JPH0137702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the capacity of an automotive storage battery.

If you can know the current capacity of the storage battery (hereinafter referred to as battery) while driving a car,
The driver will be able to take prompt measures depending on the situation, such as cutting off the electrical load within a range that does not affect driving if a reduction in capacity is detected, and this will enable drivers to take prompt action to prevent problems such as battery build-up on the road. Breakdowns can be prevented. Furthermore, by knowing the capacity reduction due to deterioration, it is possible to predict to some extent when to perform maintenance on the battery.

However, in order to accurately determine the capacity of a battery, it is necessary to completely discharge the battery. Therefore, the battery capacity must be detected on-board, or constantly monitored while driving, and the results can be communicated to the driver. Previously, no such method and apparatus existed for this purpose.

As a method for detecting an abnormality in a vehicle battery, methods such as detecting the specific gravity and liquid level of battery liquid have been conventionally used, but this type of method has the following problems. In other words, (a) Of course, when a large current is flowing, but when a current similar to the charging/discharging current in normal use is flowing, the response of the specific gravity of the battery liquid to the battery capacity is extremely poor, and when the battery is installed in a vehicle, In this case, a certain relationship does not hold between capacity and specific gravity. (c) Malfunctions may occur due to vehicle vibration; (d) Errors may occur due to fluid replacement; (e) Electrical analog signal detection results It is difficult to obtain as , etc.

Therefore, the present invention solves the above-mentioned disadvantages of the prior art, and an object of the present invention is to provide a capacity detection method that can accurately detect the capacity of an automobile battery even during driving.

A feature of the present invention that achieves the above-mentioned object is to detect battery discharge currents at a plurality of points in time showing different values during large current discharge and battery terminal voltages at the time of each discharge current outflow, and to detect the detected currents and voltages. Calculate the dead short current of the battery at the time of short circuit from the value, and calculate the capacity of the battery from the calculated dead short current using a function that expresses the correlation between the battery capacity and the dead short current, which has been experimentally determined in advance. It is in.

The theoretical basis of the present invention will be explained below with reference to the drawings.

Generally, there is a relationship as shown in FIG. 1 between the terminal voltage V _B of a discharge battery and the discharge current I _B. In the figure, the horizontal axis is the discharge current I _B , the vertical axis is the terminal voltage V _B , and the solid line a is the discharge characteristic (V _B - I _B characteristic)
are shown respectively. In a large current discharge area such as when driving the starter (during cranking),
This V _B − I _B characteristic can be approximated almost by a straight line, and therefore the terminal voltage when the discharge current is I ₁ is
V ₁ and the terminal voltage when the discharge current is I ₂ is V ₂ , then
The internal resistance r of the battery is determined from the slope of the above straight line. That is, it is expressed by the following equation.

r=V ₂ −V ₁ /I ₁ −I ₂ ……(1) Also, the electromotive force E ₀ of the battery can be obtained from the value obtained by extrapolating the straight line section of Fig. 1 to I _B =0,
Therefore, it is expressed by the following equation.

E ₀ =V ₁ +I ₁ (V ₂ -V ₁ )/I ₁ -I ₂ ...(2) Furthermore, when the battery is short-circuited, the depletion current I _S changes along the straight line section in Figure 1 up to V _B = 0. This is an extrapolated value, which can also be obtained from equations (1) and (2) as shown in the following equation.

I _S = E ₀ /r = I ₁ V ₂ −V ₁ I ₂ /V ₂ −V ₁ ...(3) The battery discharge current I _B and the terminal voltage V _B during cranking are not constant, and the second As shown in the figure,
It varies greatly depending on the rotation angle of the crankshaft. In the figure, A shows the waveform of the terminal voltage V _B and B shows the waveform of the discharge current I _B , respectively. Assuming that the discharge current when starting the starter is the starting current, this starting current is shown as I ₁ in Figure 2, and the terminal voltage at that time is
Represented by V ₁ . In addition, if the minimum current from the time when this starting current _I1 flows until the crankshaft rotates 180° _{is I2} , and the terminal voltage at this time is _V2 , then the battery depletion current _Is can be calculated as follows. It can be obtained from equation (3). As mentioned above, the minimum current required while the crankshaft rotates 180° is obtained when the engine is a 4-cylinder engine, and the minimum current obtained while the crankshaft rotates 120° is obtained when the engine is a 6-cylinder engine. become. Further, this angle is different for other numbers of cylinders.

