JPH11234910A - Method and apparatus for diagnosing fault in battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the safety of a battery pack even if a field-effect transistor becomes faulty due to process failure or thermal breakdown, by forcedly turning off the field-effect transistor during charging, and self-diagnosing whether the charging current falls below a specified value. SOLUTION: During charging of a secondary battery 2, a signal is outputted from a self-diagnosing means 12 to forcedly turn off a field-effect transistor(FET) 16 for charging. If the FET 16 for charging is faulty, the charging current does not fall below a reference value. When this state lasts for a specified period of time, however, the self-diagnosing means 12 judges that the FET 16 for charging is faulty, and causes electronic equipment to abort charging through a communicating means 14. If an overcurrent is detected by a current detecting means 11 during discharging of the secondary battery 2, it is judged that FET's 16, 17 for charging and discharging are faulty, and charging is aborted as well. As a result, various troubles which may occur during charging of a faulty battery pack can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack, and more particularly, to a method and an apparatus for diagnosing a failure of a battery pack.

[0002]

2. Description of the Related Art In recent years, the market for secondary batteries has been rapidly expanding. Among them, non-aqueous secondary batteries, for example, lithium ion secondary batteries, are used in portable electronic devices such as notebook computers and mobile phones. As widely used.

[0003] Lithium ion secondary batteries which are used as a single battery or as a battery pack and used in a battery pack maintain safety and reliability because overcharge and overdischarge cause a decrease in safety and a deterioration in quality. Therefore, a control circuit for preventing overcharge and overdischarge is generally mounted on a BMU (battery management unit) to manage battery voltage and the like.

A conventional BMU has an overcharge protection function, which detects a battery voltage and a battery current, and turns off a MOSFET provided in a charging path when an overvoltage or an overcurrent is detected. Is used to forcibly stop charging. When it is detected that the battery voltage and the battery current have returned to normal values, the MOSFET is turned off and charging is started again.

[0005]

However, in the above-mentioned conventional configuration, even when the cause of the overvoltage or overcurrent is not removed, if the battery voltage is reduced, the FET is not operated.
Is turned on and charging is repeated. Also MOSFET
Is a component that is liable to cause junction destruction due to temporary heat generation. If overcharge protection does not work because the failed MOSFET does not work, charging has to be continued without stopping. Was.

Further, when the BMU is shut down, since there is no means for recording a history of the shutdown, it is not known whether or not the battery pack is abnormal. Even if the battery pack is abnormal and is not suitable for charging, it is recharged. Was started.

The present invention solves such a conventional problem. In addition to the conventional overcharge protection, the present invention performs a failure diagnosis of an FET, a diagnosis of an overcharge control circuit, a diagnosis of a shutdown circuit, and a failure information. It is an object of the present invention to provide a BMU having a function of retaining the data and performing no recharging.

[0008]

In order to achieve the above object, the invention of a battery pack failure diagnosis method and apparatus according to claims 1 and 4 forcibly turns off the FET during charging and regulates the charging current. By diagnosing whether it is less than the value, F
It is provided with self-diagnosis means for diagnosing ET failure.

With this configuration, the safety of the battery pack can be maintained even if the MOSFET has failed due to a process failure or thermal destruction.

According to a second aspect of the present invention, there is provided a self-diagnosis means for diagnosing an overcharge control circuit by diagnosing whether or not a charging current stops when an overcharge is detected. It is provided.

With this configuration, when there is an abnormality in the overcharge control circuit, it can be detected, so that the safety of the battery pack can be maintained.

According to a third aspect of the present invention, there is provided a battery pack failure diagnosing method and apparatus which includes a self-diagnosis means for diagnosing a shutdown function by diagnosing whether a battery voltage is higher than a BMU shutdown voltage. It is.

According to this configuration, when there is an abnormality in the shutdown function, it can be detected, so that the safety of the battery pack can be maintained.

According to a seventh aspect of the present invention, there is provided a battery pack failure diagnosis apparatus, wherein the self-diagnosis means includes information holding means for holding failure information.

According to this configuration, the battery pack which has detected the abnormality by holding the failure information is not recharged, so that the safety of the battery pack can be maintained.

