power tool, the terminals TE1 and TE6 of the battery pack 100 are connected to the terminals of the corresponding device, and the battery pack 100 of the battery pack 100 is connected. Then, power can be supplied to the device. [0014] The above-described battery pack 100 housing houses a battery pack in which a lithium-ion battery group 110 and a nickel-metal hydride battery group 120 are connected in series. The circuit configuration mounted on the printed circuit board includes a battery control unit 130 having a CPU and controlling the operation of the battery pack 100, a ROM 140 storing a charge control program and parameters for charging the assembled battery, and a ROM 140. Equipped with a thermistor TM arranged near the Kel-Hydrogen battery group 120, terminals TE1 to TE6 for connecting the charger 200 or the charged battery pack 100 to the device, a switch SW1 switched by the battery control unit 130, and a resistor R1. .

The lithium ion battery group 110 is an element corresponding to the “battery group in which a plurality of first battery cells are connected” in the present invention. The battery control unit 130 is an element corresponding to the “control unit” in the present invention.

[0015] In the battery pack according to the present embodiment, lithium ion battery group 110 and nickel hydride battery group 120 are connected in series. In addition, the lithium ion battery cells 111 to 113 constituting the lithium ion battery group 110 are connected in series within the lithium ion battery group 110. On the other hand, the nickel hydride battery group 120 includes one nickel hydride battery cell 121.

The nominal voltage of one lithium-ion battery cell is set to about 3.6 V, and the nominal voltage of one nickel-metal hydride battery cell is set to about 1.2 V, so three lithium-ion battery cells connected in series By connecting the lithium-ion battery group 110 with 111-113 and the nickel-metal hydride battery group 120 with one nickel-metal hydride battery cell 121 in series, the nominal voltage of the battery pack 100 becomes 12V (3.6V X 3 + 1. 2V = 12V) can be set.

The lithium ion battery cells 111-113 correspond to the "first battery cell" of the present invention, and the nickel hydrogen battery cell 121 corresponds to the "second battery cell" of the present invention.

The positive side (upper side shown in FIG. 1) of the lithium ion battery group 110 of the battery pack thus configured is connected to the terminal TE1 of the battery pack 100, and the negative side (FIG. 1) of the nickel hydride battery group 120. Is connected to the terminal TE2 of the battery pack 100. When the battery pack 100 is mounted on the charger 200, the terminals TE1 and TE2 are connected to terminals TE11 and TE12 of the charger 200 described later, respectively, and the lithium ion battery group 110 and the nickel hydride battery group 120 are charged. Is done. When the battery pack 100 is attached to a device such as a power tool, the terminal T El and TE2 are connected to corresponding terminals of the device, and the lithium ion battery group 110 and the nickel hydrogen battery group 120 discharge to supply power to the device.

[0017] A main body of an NTC thermistor TM having a negative temperature characteristic is arranged near the nickel-metal hydride battery group 120. When the temperature of the nickel-metal hydride battery group 120 increases, the impedance of the thermistor TM decreases. T! / One end of the thermistor TM is connected to the terminal TE4 and the ground terminal 135 of the battery control unit 130, and the other end of the thermistor TM is connected to the terminal TE5 and the terminal 136 of the battery control unit 130.

As a result, the battery pack 100 is attached to the charger 200, and the terminal TE5 of the battery pack 100 is connected to the terminal TE15 of the S charger 200, and the terminal TE4 of the battery pack 100 is connected to the terminal TE14 of the charger 200. Then, the control unit 230 of the charger 200 detects the voltage value between both ends of the thermistor TM every predetermined time. Based on this, it is possible to determine a change in the impedance value of the thermistor TM and, consequently, whether the temperature of the nickel-metal hydride battery group 120 is high or not.

The battery control unit 130 of the battery pack 100 can also determine whether the temperature of the nickel-metal hydride battery group 120 is high based on the potential difference between the ground terminals 135 and 136 (the voltage value at both ends of the thermistor TM). it can.

Further, ROM 140 is connected to terminal TE6, and when battery pack 100 is mounted on charger 200, terminal TE6 is connected to terminal TE16 of charger 200 described later. The control unit 230 of the charger 200, which will be described later, can read the charge control program of the battery pack 100 and the unique parameters of the battery pack 100 stored in the ROM 140 in advance from the ROM 140 via the terminals TE6 and TE16. it can.