In this way, the present invention actively utilizes the current and voltage fluctuations during cranking, and calculates the starting current I ₁ , which is the maximum current during cranking, and the battery terminal voltage V ₁ when I ₁ flows. , by measuring _the minimum current I ₂ while the crankshaft rotates 180° from startup to 180° with 4 cylinders, for example, during a large current discharge. The purpose is to measure the discharge currents of different values and the terminal voltages at the time of each discharge current outflow, and thereby to determine the battery depletion current _IS . Note that the number of measurement points for the discharge current and terminal voltage is not limited to two, but may be any number of points.

Now, the battery capacity and depletion current I _S
There is a correlation as shown in the following equation.

Capacity=AI _S +B (4) However, A and B are constants determined by the type of battery, and are hardly affected by the battery liquid temperature and battery liquid level.

Discharge current I ₁ and I ₂ during cranking, terminal voltage
The formula for calculating battery capacity from V ₁ and V ₂ is:
It is given by the following equation by substituting equation (3) into equation (4) above.

Capacity = A (I ₁ V ₂ - _{V 1} I ₂ /V ₂ - V ₁ ) + B...(5) Figure 3 shows a battery set to the specified capacity cranked in a vehicle, and formula (5) FIG. 4 is a diagram comparing the experimental results obtained by detecting battery capacity using the battery and the true battery capacity. In the figure, the horizontal axis shows the calculated capacity, and the vertical axis shows the true capacity. The scales of the horizontal and vertical axes are the same, so the solid line b indicates the point where the calculated capacity matches the true capacity. Furthermore, the range between broken lines c and d represents the allowable error range.
During the experiment, batteries were tested for liquid levels at the upper limit display line level (F level), lower limit display line level (L level), liquid temperature at +15°C, and 0°C.
I used the one at -15℃ and the one at -15℃, but the third
As is clear from the figure, according to the present invention, the capacity can be detected with high accuracy without correction of the liquid level or liquid temperature.

Next, the present invention will be explained by examples.

FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. 5 is a circuit diagram showing FIG. 4 in more detail. In FIG. 4, 10 generates an output voltage e ₁ corresponding to the cranking current I _B
I _B detection circuit, 12 is a V _B detection circuit that generates an output voltage e ₂ corresponding to the battery terminal voltage V _B , 14 is an output voltage corresponding to the starting current at the start of cranking.
Consists of a peak hold circuit to detect e ₁
I ₁ detection circuit, 16 is a V 1 detection circuit consisting of a peak hold circuit for detecting the output voltage _{e 2 corresponding} to battery terminal voltage V 1 when starting current I ₁ flows, 18 is a V ₁ detection circuit that detects when the crankshaft is I ₂ detection circuit consisting of a peak hold circuit for detecting the output voltage e ₁ corresponding to the minimum current I ₂ during a rotation of 180°, 2
0 is the battery terminal voltage V ₂ when the minimum current I ₂ flows
₂₂ is an A/D detection circuit consisting of a peak hold circuit for detecting the output voltage e ₂ corresponding to
Converter, 24 is an arithmetic circuit consisting of a microcomputer programmed to calculate the above-mentioned formula (5), 26 is a D/A converter, and 28 is a battery charging/discharging current due to engine operation. 30 is a battery capacity during cranking calculated by the arithmetic circuit 24 and the calculation circuit 2.
8 is an addition circuit that adds the cumulative charge/discharge current value during engine operation, 32 is a monitor mechanism that displays battery capacity, and 34 is a detection circuit 14, 16, 1.
8 and 20 respectively represent control signal generation circuits that generate control signals for the arithmetic circuit 24 and charge/discharge electricity amount calculation circuit 28.

