JPH08293328A - Battery pack, equipment including the same, and control method thereof - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a battery pack capable of easily and accurately estimating the amount of charge of a battery, a device including the battery pack, and a control method thereof. [Structure] The control means 22 in the device 20 uses the battery 11
Of the charging voltage value and time, and reading / writing information as needed to detect the charging amount using the charging amount memory 12 or 32 provided in the inserted battery pack 10 as time passes. When the charge amount of the battery 11 is estimated by combining the change in the charging voltage value due to the above, the type of chemical material of the battery 11 and the operation mode of the device 20, and the estimated value is equal to or less than the charge threshold value of the battery 11. In addition, a battery pack that determines that charging is necessary and outputs a warning alarm or the like, a device including the battery pack, and a control method thereof are provided.

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 a device equipped with the battery pack, and more particularly, by estimating the charge amount of the battery according to the type of chemical material of the battery and the characteristics of the operation mode of the device. The present invention relates to a battery pack capable of accurately and easily determining the necessity / unnecessity of charging of a battery while minimizing an error in charge amount measurement due to a difference in a chemical material of the battery, a device including the battery pack, and a control method thereof.

[0002]

2. Description of the Related Art Batteries are widely used as a power supply device that can be attached to and detached from various devices. Explaining how to use a normal battery, the charge amount of the battery gradually decreases with the power consumption by the operation of the device that supplies power, but the minimum amount of power that can operate the device is the minimum. It can be used repeatedly by recharging by an external charging device until the amount of charge (threshold value) is reached.

Further, as the chemical material of the battery, depending on the characteristics of the battery, several kinds such as A (for example, nickel cadmium) and B (for example, lithium ion) are currently used.

Conventionally, as a method of detecting the amount of charge for controlling whether or not the battery needs to be charged when the battery is connected to the device, the amount of charge from the voltage value of the battery is calculated on the connected device side. It was supposed to be carried out by providing a means for detecting. Further, the calculation for detecting the charge amount from the voltage value of the battery has been performed by the same method regardless of the battery made of any chemical material. Here, a conventional method of detecting the charge amount of the battery will be described with reference to FIG. FIG. 6 is a configuration block diagram of a system that realizes a conventional battery, a device including the battery, and a control method thereof.

As shown in FIG. 6, the battery 51 is composed of a single unit, and the device 50 to which the battery 51 is connected measures A / D conversion for measuring the voltage value of the battery 51 and detecting its charge amount. A container 52 and a controller 53 are provided.

The battery 51 is used as a power source of the device 50 when it is connected to the device 50. When the charge amount of the battery 51 decreases below a threshold value specified by the device 50 and the battery needs to be charged again, the battery 51 is charged. Is removed as a single unit, charged by an external charging device, and then connected again to the device 50.

The A / D converter 52 converts the voltage of the battery 51 into a digital value and sends it to the control section 53. The control unit 53 detects the charge amount of the battery 51 based on the voltage value input from the A / D converter 52, and when the charge amount decreases to a threshold value or less defined by the device 50, Is
Outputs warning alarms, etc.

Then, the control unit 53 detects the charge amount from the voltage value of the battery 51 by performing the following arithmetic expression 1. C = K · (V−Vth) ... Formula 1 Here, C is the charge amount, V is the current voltage value of the battery, and V is
th is the remaining threshold voltage value, and K is a constant determined by the battery.

[0009]

However, in the above-mentioned conventional battery and the method for detecting the charge amount of the battery by the device including the battery, the relationship between the battery voltage and the charge amount greatly differs depending on the type of the chemical material of the battery. It is not necessary to charge the battery because the amount of charge cannot be accurately detected from the voltage due to the characteristics that it needs to be measured for a long period of time and that the battery holds an almost constant voltage until it reaches the discharge limit. There is a problem in that it may not be possible to judge accurately.

The present invention has been made in view of the above circumstances, and by estimating the charge amount of the battery according to the type of the chemical material of the battery and the characteristics of the operation mode of the device, the difference in the chemical material of the battery The error of the charge amount measurement can be minimized, and the necessity / unnecessity of charging the battery can be accurately determined, and the measurement of the charge amount immediately after charging the battery can be easily performed in the shortest possible time without any troublesome operation. An object of the present invention is to provide a battery pack that can be performed, an apparatus including the battery pack, and a control method thereof.

