Patent Description:
A non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is fully charged by constant-voltage and constant-current charging. In the constant-voltage and constant-current charging, the battery is charged at a constant current until the voltage of the charging battery rises to a preset voltage, for example, <NUM> V/cell, and after the voltage rises to the set voltage, the battery is fully charged by constant-voltage charging. Since the current of the battery charged at a constant voltage gradually decreases, when the charging current decreases to a preset charging termination current, it is determined that the battery is fully charged, and the charging is terminated. The charging termination current can be set to be small, in other words, the charging time can be extended to increase the capacity to be charged into the battery. However, decreasing the charging termination current to increase the charging amount of the battery leads to increasing deterioration of the battery to shorten its life.

In order to prevent the above adverse effects, a pack battery that determines a charging termination current in consideration of the temperature and internal resistance of the battery has been developed (see PTL <NUM>).

Since the internal resistance increases as the battery deteriorates, in the method of changing the charging termination current with the internal resistance, as the battery deteriorates and the internal resistance increases, the charging termination current of the battery is increased, and the capacity for charging the battery is gradually reduced, so that deterioration of the battery can be reduced.

As described in PTL <NUM>, in a pack battery that terminates charging by increasing a charging termination current of a battery that has deteriorated and has increased internal resistance, the degree of deterioration of the battery is reduced, and charging can be terminated particularly in a state of suppressing deterioration of a battery that has deteriorated. However, when a pack battery used for a power source of an electronic device, particularly a pack battery including a battery progressed in deterioration, is charged by being connected to a charger with a high output voltage, in other words, a charger with a high charging voltage for charging the battery, even if the charging termination current is changed in accordance with the degree of deterioration of the battery, the charged capacity increases and the battery is charged to a state progressed in deterioration, and the charging and discharging cycle life is shortened. Conversely, when a pack battery including a battery progressed in deterioration is charged by a charger with a low output voltage, there is a disadvantage that the capacity to be substantially charged is reduced, and the time available to the user is shortened.

The embodiments of the present invention have been developed for the purpose of further solving the above adverse effects, and an object of the embodiments of the present invention is to provide a pack battery charging method, a pack battery, and a power source device that can charge the battery to an ideal capacity and prolong the charging and discharging cycle life of the battery.

A pack battery charging method according to a first aspect of the present invention is a battery pack <NUM> charging method, as claimed in appended claim <NUM>.

A pack battery according to a second aspect of the present invention is a battery pack <NUM>, as claimed in appended claim <NUM>.

A power source device according to a third aspect of the present invention is a power source device <NUM>, which includes a charger <NUM> and battery pack <NUM> of the second aspect of the present invention, as claimed in appended claim <NUM>.

The embodiments of the present invention , advantageously, achieve the technical effect that while charging a deteriorated battery to an ideal capacity to prolong a use time of a user, deterioration of the charged battery is suppressed to a minimum, and a charging and discharging cycle life can be prolonged.

Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the following description, terms (for example, "upper", "lower", and other terms including those terms) indicating specific directions and positions are used as necessary, but these terms are used to facilitate understanding of the embodiments of the present invention with reference to the drawings, and should not be considered as limiting. Parts denoted by the same reference numerals in a plurality of drawings indicate the same or equivalent parts or members.

Further, the following exemplary embodiment illustrates a specific example of the technical idea of the present invention, and does not limit the present invention to the following. In addition, unless otherwise specified, dimensions, materials, shapes, relative arrangement, and the like of the components described below are not intended to limit the scope of the present invention, but are intended to be illustrative. The contents described in one exemplary embodiment and example are also applicable to other exemplary embodiments and examples. In addition, sizes, positional relationships, and the like of members illustrated in the drawings may be exaggerated for clarity of description.

A pack battery charging method according to the present invention is a charging method for connecting a pack battery to a charger and charging the pack battery at a constant voltage and a constant current, in which the pack battery detects a degree of deterioration of the battery and a supply voltage at which the charger charges the pack battery, and specifies a charging termination current from both the supply voltage of the charger and the degree of deterioration of the battery to charge the battery.