A connection point P is provided between the minus terminal of the lithium-ion battery cell 113 and the plus terminal of the nickel-metal hydride battery cell 121. The connection point P is connected to a terminal 132 of the battery control unit 130. The plus side of the lithium ion battery group 110 is connected to a terminal 131 of the battery control unit 130, and the minus side of the nickel hydride battery group 120 is connected to a terminal 133 of the battery control unit 130. Thereby, battery control unit 130 can detect the voltage value of lithium ion battery group 110 and the voltage value of nickel hydrogen battery group 120, respectively.

[0020] The connection point P is connected to one end of the switch SW1. The other end of switch SW1 , And one end of the resistor Rl. The other end of the resistor R1 is connected to the positive side of the lithium ion battery group 110. Thus, the terminal TE1, the plus side of the lithium ion battery group 110, one end of the resistor R1 (the other end described above), and the terminal 131 of the battery control unit 130 are connected.

The terminal TE2, the negative side of the nickel-metal hydride battery group 120, and the terminal 133 of the battery control unit 130 are connected.

Further, the terminal TE3 is connected to the power supply terminal 134 of the battery control unit 130, and thereby, the operation power supply of the battery control unit 130 (the output of the second power supply circuit 250 of the charger 200 described later, ) Is supplied from the charger 200.

Further, the terminal TE4 is connected to the ground terminal 135 of the battery control unit 130, whereby the ground terminal 135 of the battery control unit 130 is grounded.

The switch SW1 can be set to an open state (off) or a closed state (on) by the battery control unit 130.

When the switch SW1 is in the open state (OFF), the charging current of the assembled battery flows from the terminal TE1 to the lithium-ion battery group 110 to the nickel-metal hydride battery group 120 to the terminal TE2. The nickel hydrogen battery group 120 is charged.

When the switch SW1 is closed (ON), a part of the charging current of the lithium-ion battery group 110 (for example, 1Z100 of charging current) 1S terminal TE1 → resistance Rl → switch SW1 →-hydrogen battery group 120 → terminal Flow to TE2. As a result, the amount of charge (Ah) supplied to the lithium ion battery group 110 is relatively smaller than the amount of charge (Ah) supplied to the nickel hydrogen battery group 120.

Thus, the circuit provided with the resistor Rl and the switch SW1 and connected in parallel to the lithium ion battery cell when the switch SW1 is turned on corresponds to the "shunt circuit" of the present invention. Here, as the resistor R1, when the switch SW1 is turned on, a resistance element having a resistance value calculated based on the amount of charging current flowing in the shunt circuit is selected. By connecting the components as described above, the voltage value of the nickel-metal hydride battery group 120 calculated by the battery control unit 130 by detecting the potential difference between the terminal 132 and the terminal 133 becomes the “remaining capacity index” of the present invention. Corresponding to [0022] Battery control unit 130 has a storage unit. The storage unit previously stores a program for determining a ratio (duty ratio) for turning on / off the switch SW1 based on the charging efficiency difference from the temperature and voltage value of the nickel-metal hydride battery group 120 detected by the detection unit. You.

The charger 200 includes a power supply circuit 210 that converts AC input power into a DC power supply for charging the battery pack 100, a charge control unit 220 that controls the power supply circuit 210, and a control unit 230 that controls the operation of the charger 200. , A storage unit 240 in which parameters for charging operation of the charger 200 (depending on the type of the charger 200, etc.) are stored, and a second power supply circuit for converting DC power output from the power supply circuit 210 to control power. 250, shunt resistor Rl l for charging current detection, thermistor TM for battery pack 100 Voltage dividing resistor R12 for voltage detection at both ends, terminals for connection to battery pack 100 TE11-TE16, AC input power supply connected Input terminals SE11 and SE12 are provided.

[0024] The input side of the power supply circuit 210 is connected to input terminals SE11 and SE12 to which AC input power can be connected. The output side of the power supply circuit 210 is connected to a power supply terminal TE11 of a DC power supply that is converted from an AC input power supply by the power supply circuit 210 and charges the battery pack 100 under the control of the charge control unit 220. ing. Also, it is connected to the ground terminal TE12 via the resistor R11.

The input side of the second power supply circuit 250 that supplies control power of approximately 5 V to the battery pack 100 and the ICs in the charger 200 is connected to the power supply circuit 210. The output side of the second power supply circuit 250 is connected to the output terminal TE13 of the control power supply and the ground terminal TE14 of the control power supply, respectively.