The configuration and operation of each circuit will be explained in detail below using FIG. 5.

The battery 40 is connected to a starter 42 via a starter cable 41 and an ignition switch 46 via a fusible link 44.
It is connected to the. Ignition switch 46
is equipped with an ignition terminal (IG terminal) 46a and a starter terminal (ST terminal) 46b, and during cranking, the IG terminal 46a is first turned on, and then the ST terminal 46b is turned on. As a result, current flows through the excitation coil 48a of the starter relay 48, turning on the contact 48b, driving the magnet switch 42a of the starter 42, and supplying the cranking current from the battery 40 to the starter 42.
I _B flows and the engine starts rotating. The cranking current I _B at this time is the battery 40 and starter 4
If the wiring resistance r _S between the two is known, it can be determined by the following equation by knowing the difference between the battery terminal voltage V _B and the starter terminal voltage V _S.

I _B =V _B −V _S /r _S ...(6) Operational amplifier 50 and resistors R ₁ , R ₂ ,
A differential amplifier circuit consisting of R ₃ and R ₄ constitutes an I _B detection circuit 10 for detecting this cranking current I _B , and its output voltage e ₁ is R ₁ = R ₂ , R ₃ = _R4
Then, the value corresponds to the cranking current I _B as expressed by the following equation.

e ₁ = R ₄ (V _B - V _S ) / R ₁ = R ₄ · r _S / R ₁ · I _B ... (7) Operational amplifier 52 and resistor R ₁₉ ,
The non-inverting amplifier circuit composed of R ₂₀ constitutes the V _B detection circuit 12 that detects the battery terminal voltage V _B , and its output voltage e ₂ corresponds to the battery terminal voltage V _B as expressed by the following equation. value.

e ₂ = R ₁₉ + R ₂₀ / R ₁₉ · V _B ... (8) The circuit consisting of transistor Tr ₅ , capacitors C ₆ , C ₇ , diode D ₇ , and resistors R ₂₉ , R ₃₀ , and R ₃₁ generates control signals. In circuit 34, I ₁ detection circuit 14 and
This is a part that forms a control signal for the _V1 detection circuit 16. IG terminal 4 of ignition switch 46
When 6a turns on, the transistor
Since the base current of Tr ₅ does not flow, this transistor Tr ₅ is off, so current flows from the IG terminal 46a to the resistor R ₃₀ and the capacitor C ₆ , and the resistor R ₃₁
A positive differential pulse is generated at both ends of . however
Let R ₃₀ ≪ R ₃₁ . Next, when the ST terminal 46b of the ignition switch 46 is turned on, a base current flows through the transistor Tr ₅ through the resistor R ₂₉ and the transistor Tr ₅ is turned on. Next, when cranking is finished and the ST terminal 46b is turned off, the base current of the transistor Tr ₅ is cut off, this transistor Tr ₅ is turned off, and current flows from the IG terminal 46a to the resistor R ₃₀ and the capacitor C ₆ . A positive differential pulse is generated across the resistor _R31 . In this way the ignition voltage (IG voltage)
The positive differential pulses formed at the rise and fall of the starter voltage (ST voltage) are used as control signals for the _I1 detection circuit 14 and the _V1 detection circuit 1.
6 is applied. Note that capacitor _C7 is for preventing malfunction due to noise.