The charging method described above is characterized in that, while the deteriorated battery is connected to a charger having different charging voltages, the battery is always charged to a capacity optimal for the degree of deterioration of the battery, and the use time of the user can be extended, and moreover, the deterioration of the battery in the charged state is suppressed to a minimum, and the charging and discharging cycle life can be prolonged. This is because the charging method described above detects the degree of deterioration of the battery and the supply voltage at which the charger charges the pack battery, specifies the charging termination current based on both the supply voltage of the charger and the degree of deterioration of the battery, and terminates the charging. In the constant-voltage and constant-current charging, constant-current charging is performed in a state where the battery voltage is lower than the set voltage, and after the battery voltage rises to the set voltage, charging is performed by controlling the battery voltage of the battery not to be higher than the set voltage. In a battery charged at a constant voltage, the battery voltage gradually increases, and the charging current gradually decreases. Therefore, when the charging current decreases to a charging termination current, the charging is terminated. A battery has a characteristic that a degree of deterioration varies depending on a remaining capacity, and deterioration increases in a fully charged state. The deterioration of the battery can be suppressed by reducing the capacity to be charged, but the battery having a small charging capacity has a disadvantage that the use time of the user is shortened. Therefore, it is important to maximize the use time of the user while suppressing deterioration of the battery as much as possible. As the battery deteriorates, the capacity to be charged can be reduced to reduce the progress of deterioration, and safety can also be secured. However, for the battery, the suppression of deterioration and the lengthening of the use time of the user are mutually contradictory characteristics, and it is difficult to satisfy both of them, and it is important to control both of them to an optimum state. The charging capacity of the battery can be adjusted by a charging termination current, and the charging capacity can be increased by lowering the charging termination current and charging for a long time, and conversely, the charging capacity can be reduced by increasing the charging termination current and shortening the charging time of the battery. Furthermore, even if the charging termination current is set to the same current value, the charging capacity also changes depending on the charging voltage of the battery. When the charging voltage is high, the charging capacity is large even if the charging termination current is set to the same value, and conversely, when the charging voltage of the battery decreases, the capacity to be charged decreases even if the charging termination current is the same. Therefore, even if the battery is charged by setting the charging termination current to the same current value, if the charging voltage is high, the deteriorated battery has a large charging capacity and is greatly deteriorated in a charged state, and conversely, if the charging voltage is low, there is an adverse effect that the charging capacity decreases and the use time of the user is shortened.

In the charging method described above, in addition to controlling the charging capacity by adjusting the charging termination current in accordance with the degree of deterioration of the battery, the charging termination current is set to an optimum value based on both the degree of deterioration and the charging current in consideration of the charging voltage. Therefore, it is possible to perform charging in a positively ideal state in which the deterioration of the battery in the charged state can be minimized and the charging and discharging cycle life can be prolonged while charging the deteriorated battery to a state in which the user can use the battery at the maximum.

Further, in the above charging method, the pack battery can be connected to a plurality of chargers having different charging voltages, and deterioration can be suppressed to a minimum while charging to an ideal capacity, so that both an old type charger and a new type charger having different charging voltages can be used for charging. Therefore, there is a feature that a user can conveniently use a pack battery by using a plurality of chargers, and can charge the battery to an ideal capacity while minimizing deterioration of the battery while charging with both chargers. For this reason, there is a feature that it is possible to safely increase the charging capacity while suppressing the deterioration of the pack battery to the minimum and to prolong the time during which the user can use the pack battery as the power source of the electronic device.

A pack battery charging method according to an embodiment of the present invention increases the charging termination current as the degree of deterioration of the battery included in the pack battery increases, and further increases the charging termination current as the supply voltage increases.

In the charging method described above, as the degree of deterioration of the battery increases, the charging time is shortened by increasing the charging termination current, and further, as the charging voltage of the battery increases, the charging time of the battery is shortened by increasing the charging termination current, so that the charging capacity of the deteriorated battery can be reduced to minimize the deterioration of the battery in the fully charged state.