The output terminal TE13 is connected to the terminal TE15 and the control unit 230 via a voltage value detecting voltage dividing resistor R12 of the thermistor TM.

Further, a storage unit 240, terminals TE12 and TE16, and a charge control unit 220 are connected to the control unit 230.

Next, a general operation of charging the battery pack 100 (the lithium ion battery group 110 and the nickel hydride battery group 120) by the charger 200 will be described with reference to FIG.

AC input power is connected to input terminals SE11 and SE12 of charger 200. As a result, the DC power obtained by converting the AC input power in the power circuit 210 is input to the second power circuit 250, The DC power input to the second power supply circuit 250 is converted into a control power supply by the second power supply circuit 250. The control power is supplied to the control unit 230, the charge control unit 220, and the storage unit 240 in the charger 200, whereby the charger 200 starts operating.

When battery pack 100 is mounted on charger 200, terminals TE11-TE16 of charger 200 are connected to terminals TE1-6 of battery pack 100, respectively. Thus, the battery control unit 130 of the battery pack 100 is connected to the terminal TE3 of the battery pack 100 from the second power supply circuit 250 of the charger 200 via the output terminal TE13 of the control power supply, and the ground terminal of the control power supply. The control power is supplied to the terminal TE4 of the battery pack 100 via the TE, and the control power is supplied to the battery control unit. At this time, the switch SW1 of the battery pack 100 is opened (turned off) as an initial state.

Then, the control unit 230 of the charger 200 reads the charge control program and the unique parameters of the battery pack 100 stored in the ROM 140 of the battery pack 100 via the terminals TE4 and TE14. The control unit 230 calculates a suitable charge current value at the start of charging the battery pack 100 by using the charge control program read from the ROM 140 and information such as parameters, and instructs the charge control unit 220 of the charge current value. Output a signal. The charging control unit 220 controls the power supply circuit 210 to output the charging current value based on the signal output from the control unit 230. In this way, charging of the lithium ion battery group 110 and the nickel hydride battery group 120 of the battery pack 100 is started.

The control unit 230 monitors the charging current value using the shunt resistor R11. If the charging current value becomes equal to or less than the set value, for example, the battery pack (the lithium ion battery group 110 and the nickel hydrogen It is determined that the charging of the battery group 120) has been completed, and the charging operation ends.

[0028] Further, during the charging operation, the control unit 230 receives the output signal of the thermistor TM via the terminals TE5 and TE15. The control unit 230 monitors the voltage value across the thermistor TM by detecting the potential at the terminal TE15 by dividing the control power supply voltage of approximately 5 V using the resistor R12. Then, the control unit 230 reduces the impedance when the temperature rises. Based on the characteristics of the thermistor TM, the temperature of the nickel-metal hydride battery group 120 becomes lower than the set temperature. It monitors whether or not. When detecting that the temperature of the nickel hydrogen battery group 120 is equal to or higher than the set temperature, the control unit 230 A signal for stopping the charging operation is output to 220. Generally, the temperature of a nickel-metal hydride battery cell tends to rise due to a charging operation as compared with a lithium-ion battery cell, and at least the temperature of each battery group is monitored by monitoring the temperature of the nickel-metal hydride battery group 120. Problems can be prevented.

In this way, using the charger 200, the lithium ion battery group 110 and the nickel hydride battery group 120 of the battery pack 100 are charged.

Next, with respect to the battery pack 100 of the present invention, the operation of charging the assembled battery while preventing the occurrence of the remaining capacity difference between the lithium ion battery group 110 and the nickel hydride battery group 120 due to charging efficiency will be described. This will be described with reference to FIGS. FIG. 2 is a flowchart of a program executed by the CPU of the battery control unit 130 to prevent the remaining capacity difference between the battery groups, FIG. 3 is an example of duty ratio mapping data, and FIG. Fig. 4 is a timing chart showing a state in which is turned on and off (the shunt circuit repeats the connection Z non-connection state).

When the battery pack 100 is connected to the charger 200, the battery control unit 130 of the battery pack 100 controls the shunt of the charging current (the connection Z of the shunt circuit is not connected).

Under substantially the same environment, lithium-ion battery cells have higher charging efficiency than nickel-metal hydride battery cells. That is, when charging is performed while the switch SW1 is turned off (in a state where the shunt circuit is not connected), the lithium ion battery group 110 is likely to be fully charged first. Further, particularly during charging, the remaining capacity of the lithium-ion battery group 110 tends to be larger than that of the nickel-metal hydride battery group 120.

