JP4667276B2 - A battery pack in which multiple secondary batteries are connected in series or in parallel - Google Patents

Description

  The present invention relates to a pack battery in which a plurality of secondary batteries are connected in series and in parallel, and can accurately determine an abnormality of any of the secondary batteries, and in particular, a power source for a laptop microcomputer It relates to a battery pack that is optimal for use.

The battery pack can increase the output voltage by connecting a plurality of secondary batteries in series. Further, the discharge capacity can be increased by connecting a plurality of secondary batteries in parallel. Therefore, it is possible to adjust the output voltage while increasing the discharge capacity by connecting a plurality of secondary batteries in parallel and further connecting them in series. In a battery pack in which a plurality of secondary batteries are connected in series, it is important to charge and discharge the batteries evenly in a balanced manner, that is, the cell balance of the batteries. This is because if any battery deteriorates and cell balance is lost, the deteriorated battery is overcharged or overdischarged and cannot be used safely. In order to prevent this problem, a battery pack for detecting the cell balance of the battery has been developed. (See Patent Document 1)
JP 2002-199510 A

  The battery pack described in Patent Document 1 detects the voltage of each battery connected in series. When the detected battery voltage difference becomes larger than the set voltage, the battery with the large voltage difference is determined as an abnormal battery. The detection circuit for detecting the voltage of each battery is provided with a multiplexer on the input side in order to switch and detect the voltages of the plurality of batteries in order. The multiplexer sequentially switches the battery that detects the voltage. The multiplexer detects the voltage by switching the battery to be detected at a predetermined sampling period. For example, a detection circuit having a sampling period of 50 msec detects battery voltages in order at intervals of 50 msec. This circuit cannot detect all battery voltages simultaneously. The timing for detecting the adjacent battery voltage is shifted by 50 msec. The battery pack that detects the voltage of the battery with this circuit configuration and determines the abnormal battery from the voltage of the battery has a drawback that the abnormal battery cannot be accurately detected. This is because if the timing for detecting the voltage of the battery shifts, the current flowing through the battery may also change. The battery voltage varies with the current. The voltage of the battery changes due to a change in electrical characteristics, and the voltage fluctuates even if the flowing current changes. Therefore, if the current fluctuates when detecting the voltage of the battery, it causes a detection error.

  The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to provide a battery pack that can reliably determine an abnormal battery while connecting a plurality of secondary batteries in series and in parallel.

The battery pack of the present invention has the following configuration in order to achieve the aforementioned object.
The battery pack includes a battery group 3 formed by connecting in parallel a parallel unit 2 in which a plurality of secondary batteries 1 are connected in parallel, a charging / discharging current flowing through the battery group 3, and a voltage of each parallel unit 2. A current / voltage detection unit 4 that is switched in a time division manner by a multiplexer 6 and a control / calculation unit 5 that determines an abnormality of the parallel unit 2 from a voltage change of each parallel unit 2 detected by the current / voltage detection unit 4. With. The control / calculation unit 5 compares the amount of change in current detected by the current / voltage detection unit 4 with a set value, and in a state where the amount of change in current when the current flows is equal to or less than the set value, the parallel unit 2 The abnormality of the parallel unit 2 is determined from the voltage change.

  In the battery pack of the present invention, a plurality of secondary batteries 1 are connected in parallel through connection tabs 7 to form parallel units 2, and connection tabs 7 connected to each secondary battery 1 by control / calculation unit 5. Connection failure can be detected.

The battery pack of the present invention has a feature that an abnormal battery can be reliably determined while connecting a plurality of secondary batteries in series and in parallel. The battery pack of the present invention detects the current flowing through the battery and the voltage of each parallel unit in order at a predetermined sampling period, and determines the abnormality of the parallel unit by the control / arithmetic unit from the detected current and voltage. Furthermore, the control / calculation unit compares the detected current change amount with the set value, and in a state where the current change amount when the current flows is equal to or less than the set value, This is because the abnormality of the unit is determined. Since the battery pack according to the present invention determines an abnormality from the voltage change of the parallel unit only when the change of the current flowing through the battery is small, the influence of the voltage change of the parallel unit due to the current change is reduced or eliminated. Thus, the abnormality of the parallel unit is accurately determined.