In a pack battery charging method according to another embodiment of the present invention, the pack battery stores a charging termination current with respect to a degree of deterioration of the battery and a supply voltage in a look-up table, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of a charger in accordance with the storage of the look-up table.

In a pack battery charging method according to yet another embodiment of the present invention, the pack battery stores a function for specifying a charging termination current from the degree of deterioration of the battery and the supply voltage, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of the charger based on the function.

In a pack battery charging method according to yet another embodiment of the present invention, the pack battery incorporates a lithium ion secondary battery.

A pack battery according to the present invention is a pack battery that is connected to a charger and is charged at a constant voltage and a constant current, and includes a detection circuit that detects a charging voltage from the charger and a degree of deterioration of the battery, an arithmetic circuit that calculates a charging termination current from the charging voltage and the degree of deterioration detected by the detection circuit, and a signal terminal that detects the charging termination current calculated by the arithmetic circuit and outputs a charging stop signal to the charger.

The pack battery described above is characterized in that, even when the pack battery is charged by a charger having a different charging voltage, the pack battery is charged to a capacity optimum for the degree of deterioration, and the use time of the user can be extended, and moreover, the pack battery can be minimized in deterioration in a charged state, and the charging and discharging cycle life can be prolonged. This is because the pack battery described above detects the degree of deterioration of the battery and the supply voltage at which the charger charges the pack battery, specifies the charging termination current based on both the supply voltage of the charger and the degree of deterioration of the battery, and terminates charging. It is important to maximize the use time of the user while suppressing the deterioration of the pack battery as much as possible. The pack battery described above is charged in a positively ideal state in which deterioration of the battery in a charged state can be suppressed to a minimum and a charging and discharging cycle life can be prolonged while charging the deteriorated battery to a state in which the user can use the battery at a maximum.

In a pack battery according to an embodiment of the present invention, the arithmetic circuit includes a memory that stores a look-up table for specifying a charging termination current from the degree of deterioration of the battery and the supply voltage of the charger, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of the charger based on the look-up table stored in the memory.

In a pack battery according to another embodiment of the present invention, the arithmetic circuit includes a memory that stores a function for specifying a charging termination current from the degree of deterioration of the battery and the supply voltage of the charger, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of the charger based on the function stored in the memory.

A pack battery according to yet another embodiment of the present invention incorporates a lithium ion secondary battery.

A power source device according to yet another embodiment of the present invention includes a charger and a pack battery connected to the charger and charged at a constant voltage and a constant current. The pack battery includes a detection circuit that detects a charging voltage from the charger and a degree of deterioration of the battery, an arithmetic circuit that calculates a charging termination current from the charging voltage and the degree of deterioration detected by the detection circuit, and a signal terminal that detects the charging termination current calculated by the arithmetic circuit and outputs a charging stop signal to the charger. The charger includes a charging stop circuit that is connected to the signal terminal and stops charging of the pack battery with the charging stop signal input from the signal terminal.

The power source device described above is characterized in that, even when the pack battery is charged by a charger having different charging voltages, the battery is charged to a capacity optimum for the degree of deterioration of the battery, and the use time of the pack battery can be extended, and moreover, the deterioration of the pack battery in a charged state is suppressed to a minimum, and the charging and discharging cycle life can be prolonged. This is because the power source device detects the degree of deterioration of the battery included in the pack battery and the supply voltage at which the charger charges the power source device, specifies the charging termination current based on both the supply voltage of the charger and the degree of deterioration of the battery included in the pack battery, and terminates charging. It is important to maximize the use time of the user while suppressing the deterioration of the pack battery as much as possible. However, the power source device described above can use the deteriorated pack battery in a positively ideal state in which the deterioration of the charged pack battery can be minimized to prolong the charging and discharging cycle life while charging the battery to a state in which the user can use the battery to the maximum.

In a power source device according to yet another embodiment of the present invention, an arithmetic circuit includes a memory that stores a look-up table for specifying a charging termination current from a degree of deterioration of a battery and a supply voltage of a charger, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of the charger based on the look-up table stored in the memory.