Therefore, during charging, the CPU of the battery control unit 130 controls the lithium-ion battery group 11 of the shunt circuit.

0 Connection Z Disconnection is repeated at a predetermined duty ratio, and while controlling the amount of charge (Ah) supplied to the lithium-ion battery group 110, the remaining capacity difference between the lithium-ion battery group 110 and the nickel-metal hydride battery group 120 is controlled. Is prevented from occurring.

In the process of step S10 in the flowchart shown in FIG. 2, the battery control unit 130 determines whether or not the battery is in a fully charged state. Specifically, the remaining capacity is calculated from the voltage value at both ends of the battery pack (the potential difference between the terminals 131 and 133 of the battery control unit 130 shown in FIG. 1). In general, a method for calculating the remaining voltage capacity of a battery is known, and a detailed description thereof will be omitted. Abbreviate. Then, when determining that the battery pack is fully charged (YES in step S10), battery control unit 130 proceeds to the process in step S16. If it is determined that the battery pack is not fully charged (NO in step S10), battery control unit 130 proceeds to the processing in step SI2.

[0032] In the process of step S12, charging of the assembled battery is started under the control of the battery control unit 130. The initial value of the duty ratio at which the shunt circuit is connected to the lithium ion battery group 110 and not connected is set to "dl" shown in the mapping data of FIG. Then, battery control unit 130 proceeds to the process of step S14.

[0033] In the process of step S14, battery control unit 130 detects the voltage value and temperature of nickel-metal hydride battery group 120 at a predetermined timing as an index relating to the difference in charging efficiency. As the voltage value V (V) of the nickel-metal hydride battery group 120, a potential difference between the terminals 132 and 133 of the battery control unit 130 is detected. As the temperature T (degrees) of the nickel-metal hydride battery group 120, the potential difference between the terminals 135 and 136 of the battery control unit 130 (the voltage value at both ends of the thermistor TM) is detected, and the impedance value of the thermistor TM and the temperature are measured. Relevance can be calculated by the method described above. Then, battery control unit 130 proceeds to the process of step S15.

[0034] In the process of step S15, the battery control unit 130 determines the mapping data shown in Fig. 3 based on the voltage value V (V) and the temperature T (degrees) of the nickel hydrogen battery group 120 detected in step S14. Connect the power shunt circuit to the lithium-ion battery component 110. Extract the duty ratio for non-connection. Then, battery control unit 130 returns to the process of step S10.

Here, in the table shown in FIG. 3, the voltage value (V (V) —V (V)) of the nickel-metal hydride battery group 120 as a parameter in the horizontal direction, and the temperature (T (Degree)-1 T (degree)) indicates the duty ratio extracted by the battery control unit 130 between each voltage and temperature. For example, the temperature T (degrees) of the nickel-metal hydride battery group 120 is between the temperatures T and T (degrees), and the voltage value V (V) is between the voltage values V-V (V).

2 3 1 2

Is determined, "d5" is extracted as the duty ratio.

Further, in the present embodiment, the duty ratio is set to have a relationship of dl <d2 '· ddlO.

In this way, the duty ratio for connecting the shunt circuit to the lithium-ion battery group 110 is extracted, and the duty ratio is updated at a predetermined timing until the battery is fully charged. Charged.

[0035] On the other hand, when the processing power of step S10 also proceeds to the processing of step S16, the battery control unit 130 ends the charging and turns off the switch SW1 (disconnects the lithium ion battery group 110 and the shunt circuit from each other). And exit.

In an example shown in FIG. 4, in a state where the switch SW1 is turned on and turned off (a state in which the connection / disconnection of the shunt circuit to the lithium-ion battery group 110 is repeated), charging is started at time to. At time tO—tl, the temperature T (degrees) of the nickel-metal hydride battery group 120 is lower than the temperature T (degrees), the voltage value V (V) is lower than the voltage value V (V), and the duty ratio is the initial value. Charging is continued with "dl".

Then, at time tl, the temperature T (degrees) and the voltage value V (V) force temperature T (degrees) of the nickel-metal hydride battery group 120 detected in step S14 are determined in step S15 of the flowchart shown in FIG. The temperature is less than Τ (degrees) and the voltage value V (V) is between the voltage values V--V (V).

1 1 2

Is determined. Therefore, “d2” is extracted from the mapping data shown in FIG. 3 and set as the duty ratio of the shunt circuit.

