JPH03242574A - Apparatus for display residual power of battery - Google Patents

Abstract

PURPOSE:To improve display accuracy by calculating an index indicating an accumulation amount per hour from previous discharge until present discharge and displaying an index indicating residual power obtained based on the above index. CONSTITUTION:When a charge switch SW is turned ON and charging is performed, total discharge time tD which has been written in is read out from a non-volatile memory 9. Base on the discharge time tD, an index (%) Q1 indicat ing a calculated amount of charge per unit hour is changed as Q1=Q10XtD0/tD, where Q10 is an index (%) indicating a standard amount of accumulation per unit hour in storage battery 4 and tD0 is standard time that the accumulator can be used since it was fully charged. Thus charging is performed during discharge, that is before the storage battery 4 is empty, as well as it is possible to prevent storage battery of errors due to repetition of an error caused such that charging is terminated before the storage battery is fully charged, and there occurs an error in an index (%) Q0 indicating residual amount of the storage battery due to a fluctuation in charged current.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to electric and electric equipment using storage batteries, and particularly to a device that recognizes and displays the remaining power or usable time of a used battery.

[Conventional technology]

In electric equipment that uses rechargeable and dischargeable storage batteries, the remaining amount of battery or usable time, as well as the number of screws that can be tightened in the case of power tools, are used to inform the user of the equipment of the estimated usage time. There are known devices that display the number of holes that can be drilled.

FIG. 4 shows a display method for displaying the remaining amount or usable time of the battery. FIG. 4(a) is an example of percentage display, and FIG. 4(b) is an example of time display.

In addition, in the figure, A1 to A5 and 81 to B5 are, for example, LEDs.
These display elements are used to notify the user by lighting up each element up to the corresponding percentage or time.

Conventionally, a timer method and a current integration method, which will be described later, are known as methods for generating such display data.

The timer method is a method that sequentially changes the display according to preset charging and discharging times, as shown in Figures 5 and 6 below.
This will be explained using figures.

In Figure 5, AC type? When ll1i 1 is connected, that is, the charging switch SW is turned on, the AC power is full-wave rectified by the rectifier 2, and then converted to a predetermined charging current by the charging circuit 3, and the N i -Cd electric power lt! ! It flows into the dedicated storage battery 4 and is charged. On the other hand, when the operation switch SW is turned on and the load 6 and the storage battery 4 are connected, current is discharged from the storage battery 4 and power is supplied to the load 6. i! II
The IIII calculation unit 5 detects the states of the charging switch SW and the operation switch SW to control the charging M. That is, the control calculation unit 5 has a function of detecting full charge and outputting a charge control signal to the charging circuit 3, a function of charging the charging time during charging, a function of ejecting a discharger during discharging and storing the remaining amount, and a function of storing the remaining amount. It has a function of outputting and displaying on the display unit 7. Note that 8 is a DC-DC converter for supplying power to each part.

Next, the operation will be explained with reference to FIG.

Now, from the state where the remaining capacity of storage battery 4 is zero (step #1),
When charging is started in step #2, the control calculation unit 5 sequentially adds the capacity 1iiIQ+ to be charged to the storage battery 4 per unit time dt stored in advance to 93fflQo every dt time, and The numbing results are displayed on the display unit 7 in percentage or time units as shown in FIG.
Loop of step group 3 to step #7>. And 1 left
Nominal capacity l Q H of the storage battery 6 in which 1Qo is stored in advance
When AX is reached (YES in step #5), charging control is performed and charging is stopped (step #8).

Next, when the operation switch SW is turned on, that is, discharge is started (in step #2), the control calculation unit 5 stores the capacity Q2 consumed per unit time dt stored in advance for every dt time. While sequentially subtracting from IQo,
The subtraction result is displayed on the display unit 7 in % or time units (loop from step #9 to step #12). In this way, the display of remaining IQO is realized with an inexpensive configuration.

In addition, Q+ = d tx Ic, Q2 = d tX
It is expressed as ID, where IC and ID are predetermined charging current and consumption current.

In addition, the current integration method calculates charging current and discharging current as shown in Japanese Unexamined Patent Publication No. 61-209373; i11
This method calculates and displays the remaining amount, and will be explained below with reference to FIG. In addition, in the same figure, the same thing as in FIG. 5 indicates the same thing.