In a power source device according to yet another embodiment of the present invention, an arithmetic circuit includes a memory that stores a function for specifying a charging termination current from a degree of deterioration of a battery and a supply voltage of a charger, and specifies the charging termination current from the degree of deterioration of the battery and the supply voltage of the charger based on the function stored in the memory.

In a power source device according to yet another embodiment of the present invention, a pack battery incorporates a lithium ion secondary battery.

Power source device <NUM> of <FIG> includes charger <NUM> and pack battery <NUM> connected to charger <NUM> and charged at a constant voltage and a constant current. Pack battery <NUM> includes detection circuit <NUM> that detects the charging voltage from charger <NUM> and the degree of deterioration of battery <NUM>, arithmetic circuit <NUM> that calculates a charging termination current from the charging voltage and the degree of deterioration detected by detection circuit <NUM>, and signal terminal <NUM> that detects the charging termination current calculated by arithmetic circuit <NUM> and outputs a charging stop signal to charger <NUM>.

Charger <NUM> includes charging stop circuit <NUM> that is connected to signal terminal <NUM> of pack battery <NUM> and stops charging of pack battery <NUM> with a charging stop signal input from signal terminal <NUM>. Charger <NUM> includes charging circuit <NUM> for charging pack battery <NUM> at a constant voltage and a constant current. <FIG> shows an example of characteristics of charging circuit <NUM> charging pack battery <NUM> at a constant voltage and a constant current. In this drawing, a horizontal axis represents time, and a vertical axis represents a charging current and a charging voltage. In this drawing, charging circuit <NUM> limits the charging voltage of pack battery <NUM> to a constant voltage or less, and limits the charging current to a constant current or less to perform charging. Since the voltage of pack battery <NUM> is lower than the charging voltage in a state where charging is started, constant-current charging is performed with a constant current. When the constant-current charging is performed and the battery voltage rises to the charging voltage, the charging is performed by switching to constant-voltage charging such that the battery voltage does not rise. Since the charging current of pack battery <NUM> charged at a constant voltage gradually decreases, charging circuit <NUM> stops charging when the charging current decreases to a charging termination current. The charging termination current is calculated by pack battery <NUM> from the degree of deterioration of battery <NUM> and the charging voltage. Pack battery <NUM> calculates a degree of deterioration of battery <NUM> in order to calculate a charging termination current, and further detects a charging voltage. Pack battery <NUM> transmits the calculated charging termination current to charging circuit <NUM>. Charging circuit <NUM> stops charging with a charging termination current transmitted from pack battery <NUM>. However, when charging circuit <NUM> cannot normally stop charging, charging is stopped by a switching element (not shown) provided in pack battery <NUM>.

Charger <NUM> of pack battery <NUM> in which battery <NUM> is a lithium ion secondary battery performs charging at a charging voltage of, for example, <NUM> V/cell and a charging current corresponding to the capacity of battery <NUM>, for example, at a charging current of <NUM>. 5C to 10C, preferably <NUM>. 5C to 3C, and more preferably about 1C. Charging circuit <NUM> of pack battery <NUM> in which the two lithium ion secondary batteries are connected in series performs charging at a charging voltage of <NUM> V. When the charging termination signal is input from pack battery <NUM>, charger <NUM> sets the charging voltage of battery <NUM> to <NUM> V and terminates the charging. Charger <NUM> has signal terminal <NUM> for inputting a charging termination signal from pack battery <NUM>, and this signal terminal <NUM> is connected to signal terminal <NUM> of pack battery <NUM>.

Pack battery <NUM> also includes detection circuit <NUM> that detects the degree of deterioration of the battery and the charging voltage, and central processing unit (CPU) <NUM> that calculates a charging termination current from the parameters detected by detection circuit <NUM>. Detection circuit <NUM> detects the internal resistance of battery <NUM>, a number of times of charging and discharging, the charged and discharged current, the environmental temperature, and the like, and calculates the degree of deterioration of battery <NUM>. Since battery <NUM> deteriorates when the number of times of charging and discharging increases, the integrated value of the charged and discharged currents increases, and the environmental temperature becomes higher or lower than a set value, it is possible to determine the degree of deterioration by detecting such values. Furthermore, since the internal resistance increases when battery <NUM> deteriorates, the degree of deterioration of battery <NUM> can be calculated from the above parameters and internal resistance.