The invention of the battery pack failure diagnosis apparatus according to claim 8 is the FET failure diagnosis function according to claim 1 or 4, the overcharge control circuit diagnosis function according to claim 2 or 5, and the invention according to claim 3 or 4. 6. A self-diagnosis means having the shutdown diagnosis function described in 6.

With this configuration, it is possible to provide an inexpensive and highly reliable battery pack failure diagnosis apparatus.

According to a ninth aspect of the present invention, there is provided a battery pack failure diagnosing device, wherein the FET failure diagnosing function, the overcharge control circuit diagnosing function, and the shutdown diagnosing function are housed in the same IC package. Configuration.

By incorporating the IC into a single package, it is possible to reduce the scale and cost of the battery pack failure diagnosis device. Needless to say, this can also reduce the scale and cost of the battery pack itself.

According to a tenth aspect of the invention, there is provided a battery pack including the battery pack failure diagnosis apparatus according to any one of the fourth to ninth aspects.

According to this configuration, a highly safe battery pack can be provided. According to an eleventh aspect of the invention, there is provided an electronic device including the battery pack according to the tenth aspect.

Since abnormalities in the battery pack can lead to secondary disasters such as damage to the electronic equipment in which the battery pack is incorporated, taking thorough safety measures on the battery pack reduces the safety and reliability of the electronic equipment. It will also increase.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a battery pack showing a configuration example according to an embodiment of the present invention. The battery pack shown in FIG. 1 includes a BMU 1 (battery management unit, battery management device) including the battery pack failure diagnosis device of the present invention and other control devices, and a secondary battery 2 configured as a single or assembled battery. It comprises a positive terminal 3 and a negative terminal 4 connected to the electronic device, and an information terminal 5 for outputting information. In the present embodiment, a lithium ion secondary battery will be described as an example of the secondary battery 2, but the battery system of the secondary battery 2 is not limited, and a nickel hydride storage battery, a lithium polymer secondary battery, or the like may be used. The present invention can be appropriately modified and applied to the case of using the battery of the above type.

The battery pack failure diagnosis apparatus of the present invention incorporated in the BMU 1 includes a current detection resistor 10, a current detection unit 11, a self-diagnosis unit 12, a voltage detection unit 13, a communication unit 14, an FET control unit 15, And a discharging FET 17.

In the present embodiment, the current detection resistor 10, the charging FET 16, and the discharging FET 17 are arranged on the negative electrode side, but they have substantially the same functions even if they are arranged on the positive electrode side.

The operation of each component will be described below. In the present embodiment, the current detection resistor 10 disposed on the negative electrode side detects a charge / discharge current flowing through the secondary battery 2.
The current detection means 11 always receives a signal from the current detection resistor 10 and outputs a signal of a charge / discharge current flowing through the secondary battery 2 to the self-diagnosis means 12 as appropriate. The signal output from the current detection unit 11 to the self-diagnosis unit 12 may be performed at all times, or may be performed, for example, every few seconds.

The voltage detecting means 13 detects the voltage of the secondary battery 2 and outputs an appropriate signal to the self-diagnosing means 12. At this time, the voltage signal output to the self-diagnosis unit 12 is
When the secondary battery 2 is a single battery, there is no problem because the voltage of the single battery is only output as a voltage signal.
If the secondary battery 2 is a battery pack, the voltage detecting means 13
May detect the voltage of each single cell and output the voltage signal of each single cell as it is, or may output the sum of some or all of the single cells. Alternatively, the sum of the battery voltages of the assembled batteries may be simply detected, and the voltage signal may be output.
When detection is performed for each unit cell, it is preferable because the detection of variation and its elimination can be performed, but it is needless to say that a preferable method may be selected in consideration of cost and the like.

The self-diagnosis means 12 receives signal inputs from the current detection means 11 and the voltage detection means 13 and
Diagnosis is made by comparing the current value with a reference value.

In this embodiment, the BMU 1 is integrated into an IC. However, when the integrated circuit is not used, the output of the comparison result by the comparator is simply performed by the communication means 14 and The output to the FET control unit 15 may be adopted.

If no overvoltage or overcurrent is detected as a result of the diagnosis by the self-diagnosis unit 12, a signal indicating that the battery pack is normal is output to the communication unit 14, and the FE is output.
A signal for keeping the charge and discharge FETs 16 and 17 on is output to the T control unit 15.