Also, packs battery of the present invention, there is precisely detectable features of each of the secondary batteries of the connection tab being parallel unit connected connection failure.

  Embodiments of the present invention will be described below with reference to the drawings. However, the example shown below illustrates the battery pack for embodying the technical idea of the present invention, and the present invention does not specify the battery pack as follows.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The battery pack 10 shown in FIG. 1 is set so that it can be attached to and detached from a portable device 20, which is an electronic device equipped with a power source for charging it, for example, a portable PC. The portable PC is a portable personal computer such as a notebook type. The portable device 20 is connected to a power adapter (not shown) that converts AC commercial power from the outlet into DC power. The power adapter supplies DC power to the portable device 20. The portable device 20 includes a control / power supply unit 21 with a built-in microcomputer that controls supplied power. The control / power supply unit 21 outputs power to the battery pack 10 and supplies power to the load 22 of the portable device 20. When power is not supplied from the power adapter, power is supplied from the battery pack 10 to the portable device 20.

  A battery pack 10 shown in FIG. 1 has a plurality of secondary batteries 1 connected in parallel to form a parallel unit 2. Further, a plurality of parallel units 2 are connected in series to form a battery group 3. Further, the battery pack includes the parallel unit 2 based on the charge / discharge current flowing in the battery group 3, the current / voltage detection unit 4 that detects the voltage of each parallel unit 2, and the current and voltage detected by the current / voltage detection unit 4. And a control / arithmetic unit 5 for determining the abnormality.

  The secondary battery 1 of the parallel unit 2 is a lithium ion secondary battery. However, the secondary battery can be a rechargeable battery such as a nickel metal hydride battery or a nickel cadmium battery. In the illustrated battery pack, three secondary batteries 1 are connected in parallel as parallel units 2. However, in the battery pack of the present invention, two secondary batteries can be connected in parallel to the parallel unit, or four or more secondary batteries can be connected in parallel. The parallel units 2 are connected in parallel via connection tabs 7 that are metal plates or lead wires.

  The current / voltage detection unit 4 includes a current detection unit 8 that detects the current of the battery group 3, a current signal that is input, a multiplexer 6 that switches and outputs a voltage signal at a predetermined sampling period, and an output from the multiplexer 6. An A / D converter 9 that converts the analog signal to be converted into a digital signal and outputs the digital signal to the control / arithmetic unit 5.

  Although not shown, the current detection unit 8 includes a current detection resistor connected in series with the battery group 3 and an amplifier that amplifies the voltage across the current detection resistor. The output voltage of the amplifier is proportional to the current flowing through the battery group 3. Therefore, the battery current can be detected from the output voltage of the amplifier. In addition, since the charging current and discharging current of the battery flow in opposite directions, the polarity of the output voltage of the amplifier, that is, positive / negative is reversed between the charging current and the discharging current. If the amplifier uses the discharge current as a positive output voltage, the charge current becomes a negative output voltage. Therefore, the charge current and the discharge current can be identified by the sign of the signal output from the amplifier.

  Furthermore, the battery pack of the figure includes a temperature detection unit 11 that detects the temperature of the battery. The temperature detection unit 11 includes a temperature sensor 12 such as a thermistor disposed in close contact with the battery. The temperature detection unit 11 also includes a temperature-voltage conversion circuit that converts a change in electrical resistance of the temperature sensor 12 into a change in voltage. The battery temperature is detected from the signal output from the temperature-voltage conversion circuit.

  The multiplexer 6 switches the current signal output from the current detection unit 8 and the voltage signal of each parallel unit 2 in order, and outputs to the A / D converter 9. The battery pack 10 shown in the figure has three sets of parallel units 2 connected in series. Therefore, the multiplexer 6 switches the current signal of the current detection unit 8 and the voltage signals of the three sets of parallel units 2 in order at a predetermined sampling period, and outputs them to the A / D converter 9. Since the multiplexer 6 shown in the figure switches between a current signal of 1 channel and a voltage signal of 3 channels, a multiplexer capable of sequentially switching inputs of 4 channels or more is used. However, the pack battery that converts the temperature signal output from the temperature detection unit into a digital signal by the A / D converter uses a 5-channel multiplexer.