[0011]

The invention according to claim 1 for solving the problems of the above-mentioned conventional example is, in a battery pack, a battery type, an access date and time, a charging voltage at the access date and time, an estimated charge amount, It is characterized by having a charge amount memory that stores information about a threshold value of the remaining amount indicating the limit of the remaining charge amount.

According to a second aspect of the present invention for solving the above-mentioned problems of the conventional example, an apparatus including the battery pack according to the first aspect is provided with a timer for indicating a date and time and stored in a charge amount memory. The consumption amount of the charge amount is calculated from the information, the value obtained by subtracting the consumption amount from the charge amount estimated value shown in the information is updated as a new charge amount estimated value, the access date and time, the charge voltage is updated, and the new It is characterized by further comprising control means for comparing the charge amount estimated value and the remaining amount threshold value and generating an alarm when the new charge amount estimated value is smaller than the remaining amount threshold value.

According to a third aspect of the present invention for solving the problems of the conventional example, in the device control method according to the second aspect, when the control means accesses the charge amount memory, the charge amount memory is stored in the charge amount memory. The consumption amount of the charge amount is calculated from the stored information, the value obtained by subtracting the consumption amount from the charge amount estimated value shown in the information is updated as a new charge amount estimated value, and the access date and time and the charge at the access date and time are further updated. It is characterized in that the voltage is updated, the new estimated charge amount is compared with the remaining amount threshold value, and an alarm is generated when the new estimated charge amount value is smaller than the remaining amount threshold value.

[0014]

According to the present invention, the new estimated charge amount is calculated based on the information in the charge memory of the battery pack, and the new estimated charge amount remains. Since the battery pack generates an alarm when it is smaller than the threshold value, the device including the battery pack, and the control method thereof, the amount of charge of the battery of the battery pack can be easily and accurately estimated.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. A battery pack, a device including the battery pack, and a control method thereof according to an embodiment of the present invention are provided with a battery and a charge amount memory that stores information for detecting a charge amount. A device equipped with a pack has a means for measuring the battery voltage,
A means for managing the information stored in the charge amount memory in the battery pack and detecting the charge amount of the battery is provided,
Estimate the amount of battery charge according to the chemical material of the battery based on the change in voltage value over time, the information stored in the charge amount memory and the operation mode of the device, and it is not necessary to charge the battery It is to judge whether or not.

Next, regarding a configuration according to an embodiment of the present invention, an embodiment using a RAM as a charge amount memory of a battery pack will be described as a first embodiment, and an embodiment using an E ² PROM will be described as a second embodiment. .

First, the structure of the battery pack of the first embodiment and the equipment including the same will be described with reference to FIG.
First Embodiment FIG. 1 is a configuration block diagram of a system that realizes a battery pack, a device including the battery pack, and a control method thereof according to a first embodiment of the present invention.

As shown in FIG. 1, the battery pack 10 of this embodiment comprises a battery 11 and a RAM 12 which is a charge amount memory for storing various information for detecting the charge amount. In addition, the battery pack 10 of this embodiment
The device 20 including an A / D converter 21 for converting the voltage of the battery 11 into a digital value, and the battery pack 10
A control unit 22 that manages the information stored in the internal RAM 12 and detects the charge amount of the battery is provided. The RAM 12 in the battery pack 10 and the control means 22 in the device 20 perform input / output of data via the bus 13.

Next, each component will be specifically described with reference to FIGS. 1 and 3. FIG. 3 is a content configuration diagram of the charge amount memory for explaining the information stored in the charge amount memory in the battery pack 10 of the present embodiment.

The RAM 12 in the battery pack 10 stores various kinds of information for detecting the charge amount. Each piece of information is controlled by the control means 22 in the device 20 as required.
Are written to the specific addresses respectively determined by. Further, the control means 22 reads out these pieces of information stored in the RAM 12 as necessary, and detects the charge amount of the battery 11.

The battery 11 supplies the voltage required for the RAM 12. The RAM usually does not retain the stored contents unless a voltage is supplied from the voltage terminal of the RAM. In the first embodiment, if the battery 11 has a sufficient amount of charge to supply a voltage that can hold the contents of the RAM 12, the battery pack 10 can be charged by the device 2 in order to charge the battery 11 by the external charging device.
The contents of the RAM 12 are retained even when the RAM 12 is removed. If the contents of the RAM 12 are not retained due to overdischarge of the battery 11,
Required information is initialized via the control means 22 in the device 20.