At time t2, the temperature T (degree) of the nickel-metal hydride battery group 120 and the voltage value V (V) force The temperature T (degree) is between the temperature T and T (degree), and the voltage value V (V) is the voltage. Between values V -V (V)

1 2 2 3

It is determined that there is. Therefore, “d5” is extracted and set from the mapping data shown in FIG. 3 as the duty ratio of the shunt circuit.

At time t3, the temperature T (degrees) and the voltage value V (V) force of the nickel-metal hydride battery group 120 become the temperature T (degrees).

2 Between T (degrees) and when the voltage value V (V) is between the voltage values V-V (V) 3 3 4

It is determined that there is. Therefore, "d9" is extracted from the mapping data shown in Fig. 3 and set as the duty ratio of the shunt circuit.

At time t4, full charge is detected in the process of step S10, and charging is stopped.

As described above, in the present embodiment, as the voltage value of nickel-metal hydride battery group 120 increases, and as the temperature of nickel-metal hydride battery group 120 increases, the shunt circuit is connected to lithium ion battery group 110. The connection time ratio is increased, and the amount of charge electricity (Ah) supplied to the lithium ion battery group 110 is reduced. That is, the temperature of the battery cell As the battery capacity increases, the effect of the difference in charging efficiency between the lithium-ion battery cells and nickel-metal hydride battery cells increases as the remaining capacity of the battery cells increases. The ratio is configured to be large to avoid this.

[0038] The values of the duty ratio mapping data shown in Fig. 3 are arbitrarily set based on the characteristics of the battery cell for detecting the temperature and the voltage value and the characteristics of the battery cell to which the shunt circuit is connected. be able to. For example, in the case of a battery cell whose charging efficiency changes from 80% to 99% y to 85% as the remaining capacity of the battery cell changes from small to medium to large, the duty ratio shown in Fig. 3 Is set to have a relationship of d2 <d3′′dl <dlO <dl.

[0039] In this way, the shunt circuit is provided on the lithium ion battery cell side having relatively high charging efficiency, and the duty ratio is updated and the connection Z disconnection of the shunt circuit to the lithium ion battery group 110 is repeated. Thus, it is possible to control charging of the assembled battery in a well-balanced manner while preventing a remaining capacity difference from the nickel-metal hydride battery cell due to a difference in charging efficiency.

In the first embodiment, the temperature T (degrees) and voltage value V (V) of nickel-metal hydride battery group 120 are detected as indices relating to the difference in charging efficiency, and the charging current of lithium-ion battery group 110 is A case has been described where the duty ratio for shunting is determined, but the type of index relating to the difference in charging efficiency is not limited to the present embodiment. For example, a charge current value of the assembled battery, the remaining capacity of the lithium ion battery group 110, or the like may be used as an index relating to the difference in charge efficiency.

(Second Embodiment)

A battery pack 101 according to a second embodiment in which a shunt circuit is also provided on the nickel-metal hydride battery group 120 side is schematically shown in the block diagram of FIG. In FIG. 5, components substantially equivalent to those of the battery pack 100 according to the first embodiment shown in FIG. 1 are denoted by the same reference numerals.

The difference between the battery pack 101 and the battery pack 100 according to the first embodiment is that the nickel hydrogen battery group 120 is also provided with a shunt circuit (see also FIG. 1). so Has a connection point Q between the positive terminal of the nickel-metal hydride battery cell 121 and the connection point P. The connection point Q is connected to one end of the resistor R2. The other end of the resistor R2 is connected to one end of the switch SW2. The other end of the switch SW2 is connected to the negative side of the nickel hydride battery group 120. The switches SW1 and SW2 can be opened (off) or closed (on) by the battery control unit 130.

When both the switches SW1 and SW2 are open (off), the charging current of the assembled battery flows from the terminal TE1 to the lithium-ion battery group 110 to the nickel-metal hydride battery group 120 to the terminal TE2. The ion battery group 110 and the nickel hydride battery group 120 are charged. When switch SW1 is closed (on) and switch SW2 is open (off), a part of the charging current of lithium ion battery group 110 Terminal TE1 → resistance Rl → switch SW1 → connection point P, Q → The nickel-hydrogen battery group 120 flows from the terminal TE2 to the terminal TE2, whereby the amount of charge electricity (Ah) of the nickel-hydrogen battery group 120 is relatively larger than that of the lithium-ion battery group 110.