  The multiplexer 6 switches the input of a plurality of channels at a sampling period of 50 msec and outputs it to the A / D converter 9. However, the sampling period of the multiplexer 6 can be set to 10 msec to 500 msec. Changes in battery current, temperature, and voltage can be quickly detected by shortening the sampling period. Conversely, the sampling cycle can be lengthened to reduce the component cost. Therefore, the sampling period of the multiplexer 6 is set to the above-mentioned range in consideration of the component cost and the state where the current and voltage change.

  The A / D converter 9 converts the analog signal input from the multiplexer 6 into a digital signal and outputs it. The A / D converter 9 converts the input analog signal into a digital signal in synchronization with the timing at which the multiplexer 6 switches the input. Therefore, the A / D converter 9 converts the input analog signal into a digital signal every time the multiplexer 6 switches the input, and outputs the digital signal. That is, after the multiplexer 6 switches the input, the A / D converter 9 converts the input signal into a digital signal, and then the multiplexer 6 repeats the operation of switching the input to convert the input signal into a digital signal.

  The output of the A / D converter 9 is input to the control / calculation unit 5. The digital signal input from the A / D converter 9 to the control / arithmetic unit 5 is a current signal indicating a charge / discharge current value flowing through the battery, and a voltage signal which is a positive voltage of the parallel unit 2. In addition to this signal, the battery pack that detects the temperature signal also outputs a temperature signal indicating the temperature of the battery. These signals are input to the control / calculation unit 5 at the sampling period of the multiplexer 6 and the A / D converter 9, that is, at a period of 50 msec. The control / arithmetic unit 5 calculates an input signal and determines an abnormality of each parallel unit 2.

  The abnormality of the parallel unit 2 is determined from the voltage change of the parallel unit 2 in consideration of the flowing current. The abnormality of the parallel unit 2 is an internal short circuit of any of the secondary batteries 1 or a connection failure of the connection tab 7 that connects the plurality of secondary batteries 1 in parallel. The control / calculation unit 5 determines the internal short circuit of the secondary battery 1 and the connection failure of the connection tab 7 from the voltage change of each parallel unit 2. The control / calculation unit 5 compares the amount of change in current detected by the current / voltage detection unit 4 with a set value, and in a state where the amount of change in current is equal to or less than the set value, 2 is judged abnormal. The control / calculation unit 5 does not determine the abnormality of the parallel unit 2 when the battery current change is larger than the set value. This is because when the current change is large, the voltage of the parallel unit 2 changes due to the current. The set value for comparing the amount of change in the current for determining the abnormality of the parallel unit 2 is, for example, 0.5C or less, preferably 0.3C or less, in terms of the current that flows through each secondary battery 1 in a diverted state. More preferably, it is 0.1 C or less. In the illustrated battery pack, three secondary batteries 1 are connected in parallel to form a parallel unit 2, so that the total current flowing in the parallel unit 2 is three times the current flowing in each secondary battery 1. Therefore, the current flowing through each secondary battery 1 is 1/3 of the charge / discharge current of the battery pack. The abnormality of the parallel unit 2 is determined only when the current flowing through each secondary battery 1 is smaller than the above set value.

The control / arithmetic unit 5 determines the abnormality of the parallel unit 2 in the flowchart of FIG.
[Step of S = 1]
In this step, n = 1. In the illustrated battery pack, three secondary batteries 1 are connected in series. In other words, since three sets of parallel units 2 are connected in series, n is 1, 2, and 3.
[Step of S = 2]
In this step, the current In is detected. In is the current of the battery pack at this timing.
[Step S = 3]
In this step, the voltage Vn is detected. Vn is the voltage of each parallel unit 2 connected in series. That is, V1 is the voltage of the first parallel unit 2, V2 is the voltage of the second parallel unit 2, and V3 is the voltage of the third parallel unit 2.
[Step S = 4]
In this step, n = n + 1.
[Step S = 5]
In this step, it is determined whether n is larger than the number of parallel units 2 (three battery packs in the figure). If smaller than the number of parallel units 2, the steps of S = 2 to 4 are looped, Detection is performed in a predetermined sampling cycle in the order of I1, V1, I2, V2, I3, and V3.
[Step S = 6]
In this step, the maximum current Imax and the minimum current Imin of I1 to I3 are obtained.
[Steps of S = 7, 8]
In this step, a difference between the maximum current Imax and the minimum current Imin is detected, and it is determined whether the current difference is smaller than a set value. When the current difference is smaller than the set value, the abnormality of the parallel unit 2 is determined from the detected V1 to V3. If the current difference is larger than the set value, the detected V1 to V3 are not used for abnormality determination of the parallel unit 2. Thereafter, the process jumps to the step of S = 1, and the determination of abnormality of the parallel unit 2 is repeated again.