Here, various kinds of information stored in the RAM 12 will be specifically described with reference to FIG. Information about the battery 11 is stored in the area of the battery type 41. The battery type 41 is data obtained by digitizing and classifying the types of chemical materials of the battery 11 and the battery 11
The standard voltage value of

Battery type 41 and remaining capacity threshold value 4 described later
4 is written via the control means 22 in the device 20 as an initial setting operation when the battery pack 10 is inserted into the device 20 for the first time or when the content of the RAM 12 is not retained due to overdischarge or the like. However, once set, it is not changed while the contents of the RAM 12 are held.

In the area of the charging voltage value 42, the charging voltage value of the battery 11 measured by the control means 22 in the device 20 is stored. The charging voltage value 42 is read when the control unit 22 detects the amount of charge of the battery 11, and then changed to the latest value. Therefore,
The value read at this time is the value measured at the time of detecting the immediately preceding charge amount, and the change in the charge voltage value can be obtained by the difference between this value and the latest value. The battery 1
The charging voltage value of 1 is measured by the A / D converter 2 in the device 20.
1 is a value obtained by converting the voltage of the battery 11 into a digital value,
The reading is performed by the control means 22.

In the area of the estimated charge amount 43, the latest estimated charge amount of the battery 11 is stored. The estimated charge amount value 43 is calculated and written by the control means 22 in the device 20 based on the change in voltage value over time, the information stored in the RAM 12 and the operation mode of the device.

In the area of the remaining capacity threshold 44, the battery 11 for the device 20 connected to the battery pack 10 is
Stores the threshold value of the charge amount of. Remaining amount threshold 4
4 is a value indicating the minimum charge amount of the battery 11 required to supply the operable voltage of the device 20.

In the area of the charging voltage value measurement date / time 45, the date / time when the control means 22 in the device 20 measures the charging voltage value 42 is stored. The charging voltage value measurement date / time 45 is read when the charge amount of the battery 11 is detected by the control means 22, and then changed to the date / time at which the latest charging voltage value 42 was measured. Therefore, the date / time read at this time is the date / time at which the previous charging voltage value 42 was measured, and the time interval at which the charging voltage value changes is between this date / time and the current date / time. It can be obtained by the difference.

The A / D converter 21 in the device 20 is for converting the voltage of the battery 11 into a digital value at any time.
The converted value is read from the control means 22 as needed.

The control means 22 in the device 20 initializes the information stored in the RAM 12 in the battery pack 10, estimates the charge amount of the battery, and determines whether or not the battery needs to be charged. And R in the process of processing
The contents of the AM 12 are read / written as necessary. Further, the control means 22 includes means for recording the operation mode of the device 20 for estimating the charge amount, and a timer for measuring the date / time for writing in the charging voltage value measurement date / time 45 area. It is provided.

That is, when the battery pack 10 is inserted into the device 20, the control means 22 initializes each information stored in the RAM 12 in the battery pack 10 depending on the situation.

The battery type 41 and the remaining capacity threshold value 44 are initialized by the judgment of the user. Initialization is required when the battery pack 10 is inserted into the device 20 for the first time, or when the contents of the RAM 12 are not retained due to overdischarge or the like.

As a method of initializing the battery type 41 and the remaining capacity threshold value 44, the device 20 is provided with means for instructing whether the user of the device 20 sets these information and information input means. The control means 22 digitizes the input information and writes it in the corresponding area of the RAM 12 to perform the operation.

Further, the estimated charge amount 43 and the charged voltage value 42
And the charging voltage value measurement date / time 45, the device 2
Control means 22 after the battery pack 10 is inserted into 0
Is set automatically by.

As a method of setting the estimated charge amount 43, the control means 22 is provided with information on the initial charge amount corresponding to the chemical material and voltage value of the battery, and the control means 22 stores this information and the RAM 12 in the RAM 12. The initial charge amount is estimated from the information obtained by reading the stored battery type 41 and is written in the area of the estimated charge amount value 43.