Operational amplifier 54, diode D ₁ ,
Transistor Tr ₁ , field effect transistor (FET) F ₁ , F ₂ , F ₃ , capacitor C ₁ , resistor R ₅ ,
The peak hold circuit composed of R ₆ , R ₇ , and R ₈ constitutes an I ₁ detection circuit 14 that detects the starting current I ₁ immediately after cranking. The aforementioned differential pulse from the control signal generation circuit 34 is generated by the field effect transistor _F2.
and the gate of transistor Tr ₁
A base current flows through resistor _R5 to turn on this transistor _Tr1 . As a result, a collector current flows through the resistor _R6 , so that the gate voltage of the field effect transistor _F1 becomes zero potential. As a result, the output of the operational amplifier 54 becomes open, and at the same time, the capacitor _C1 is discharged. The resistor _R7 is provided to open the output of the operational amplifier 54 before the discharge of the capacitor _C1 . In this state, when the ST terminal 46b of the ignition switch 46 is turned on and cranking current I _B flows, I _B
The output voltage e ₁ of the operational amplifier 50 of the detection circuit 10 rises, and the capacitor C ₁ is charged by the allowable output current I _MAX of the operational amplifier 54, and if the slew rate of the operational amplifier 54 is ignored, there is no time delay. e ₁ = e ₃ . Here, e ₃ is the output voltage of the operational amplifier 54. Start-up ends and cranking current
Even if I _B starts to decrease, in the state where e ₁ < e ₃ , the input stage of the operational amplifier 54 is not conductive, so the capacitor C ₁ maintains the maximum voltage, which causes a voltage to be applied to the gate of the field effect transistor F ₃ . is applied. As a result, a drain current flows through this field effect transistor _F3 via the resistor _R8 ,
An output voltage corresponding to the starting current I ₁ is obtained from this I ₁ detection circuit 14 .

Operational amplifier 56, diode _D5 ,
Transistor Tr ₃ , field effect transistor F ₇ ,
F ₈ , F ₉ , capacitor C ₃ , resistor R ₂₁ , R ₂₂ , R ₂₃ ,
The peak hold circuit consisting of R ₂₄ has a starting current I ₁
A V ₁ detection circuit 16 is configured to detect the battery terminal voltage V ₁ when V 1 flows. The above-mentioned differential pulse from the control signal generation circuit 34 is applied to the gate of the field effect transistor _F8 , and at the same time causes a base current to flow through the transistor _Tr3 through the resistor _R21 , turning on this transistor _Tr3 , and turning on the resistor Tr3.
A collector current flows through R ₂₂ to bring the gate voltage of the field effect transistor F ₇ to zero potential. This opens the output of the operational amplifier 56, and at the same time, the drain current of the field effect transistor _F8 via the resistor _R23 causes the capacitor _{C3 to}
is charged. Note that this resistor _R23 is provided to open the output of the operational amplifier 56 before the capacitor _C3 is charged. In this state, turn off the ignition switch 46.
When the ST terminal turns on and cranking current I _B flows, the battery terminal voltage V _B decreases and
Operational amplifier 52 of V ₁ detection circuit 16
The output voltage e ₂ of the operational amplifier 56 also decreases, and the capacitor C ₃ is discharged by the allowable output current I _MAX of the operational amplifier 56.
If you ignore the slew rate of e ₂ without time delay
= e ₄ . Here, e ₄ is the output voltage of the operational amplifier 56. Even if the battery terminal voltage V _B starts to rise after startup has finished, the input stage of the operational amplifier 56 will not conduct in a state where e ₂ > e ₄ , so the capacitor C ₃ will connect the lowest voltage to the field effect transistor F ₉ . A voltage is applied to the gate. This causes the field effect transistor _F9 to resist
A drain current flows through _R24 , and an output voltage corresponding to the battery terminal voltage _V1 when the starting current _I1 flows is obtained from the _V1 detection circuit 16.

Operational amplifiers 58, 60, diodes D ₃ , D ₄ , capacitor C ₅ , resistors R ₁₃ , R ₁₄ , R ₁₅ ,
The circuit composed of R ₁₆ , R ₁₇ , and R ₁₈ is a part of the control signal generation circuit 34 that forms control signals for the I ₂ detection circuit 18 and the V ₂ detection circuit 20. Considering the period from when the ST terminal 46b of the ignition switch 46 is turned on until the starting current I ₁ is held at its peak, the output voltage e ₁ of the operational amplifier 50 of the I _B detection circuit 10 and the I ₁ detection circuit 1
4 operational amplifier 54 output voltage e ₃
(gate voltage of field effect transistor F ₃ ), there is a relationship e ₁ = e ₃ , and due to the circuit configuration, the output voltage e ₅ of the operational amplifier 58 is R ₁₃ = R ₁₄ ,
If R ₁₅ = R ₁₆ , it is expressed as the following formula, so e ₅
=0.

