Battery charging device, battery charging method, and battery charging program

Abstract

The present invention is for efficiently measuring internal resistance for use as a battery degradation index during battery charging, and comprises: a battery charging unit 2 that supplies charging current and / or voltage to a battery B; a battery management unit 3 that manages the charging state of the battery B; a pulse signal generation unit 4 that superimposes, at one or more charging points corresponding to the charging state of the battery B, pulse current or voltage on the charging current or voltage and supplies the same to the battery; an internal resistance calculation unit 5 that calculates the internal resistance of the battery B on the basis of the current value and the voltage value of the battery obtained when charging power superposed with pulse power has been supplied; and a data management unit 6 that records, in a memory, the internal resistance calculated by the internal resistance calculation unit 5.

Description

Battery charging device, battery charging method, and battery charging program

[0001] The present invention relates to a battery charging device, a battery charging method, and a battery charging program.

[0002] The internal resistance of a battery gradually increases with repeated charging and discharging, which causes a decrease in battery output. Therefore, it is considered to measure the internal resistance of a battery and use the measured internal resistance as an indicator of the battery's deterioration.

[0003] The method for measuring the internal resistance of a battery is the current interruption method as shown in Patent Document 1, in which a direct current is passed through the battery and the internal resistance is calculated from the change in voltage using Ohm's law.

[0004] Here, the internal resistance of a battery depends on the state of charge (SOC) of the battery. Therefore, in order to use the internal resistance of a battery as an index of the progress of battery degradation, it is necessary to measure the internal resistance at multiple SOCs.

[0005] However, in order to measure the internal resistance at a plurality of SOCs, it is necessary to adjust the battery to each of the plurality of SOCs, and measuring the internal resistance for each of the plurality of SOCs takes a very long time.

[0006] Japanese Patent Application Laid-Open No. 2021-140991

[0007] Therefore, the present invention has been made in consideration of the above-mentioned problems, and its main objective is to efficiently measure the internal resistance used as an indicator of battery deterioration while the battery is being charged.

[0008] That is, the battery charging device of the present invention is characterized by comprising a battery charging unit that supplies a charging current and / or voltage to a battery, a battery management unit that manages the charging state of the battery, a pulse signal generation unit that superimposes a pulse current or voltage on the charging current or voltage and supplies it to the battery at one or more charging points according to the charging state of the battery, an internal resistance calculation unit that calculates the internal resistance of the battery from the current value and voltage value of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied, and a data management unit that records the internal resistance calculated by the internal resistance calculation unit in memory.

[0009] With this battery charging device, when charging the battery, a pulse current or voltage is superimposed on a charging current or voltage at one or more charging points according to the state of charge, and the internal resistance is calculated from the current and voltage values ​​of the battery when the pulse current or voltage is supplied, so that the internal resistance used as a battery degradation indicator can be efficiently measured when the battery is being charged.In addition, because the calculated internal resistance is recorded in memory by the data management unit, the internal resistance for each charging cycle at each of the multiple charging points can be managed, and the progress of battery degradation can be monitored.

[0010] Here, it is desirable to set multiple charge points because, depending on the state of charge of the battery at the start of charging (for example, the state of charge (SOC) of the battery or the filling rate (FR) of lithium ions in the active material, etc.), the charge point may not be passed during charging (the state may not reach the charge point). Furthermore, it is desirable to set the charge points based on the state of charge, filling rate, cumulative charge amount, charging time from the start of charging, and voltage and / or current of the battery.

[0011] The degree of battery deterioration can be determined by monitoring the calculated internal resistance, but in order to make it easier to determine the degree of battery deterioration, it is desirable that the battery charging device of the present invention further includes a deterioration index calculation unit that calculates a deterioration index of the battery based on multiple internal resistances calculated over multiple charging cycles.

[0012] As a specific embodiment of the deterioration index calculation unit, it is desirable that the deterioration index calculation unit calculates the deterioration index of the battery based on internal resistance calculated at the same charging point in a plurality of charging cycles.

[0013] In a battery, the active material expands and contracts during charging and discharging, causing rupture. The rupture of the active material narrows the conductive path, increasing the internal resistance. The increase in internal resistance due to this rupture of the active material serves as an indicator of the progress of battery degradation. Therefore, it is desirable for the degradation index calculation unit to calculate, as the degradation index, the increase in the internal resistance calculated in the current charging cycle relative to the internal resistance calculated in the previous charging cycle. Here, the internal resistance calculated in the previous charging cycle may be the internal resistance calculated in the previous (most recent) charging cycle, the internal resistance calculated in the charging cycle a predetermined number of times before, or the internal resistance calculated in a reference charging cycle, such as the first charging cycle.