As a method of setting the charging voltage value 42 and the charging voltage value measurement date / time 45, the control means 22 reads the charging voltage value of the battery 11 output from the A / D converter 21 and uses the value as the charging voltage. In the area of the value 42, the date / time when the charging voltage value was read is displayed as the charging voltage value measurement date / time 45.
This is done by writing in each area.

As a setting for the timer for writing the date / time in the charging voltage value measurement date / time 45 area, the device 20 is provided with an input means for the user of the device 20 to set the date / time. Immediately after the battery pack 10 is inserted into the device 20, the control means 22 sets the input date / time in a timer.

When estimating the charge amount of the battery 11 during the operation of the device 20, the control means 22 obtains the charge voltage value measured last time and the charge voltage value measurement date / time from the RAM 12 as the current charge voltage value. The current date / time is read from the timer from the A / D converter 21, and the difference between the charging voltage value and the date / time is calculated to obtain the difference between the charging voltage value and the current time. The change in the voltage value is calculated, and the calculation result, the operation mode of the device 20 from the time when the charging voltage value is measured to the present and the information of the battery type 41 are integrated, and the consumption amount of the charge amount of the battery 11 within this time is calculated. calculate. Then, the current charge amount is estimated by subtracting the calculated consumption amount from the charge amount estimated value 43 read from the RAM 14.

For example, when the battery of the chemical material A is used as the battery 11, the control means 22 estimates the current charge amount of the battery 11 using the following arithmetic expression 2. C = CM-Cc ... Equation 2 Here, C is the charge amount, CM is the charge amount estimated value 43, Cc
Indicates the calculated consumption amount.

Then, when the estimated charge amount is less than or equal to the remaining threshold value 44 read from the RAM 12, the control means 22 outputs an alarm or the like to notify the device 20 that the charge is necessary. It informs the user.

The measured current charging voltage value and date
The time and the calculated charge amount are written in a predetermined area of the RAM 12 at the time when they are found.

Further, the control unit 22 counts the time since the charging voltage value was measured by the timer for writing the date / time in order to maintain the time interval necessary for observing the change of the charging voltage. The next charging voltage value is measured after a certain time has elapsed.

Next, the configuration of the battery pack of the second embodiment and the equipment equipped with the battery pack will be described with reference to FIGS. 2 and 3. Second Embodiment FIG. 2 is a configuration block diagram of a system that realizes a battery pack, a device including the battery pack, and a control method thereof according to a second embodiment of the present invention.

As shown in FIG. 2, the battery pack 10 of this embodiment is an E ² PROM 3 which is a charge amount memory for storing various information for detecting the battery 11 and the charge amount.
2 and a power supply 33 for supplying a write voltage to the E ² PROM 32.

Since the E ² PROM 32 generally requires a high voltage for writing, the writing voltage is the battery 11
Power is not supplied from the battery 11 but is supplied separately from the battery 11, and only the operating voltage is supplied from the battery 11.

Further, since the E ² PROM retains the stored contents even if the voltage is not supplied from the voltage terminal, when the battery pack 10 is inserted into the device 20 for the first time, the control means 22 in the device 20 is controlled. By initializing necessary information via the device, the contents of the E ² PROM 32 are retained even after the battery pack 10 is removed from the device 20 in order to charge the battery 11 by the external charging device, and thereafter. Does not need to be initialized.

Other than the above, the information stored in the E ² PROM 32 and the device 2 into which the battery pack 10 is inserted
Since the configuration of 0 is the same as that of the first embodiment, the description will be omitted.

Next, the processing of the control means 22 in the device 20 of the first and second embodiments will be specifically described with reference to FIG.
4 and 5 are flowcharts for detecting the charge amount of the battery 11 in the control means 22 of this embodiment. It should be noted that due to space limitations, the flow of detecting the charge amount of the battery 11 in the control means 22 is shown separately in FIG. 4 and FIG.
First, as shown in FIG. 4, when the battery pack 10 is inserted and the power of the device 20 is turned on, the control unit 22 determines whether or not immediately after the battery pack 10 is inserted (1
00). If it is determined that it is not immediately after insertion, the battery type 41 and the remaining amount threshold value 44 read from the charge amount memory 12 or 32 in the battery pack 10 are set in the control means 22 (103), and the charge voltage is set. The process moves to the process 110 of measuring the value and the date / time.