Further, detection circuit <NUM> includes A/D converter <NUM> for detecting a charging voltage of pack battery <NUM> and converting the charging voltage into a digital signal. Detection circuit <NUM> detects the charging voltage in a state where pack battery <NUM> is connected to charger <NUM>. Arithmetic circuit <NUM> can detect the charging voltage by disconnecting pack battery <NUM> from charging circuit <NUM> while pack battery <NUM> is set in charger <NUM>. Since pack battery <NUM> incorporates a charging switch (not shown) connected in series with battery <NUM>, it is possible to detect the charging voltage by setting this charging switch (not shown) to the off-state, and disconnecting battery <NUM> from charging circuit <NUM>. The charging voltage is converted into a digital signal by A/D converter <NUM> and input to CPU <NUM>. The charging switch is switched to the on-state in a state of charging pack battery <NUM>.

CPU <NUM> calculates a charging termination current from the battery voltage detected by detection circuit <NUM> and the degree of deterioration of battery <NUM>. Data specifying the charging termination current from the battery voltage and the degree of deterioration is stored in memory <NUM> of pack battery <NUM> as a look-up table. However, the pack battery can also store data specifying the charging termination current from the battery voltage and the degree of deterioration as a function in memory <NUM> without necessarily storing the data as a look-up table. CPU <NUM> calculates a charging termination current from the battery voltage and the degree of deterioration based on the look-up table or the function stored in memory <NUM>.

CPU <NUM> increases the charging termination current as the degree of deterioration of battery <NUM> increases, and increases the charging termination current as the supply voltage increases. That is, as the degree of deterioration of the battery increases and the charging voltage of charger <NUM> increases, CPU <NUM> sets the charging termination current to be large, and gradually reduces the capacity to charge battery <NUM>, thereby suppressing the deterioration of battery <NUM>. This is because when deteriorated battery <NUM> is charged at a high charging voltage, the charging capacity increases and the deterioration becomes severe. CPU <NUM> increases the charging termination current to shorten the charging time as the degree of deterioration of battery <NUM> increases, and further increases the charging termination current as the charging voltage of battery <NUM> increases to shorten the charging time of battery <NUM>, thereby limiting the charging capacity of the deteriorated battery to be small, and minimizing the deterioration of battery <NUM> in the fully charged state.

<FIG> illustrates a specific example of a look-up table for specifying a charging termination current from a charging voltage and a degree of deterioration. In the look-up table of this drawing, the degree of deterioration of battery <NUM> is specified in six stages of degrees of deterioration <NUM> to <NUM> as the deterioration progresses, and the charging voltage is specified in <NUM> stages from <NUM> V/cell or more to <NUM> to <NUM> V. Pack battery <NUM> charged by charger <NUM> whose charging voltage is <NUM> V or higher stops charging when the battery voltage rises to <NUM> V, that is, when the constant-current charging terminates. In pack battery <NUM> charged by charger <NUM> at a charging voltage of <NUM> V to <NUM> V, the charging termination current is set to <NUM> mA in the state of the degree of deterioration <NUM>, and is set to <NUM> mA in the state of the degree of deterioration <NUM> to suppress the deterioration in the charged state.

Claim 1:
A battery pack (<NUM>) charging method, for a battery pack (<NUM>) connected to a charger (<NUM>) and charging the battery pack (<NUM>) at a constant voltage and a constant current, the method comprising:
detecting, by the battery pack (<NUM>), a degree of deterioration of a battery (<NUM>) comprised in the battery pack (<NUM>) and
characterized in that, the method further comprises the steps of:
detecting, by the battery pack (<NUM>), a supply voltage at which the charger (<NUM>) charges the battery pack (<NUM>); and
determining a charging termination current based on both the supply voltage of the charger (<NUM>) and the degree of deterioration of the battery (<NUM>) to charge the battery pack (<NUM>).