If the self-diagnosis unit 12 detects an overvoltage, the communication unit 14 outputs a signal indicating that the battery pack is overvoltage. If the overcharge is detected, the self-diagnosis unit 12 outputs a signal indicating that the battery pack is overvoltage. FET 16 off,
If discharging, a signal for turning off the discharging FET 17 is output.

If an overcurrent is detected as a result of the diagnosis by the self-diagnosis means 12, a signal indicating that the battery pack is overcurrent is output to the communication means 14, and an FET is output.
The controller 15 outputs a signal to turn off the charge / discharge FETs 16 and 17.

In the BMU 1 that performs the above-described safety control, the charge and discharge are all turned off by the FET. When the FET is out of order, the battery pack and the electronic This may cause damage to the equipment.

In order to prevent this, a failure diagnosis of the FET is performed as shown in the flowchart of FIG. First, a signal is output from the self-diagnosis unit during charging of the secondary battery 2 to forcibly turn off the charging FET 16. As a result, the charging current hardly flows through the charging path during normal operation.
For example, 100 mA can be used as the reference value. When the charging FET 16 is abnormal, the charging current detected by the current detecting means 11 does not become less than 100 mA. If, for example, 4 seconds have elapsed in this state, the charging F
The ET 16 diagnoses that the battery pack is abnormal, and the self-diagnosis unit 12 outputs a signal indicating that the battery pack is abnormal, a signal for stopping charging, or both signals to the electronic device through the communication unit 14.

The overcharge control circuit is diagnosed when overcharge is detected as shown in the flowchart of FIG. First, when an overcurrent is detected by the current detecting means 11 during charging / discharging of the secondary battery 2, the self-diagnosing means 12 outputs a signal for turning off the charging / discharging FETs 16 and 17 through the FET control unit 15. In this state, if the charging current is still detected for more than 4 seconds, for example, the overcharge control circuit or the charging / discharging FE
Diagnosis that T16, 17 is abnormal and self-diagnosis means 1
Reference numeral 2 indicates to the electronic device via the communication means 14 a signal indicating that the battery pack is abnormal, a signal for stopping charging, or both signals.

Further, a diagnosis of the shutdown function as shown in the flowchart of FIG. 4 is performed. First, the shutdown function will be described. In recent battery packs, a microcomputer (BMU) is built in the battery pack itself, and information such as voltage, capacity, and temperature is internally notified to connected electronic devices to reduce the load on the electronic devices. Some microcomputers with built-in microcomputers cut their own electric circuits in order to protect the secondary battery 2 from overdischarge when the voltage drops considerably. This is called a shutdown. In this case, since the information stored in the microcomputer is lost once, it is inconvenient if there is useful information stored up to now, and in general, control is performed so as not to shut down except in an emergency.

Normally, the voltage of the secondary battery 2 is
3, when the total voltage is, for example, 5 V or less, the battery pack is shut down on the assumption that the voltage is abnormally low. Therefore, when the shutdown is not performed even when the total voltage becomes 5 V or less,
Upon diagnosing that the shutdown function is abnormal, the self-diagnosis unit 12 outputs a signal indicating that the battery pack is abnormal, a signal for stopping charging, or both signals to the electronic device through the communication unit 14. Thereby, the danger of the secondary battery 2 being over-discharged can be avoided more reliably.

The EEPRO provided in the BMU 1
M18 is a memory as an information holding unit that holds a history of abnormalities and holds that charging is not possible. As a result, in the case of a battery with an abnormality, the history of the abnormality remains,
Before the battery pack is connected to the electronic device and charging is started, the self-diagnosis unit 12 reads information from the EEPROM 18 so that charging is not started in the case of a battery pack having a history of abnormalities. Thus, various inconveniences caused by charging the abnormal battery pack can be avoided in advance.

Note that the failure diagnosis function of the FET, the overcharge control circuit and the overcharge control circuit diagnosis function, the shutdown function and the shutdown function diagnosis function are included in the self-diagnosis means 12 controlled by microcomputer software, and are implemented as ICs. 1
It is stored in the package.