The charging current and Tll current detected from both ends of the current detection resistor 12 connected in series to the storage battery 4 are amplified by the amplifier 13, and further converted into digital data by the A/D converter 14. We are led to part 5.

AII The tm operator unit 5 appropriately changes the ratio of addition and subtraction of each uQ+ and Q2 according to the magnitude of the input actually measured current value. The control calculation unit 5 displays the calculated remaining amount in % or in units of time.

By using the measured current value in this way, accuracy can be improved.

[Problems to be Solved by the Invention] Although the timer method can be constructed at low cost, it does not reduce the variation in the charging current 1c of the charging circuit 3 and the current consumption I to the load.
Display accuracy is low because errors occur due to variations in D.
This is not desirable because it gives the user a sense of distrust. Furthermore, although the current integration method absorbs errors due to variations in charging current and discharging current, since a current measuring resistor 12 is inserted, the voltage drop across the resistor 12 deteriorates the starting performance of a motor such as a motor. In addition, in recent years, with the demand for shortening charging time, it is necessary to increase the charging current, but it is necessary to increase the charging current.
2 causes a new problem of heat generation.

Furthermore, if a low-resistance resistor 12 is used as a solution to the heat generation problem, the detection level will become smaller and the measurement error will increase, or noise countermeasures for the amplifier 13 will be required to ensure the desired accuracy, making it expensive. Become.

The present invention has been made in view of the above, and it is possible to easily determine the remaining amount without measuring the charging current during charging and the current consumption during discharging, and without being affected by variations in the charging current and current consumption. The present invention aims to provide a battery remaining amount display device that calculates and displays the usable time.

[Means to solve the problem]

The present invention provides a battery remaining capacity display device that displays an index indicating the remaining capacity of a storage battery obtained by sequentially adding an index indicating the amount of charge per unit time during charging, from full charge until the storage battery becomes empty. a non-volatile memory for writing the obtained discharge time; and a non-volatile memory for writing the discharge time obtained, and a discharge time stored in the non-volatile memory during the previous discharge when charging the storage battery from empty to fully charged. This is done in cooperation with a control means that calculates an index indicating the amount of charge per unit time from the time and uses the calculated index in place of the index indicating the amount of charge per unit time at the time of previous charging.

Further, claim 2 provides a battery remaining capacity display device that displays an index indicating the remaining capacity of the storage battery obtained by sequentially adding an index indicating the charge of 74 m per unit time during charging,
A charging time measuring means for measuring the charging time required for the storage battery to become fully charged from empty, a memory for writing the obtained charging time, and a charging time stored in the memory when charging the storage battery. The control means calculates an index indicating the amount of charge per unit time at a medium time, and uses the calculated index in place of the amount of charge per unit time at the time of previous charging.

(Function) According to the battery remaining capacity display device configured as described above, when discharging is started, the discharging time required from full charge to emptying of the storage battery is measured, and this rli battery time open time volatile memory is stored. written. Then, when charging from empty to full, an index indicating the amount of charge per unit time is calculated from the discharge time at the previous discharge stored in the non-volatile memory, and the calculated index indicates the amount of charge per unit time at the previous charge. It is used in place of an index indicating the amount of charge, and an index indicating the remaining amount of the storage battery is determined and displayed using the index indicating the amount of charge.

Further, according to the battery remaining amount display device according to the second aspect, when charging is started, the charging time required for the storage battery to become fully charged from empty is measured. Then, at the time of next charging or during recharging from the middle of discharging after full charge, an index indicating the amount of charge per unit time is extracted from the charging time stored in the memory, and this calculated index is used for the current charging time. This new index is used as an index indicating the amount of charge per unit time, and an index indicating the remaining capacity of the storage battery is determined and displayed.

[Embodiment] FIG. 1 is a block diagram showing an example of a battery remaining amount display device according to the present invention.

Reference numeral 1 is an AC power source such as a commercial power source, and reference numerals 2 to 11 are circuit blocks constituting an electric device to which the present residual sun display device is applied.

2 is a rectifier consisting of a diode bridge or the like that performs full-wave rectification of the alternating current from the AC power supply 1; 3 is a charging circuit that converts the rectified current from the rectifier 2 into a charging current of a predetermined level; 4 is a charging circuit that performs charging from the charging circuit 3; It is a storage battery, such as an N1-Cd battery, which is charged by current and supplies a depleted current to a load 6, which will be described later. The charging switch SW is for connecting the electric device to the AC power source 1 to charge the storage battery 4, and the operation switch SW is for connecting the storage battery 4 to the load 6.