e ₅ = R ₁₅ (e ₁ − e ₃ )/R ₁₃ (9) When the starting current I ₁ is held at its peak, the output voltage e ₃ of the operational amplifier 54 becomes a constant value, and the cranking current Since I _B starts to decrease, the output voltage e ₁ of the operational amplifier 50
decreases. That is, in this case, the output voltage e ₅ of the operational amplifier 58 becomes e ₅ <0, and the output voltage e ₆ of the zero crossing detection circuit mainly composed of the operational amplifier 60 saturates to the positive side. And at the rise of this output voltage e ₆ , capacitor C ₅
A current flows through the resistor R18, and a positive differential pulse is generated across the resistor _R18 . The positive differential pulse formed at the moment when the starting current I ₁ is detected is applied as a control signal to the I ₂ detection circuit 18 and the V ₂ detection circuit 20.

Operational amplifier 62, diode D ₂ ,
Transistor Tr ₂ , field effect transistor F ₄ ,
F ₅ , F ₆ , capacitor C ₂ , resistor R ₉ , R ₁₀ , R ₁₁ , R ₁₂
The peak hold circuit constitutes an I ₂ detection circuit 18 that detects the minimum current I ₂ from startup until the crankshaft rotates 180 degrees. The above-mentioned differential pulse from the control signal generation circuit 34 is applied to the gate of the field effect transistor _F5 , and at the same time, a base current is caused to flow through the transistor _Tr2 through the resistor _R9 to turn on the transistor _Tr2 , and the resistor R _Ten
A collector current is caused to flow through F4 to bring the gate voltage of the field effect transistor _F4 to zero potential. As a result, the output of the operational amplifier 62 becomes open, and at the same time, the capacitor _C2 is charged by the drain current of the field effect transistor _F5 via the resistor _R11 . Note that this resistor R ₁₁ is provided to open the output of the operational amplifier 62 before the capacitor C ₂ is charged. When the cranking current I _B starts to decrease in this state, the output voltage e ₁ of the operational amplifier 50 of the I _B detection circuit 10 decreases, and the capacitor C ₂ is discharged by the allowable output current I _MAX of the operational amplifier 62. , if the slew rate of this operational amplifier 62 is ignored, e ₁ =e ₇ with no time delay. Here, e ₇ is the output voltage of the operational amplifier 62. Even if the crankshaft rotation angle exceeds a certain angle and the cranking current I _B begins to increase, the input stage of the operational amplifier 62 will not conduct when e ₁ > e ₇ , so the capacitor C ₂ will maintain the minimum voltage. However, a voltage is applied to the gate of field effect transistor _F6 . As a result, a drain current flows through the field effect transistor F ₆ through the resistor R ₁₂ , and an output voltage corresponding to the minimum current I ₂ from the start until the crankshaft rotates 180° is obtained from the I ₂ detection circuit 18. It will be done.