[0014] As a specific embodiment of superimposing a pulse current or voltage on the charging current or voltage, it is desirable that the pulse signal generating unit superimposes a negative pulse current or voltage on the charging current or voltage.

[0015] It is desirable that the battery is a lithium-ion battery, and that the pulse signal generator superimposes a pulse current or voltage on the charging current or voltage at the charging point based on the state of charge (SOC) of the battery or the filling rate (FR) of lithium ions in the active material of the battery. Alternatively, the charging point may be based on the accumulated charge amount of the battery, the charging time from the start of charging, the voltage or current of the battery, or the like.

[0016] The reason for calculating the internal resistance for each charging point is as follows: The internal resistance of a lithium-ion battery includes the insertion / extraction resistance of lithium ions, which is unrelated to degradation. The insertion / extraction resistance depends on the battery's state of charge (SOC) or the filling rate (FR) of lithium ions in the active material. Therefore, by comparing the internal resistance calculated at the same charging point over multiple charging cycles, the degree of degradation excluding the insertion / extraction resistance can be confirmed.

[0017] The capacity of a battery decreases as it is repeatedly charged and discharged. Therefore, if the charging point is set based on the SOC of the battery, the charging point will shift as the charging is repeated. Therefore, it is desirable that the battery management unit updates the capacity of the battery and manages the state of charge of the battery.

[0018] The internal resistance varies depending on the temperature of the battery or the ambient temperature of the battery. Therefore, in order to accurately calculate the internal resistance, it is preferable that the battery charging device of the present invention further includes a temperature correction unit that corrects the internal resistance calculated by the internal resistance calculation unit based on the temperature of the battery or the ambient temperature of the battery.

[0019] Here, a temperature range for calculating the internal resistance may be set without temperature correction. In other words, the internal resistance of a battery includes the ion migration resistance in the electrolyte, which is unrelated to deterioration, and the ohmic resistance of the current collector, both of which depend on temperature. Therefore, a temperature range that has little effect on the ion migration resistance and ohmic resistance may be set, and the internal resistance calculated outside that range may not be recorded in the data storage unit.

[0020] Furthermore, a battery charging method according to the present invention is a battery charging method for charging a battery, which is characterized in that a pulse current or voltage is superimposed on a charging current or voltage and supplied to the battery at one or more charging points according to the charging state of the battery, an internal resistance of the battery is calculated from the current value and voltage value of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied, and the calculated internal resistance is recorded.

[0021] Furthermore, the battery charging program of the present invention is a battery charging program for charging a battery, and is characterized in that it has the following functions: a charging control unit that controls a battery charging circuit to supply a charging current or voltage to the battery, and superimposes a pulse current or voltage on the charging current or voltage at one or more charging points according to the charging state of the battery and supplies the superimposed pulse current or voltage to the battery; an internal resistance calculation unit that calculates the internal resistance of the battery from the current value and voltage value of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied; and a data management unit that records the internal resistance calculated by the internal resistance calculation unit in memory.

[0022] According to the present invention as described above, the internal resistance used as an indicator of battery deterioration can be efficiently measured while the battery is being charged.

[0023] Fig. 1 is an overall schematic diagram of a battery charging device according to an embodiment of the present invention; Fig. 2 is a diagram showing the charging current (including pulse current) and battery voltage of the same embodiment; Fig. 3 is a table showing the internal resistance and the rate of increase in internal resistance of each SOC for each number of charging times of the same embodiment; Fig. 4 is a table showing the internal resistance and the rate of increase in internal resistance of each FR for each number of charging times of the same embodiment; Fig. 5 is a flowchart of a battery charging method of the same embodiment; Fig. 6 is an overall schematic diagram of a battery charging device according to a modified embodiment;

[0024] <One embodiment of the present invention> Hereinafter, one embodiment of a battery charging device according to the present invention will be described with reference to the drawings. Note that in all of the drawings shown below, parts are appropriately omitted or exaggerated for clarity. Identical components are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0025] <Basic Configuration of Battery Charging Device 100> The battery charging device 100 of this embodiment is capable of determining the degree of degradation of a secondary battery (hereinafter simply referred to as battery B), such as a lithium ion battery, while charging the battery B. In this embodiment, as will be described later, the battery charging device 100 calculates a degradation index that is an index of the progress of degradation of battery B, thereby enabling the user to determine the degree of degradation of battery B.