5 detects the connection state of the charging switch SW and operation switch SW, and at the time of charging, a temperature sensor 1 such as a thermistor is used.
This is a control calculation unit that detects full charge from the storage battery temperature obtained from 0 and outputs a charge control signal to the charging circuit 3 to stop charging. 11 is a temperature measurement circuit that outputs an analog voltage corresponding to the storage battery temperature detected by the temperature sensor 10;
2 is an A/D converter that converts the analog voltage from the temperature measurement circuit 11 into a digital value and inputs it to the control calculation section 5. In addition, as a method of detecting full charge, the so-called -d method uses the charging characteristics of the storage battery to detect when the battery voltage has dropped by dV (V) from the peak value and determines that the battery is fully charged.
V control method and other known methods can be used.

Further, the control calculation section 5 detects the connection state of the power switch SW and the operation switch SW, and applies an index indicating the decay according to the charging time during charging, while applying an amount corresponding to the discharging time during discharging. A function to reduce the index indicating the remaining capacity of the storage battery 4 (a function to obtain the usable time), a display control function to display the index indicating the current remaining capacity on the display section 7, and a charging time and It has a function of storing the discharge time and other required numerical values as needed in the nonvolatile memory 9 as described below. The display unit 7 displays an index indicating the remaining amount (usable time), for example, as a percentage or in the middle of time, in a numerical display or in a graph format, and is provided at a suitable external location of the electrically powered device. The non-volatile memory 9 is timely written with charging time, discharging time, and other required values as necessary based on commands from the control calculation unit 5, so that the values are continuously stored even when the storage battery is discharged and empty. It retains the stored content and allows it to be reloaded at subsequent restarts (charging). Incidentally, the DC-DC converter 8 transfers the electric power from the storage battery 4 to the control calculation section 5 and the display section 7 until the storage battery 4 becomes empty.
The voltage is converted to each voltage level required by the A/D converter 12, etc., and then supplied.

Next, a first example of the remaining amount display operation will be described with reference to the flowchart of FIG. 2.

In this first embodiment, a discharge time tD is stored in the non-volatile memory 9, and from this discharge time tD, an index 01 indicating the amount charged per unit time dt and an index 0 indicating the amount consumed per unit time dt are stored.
2.

In addition, the definition of each symbol is as follows.

Qo: Index (%) for display indicating remaining capacity of storage battery 4 Q Index (%) for display indicating HAX full charge Q+o
: Index showing the standard amount stored in the storage battery 4 per unit time dt (%) Q20: Index showing the standard amount consumed per unit time dt (%) Ql : Calculation of charging per unit time dt An index (%) indicating the above-mentioned conditions Ql: An index (%) indicating the calculated amount of electricity consumed per unit time dt (111 electric current) tcO: Standard required for full charging when the charging current is set to the specified current Ic Time tDO: Standard time that can be used from full charge when current consumption is set to predetermined current ID t-o: Actual discharge time from fA full charge To: Storage battery temperature at the start of charging TN; Storage battery temperature every unit time dt elapses TEND: Fully charged 1 [value of (TN-To) of kj In addition to %, the unit of Qo, etc. may be time (minutes), number of screws that can be tightened, number of holes that can be drilled, and other amperes)' watt (Ah) . For example, when displaying an index indicating the actual product such as ampere hours, the above symbols are as follows: t CO= Q HAX / I c Qso=dtxIc (Ah) t DO= QHAX , /f D Q2o=dtXIn (Ah ) and can be defined in ampere-hours per unit time. Other time units can also be obtained in the same way.

Now, when the storage battery 4 is empty and charging is started by turning on the charging switch SW, first, Qo, the discharging time t
The initial values of internal counters (not shown) that measure D are both reset to O (step S1), and then the discharge time tD is read from the nonvolatile memory 9 (step S2).
), it is determined whether the discharge time tD is stored (step S3).

At first, the nonvolatile memory 9 does not store the discharge time tD (NO in step S3), so the process moves to step S4, and the indices Q1o and Q2 indicating standard amounts as Ql and Ql are used.
0 is used respectively. Then, it is determined whether it is a charging state or a discharging state (step S6), and by continuing charging (charging in step S6), the discharging time tD is reset to O, and the tD flag indicating full charge is reset (step S6).
7) Furthermore, the storage battery temperature Ta from the temperature measurement circuit 11 is taken in (step Ss').

