JPH0526987A - Residual-capacity measuring apparatus for secondary-battery pack - Google Patents

Abstract

PURPOSE:To measure the remaining amounts of capacities of a secondary battery or a secondary-battery pack. CONSTITUTION:A secondary battery 11 is contained in a secondary-battery pack 10. A current (i) is determined by a charge current i1 which is supplied to the secondary battery 11 from a battery charger, and a discharging current i2 which is discharged from the secondary battery 11 and supplied to a host apparatus. The current (i) which flows into the secondary battery 11 is converted into a voltage across the terminals of a resistor R. A hexadecimal code A which is used for computing the residual capacity of the secondary battery is formed with a differential amplifier 14 and an A/D converter 15 at a specified sampling period based on the voltage V across the terminal. The computation is performed with a computing circuit 16 by using the hexadecimal code A. The residual capacity data B corresponding to the residual capacity of the secondary battery 11 are outputted into the external host apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery pack residual capacity measuring device for measuring and outputting the residual capacity of a secondary battery to be stored.

[0002]

2. Description of the Related Art A rechargeable secondary battery such as a nickel-cadmium battery, a nickel-hydrogen battery, a lead battery, and a lithium secondary battery, or a secondary battery pack containing a plurality of such secondary batteries is economical. It is a notebook computer, notebook word processor,
It is used as a power source for various portable small and lightweight electronic devices such as a handy terminal, a portable telephone, a portable magnetic tape reproducing device, an electric shaver or a transceiver.

Conventionally, the measurement of the remaining capacity (remaining capacity) of the secondary battery pack has been performed in the case of measuring the terminal voltage of the battery which drops with discharge or in the case of constant current load (discharge). It was done by integrating the discharge time.

[0004]

However, in the case of the former method, the state of the secondary battery before discharging, for example, the difference in charging method and the difference in charging state (whether the battery is completely charged before starting charging). ), The voltage between terminals may be different, so that the measurement accuracy is not high. Also,
In the latter method, if the discharge current is not constant,
It is difficult to accurately identify the discharge current, and it is difficult to measure the remaining capacity with high accuracy as in the former method. In addition, many of electronic devices that use a secondary battery or a secondary battery pack as a power source have a specific device (for example,
Except for electric shavers, etc., a dedicated charger is used for charging, so the amount of charge is measured on the charger side and the amount of discharge is measured individually on the device side. For this reason, it is difficult to measure the total remaining battery capacity,
There is a drawback that the remaining capacity cannot be measured with high accuracy.

The cause of this is that even if the discharge state of the secondary battery fluctuates significantly with the passage of time, a measuring method that does not consider the operating state of such secondary battery is adopted. is doing.

In view of this, if the amount of increase / decrease in the capacity of the secondary battery is integrated at regular time intervals and the remaining capacity data corresponding to the remaining capacity of the secondary battery at that time is obtained, this remaining capacity is calculated. It is clear that the accurate remaining capacity of the secondary battery can be known based on the data.

An object of the present invention is to integrate the increase / decrease amount of the capacity of the secondary battery at regular time intervals and obtain the remaining capacity data corresponding to the remaining capacity of the secondary battery at that time. is there.

[0008]

The means of the present invention are as follows. The data output means 1 (see the block diagram of FIG. 1, the same applies hereinafter) changes the current flowing into the accommodated secondary battery and the current flowing out of the secondary battery into and out of the secondary battery. The corresponding data (for example, digital code) is output. The remaining capacity data output means 2 integrates the amount of increase / decrease in the capacity of the secondary battery at regular time intervals based on the data output from the data output means 1, and the value obtained by the integration is stored in the secondary battery. The remaining capacity data corresponding to the remaining capacity is output.

[0009]

[Operation] The operation of the means of the present invention is as follows. From the data output means 1, data such as a digital code corresponding to the current flowing in and out of the secondary battery is output momentarily at fixed time intervals. The remaining capacity data output means 2 is
For example, the amount of increase or decrease in the capacity of the secondary battery is calculated from the data input this time and the data input last time. Then, the calculated increase / decrease amount is integrated every time new data is input from the data output means 1, and the integrated value is output as the remaining capacity data. Therefore, it is possible to obtain the remaining capacity data corresponding to the remaining capacity of the secondary battery at that time by accumulating the increase / decrease amount of the capacity of the secondary battery at regular time intervals.

[0010]

[Examples] One example will be described in detail below with reference to FIGS. FIG. 2 is a diagram showing the configuration of the internal circuit of the secondary battery pack. In the figure, the secondary battery pack 10
A secondary battery 11 made of, for example, a nickel-cadmium battery or the like is housed inside. The plus terminal of the secondary battery 11 is connected to the plus electrode 12 for charging formed in the secondary battery pack 10 via the resistor R.
On the other hand, the negative terminal of the secondary battery 11 is the negative electrode 1 for charging, which is also formed in the secondary battery pack 10.
Connected to 3.