  When determining a connection failure of the connection tab 7 connecting the secondary batteries 1 in parallel and an internal short circuit of the secondary battery 1 of the parallel unit 2 as an abnormality of the parallel unit 2, the determination condition is determined by the abnormality of both. Different.

  The disconnection of the connection tab will be described below. In the battery group 3, the positive electrode terminal and the negative electrode terminal of the battery 1 are electrically connected by a metal connection tab, and are connected in three-three in parallel. For example, in the case of disconnection of the connection tab, when a total current of 1.5 A flows (0.5 A flows in each cell), assuming that 3 parallels become 2 parallels due to the disconnection of the connection tabs, As an example of the change, the current increases from 0.5 A to 0.75 A, so that the two parallel currents increase and the voltage change also increases.

  In order to determine the connection failure of the connection tab 7, that is, the disconnection of the connection tab 7, in a state where the change amount of the current flowing through the battery pack is smaller than the set value, the voltage change after 3 minutes is 50 mV or more, A parallel unit whose voltage changes more than twice that of the other parallel units is determined as a connection failure of the connection tab. Also, the parallel unit in which the voltage change is 1.5 times the average value of the voltage change of all the parallel units 2 is also determined as a connection tab connection failure. A parallel unit having a voltage change of twice or more is also determined as a connection failure of the connection tab.

  Furthermore, the determination of the internal short circuit of the secondary battery 1 of the parallel unit 2 is 30 minutes in a state where the change in the current flowing through the battery pack 10 is not more than the set value and the current magnitude is smaller than the set value. A parallel unit in which the voltage change of the parallel unit after the lapse is 15 mV or more and the voltage change is twice or more that of the other parallel units is determined as one of the secondary batteries being an internal short circuit. In addition, the parallel unit in which the voltage change is 1.5 times the average value of the voltage change of all the parallel units is determined as any secondary battery short-circuited, and the parallel unit with the least voltage change In contrast, a parallel unit having a voltage change more than twice as large as one of the secondary batteries determines that an internal short circuit has occurred.

  Furthermore, the internal short circuit of the secondary battery 1 is a state in which charging / discharging of the battery pack 10 is stopped, that is, a state in which the mobile device 20 is not used or a state in which the mobile device 20 is used. In a state in which power is not supplied to the device 20 and power is supplied from the commercial power source to the portable device 20, the voltage change of the parallel unit after 30 minutes is 15 mV or more, and the voltage is more than twice that of the other parallel units. The changing parallel unit determines that any of the secondary batteries is an internal short circuit. In addition, the parallel unit in which the voltage change is 1.5 times the average value of the voltage change of all the parallel units is determined as any secondary battery short-circuited, and the parallel unit with the least voltage change In contrast, a parallel unit having a voltage change more than twice as large as one of the secondary batteries determines that an internal short circuit has occurred.

  Furthermore, the control / calculation unit 5 calculates the remaining capacity by integrating the charge / discharge current of the battery, detects the full charge of the battery from the charge current and voltage, and detects abnormal current, abnormal temperature, abnormal voltage, etc. Then, charge / discharge is controlled. The control element 13 composed of a switching transistor or the like is on / off controlled by the control / calculation unit 5 and is switched off to cut off the current when an abnormal current, abnormal temperature, or abnormal voltage is detected.

  The control / calculation unit 5 integrates the value obtained by multiplying the charging / discharging current converted by the A / D converter 9 by a sampling period (for example, 50 msec), and subtracts the integrated amount from the full charge at the time of discharging, or During charging, the integrated amount is added to the remaining capacity at the start of charging. The battery remaining capacity is calculated by such calculation.