Next, a built-in timer (not shown) of the control calculation unit 5 is used to determine whether the dt waiting time has elapsed. That is,
When the dt waiting time has elapsed (YES in step S9), the Qo
Qto is added to , and the storage battery temperature TN at this time is further measured (steps S+o, S++). Then, the difference (TN-
To) and a predetermined value T END are compared and determined (step 512). The above temperature is reached until fully charged!
Since the i difference is smaller than T END (N
o), Q at that time.

is displayed on the display section 7 (step 513).

Next, it is determined whether the charging state continues (
Step S14>, if charging is continued (YES in step S14), the process returns to step S9, and steps 39 to S14 are repeated until the battery is fully charged. In other words, each time dt time passes, Qo
l, :Q+o are added, and the added Qo is displayed. Then, when the temperature difference becomes equal to or greater than T END (YES in step S12), charging is stopped by a charging control signal output from the control section 5 (step S5).
15), index Q HA for displaying full charge on Qo
100 (%) is written as X (step 51a),
Furthermore, the tD flag is set (step 817).

After this, when the operation switch SW is turned on and the storage battery 4 is connected to the load 6 (discharged in step S6), it is determined whether the dt waiting time has elapsed using the built-in timer of the control calculation unit 5 (step 518). That is, when the dt waiting time has elapsed (YES at step S+a), the index 020 indicating standard numbness is subtracted from Qo, and the discharge time tD is further subtracted from Qo.
The unit time dt is added to (step S19.520
). Next, it is determined whether the 1D flag is set (step 521). Since the tD flag is set when discharging after full charge (YES in step S21), this discharging time 1D is written in the nonvolatile memory 9 each time (step 522). and,
The Qo at this time is displayed on the display section 7 (step 523
). On the other hand, when it is 111ffi before full charge, the tD flag remains reset (step S2
1 (NO), the process moves to step S23 without writing the discharge time tD into the non-volatile memory 9, and the Q at this time
o is displayed on display al17 (step 523).

Next, it is determined whether the above-mentioned tli lightning condition continues (step 524), and if the discharge continues (YES in step S24), the process returns to step S+a and the operation switch SW is turned off. Until (No in step S24), steps S+a to mill step 24 are repeated. That is, (every time jtt elapses, subtract Q20 from QO, add unit time dt to discharge time tD, write the discharge time 1D to non-volatile memory 9, and display QO on display section 7. Therefore, when the storage battery 4 becomes empty due to continued discharging, the discharge time tD calculated immediately before is finally written into the nonvolatile memory 9 as the total tli discharge time.

Note that the tD flag should be set only when the battery is fully charged (YES in step S12), and the set state of this tD flag should be checked at all times (step S21).
YES), write the discharge time tD, and write the discharge time tD based on the current discharge obtained up to that point, unless it is selected to continue discharging until the storage battery 4 is empty. Since the time tD is reset (cancelled) (step S7), the discharge time of 1 - 1 tal is written only when the storage battery 4 is emptied after full charge, and in other conditions, the previous storage battery 4 The total discharge time when the battery is discharged until empty is still retained. Further, until the storage battery 4 becomes empty, the processes from step S6 onwards are performed.

Then, when the storage battery 4 becomes empty and the charging switch SW is turned on to perform charging again, the written total discharge time tD is read out from the nonvolatile memory 9 (step S2). At this time, tJ! Since the i-den time is always stored (YES in step S3), the process moves to step S5. In step S5, the read discharge time t
Ql and Ql are respectively changed based on D.

In other words, the charging time is tco for the 11i charging time tD.
x tD/tDo, so Ql changes from Qlo to 0+
=Qv x tDo/ID. As a result, if you switch to charging during discharging, that is, before the storage battery 4 is empty, and end charging before it is fully charged, a difference in Qo will occur due to variations in the charging current, and this will not occur repeatedly. This prevents the accumulation of errors caused by On the other hand, similarly to Q1 above, Ql is changed from Q20 to Q2=Q20Xt Do,/tD. As a result, Q.

display and the actual charging and discharging status of the storage battery 4, e.g. Qo
=The time when O is displayed, the time when the storage battery 4 becomes empty, and Qo=1
00 and the time when the storage battery 4 is fully charged can be maintained.