If it is determined in the process 100 that the device has just been inserted, the timer initialization state in the control unit 22 is entered, and the user inputs to set the date and time provided on the device 20. It is determined whether or not the date / time has been input by the means (101). If not, the operation of process 101 is repeated. If the input is confirmed,
The input date / time is set in the timer (102).

When the timer setting process 102 is completed, it is then determined whether or not the charge amount memory 12 or 32 in the battery pack 10 needs to be initialized with respect to the battery type 41 and the remaining amount threshold 44 (104). Here, the determination as to whether or not this initial setting is necessary is made by detecting that the user of the device 10 has input an instruction from the input means of the device 10. When it is determined that the initial setting is not necessary, the battery type 41 and the remaining amount threshold value 44 read from the charge amount memory 12 or 32 in the battery pack 10 are set in the control means 22 (108). , The process shifts to a process 109 for initializing the charge amount estimated value.

When it is determined in step 104 that the initial setting is necessary, the user uses the input means for setting the battery type 41 and the remaining capacity threshold value 44 provided in the device 20. It is determined whether or not the information has been input (105). If not input, the operation of process 105 is repeated.

When the input is confirmed, the input battery type 41 and the remaining capacity threshold value 44 are set in the control means 22, and the charge amount memory 1 in the battery pack 10 is set.
The data is written into 2 or 32 (106), and the process proceeds to the process 109 of initializing the charge amount estimated value.

The battery type 41 and the remaining capacity threshold value 44
The initial settings for and are when the battery pack 10 is inserted into the device 20 for the first time, or when the charge amount memory is RAM.
This is required when the contents of the RAM 12 are not retained due to over-discharge or the like, but the user performs charging according to an alarm or the like output from the device 20 to warn that charging is required. If so, over-discharging can be prevented, so it is usually performed only when the device is inserted for the first time. After that, since the control means 22 automatically reads and sets the information already written in the charge amount memory 12 or 32, the user does not need to perform a troublesome operation of initial setting.

In process 109, the control means 22 estimates the initial charge amount by comparing the information of the battery type 41 with the information of the initial charge amount corresponding to the chemical material and voltage value of the battery managed by itself. , The charge amount memory 12 or 32 in the battery pack 10.

After the initialization of the timer, the battery type 41, the remaining amount threshold value 44, and the charge amount estimated value is completed, the charge voltage value of the battery 11 is changed from the A / D converter 12 in the control means 20 to the timer. Measure the date and time respectively (11
0), the charge amount memory 12 or 3 in the battery pack 10
Write to 2 (112).

Next, as shown in FIG. 5, after setting the time interval necessary for observing the change of the charging voltage in the timer (114), the timer is checked to determine whether a certain time has elapsed. (116), the process 116 is repeated until a fixed time has elapsed. In addition, when the certain time has elapsed in the process 116, the process proceeds to the process 118 and the battery pack 10
The charge voltage value 42 and the charge voltage value measurement date / time 45 are read from the charge amount memory 12 or 32 therein.

Further, the A / D converter 1 in the control means 20
2 to the charging voltage value of the battery 11, from the timer
Each time is measured (120) and the battery pack 10
Write to the charge amount memory 12 or 32 inside (122),
The current charge amount of the battery 11 is estimated (124).

The charge amount is estimated by the charge voltage value read in the process 118, the charge voltage value measurement date / time, the process 1
The difference between the charging voltage value measured in 20 and the date / time is calculated to calculate the elapsed time from the last charging voltage value measurement to the present and the change in the charging voltage value, and the calculation result and the charging voltage value. The operation mode of the device 20 from the time of measurement to the present and the information of the battery type 41 are integrated, and the consumption amount of the charge amount of the battery 11 within this time is calculated. Then, the current charge amount is estimated by subtracting the calculated consumption amount from the charge amount estimated value 43.

Then, in process 124, the estimated charge amount and the remaining amount threshold value 44 are compared. If the estimated charge amount is less than or equal to the remaining threshold value 44, it is determined that charging is necessary, an alarm is output (130), and the process ends.

When the estimated charge amount is larger than the remaining amount threshold value 44 in the process 124, the calculated estimated charge amount is written in the charge amount memory 12 or 32 in the battery pack 10 (128), and the process 114. The process of detecting the charge amount is repeated until the power is turned off. In this way, the battery pack of the present embodiment, the device including the battery pack, and the control method thereof detect the charge amount.