[0026] Specifically, the battery charging device 100 charges the battery B using a constant current charging method, and as shown in FIG. 1, includes a battery charging unit 2 that supplies a charging current to the battery B, and a battery management unit 3 that manages the charging state of the battery B.

[0027] The battery charging unit 2 includes an AC-DC converter 21 that converts AC voltage from an AC power source E into DC voltage, a DC-DC converter 22 that adjusts the DC voltage, and a constant current controller 23 that converts the adjusted DC voltage into a constant current and supplies it to the battery B. An open / close switch 24 is provided between the AC-DC converter 21 and the AC power source E.

[0028] The battery management unit 3 is a so-called battery management system (BMS) that can measure the current flowing through battery B, the voltage of battery B, and the like, and calculate the state of charge (SOC) or the filling rate (FR) of lithium ions in the active material of battery B. The battery management unit 3 also functions as a charge control unit that charges battery B by controlling the battery charging unit 2.

[0029] <Calculation Function of Deterioration Index of Battery B> The battery charging device 100 of this embodiment is configured to be able to calculate the deterioration index of battery B.

[0030] Specifically, the battery charging device 100 includes a pulse signal generating unit 4 that superimposes a pulse current on the charging current and supplies it to the battery B at a charging point corresponding to the charging state of the battery B, an internal resistance calculating unit 5 that calculates the internal resistance of the battery B from the current value and voltage value of the battery B when the charging current superimposed with the pulse current is supplied, and a data management unit 6 that records the internal resistance calculated by the internal resistance calculating unit 5 in memory.

[0031] The pulse signal generating unit 4 superimposes a pulse current on the charging current supplied by the battery charging unit 2, and supplies the pulse current to battery B. As shown in FIG. 2 , the pulse signal generating unit 4 of this embodiment superimposes a negative pulse current on the charging current. When a negative pulse current is superimposed on the charging current, the overall current with the superimposed pulse current is a negative current. By superimposing such a negative pulse current, an overvoltage is prevented from being applied to battery B.

[0032] The pulse signal generator 4 superimposes a pulse current on the charging current and supplies it to the battery B at a plurality of charging points based on the state of charge (SOC) of the battery B or the filling rate (FR) of lithium ions in the active material. The pulse signal generator 4 is controlled by the battery management unit 3. Note that the charging points may be based on the state of charge (SOC) of the battery B or the filling rate (FR) of lithium ions in the active material, or may be based on the integrated charge amount of the battery B, the charging time from the start of charging, the voltage or current of the battery, or the like.

[0033] Here, the filling rate (FR) of lithium ions in the active material is defined as an absolute standard, unlike the SOC, which is a relative standard, by the following formula: FR=Q ｉ ・SOC / Q ０ Here, SOC = SOC ０ + (1 / Q ｉ ) ∫Idt Also, Q ｉ is the capacity (i is the number of updates, i = 0, 1, 2, 3, ...), Q ０ is the initial capacity, SOC ０ is the SOC at the start of charging, and I is the charging current.

[0034] For example, the initial capacity Q ０ When the battery capacity is 10 Ah and the charging point based on the filling rate FR is set to "0.5", the charging point based on the SOC in a state where the capacity is not deteriorated (not updated) is "0.5", which is the same as the check point of the filling rate FR. ｉ ・SOC / Q ０ From the above formula, 0.5 = 10·SOC / 10. In other words, SOC = 0.5.

[0035] On the other hand, if the capacity drops to 8 Ah due to aging, the charging point based on the filling rate FR is an absolute standard and is fixed at "0.5", but the charging point based on the SOC increases to "0.625". FR = Q ｉ ・SOC / Q ０ From the above formula, 0.5 = 8·SOC / 10. In other words, SOC = 0.625.