Operational amplifier 64, diode D ₆ ,
Transistor Tr ₄ , field effect transistor F ₁₀ ,
R ₁₁ , F ₁₂ , capacitor C ₄ , resistor R ₂₅ , R ₂₆ , R ₂₇ ,
The peak hold circuit consisting of R ₂₈ has a minimum current I ₂
A V ₂ detection circuit 20 is configured to detect the battery terminal voltage V ₂ when V 2 flows. The aforementioned differential pulse from the control signal generation circuit 34 is applied to the gate of the field effect transistor _F11 , and
The base current flows through the transistor Tr ₄ through the resistor R ₂₅ to turn on this transistor Tr ₄ , and the resistor
A collector current is caused to flow through _R26 to bring the gate voltage of the field effect transistor _F10 to zero potential. As a result, the output of the operational amplifier 64 becomes open, and at the same time, the capacitor _C4 is discharged. The resistor _R27 is provided to open the output of the operational amplifier 64 before the discharge of the capacitor _C4 . When the battery terminal voltage V _B starts to rise in this state, the output voltage e ₂ of the operational amplifier 52 of the V _B detection circuit 12 rises, and the capacitor C ₄ is charged by the allowable output current I _MAX of the operational amplifier 64. , if the slew rate of this operational amplifier 64 is ignored, e ₂ =e ₈ without any time delay. Here, e ₈ is the output voltage of the operational amplifier 64. Even if the rotation angle of the crankshaft exceeds a certain angle and the battery terminal voltage V _B begins to decrease, if e ₂ < e ₈ , the operational amplifier 6
Since the input stage 4 is not conducting, the capacitor C ₄ holds the lowest voltage and a voltage is applied to the gate of the field effect transistor F ₁₂ . As a result, a drain current flows through the field effect transistor _F12 via _{the resistor R28, and the output voltage corresponding to the battery terminal voltage V2 when the} minimum current I2 flows is this _V2 detection circuit 2.
It will be obtained from 0.

The starting current I ₁ obtained from each detection circuit 14, 16, 18, 20, the battery terminal voltage V ₁ at that time, the minimum current I ₂ , and the output voltage corresponding to the battery terminal voltage V ₂ at that time are determined by the A/D converter. 22, the signal is converted into a digital signal of predetermined bits, and sent to the arithmetic circuit 24.

The arithmetic circuit 24 is constituted by a well-known microcomputer including a microprocessor, memory, etc., and an arithmetic processing routine for performing the arithmetic operation of the above-mentioned equation (5) is programmed in the memory.
When a control signal is sent to the control signal generating circuit 34 via the line 66, this microcomputer executes the above-described arithmetic processing routine. That is, first, input data from the A/D converter 22 is read, then the calculation of equation (5) is performed using these input data, and the calculation result regarding the obtained battery capacity is sent to the D/A converter 26. and stores it in a predetermined area of memory. The calculation result regarding the battery capacity is held in the memory until the ignition switch 46 is turned off. D/A converter 2
6, the above-mentioned calculation result expressed as a digital signal is converted into an analog voltage signal.

For example, a rotation angle sensor 68 composed of a rotating disk 68a that rotates in synchronization with the crankshaft and a magnetic detection coil 68b, an ignition signal generation circuit 70, a diode _D8 , constant voltage diodes _D9 , _D10 , a resistor _R33 ,
The circuit composed of R ₃₄ and the AND gate 72 is
This is a portion of the control signal generation circuit 34 described above that forms a control signal for the arithmetic circuit 24. As is well known, the ignition signal generating circuit 70 generates an ignition signal every time the crankshaft rotates 180 degrees in a four-cylinder engine. A pulse is generated when the starting current I ₁ is held at its peak and the output voltage e ₆ of the operational amplifier 60 is saturated to the positive side and the first ignition signal is generated (that is, when the crankshaft rotates approximately 180 degrees). However, by sending this pulse as a control signal to the arithmetic circuit 24, the above-mentioned arithmetic processing routine is started to be executed.

Operational amplifier 74, resistors _R35 , _R36 ,
Field effect transistors F ₁₄ , F ₁₅ , capacitors C ₈ ,
_C9 constitutes the aforementioned charging/discharging electricity quantity calculation circuit 28 that integrates the charging/discharging current during running. Gate voltages are applied to the field effect transistors F ₁₃ and F ₁₄ by differential pulses applied from the control signal generation circuit 34 at the rise of the IG voltage and the fall of the ST voltage, so these field effect transistors are rendered conductive. Then, capacitors C ₈ and C ₉ are discharged. When the engine starts and starts running, the battery 40 is repeatedly charged and discharged, but the resistance R _f of the fusible link 44 is known, and this fusible link 44 on the ignition switch 46 side Assuming that the terminal voltage V _{f of}
The above-mentioned charging/discharging current is given by the following equation.