When switch SW1 is open (off) and switch SW2 is closed (on), a part of the charging current of nickel hydrogen battery group 120 Terminal TE1 → lithium ion battery group 110 → connection points P, Q → Resistance R2 → Switch SW2 → Terminal TE2, whereby the charge amount (Ah) of the lithium ion battery group 110 is relatively larger than that of the nickel hydrogen battery group 120.

The circuit provided with the resistor R2 and the switch SW2 and connected in parallel to the nickel-metal hydride battery cell when the switch SW2 is turned on also corresponds to the “shunt circuit” of the present invention.

Here, the resistance values of the resistors Rl and R2 of the shunt circuit are selected such that when the switches SW1 and SW2 are turned on, approximately 1Z5 of the charging current flows through each shunt circuit.

When the battery pack 101 is attached to the battery pack 101 configured as described above and the charger 200 is mounted, charging starts. At this time, the CPU of the battery control unit 130 connects the shunt circuit provided in the lithium-ion battery group 110 and the shunt circuit provided in the nickel-metal hydride battery group 120 to each battery group. To control the amount of charge electricity (Ah) supplied to each battery group. As a result, charging can be performed while preventing a remaining capacity difference from occurring in each battery group. FIG. 6 shows a flowchart of a program executed by the CPU of the battery control unit 130 of the battery pack 101 to prevent the remaining capacity difference between the battery groups from occurring.

First, in the process of step S20 shown in FIG. 6, battery control unit 130 determines whether or not the battery pack is fully charged. Then, when determining that the battery pack is fully charged (YES in step S20), battery control unit 130 proceeds to the process in step S34. If it is determined that the battery pack is not fully charged (NO in step S20), battery control unit 130 proceeds to the process in step S22.

In the process of step S22, charging of the assembled battery is started under the control of the battery control unit 130. Note that an initial value is set as the duty ratio at which the shunt circuit is connected to each of the battery groups 110 and 120 and Z is not connected. Then, battery control unit 130 proceeds to the process of step S24.

In the process of step S24, battery control unit 130 detects the voltages of nickel hydrogen battery group 120 and lithium ion battery group 110, and proceeds to step S26.

In the process of step S26, first, the voltage value of the lithium ion battery cell of the lithium ion battery group 110 is calculated. In the battery pack 101 shown in FIG. 5, the lithium ion battery group 110 is composed of three lithium ion battery cells. Therefore, the value obtained by dividing the voltage value of the lithium ion battery group 110 by 3 by 3 is The voltage value. In addition, since the nickel-metal hydride battery group 120 includes one nickel-metal hydride battery cell, the voltage value of the nickel-metal hydride battery group 120 becomes the voltage value of the nickel-metal hydride battery cell. Further, it is known that the voltage value of a nickel-metal hydride battery cell is about 1Z3 of a lithium-ion battery cell (a lithium-ion battery cell has a nominal voltage of 3.6 V, whereas a nickel-metal hydride battery cell has a nominal voltage of 1 V). .2V) _{0 The} battery control unit 130 calculates the voltage value of one lithium-ion battery cell by dividing it by three (hereinafter, referred to as a lithium-ion battery cell comparison value). It is determined whether or not the value obtained by subtracting the cell voltage value is equal to or greater than the set value S1. If the value is equal to or greater than the set value S1 (YES in step S26), the battery control unit 130 proceeds to the process in step S28, and if the value is less than the set value S1 (NO in step S26), the process proceeds to step S3. Proceed to processing of 0.

[0048] In the process of step S28, the duty ratio of each shunt circuit is updated. Here, lithium-ion battery cells are charged at a rate closer to full charge than nickel-metal hydride battery cells. Therefore, the battery control unit 130 increases the duty ratio of the shunt circuit provided in the lithium-ion battery group 110 by a predetermined ratio, and increases the duty ratio of the shunt circuit provided in the nickel-metal hydride battery group 120. Lower by a specified percentage. Then, the battery control unit 130 returns.

On the other hand, when it is determined in step S26 that the value obtained by subtracting the voltage value of the nickel-metal hydride battery cell from the comparison value of the lithium ion battery cell is smaller than the set value S1, the process proceeds to step S30. In the process, it is determined whether or not a value obtained by subtracting the comparison value of the lithium ion battery cell from the voltage value of the nickel hydrogen battery cell is equal to or greater than the set value S2. If this value is equal to or greater than set value S2 (YES in step S30), battery control unit 130 proceeds to the process in step S58. If the value is less than the set value S2 (NO in step S30), the process returns. This is because the ratio of the remaining capacity to the full charge of the lithium ion battery cell and the ratio of the remaining capacity to the full charge of the nickel metal hydride battery cell are determined to be the same (it is determined that the battery is charged in a well-balanced state), and the duty ratio is not updated without updating This shows the case where charging is continued.