[0036] In the case of SOC, the multiple charge points for calculating the internal resistance are, for example, SOC 5%, SOC 25%, SOC 50%, SOC 75%, and SOC 95%, as shown in Fig. 3. In the case of FR, the multiple charge points are, for example, FR 25%, FR 50%, and FR 75%, as shown in Fig. 4. Whether or not each charge point has been reached is determined by the battery management unit 3. When the battery management unit 3 determines that each charge point has been reached, the battery management unit 3 sends an output command to the pulse signal generation unit 4, and the pulse signal generation unit 4 superimposes a pulse current on the charging current.

[0037] The internal resistance calculation unit 5 calculates the internal resistance of the battery B from the current value and voltage value of the battery B when the charging current on which the pulse current is superimposed is supplied. Specifically, as shown in FIG. 2, the internal resistance calculation unit 5 calculates the internal resistance of the battery B from the voltage drop ΔV caused by the pulse current and the amplitude I of the pulse current. ｐｌｕｓｅ From the internal resistance R (= ΔV / I ｐｌｕｓｅ The internal resistance calculation unit 5 calculates the internal resistance every time the pulse signal generation unit 4 supplies a pulse current to the battery B.

[0038] The data management unit 6 records the internal resistance calculated by the internal resistance calculation unit 5 in a data storage unit D1 composed of a memory. Specifically, the data management unit 6 associates the internal resistance calculated by the internal resistance calculation unit 5 with the number of times battery B has been charged and / or each charging point, and records the results in the data storage unit D1. If the temperature during charging is outside a specified temperature range (e.g., 10 to 40°C), the calculated internal resistance does not need to be stored in the data storage unit D1. In other words, the internal resistance of that charging point becomes "no data" in the data storage unit D1. The data storage unit D1 may be provided in the battery charging device 100 or external to the battery charging device 100. The data management unit 6 may also acquire and store the internal pressure or ambient pressure of battery B, or the ambient temperature or ambient temperature of battery B.

[0039] Furthermore, the battery charging device 100 of this embodiment may further include a deterioration index calculation unit 7 that calculates a deterioration index, which is an index of the deterioration progress of battery B, based on multiple internal resistances calculated in multiple charging cycles.

[0040] The deterioration index calculation unit 7 calculates the deterioration index of the battery B based on the internal resistance calculated at the same charging point in a plurality of charging cycles.

[0041] Specifically, the deterioration index calculation unit 7 calculates, as the deterioration index, the amount of increase in the internal resistance calculated in the current charge cycle relative to the internal resistance calculated in the previous charge cycle. Here, the previous charge cycle may be, for example, the previous charge cycle, a charge cycle a predetermined number of times ago, or a reference charge cycle such as the first charge cycle. Note that, in the following, the increase rate of the internal resistance in the current charge cycle relative to the internal resistance in the previous charge cycle is calculated as the amount of increase in resistance, but it may also be the difference between the internal resistance in the current charge cycle and the internal resistance in the previous charge cycle.

[0042] In this embodiment, the degradation index calculation unit 7 calculates, at each charge point, the resistance increase rate of the internal resistance calculated in the current charge cycle relative to the internal resistance calculated in the previous charge cycle. Then, the degradation index calculation unit 7 sets the average or median of the resistance increase rates at each charge point in the current charge cycle as the degradation index of battery B. The degradation index calculated by the degradation index calculation unit 7 is linked to the number of times battery B has been charged and recorded in the data storage unit D1 by the data management unit 6.

[0043] Alternatively, the degradation index calculation unit 7 may use the following calculation as the degradation index: The degradation index calculation unit 7 calculates the average or median value of the internal resistance calculated at each charging point in the previous charging cycle, and also calculates the average or median value of the internal resistance calculated at each charging point in the current charging cycle. The degradation index calculation unit 7 then calculates the resistance increase rate of the average or median value of the internal resistance in the current charging cycle relative to the average or median value of the internal resistance in the previous charging cycle, and uses this resistance increase rate as the degradation index.

[0044] <Specific Example of Battery Charging Method> Next, a specific example of a battery charging method using the battery charging device 100 described above will be described with reference to FIG.

[0045] First, the ID (identifier) ​​of battery B to be initially charged is registered in the internal memory (database) of the battery charging device 100 (step S1). The battery ID may be a preset ID read by the battery management unit 3 and registered in the memory (database), or may be set by the user and registered in the memory (database).