Note that full charge may be detected by the above-mentioned 1d control method or other methods.

Next, a second embodiment of the remaining amount display operation will be described with reference to the flowchart of FIG. 3.

In the second embodiment, the charging time tc and the discharging time tD are stored in the nonvolatile memory 9, and these times 1c, 1D to Q
l and Ql are changed.

Note that the same symbols as in the first embodiment have the same definitions.

Now, when charging is started by turning on the charging switch SW from a state where the Qo of the storage battery 4 is empty, the initial 1iIl values of the internal counters (not shown) that measure the charging time tc and the tli period D are both set to O. It is reset (step 531), and then the charging time tc and the charging time 1D are read from the nonvolatile memory 9 (step 5321). It is determined whether these times tC and tD are stored. Initially, the nonvolatile memory 9 does not store times 1c and 1D (at step 833, N
O), move to step 334 and set Q as Ql and Ql.
1o and Q20 are used, respectively. Subsequently, a tc flag indicating that the N battery 4 is being charged from empty is set (step 83[1), and then it is determined whether it is in a charging state or a discharging state (step 537).

When charging continues (charging in step S37), li
The t time tD is reset to O, the tD flag indicating full charge is reset (step 838), and then the storage battery temperature TO is taken in from the humidity measuring circuit 11 (step 539). From then on, Qla is added to QO every time dt time elapses until it is fully charged, and each time the charging time tc
The unit time dt is added to the above Qo and the above Qo is displayed (step 840 to step 546). Then, when the temperature difference (TEND) exceeds a predetermined value TEND (YES in step S44), charging is stopped by a charging control signal from the controller 5 (step 847). In addition, the index Q for displaying Qo L is fully charged.
100 (%) is written as HAX (step 54
8).

Subsequently, it is determined whether the tc flag is set (step 549). Now, in step S36, t
Since the c flag is set (YES in step S49), the charging time tc is written to the nonvolatile memory 9 (step 850), and the tD flag is set (
Step 551). On the other hand, when the tc flag is reset (step 552) after a discharging operation to be described later is performed (
(NO in step S49), the process proceeds to step S51 without writing the charging time tc to the nonvolatile memory 9;
The tD flag is set.

In other words, Qt changes to Qo every time dt time elapses.

addition of unit time dt to charging time tc and Qo
is repeatedly displayed on the display unit 7, and when the charging continues and the battery reaches full charge, the charging time tc that has been depleted at that time is finally written into the nonvolatile memory 9 as the total charging time.

After that, when the operation switch SW is turned on and the storage battery 4 is connected to the load 6 (discharged in step S37), the jc
A flag is reset (step 552). continue,
Similar to steps 818 to S24 described above, d
Every time t time elapses, Q20 is subtracted from Qo, unit time dt is added to tll discharge time D, writing of the added discharge time tD to non-volatile memory 9, and Qo display section 7
is displayed repeatedly (step 353 to step 5).
59).

Then, when the discharge continues and the storage battery 4 becomes empty, the discharge time 1D calculated immediately before becomes the total IIl\i
It is finally written into the non-volatile memory 9 as time passes.

After that, when the charging switch SW is turned on and charging is performed again, the total charging time tc and the total discharging time 1D are read from the nonvolatile memory 9 (step 5).
32). These times 1c, 1D are stored in the non-volatile memory 9.
is stored (YES in step S3), the process moves to step S35. In step S35, the read time tc.

Based on tD, Ql and Ql are each Q10°Q 2
Changed from 0.

In other words, Ql is Q1= d t X QHAX /
t (changed as follows. This prevents the occurrence of Qo display errors caused by inconsistent charging time due to variations in the charging current of individual devices, deterioration of storage batteries, etc. Ql = QHAX x t
DO/' t D. As a result, Qo
display and the actual charging of the storage battery 4, 11i power status, for example, the display time of Qo = O, the time when the storage battery 4 becomes empty, and the Qo
=100 and the time when the storage battery 4 is fully charged can be maintained.

Also, if the switch is switched to discharging during charging (step 8)
46: NO, step S37: discharge), step S5
Since the tc flag is reset in step S2, the charging time tc obtained up to that point is not written (step S4
9), the total charging time 1c until the storage battery 4 was fully charged last time is still held in the nonvolatile memory 9.