[0050] On the other hand, in the process of step S32, the duty ratio of each shunt circuit is updated. Here, since the nickel-metal hydride battery cell is charged at a rate closer to full charge than the lithium-ion battery cell, the battery control unit 130 sets the duty ratio of the shunt circuit provided in the lithium-ion battery group 110 as the duty ratio. Extract something smaller than before. The duty ratio of the shunt circuit provided in the nickel-metal hydride battery group 120 is extracted to be larger than before. Then, the battery control unit 130 returns.

As described above, the battery control unit 130 detects the voltage values of the lithium-ion battery group 110 and the nickel-metal hydride battery group 120 at a predetermined timing, and uses the detected values to control the respective battery groups 110 and 120. The charging is continued while updating the duty ratio of the shunt circuit that can be connected in parallel. Note that the set values SI and S2 are preferably set to be smaller and closer to the full charge so that each battery cell can be controlled more densely as it approaches full charge.

[0052] In this way, battery control section 130 provides a shunt circuit in lithium-ion battery group 110 and nickel-metal hydride battery group 120, and updates the duty ratio of connection Z disconnection of each shunt circuit to each battery group. By doing so, it is possible to prevent a remaining capacity difference due to a difference in charging efficiency from occurring. As a result, even if charging is stopped during charging, The capacity difference is unlikely to occur. In addition, it is possible to prevent a situation in which some battery cells are fully charged first and overcharge occurs. Furthermore, when each battery cell is incorporated into the battery pack 100, for example, even if the nickel-metal hydride battery cell has a considerable remaining capacity, the shunt circuit provided with the nickel-metal hydride battery group 120 is controlled by the battery. By charging while turning on and off at the duty ratio determined by the unit 130, the charge amount difference (remaining capacity difference) in the initial state can be reduced, and charging can be performed with good tolerance.

In each of the above-described embodiments, as an index relating to the difference in charging efficiency, the temperature T (degrees) of nickel-metal hydride battery group 120, the voltage value V (V) of nickel-metal hydride battery group 120, the lithium ion battery group Although the case where 110 is detected has been described, the charging current of the battery pack may be detected and used. To detect the charging current of the battery pack, connect a current detection resistor in series with the battery pack. The voltage drop across the resistance element is configured to be detectable by the battery control unit 130, whereby the battery control unit 130 calculates the charging current. Further, if this configuration is further added to the battery packs 100 and 101 of the embodiment, more reliable charging control can be performed.

In each embodiment, a shunt circuit is provided in the lithium-ion battery group 110 collectively. In this case, the shunt circuit is individually provided for each of the lithium-ion battery cells 111 to 113 described above. It may be provided. In this case, whether to divide the charging current to the shunt circuit provided in each of the lithium ion battery cells 111 to 113 is determined based on the difference in the charging efficiency of each of the lithium ion battery cells 111 to 113. In addition, each battery cell can be charged in a well-balanced manner.

Further, in each of the embodiments, the case where the duty ratio for connecting the shunt circuit to the lithium ion battery group 110 while determining the index regarding the difference in charging efficiency as needed is described. In the battery control unit 130, the predicted value of the change of the difference in the charging efficiency of the battery cells constituting the assembled battery from the start of charging is stored in advance, and based on this, the estimated value from the start of charging is stored. The configuration may be such that the duty ratio for connecting the shunt circuit to the Z-disconnected state is determined according to the passage of time.

Further, in each embodiment, the case where battery control unit 130 determines the duty ratio for connecting a shunt circuit having a predetermined impedance value to lithium-ion battery group 110 will be described. I am clear. For example, a plurality of impedance circuits that can be connected in parallel to the lithium ion battery group 110 are provided, and the impedance circuits are selectively connected in accordance with the amount of charge (Ah) of the divided charging current. May be adopted. In this case, by adjusting the current value (A) shunted from the first battery cell, the amount of charge (Ah) of the shunted charging current can be easily adjusted.

In the embodiment, a circuit (shunt circuit, predetermined steps of processing executed by battery control unit 130, etc.) that shunts the charging current of lithium ion battery group 110 is incorporated in battery pack 100. Force described in the case For example, the shunt circuit may be configured as an adapter-shaped separate body independent of the battery pack 100. In this case, by arranging the adapter-shaped separate body in the battery packs 100 and 101 or the charger 200, the battery cells constituting the assembled battery can be charged in a well-balanced manner.