[0046] When battery B, whose ID has been registered, is connected to battery charging device 100, the initial SOC of battery B is acquired (step S2). Battery charging device 100 then starts charging (step S3) and measures the internal resistance at a plurality of predetermined charging points, and has the data management unit 6 record the results in data storage unit D1 (step S4). For the second and subsequent charging cycles, the internal resistance is similarly measured at a plurality of predetermined charging points, and has the data management unit 6 record the results in data storage unit D1. For the second and subsequent charging cycles, the amount of increase in internal resistance for each charging cycle is calculated, and has the data management unit 6 record the results in data storage unit D1.

[0047] Here, in the second and subsequent charging operations, the capacity of battery B can be corrected at each predetermined charging cycle (around the capacity correction) (step S5). This capacity correction may be performed by re-obtaining and updating the capacity of battery B through a capacity test, or by correcting and updating the capacity based on the root law or the trend of an aging test. Furthermore, the capacity correction may be performed by re-obtaining and updating the SOC-OCV curve through an SOC-OCV test, or by correcting the SOC-OCV curve from the corrected capacity obtained through the capacity test.

[0048] In this way, the internal resistance and resistance increase amount of each battery B recorded in the data storage unit D1 by the data management unit 6 can be output to a display or the like by the user inputting the ID of the battery B. Here, the content to be displayed on the display may be, for example, a graph with one axis (horizontal axis) representing the number of charges and the other axis (vertical axis) representing the internal resistance, a diagram displaying the internal resistance at each charging point in a table format, or a diagram displaying the resistance increase amount of the internal resistance in each charging cycle in a table format.

[0049] <Effects of this embodiment> According to the battery charging device 100 of this embodiment configured as described above, during charging of battery B, a pulse current is superimposed on the charging current and supplied to battery B at one or more charging points according to the state of charge of battery B, and the internal resistance is calculated from the current value and voltage value of battery B when the pulse current is supplied, so that the internal resistance used as a deterioration index of battery B can be efficiently measured during charging of battery B. Furthermore, since the calculated internal resistance is recorded in the data storage unit D1 by the data management unit 6, it is possible to manage the internal resistance for each charging cycle at each of the multiple charging points, and it is possible to monitor the degree of deterioration of battery B.

[0050] <Other Embodiments> For example, in addition to the configuration of the above-described embodiment, as shown in Fig. 6, the battery charging device 100 may further include a temperature correction unit 8 that corrects the internal resistance calculated by the internal resistance calculation unit 5 based on the temperature of the battery B or the ambient temperature of the battery B. In this case, the temperature correction unit 8 corrects the internal resistance R before correction calculated by the internal resistance calculation unit 5. ｍｓｒ , the ambient temperature T ａｍｂ and the reference temperature T ｓｔｄ The difference ΔT between the temperature and the internal resistance of the battery K ｇｒａ and the corrected internal resistance R ｃｏｒ Specifically, the temperature correction unit 8 calculates R ｃｏｒ =R ｍｓｒ +K ｇｒａ × (T ａｍｂ -T ｓｔｄ ) formula, the corrected internal resistance R ｃｏｒThe corrected internal resistance is linked to the number of times battery B has been charged and each charging point, and is recorded in the data storage unit D1 by the data management unit 6.

[0051] Furthermore, the lithium ion battery of the above embodiment may be mounted on a moving body such as an automobile, ship, airplane, forklift, or AGV (automated guided vehicle), or may be a stationary or emergency power source for communication equipment, security equipment, or facilities.

[0052] Furthermore, the battery charging device 100 of the above embodiment may be configured to charge a lead-acid battery, a nickel-metal hydride battery, a nickel-cadmium battery, and / or an all-solid-state battery, in addition to a lithium-ion battery, and calculate an index of the degradation progress thereof. Also, the battery charging device 100 of the above embodiment may be configured to charge a next-generation battery, such as a sodium-ion battery, a lithium-air battery, a metal lithium load battery, a lithium-sulfur battery, or a fluoride battery, and calculate an index of the degradation progress thereof.

[0053] Furthermore, although the above embodiment is configured to calculate the internal resistance at multiple charging points, it may be configured to calculate the internal resistance at one charging point. Also, the number of charging points at which the internal resistance is calculated may be changed depending on the degree of battery deterioration, or the charging point may be changed.