One end b of the resistor R is connected to the non-inverting input terminal (+) of the differential amplifier 14 composed of an operational amplifier (operational amplifier), and the other end a.
Is connected to the inverting input terminal (-) of the differential amplifier 14. The output V _OUT of the differential amplifier 14 is A
The signal is input to the analog signal input terminal of the / D converter (analog / digital converter) 15. This differential amplifier 14
, As described in detail later, the value of both ends of the potential difference V of the resistor R (positive, negative, 0) and outputs an output voltage V _{OU T} corresponding to. 8 output from this A / D converter 15
The bit digital data A is input to an integrating circuit 16 including a microprocessor or the like. The integrating circuit 16 measures the remaining capacity of the secondary battery 11 based on the digital data A input at a sampling period of a fixed time. Then, the data B corresponding to the remaining capacity of the battery capacity of the secondary battery 11 measured by the integrating circuit 16 is GP-IB (General Purpos).
It is designed to be output to a host device (not shown) such as a personal computer or a handy terminal via a parallel data input / output interface such as an e interface bus).

Further, the plus electrode 12 formed in the secondary battery pack 10 is connected to the diode D _i1 via the resistor r.
And the anode of the diode D _i3 . The anode of the diode D _{i1 and} the anode of the diode D _i2 are connected to the positive terminal of a charger (not shown), and the diode D _i1 is connected to the positive terminal of the charger.
The cathode of _{i2 and} the cathode of the diode D _i3 are both connected to the power supply circuit of the host device. Then, the negative electrode 1 formed in the secondary battery pack 10
3 is connected to the negative terminal of the charger.

Next, the operation of the remaining capacity measuring process of the secondary battery 11 in the embodiment having the above-mentioned structure will be described. When the current flowing through the resistor R is i, when i> 0, that is, when the current i flows from point b to point a shown in FIG. 2, the secondary battery 11 is in a charged state. .. Further, when the current i is i <0, that is, when the current i flows from the point a to the point b, the secondary battery 11 is in a discharged state. Therefore, by measuring the potential difference V between the points a and b, it is possible to know whether the secondary battery 11 is being charged or discharged, and i = V / obtained from Ohm's law. The value of charge / discharge current can be known from R.

Further, in measuring the potential difference V, the input / output conditions of the differential amplifier 14 are set in advance when V _iN = V = 0, V _OUT = V _TH V _iN = V> 0, and V _OUT = V _TH + | V | (during charging) When _ViN = V <0, V _OUT = V _TH − | V | (during discharging) is set in advance, and the difference is calculated by the A / D converter 15. This is performed by reading the analog output V _OUT of the dynamic amplifier 14 as 8-bit digital data (hexadecimal code) A. In addition, V _iN is an input voltage of the differential amplifier 14, V _OUT is an output voltage of the differential amplifier 14, and V _TH is an input offset voltage of the differential amplifier 14.

In this embodiment, an 8-bit A / D converter 15 is used. In this case, first, V
_iN = V = 0, that is, when the secondary battery 11 is not charged / discharged and the output of the differential amplifier 14 is equal to the input offset voltage (V _OUT = V _TH ), A /
D converter 15 is "80H" (H indicates a hexadecimal value)
Is output as digital data A. Then, the A / D converter 15 sets V _iN = in accordance with the change in the potential difference V, using “80H” as a reference value.
When V> 0, 80H <A ≦ FFH, and when V _iN = V <0, 00H ≦ A <80H is quantized and output.
The digital data A of hexadecimal code in the range of 00H to FFH is set to be output.

Then, the integrating circuit 16 integrates the digital data A of the hexadecimal code output from the A / D converter 15 using the following equation (1),

[0017]

[Equation 1]

The integrated value B, that is, the remaining capacity data B of the battery capacity of the secondary battery 11 is obtained. In the equation (1), t is an integration time interval of the integration circuit 16 and is a time equal to the sampling cycle of the A / D converter 15.

Also, the displacement of the remaining amount data B is B _t = B _t-1 + (A by charging or discharging, where B _t is the integrated value obtained this time and B _{t - 1} is the previously obtained integrated value. -80H) _t , of course, (A-80
H)> 0, the integrated value B increases, and (A-
Since 80H) <0, the integrated value B decreases.

If the initial value of the integrated value B when the secondary battery 11 is in the completely discharged state is 0 (B ₀ = 0), the value of the integrated value B increases with charging, and Saturates at the maximum value B _max according to the capacity of.