According to the battery pack of the present embodiment, the device including the battery pack, and the control method thereof, the time change of the charging voltage value, the chemical material of the battery, and the operation mode of the device are used as a method of measuring the charge amount of the battery. Since this is done comprehensively, it is possible to easily and accurately estimate the charge amount of the battery by minimizing the error in the charge amount measurement due to the difference in the chemical materials of the battery, and to determine whether charging the battery is necessary or not. There is an effect that can be accurately judged.

Even when the battery pack 10 is removed from the device 20 and reinserted for charging, the E ² PROM is used as the charge amount memory or the R ² is used as the charge amount memory.
If the user of the device 20 is using the AM,
By discharging according to the alarm etc. that warns that the battery needs to be charged, over-discharge is not performed and RA
If the content of M is stored, the control means 22 automatically reads and sets the information already written in the charge amount memory 12 or 32, which is troublesome for the battery type 41 and the remaining amount threshold value 44. The effect is that there is no need to repeat the initial setting.

Further, the battery pack 10 has a RAM or an E ² PROM having a very small capacity as compared with the conventional battery 11.
Since it is a configuration in which only the above is added, the manufacturing cost and the increase in size can be suppressed very slightly.

[0063]

According to the invention described in claims 1, 2 and 3,
A battery pack that calculates a new estimated charge amount value based on the information in the charge amount memory of the battery pack, and generates an alarm when the new estimated charge amount value is smaller than the remaining amount threshold value, and a device including the battery pack And the control method thereof, there is an effect that the charge amount of the battery of the battery pack can be easily and accurately estimated.

[Brief description of drawings]

FIG. 1 is a block diagram of a system configuration that realizes a battery pack, an apparatus including the battery pack, and a control method thereof according to a first embodiment of the present invention.

FIG. 2 is a configuration block diagram of a system that realizes a battery pack, a device including the battery pack, and a control method thereof according to a second embodiment of the present invention.

FIG. 3 is a content configuration diagram of a charge amount memory for explaining information stored in the charge amount memory of the present embodiment.

FIG. 4 is a battery 11 in the control means 22 of the present embodiment.
FIG. 3 is a flowchart of a charge amount detection process of FIG.

FIG. 5 is a battery 11 in the control means 22 of the present embodiment.
FIG. 3 is a flowchart of a charge amount detection process of FIG.

FIG. 6 is a configuration block diagram of a system that realizes a conventional battery, a device including the battery, and a control method thereof.

[Explanation of symbols]

10 ... Battery pack, 11 ... Battery, 12 ... R
AM (charge amount memory), 13 ... bus, 20 ... equipment,
21 ... A / D converter, 22 ... Control means, 32 ... E ²
PROM (charge amount memory), 33 ... E ² PROM writing power source, 41 ... Battery type, 42 ... Charging voltage value, 43 ... Charge amount estimated value, 44 ... Remaining amount threshold value,
45 ... Charging voltage value measurement date / time, 50 ... Equipment, 5
1 ... Battery, 52 ... A / D converter, 53 ... Control unit

Claims (3)

[Claims] 1. A charge amount memory for storing information on a battery type, an access date and time, a charge voltage at the access date and time, a charge amount estimated value, and a remaining amount threshold value indicating a limit of the remaining charge amount. Battery pack. 2. A timer for indicating the date and time is provided, the consumption amount of the charge amount is calculated from the information stored in the charge amount memory, and a value obtained by subtracting the consumption amount from the estimated charge amount value shown in the information is newly generated. Update as a charge amount estimated value, update access date and time, charge voltage, compare the new charge amount estimated value with the remaining amount threshold value, and the new charge amount estimated value is smaller than the remaining amount threshold value. The device equipped with a battery pack according to claim 1, further comprising a control means for occasionally generating an alarm. 3. When the control means accesses the charge amount memory, the charge amount consumption amount is calculated from the information stored in the charge amount memory, and the consumption amount is subtracted from the charge amount estimated value indicated in the information. The value is updated as a new charge amount estimated value, the access date and time and the charge voltage at the access date and time are further updated, and the new charge amount estimated value and the remaining amount threshold value are compared to obtain the new charge amount. 3. The device control method according to claim 2, wherein an alarm is generated when the estimated value is smaller than the remaining amount threshold value.