[0054] Although the above embodiment describes charging one battery B, the battery charging device 100 may also be configured to charge multiple batteries B. In this case, the battery charging device 100 may be configured to include multiple battery charging units 2 and pulse signal generating units 4 corresponding to the respective batteries B, an internal resistance calculating unit 5 that calculates the internal resistance of the multiple batteries B from the current and voltage values ​​of the multiple batteries B, and a data managing unit 6 that records the internal resistance calculated by the internal resistance calculating unit 5 in memory. In this case, the multiple batteries B are managed by their respective IDs, and charging information, internal resistance information, deterioration information, etc. of each battery B can be managed regardless of the battery charging unit 2 to which it is connected. Alternatively, a central control device may be configured to manage multiple battery charging devices 100.

[0055] Furthermore, the battery charging device 100 of the above embodiment may be provided with a display unit that displays the charging state of the battery B or various data stored in the data storage unit D1.

[0056] The battery charger in the above embodiment is a constant current charging system that supplies a charging current and a pulse current to the battery, but it may also be a constant voltage charging system that supplies a charging voltage and a pulse voltage to the battery. Also, the battery charger may be configured to be switchable between the constant current charging system and the constant voltage charging system.

[0057] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention.

[0058] According to the present invention, the internal resistance used as an indicator of battery deterioration can be efficiently measured while the battery is being charged.

[0059] REFERENCE SIGNS LIST 100: Battery charging device B: Battery 2: Battery charging section 3: Battery management section (charging control section) 4: Pulse signal generation section 5: Internal resistance calculation section 6: Data management section D1: Data storage section 7: Deterioration index calculation section 8: Temperature correction section

Claims

1. A battery charging device comprising: a battery charging unit that supplies a charging current and / or voltage to a battery; a battery management unit that manages the charging state of the battery; a pulse signal generation unit that superimposes a pulse current or voltage on the charging current or voltage and supplies it to the battery at one or more charging points according to the charging state of the battery; an internal resistance calculation unit that calculates the internal resistance of the battery from the current and voltage values ​​of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied; and a data management unit that records the internal resistance calculated by the internal resistance calculation unit in memory.

2. The battery charging device according to claim 1, further comprising a deterioration index calculation unit that calculates a deterioration index of the battery based on a plurality of internal resistances calculated in a plurality of charging cycles.

3. The battery charging device according to claim 2, wherein the deterioration index calculation unit calculates the deterioration index of the battery based on the internal resistance calculated at the same charging point in a plurality of charging cycles.

4. A battery charging device as described in any one of claims 1 to 3, wherein the charging point is set based on the charging rate, filling rate, accumulated charge amount, charging time from the start of charging, and the voltage and / or current of the battery.

5. A battery charging device as described in claim 2 or 3, wherein the deterioration index calculation unit calculates, as the deterioration index, the amount of resistance increase of the internal resistance calculated in the current charging cycle relative to the internal resistance calculated in the previous charging cycle.

6. A battery charging device according to any one of claims 1 to 5, wherein the pulse signal generating section superimposes a negative pulse current or voltage on the charging current or voltage.

7. A battery charging device as claimed in any one of claims 1 to 6, wherein the battery is a lithium ion battery, and the pulse signal generating unit superimposes a pulse current or voltage on the charging current or voltage and supplies it to the battery at the charging point based on the charging rate of the battery or the filling rate of lithium ions in the active material.

8. The battery charging device according to any one of claims 1 to 7, wherein the battery management unit updates the capacity of the battery to manage the state of charge of the battery.

9. The battery charging device according to any one of claims 1 to 8, further comprising a temperature correction section that corrects the internal resistance calculated by the internal resistance calculation section based on the temperature of the battery or the ambient temperature of the battery.

10. A battery charging method comprising the steps of: supplying to the battery a charging current or voltage superimposed with a pulse current or voltage at one or more charging points according to the charging state of the battery; calculating an internal resistance of the battery from the current value and voltage value of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied; and recording the calculated internal resistance.

11. A battery charging program for charging a battery, comprising: a function as a charging control unit that controls a battery charging circuit to supply a charging current or voltage to the battery and superimposes a pulse current or voltage on the charging current or voltage at one or more charging points according to the charging state of the battery and supplies the superimposed current or voltage to the battery; a function as an internal resistance calculation unit that calculates the internal resistance of the battery from the current value and voltage value of the battery when the charging current or voltage superimposed with the pulse current or voltage is supplied; and a function as a data management unit that records the internal resistance calculated by the internal resistance calculation unit in memory.

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