  The control / calculation unit 5 detects a full charge by detecting a voltage. In the case of a nickel metal hydride battery or a nickel cadmium battery, full charge can be detected by detecting a peak voltage or by detecting −ΔV (= voltage drop) from the peak voltage of the voltage. This battery pack can detect the full charge of the battery from all the voltages connected in series. However, it is also possible to detect the full charge of each parallel unit by detecting the voltage of the parallel unit.

  A battery pack that uses a lithium-ion battery as a secondary battery uses a constant current (MAX current of about 0.5 to 1C) / constant voltage (MAX 4.2V / parallel unit) charging that regulates current and voltage, and is a parallel unit. When the voltage 2 is equal to or higher than the predetermined value and the charging current is equal to or lower than the predetermined value, it is determined that the battery is fully charged. When the full charge of the battery is detected, the control / calculation unit 5 switches off the charging control element 13 to stop the charging, and outputs information indicating that the remaining capacity is 100% from the communication processing unit 14. Fully charged information is transmitted to the mobile device 20 via the communication line 15.

  In the battery pack 10 shown in the figure, a charging FET 13A, which is a P-channel FET, and a discharging FET 13B are connected as a control element 13 in series with the battery. A P-channel FET is switched off by inputting a “High” voltage. In this pack battery, when the secondary battery 1 is a lithium ion secondary battery, the voltage of any of the parallel units 2 is an overcharge voltage of the lithium ion secondary battery, for example, 4.2 V or more. The charging FET 17A is controlled to be off. Therefore, in this state, the control / calculation unit 5 inputs the “High” voltage of the off signal to the gate of the charging FET 13A. The charging FET 13A in the off state can flow a discharge current by a parasitic diode. Therefore, the battery can be discharged while the charging FET 13A is off. In this state, when the battery is discharged by the portable device 20 and the voltage drops, the charging FET 13A is switched on.

  Further, the battery pack 10 controls the discharge FET element 13B to be turned off when the battery voltage of any one of the parallel units 2 is, for example, 2.7 V or less, which is the overdischarge voltage of the lithium ion secondary battery. Therefore, in this state, the control / calculation unit 5 inputs the “High” voltage, which is an off signal, to the gate of the discharging FET 13B. The discharging FET 13B in the OFF state can flow a charging current by a parasitic diode. Therefore, the battery can be charged with the discharging FET 13B turned off. In this state, when the battery is charged from the portable device 20 and the voltage rises, the discharging FET 13B is switched on.

It is a schematic block diagram of the battery pack concerning one Example of this invention. It is a flowchart in which the control and calculation part of the battery pack concerning one Example of this invention determines the abnormality of a parallel unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Parallel unit 3 ... Battery group 4 ... Current and voltage detection part 5 ... Control and calculation part 6 ... Multiplexer 7 ... Connection tab 8 ... Current detection part 9 ... A / D converter 10 ... Pack battery 11 ... Temperature detector 12 ... Temperature sensor 13 ... Control element 13A ... FET for charging
13B ... Discharge FET
DESCRIPTION OF SYMBOLS 14 ... Communication processing part 15 ... Communication line 20 ... Portable apparatus 21 ... Control and power supply part 22 ... Load

Claims (1)

A battery group (3) in which a parallel unit (2) formed by connecting a plurality of secondary batteries (1) in parallel is connected in series, a charge / discharge current flowing through the battery group (3), and each parallel The voltage of each unit (2) detected by the current / voltage detection unit (4) and the current / voltage detection unit (4) detected by time division by switching the voltage of the unit (2) with the multiplexer (6) A control / calculation unit (5) that determines the abnormality of the parallel unit (2) from the change.The control / calculation unit (5) sets the amount of change in the current detected by the current / voltage detection unit (4) to the set value. compared to, in a state where the amount of change in current becomes less than the set value when the current flows, to determine the abnormality of the parallel unit from the voltage change of the parallel unit (2) (2),
Each parallel unit (2) connects a plurality of secondary batteries (1) in parallel via a connection tab (7), and a control / calculation unit (5) is connected to each secondary battery (1). A battery pack in which a plurality of secondary batteries are connected in series and in parallel to detect a connection failure in the connected connection tab (7) .

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