[0040]

As is apparent from the above embodiment, according to the present invention, the failure diagnosis of the FET, the diagnosis of the overcharge control circuit, and the diagnosis of the shutdown circuit are performed, so that the double protection of the battery pack is achieved. Since it can play a role and can quickly detect an abnormality at a low battery voltage stage, inconveniences such as overcharging can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a battery pack failure diagnosis device of the present invention.

FIG. 2 is a flowchart showing a method for diagnosing a failure of an FET according to the present invention.

FIG. 3 is a flowchart illustrating a method for diagnosing an overcharge control circuit according to the present invention.

FIG. 4 is a flowchart illustrating a method for diagnosing a shutdown function according to the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 BMU 2 Secondary battery 3 Positive electrode terminal 4 Negative terminal 5 Information terminal 10 Current detection resistor 11 Current detection means 12 Self-diagnosis means 13 Voltage detection means 14 Communication means 15 FET control unit 16 Charge FET 17 Discharge FET 18 EEPROM

Claims (11)

[Claims] 1. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing through a charging path, and a self-diagnosis performed by using outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
A FET control unit for controlling T, and communication means for receiving an output of the self-diagnosis means as input and outputting information to an externally connected electronic device, forcibly turning off the FET during charging, By diagnosing whether the charging current is less than a prescribed value,
A battery pack failure diagnosis method comprising self-diagnosis means for performing failure diagnosis of ET. 2. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing through a charging path, and a self-diagnosis performed by using outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
An FET control unit for controlling T; and a communication unit that receives an output of the self-diagnosis unit as input and outputs information to an externally connected electronic device, and determines whether the charging current stops when overcharge is detected. A battery pack failure diagnosis method, comprising: self-diagnosis means for diagnosing an overcharge control circuit by performing a diagnosis. 3. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing in a charging path, and a self-diagnosis performed by using outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
A FET control unit for controlling T; and a communication unit that receives an output of the self-diagnosis unit as input and outputs information to an externally connected electronic device, and diagnoses whether a battery voltage is higher than a BMU shutdown voltage. A self-diagnosis means for diagnosing a shutdown function by performing a self-diagnosis. 4. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing in a charging path, and a self-diagnosis performed by using outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
A FET control unit for controlling T, and communication means for receiving an output of the self-diagnosis means as input and outputting information to an externally connected electronic device, forcibly turning off the FET during charging, A battery pack failure diagnosis device, comprising: self-diagnosis means for performing a failure diagnosis of the FET by diagnosing whether or not a current is less than a specified value. 5. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing in a charging path, and a self-diagnosis performed by using outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
An FET control unit for controlling T; and a communication unit that receives an output of the self-diagnosis unit as input and outputs information to an externally connected electronic device, and determines whether the charging current stops when overcharge is detected. A battery pack failure diagnostic device comprising self-diagnosis means for diagnosing an overcharge control circuit by performing a diagnosis. 6. A voltage detecting means for detecting a battery voltage of a secondary battery, a current detecting means for detecting a current flowing through a charging path, and a self-diagnosis performed by using the outputs of the voltage detecting means and the current detecting means as inputs. Self-diagnosis means, a charge / discharge control FET, and an output of the self-diagnosis means,
A FET control unit for controlling T; and a communication unit that receives an output of the self-diagnosis unit as input and outputs information to an externally connected electronic device, and diagnoses whether a battery voltage is higher than a BMU shutdown voltage. And a self-diagnosis means for diagnosing a shutdown function by performing a self-diagnosis. 7. The battery pack failure diagnosis apparatus according to claim 4, wherein said self-diagnosis means includes information holding means for holding failure information. 8. A self-diagnosis provided with a failure diagnosis function of an FET according to claim 1 or 4, an overcharge control circuit diagnosis function according to claim 2 or 5, and a shutdown diagnosis function according to claim 3 or 6. A battery pack failure diagnosis device characterized by comprising means. 9. A battery pack failure diagnosis apparatus according to claim 8, wherein the failure diagnosis function of the FET, the overcharge control circuit diagnosis function, and the shutdown diagnosis function are housed in the same IC package. 10. A battery pack comprising the battery pack failure diagnosis device according to claim 4. 11. An electronic device comprising the battery pack according to claim 10.