V _f −V _B /R _f ...(10) Here, if the result of equation (10) is positive, it means charging, and if it is negative, it means discharging.

Since both input terminals of the operational amplifier 74 are connected to both terminals of the fusible link 44 via resistors R ₃₅ and R ₃₆ , respectively, the output voltage e ₉ of the operational amplifier 74 is
If R ₃₅ = R ₃₆ and C ₈ = C ₉ , it is expressed by the following formula.

e ₉ = 1/R ₃₅・C ₈・∫(V _f −V _B ) dt ……(11) In other words, the output voltage e ₉ corresponding to the integrated value of the charging and discharging current of the battery 40 is calculated as the amount of electricity for charging and discharging. circuit 2
It will be obtained from 8.

Operational amplifier 76, resistors _R37 , _R38 ,
_R39 constitutes an adder circuit 30 for constantly detecting the battery capacity during engine operation, and the D/A
The battery capacity calculation value during cranking obtained from the converter 26 and the integrated value of charging/discharging current during engine operation obtained from the calculation circuit 28 are added. Therefore, the output voltage of the adder circuit 76 represents the current capacity of the battery 40, and is displayed by the capacity monitor mechanism 32, which includes, for example, a voltmeter.

The field effect transistors used in the circuit shown in FIG. 5 are all enhancement type, and the operational amplifiers 54, 56, 6
2, 64, 74, and 76 have input stages of field effect transistors.

In the above-mentioned embodiment, the current and voltage at startup and the minimum current and voltage at that time while the crankshaft rotates 180 degrees from startup are measured, but the method of the present invention measures the current and voltage at startup, but the method of the present invention measures You can focus on the maximum and minimum values of the pulsating current and voltage waveforms during ranking, or arbitrary values that are different from each other, or you can focus on the maximum and minimum values of the current and voltage waveforms that fluctuate during large current discharge, excluding during cranking. You may focus on values or arbitrary values that are different from each other.

As explained in detail above, the method of the present invention detects the battery discharge currents at multiple points in time showing different values during large current discharge and the battery terminal voltage when the discharge currents flow out, and calculates these detected currents and Calculate the dead short current when the battery is short-circuited from the voltage value, and substitute the dead short current calculated above into the equation that expresses the correlation between the battery capacity and dead short current, which has been experimentally determined in advance, to find the battery capacity. Therefore, the battery capacity can be accurately detected purely electrically without installing any sensors on the battery itself. In addition, since the current battery capacity can be known at all times, extremely beneficial effects can be obtained, such as preventing battery build-up and predicting maintenance timing.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between discharge current and battery terminal voltage, Figure 2 is a waveform diagram of battery discharge current and terminal voltage during cranking, and Figure 3 is a graph showing the relationship between the battery's true capacity and battery terminal voltage. FIG. 4 is a block diagram showing a schematic configuration of an embodiment of the present invention, and FIG. 5 is a circuit diagram showing the embodiment of FIG. 4 in more detail. 10...I _B detection circuit, 12...V _B detection circuit, 1
4...I ₁ detection circuit, 16...V ₁ detection circuit, 18...
...I ₂ detection circuit, 20...V ₂ detection circuit, 22...
A/D converter, 24... Arithmetic circuit, 26... D/
A converter, 28... Charge/discharge electricity amount calculation circuit, 30
... Addition circuit, 32 ... Battery capacity monitoring mechanism, 40 ... Battery, 42 ... Starter, 46
...Ignition switch.

Claims (1)

[Claims] 1. Detect the storage battery discharge current at multiple points in time showing different values during large current discharge and the storage battery terminal voltage at each discharge current outflow, and calculate the dead shot current at the time of a short circuit of the storage battery from the detected current and voltage values. A method for detecting the capacity of a storage battery for an automobile, characterized in that the capacity of the storage battery is calculated from the calculated depletion current using a function representing the correlation between the depletion current and the capacity of the storage battery determined experimentally in advance. .