FIG. 7 shows an example of an electric tool in a state where the battery packs 100 to 101 used as the above embodiments are mounted as a drive power supply.

Brief Description of Drawings

FIG. 1 shows a block diagram of a battery pack 100 according to a first embodiment, together with a block diagram of a charger 200 that charges the battery pack 100.

[FIG. 2] A process for preventing the occurrence of a remaining capacity difference based on the charging efficiency difference between the battery groups 110 and 120 in the battery control unit 130 of the battery pack 100 and charging the battery cells constituting the assembled battery in a well-balanced manner. , As a flowchart.

FIG. 3 shows duty ratio mapping data used when the battery control unit 130 determines a duty ratio for connecting / disconnecting the shunt circuit to the lithium ion battery group 110.

[FIG. 4] FIG. 4 is a timing chart showing a state in which switch SW1 is turned on and off by battery control unit 130, and a shunt circuit provided in lithium ion battery group 110 repeatedly connects and disconnects to lithium ion battery group 110. Show.

FIG. 5 shows a block diagram of a battery pack 101 according to a second embodiment.

[FIG. 6] A battery pack 101 according to the second embodiment is used to prevent the occurrence of a remaining capacity difference based on the charging efficiency difference between the battery groups 110 and 120 to charge the battery cells constituting the assembled battery in a well-balanced manner. The process executed by the battery control unit 130 is shown in a flowchart. FIG. 7 shows an example of a power tool with battery packs 100 to 101 attached. Explanation of reference numerals

100 Battery pack

110 Lithium-ion battery group

111, 112, 113 Lithium-ion battery cells

120 Nickel-metal hydride battery group

121 Nickel metal hydride battery cell

130 Battery control unit

200 charger

SW1, SW2 switch

TM thermistor

Rl, R2 resistance

Claims

The scope of the claims

[1] An assembled battery having a plurality of battery cells,

The charging current for charging the first battery cell is divided based on V based on the difference in charging efficiency between the first battery cell and the second battery cell that constitute the battery pack. Battery pack

[2] The battery pack according to claim 1, wherein

The battery pack according to claim 1, wherein the first battery cell is different in type from the second battery cell.

[3] The battery pack according to claim 1 or 2,

The first battery cells form a battery group in which a plurality of the first battery cells are connected, and charge one or more battery cells in the battery group based on the difference in the charging efficiency. Wherein the charging current is divided.

[4] The battery pack according to any one of claims 1 and 2,

A shunt circuit that shunts a charging current for charging the battery cell can be connected in parallel to the first battery cell, and the amount of charging current shunted to the shunt circuit is based on the difference in charging efficiency. Assembled battery determined.

[5] The battery pack according to claim 4, wherein

Based on the difference in the charging efficiency, a ratio of a time in which the shunt circuit is connected to the first battery cell and a time in which the shunt circuit is not connected is determined, and the connection state and the connection time are determined based on the determined ratio. A battery pack that repeats a disconnected state.

[6] A battery pack comprising the battery pack according to any one of claims 1 to 5,

A detecting unit that detects an index related to the difference in charging efficiency, and a control unit that determines a timing of shunting a charging current for charging the first battery cell, and an index force related to the difference in charging efficiency. A battery pack characterized in that:

[7] The battery pack according to claim 6, wherein

The battery pack, wherein the index regarding the difference in charging efficiency detected by the detection unit is at least one of a remaining capacity index, a temperature index, and a charging current.

[8] The battery pack according to claim 6 or 7, The control unit is configured to determine, at a predetermined detection timing, a time required to connect the shunt circuit included in the Ito battery to the first battery cell based on an index regarding a difference in charging efficiency detected by the detection unit. A battery pack that includes a ratio update unit that determines a ratio of time to be in a non-connection state and, when the determined ratio is different from a ratio determined at a previous detection timing, updates the ratio.

[9] The battery pack according to any one of claims 6 to 8, wherein:

A battery knock, wherein a nominal voltage of the battery pack based on a nominal voltage of each battery cell constituting the battery pack is a predetermined voltage value corresponding to a device operated by the battery pack.

[10] An electric tool, wherein the battery pack according to any one of claims 11 to 5 or the battery pack according to any one of claims 6 to 9 is used as a driving power source.