Next, the secondary battery 11 is set to the maximum value B.
_{When the} battery is charged up to _{max and} then discharged, the integrated value B gradually decreases and finally becomes zero. By reading the value of the integrated value B which changes with the charging / discharging of the secondary battery 11 as described above at a predetermined time interval, the remaining capacity of the secondary battery 11 can be determined. By displaying the screen on a display device or the like, the user can be notified of the remaining capacity of the secondary battery 11 in real time.

3 (a) to 3 (d), the potential difference V associated with charging / discharging of the secondary battery 11 and the differential amplifier 1 are shown.
4, the output voltage V _OUT , the hexadecimal code digital data A output from the A / D converter 15, and the integrating circuit 1
FIG. 6 is a diagram showing a graph of a temporal history of an integrated value B that is integratedly output by 6; In the initial state (t = 0), the secondary battery 11 is in a completely discharged state. Then, the period from the integration time points t _{1 to} t ₄ corresponds to the period in the charged state, and at the integration time point t ₄ , the secondary battery 11 is fully charged (fully charged). Next, since neither charging nor discharging is performed at the integration time point t ₅ , the state at the integration time point t ₄ is maintained. Furthermore, the duration of the integration time t ₆ ~t ₉ corresponds to the period of the discharge state, the at integration time t ₉ the secondary battery 11
Is in a completely discharged state. That is, the integrated value B corresponding to the remaining capacity (remaining capacity) of the secondary battery 11 is 0 ≦ B ≦ B _max.
Changes in the range of.

In the above description, for ease of understanding, a case has been described in which charging and discharging of the secondary battery 11 are performed separately and independently, but in practice, the charger and the host device are actually used. Both of the secondary battery 11
Often used by connecting to
For the current i flowing through the resistor R, it is necessary to consider both the charging current i ₁ supplied from the charger and the discharging current i ₂ supplied from the secondary battery 11 to the host device as shown in FIG. Therefore, the current i is the difference (i = i ₁ −i ₂ ) between the charging current i ₁ and the discharging current i ₂ .

As a result, when i ₁ > i ₂ , i> 0
Therefore, the host device can be used while charging the secondary battery 11. Conversely, larger than the consumption current is the current supply capacity of the charger of the host device, i ₁ <In the case of i ₂ are, i <0, and the current supply is the battery and the charger to the host device 11 Therefore, the secondary battery 11 is used while being substantially discharged. Furthermore, when i ₁ = i ₂ ,
The current i ₂ is supplied to the host device without changing the battery capacity of the secondary battery 11.

As described above, the current flowing in or out of the secondary battery 11 becomes equal to the current i flowing in the resistor R no matter how it is used.
The charging current i ₁ or the discharging current i ₂ for the secondary battery 11 can be measured, and the remaining amount of the battery capacity of the secondary battery 11 can be measured in real time by the integrating circuit 16 and output to the host device. It will be possible. The integrating circuit 16 can be configured by, for example, a digital logic circuit in which a gate circuit or a flip-flop is combined, or a one-chip microprocessor.

[0026] In the above embodiment, after once converted into digital data A, is performed the integration, without having to be limited to this, the analog operation circuit, an integrated directly using analog data V _{ou t} It is also possible to do
The remaining data of analog data may be output to the host device.

[0027]

According to the present invention, it is possible to obtain the remaining capacity data corresponding to the remaining capacity of the secondary battery at that time by accumulating the increase / decrease amount of the capacity of the secondary battery at regular time intervals. Based on this remaining capacity data, it becomes possible to know the accurate remaining capacity of the secondary battery.

[Brief description of drawings]

FIG. 1 is a block diagram of a residual capacity measuring device for a secondary battery pack of the present invention.

FIG. 2 is a diagram showing a configuration of an internal circuit of a secondary battery pack.

3 (a) to (d) are potential difference V due to charging / discharging of the secondary battery 11, output voltage V _OUT of the differential amplifier 14, and A /
FIG. 3 is a graph showing the time history of the hexadecimal code digital data A output from the D converter 15 and the integrated value B integrated and output by the integrating circuit 16.

[Explanation of symbols]

 1 data output means 2 remaining capacity data output means

Claims (1)

Claim: What is claimed is: 1. A data output for outputting data corresponding to a current flowing into a secondary battery and a current flowing out of the secondary battery from a current flowing out from the secondary battery. Means and the amount of increase or decrease in the capacity of the secondary battery is integrated at regular intervals based on the data output from the data output means, and the value obtained by the integration corresponds to the remaining capacity of the secondary battery. A remaining capacity measuring device for a secondary battery pack, comprising: a remaining capacity data output means for outputting as remaining capacity data.