In this way, by taking into consideration the variations in the Class II flow due to individual Mt, more accurate Qo expression display can be achieved.

In this embodiment, the charging time tc is written in the non-volatile memory 9, but since the control calculation unit 5 is in operation during charging and after full charging, it may be written in other storage means. . That is, since the storage battery 4 is usually recharged from the time it starts discharging after full charge until the storage battery 4 is completely empty, the charging time tc measured when the storage battery 4 is fully charged from an empty state is is used during charging in steps 837 to S59 (N in step 859).
o, charged in step S37), set 01 to Q1 as described above.
=d t xQHAX / tc and use this calculation result Q1 in step S4+, it is possible to further reduce errors due to variations in charging current.

Furthermore, in each of the above embodiments, data is not written in the non-volatile memory 9 during the first tIi battery, so accuracy is not achieved. The first data (jc.

By storing tD), the user can use the torpedo 8 device with relatively accurate display from the first use. In this case, regarding the second actual pus case, QX] and Q20 do not need to be indices indicating accurate standard amounts, but may be appropriate values.

Furthermore, as described above, in the first and second embodiments, the data (tc, to) stored in the nonvolatile memory 9 is updated every time the storage battery 4 is charged until it becomes empty after being fully charged. Therefore, even if the storage battery capacity deteriorates, for example, a new Q+,
Ql can be updated and accuracy can be maintained.

Roughly speaking, Qo may be calculated in units of ampere hours or the like, and only the display may be converted to units of % or hours and displayed.

Further, as the unit time dt, for example, 1 second, 1 minute, or any other suitable time during design can be set.

[Effects of the Invention] As explained above, according to the present invention, an index indicating the accumulation field per unit time during the current charging is calculated from the previous discharge state by so-called learning, and the new intermediate Since the index indicating the remaining amount obtained based on the index indicating the charge In per hour is displayed, the display state of the index indicating the stack volume corresponds to the actual charging state of the storage battery, for example, when the index 100 is displayed. This makes it possible to match the time when the storage battery becomes fully charged, making it possible to display highly accurate information. Furthermore, since the discharge time is written in the non-volatile memory, even if the storage battery becomes empty and each means becomes inoperable, the discharge time is maintained as it is.

In addition, an index indicating the amount of charge per medium time during the current charging is calculated from the previous charging state, and an index indicating the remaining amount obtained based on this new 0-output index is displayed. , the influence of variations in charging current can be reduced, and display accuracy can be further improved.

[Brief explanation of drawings]

Fig. 1 is a block configuration diagram of an electric device to which the battery remaining amount display device according to the present invention is applied, Fig. 2 is a flowchart showing the first embodiment, and Fig. 3 shows a second example. Flowchart, FIG. 4 is a diagram showing a conventional display method, FIG. 5 is a block configuration diagram illustrating a conventional battery remaining amount display device,
FIG. 6 is a flowchart explaining its operation, and FIG. 7 is a block diagram explaining another conventional battery remaining amount display device. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifier, 3... Charging circuit, 4... Storage battery, 5... Control section, 6... Load, 7... Display section, 8...・・DC-DC converter, 9
...Nonvolatile memory, 10...Temperature sensor, 11.
...Temperature measurement circuit, 12...A/D converter.

Claims (1)

[Claims] 1. In a battery remaining capacity display device that displays an index indicating the remaining capacity of the storage battery obtained by sequentially adding up indices indicating the amount of charge per unit time during charging, A discharge time measuring means for measuring the discharge time required until the battery becomes empty; a non-volatile memory for writing the obtained discharge time;
When charging the storage battery from empty to fully charged, an index indicating the amount of charge per unit time is calculated from the discharge time of the previous discharge stored in the non-volatile memory, and the calculated index is calculated per unit time of the previous charge. 1. A battery remaining amount display device comprising: a control means used in place of an index indicating the amount of charge of the battery. 2. In a battery remaining capacity display device that displays an index indicating the remaining capacity of the storage battery obtained by sequentially adding an index indicating the amount of charge per unit time during charging, the time required for the storage battery to go from empty to fully charged A charging time measuring means for measuring the charging time, a memory for writing the obtained charging time, and an index indicating the amount of charge per unit time calculated from the charging time stored in the memory at the time of charging the storage battery. and a control means for using the calculated index in place of the amount of charge per unit time at the time of previous charging.