JPH06331714A - Residual capacity meter for battery - Google Patents

Abstract

PURPOSE:To provide a residual capacity meter for battery in which an open circuit voltage system functioning only when the current value is zero is combined with an ammeter system functioning continuously when the current flows forward in the discharging direction so that the disadvantages are complemented and the residual capacity of battery is displayed while being expressed in terms of the residual capacity of a battery driver. CONSTITUTION:The residual capacity meter for battery comprises a terminal voltage detecting circuit 1, and a terminal current detecting circuit 2, and the current detecting section of device is constituted such that only the discharge current is measured as a positive value. Detected terminal voltage and discharge current are passed through low-pass filters 4, 5 and the signals, from which the AC component is removed, are fed along with a temperature detection signal to an A/D converter 9 through sample & hold circuits 6, 7, 8. A ROM 11 stores a function between the battery capacity and the open circuit voltage, a function of PeuKert formula for determining the accumulated capacity consumption, and various constants, and a muCPU 10 executes a program command received from the ROM 11 and delivers a calculated residual capacity through a latch circuit 12 thus indicating the residual capacity of battery in the form Km, for example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery remaining capacity meter suitable for detecting the remaining capacity of a battery used as a driving source for driving an electric vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, several different methods have been used as means for detecting the remaining capacity of a battery used as a drive source for running an electric vehicle. One is to measure the open circuit voltage of the battery, which is related to the capacity of the battery with a simple linear or quadratic function. A residual capacity meter based on this type of mutual relationship is described in Japanese Patent Laid-Open No. 57-149144.

Another method is to measure the output current of the battery while using the battery as an energy source. This type of detection is commonly known as Peukert
Take advantage of formula I ⁿ t = C. Where I is the discharge current, n is a value greater than 1 based on the battery type, t is the discharge time,
C is a constant. The Peukert equation shows the well-known phenomenon that the capacity of a battery decreases as the current increases. In Japanese Patent Laid-Open No. 59-56177, NASA technical note D-5773, 1970, etc., a remaining capacity meter of a method of measuring a battery current, converting the signal using the Peukert equation, and integrating the converted signal over time Some have been reported. The accumulated used capacity is continuously deducted from the current value of the battery capacity.

[0004]

However, the above two methods of measuring the remaining capacity of a battery have important drawbacks. The state-of-charge meter, which is based on the measurement of open circuit voltage, shows an accurate value only when the battery is near the equilibrium voltage with no current flowing. When an electric vehicle travels in a typical urban driving pattern, there are very few opportunities to measure the open circuit voltage. This is because the vehicle is always moving and the current is flowing from the battery. In the worst case, where the vehicle never stops at a stop before it runs out of battery capacity, after the vehicle has started a start, no measurements are taken until the battery capacity is exhausted.

Remaining capacity meters based on the method of converting the input current signal into a value that can be integrated over time using the Peukert equation are known to cause significant errors in normal operating conditions. With the battery fully charged by the usual method, the reset switch is turned on to restart the integration from the starting point. However, if the battery is to be partially charged, the remaining capacity meter must also be able to integrate current in the opposite direction of discharge, as it cannot be reset, for example if 60% of the capacity is charged by a quick charger. Unfortunately, it is difficult to perform reverse current integration accurately. This is because the charging efficiency of the battery changes unpredictably depending on the temperature, the depth of discharge, and the charging status. If the battery is partially charged and discharged continuously and the reset cannot be performed continuously, the degree of error will be severe.

In addition, all well-known types of remaining capacity meters cannot compensate for aging of the battery. The main reason is that the aging of the battery changes considerably depending on the situation in which the battery is charged or discharged. Another problem associated with the well-known remaining capacity meter is the display format in which output information is displayed. Typically, capacity is displayed as a fraction or percentage of battery capacity. This requires the user to know the interrelationship between the displayed value and the corresponding usage emitted by the battery-powered device for each output unit displayed. The discharge of the battery to zero capacity occurs earlier than the user expects before the correlation is confirmed by the user, which is a great inconvenience to the user.

The object of the present invention is to combine the convenient features of the two types of remaining capacity meters described above into one remaining capacity meter,
The purpose is to eliminate the disadvantages while making the best use of both. Further, the remaining capacity meter includes a simple method for correcting the aging of the battery. Finally, a method of converting the output of the remaining capacity meter into a value indicating the remaining usage of the battery-operated device is included. The converted output is in the form of kilometers for electric vehicles and hours of use for portable computers.

[0008]

A battery remaining capacity meter according to the present invention comprises a means for measuring a terminal voltage of a battery, a means for measuring a terminal current of a battery, a means for measuring a temperature of a battery, and the voltage / current It has means for calculating the remaining capacity from temperature, means for storing the calculation result, and means for displaying the calculation result. The remaining capacity is calculated by using the relationship between the open circuit voltage and the capacity defined in (2) When the current flows in the discharge direction of the battery of zero or more, the consumed capacity is integrated with respect to time, and the remaining capacity of the battery is calculated. The means of (1) and (2) for calculating the remaining capacity at the next moment by subtracting from the present value of is used complementarily. Continuous 2 obtained by means of (1)
The difference in the remaining capacity of the value can be obtained by integrating the consumed capacity with respect to time using the method (2). Using the integrated consumed capacity, the calculation function of the current battery capacity value in the means (1) is adjusted so that the capacity calculated values by the two means are numerically identical. Further, in the data calculation means (1) which functions when the current value is zero for a certain period of time, time and voltage data are accumulated in a memory device, the combination of accumulated time and voltage data is related by a logarithmic function, and the logarithmic function thereof Is used to calculate the open circuit voltage value for a time value of 10 ³ seconds or more. The data calculation means (2), which functions when the current flows in the discharge direction of the battery at zero or more.
In, the average current and temperature for a certain period of time were measured, the time corresponding to the lowest usable current corrected by the current value was calculated using the Peukert equation having an index corresponding to the measured temperature, and the battery capacity was measured. Calculate the time corresponding to the lowest usable current corrected by the temperature using the temperature correction function with the temperature at the standard, and multiply the minimum usable current value at the standard temperature by the correction time by the current and temperature. Accordingly, it has a means for integrating the consumed capacity in a certain fixed time. During operation of the battery-operated device, the voltage and current and temperature of the battery are continuously measured, the data is analyzed to calculate the existing battery capacity, and the value is multiplied by the maximum drivable amount of the device per unit battery capacity. It is characterized in that the maximum remaining usage amount is calculated and indicated to the indicating device.

[0009]

In the present invention, 2 having different calculation principles
Combining the two basic methods of calculating remaining capacity provides a remaining capacity meter with the best features of both methods. The first basic remaining capacity calculation method is a method using an open circuit voltage. In this method, the open circuit voltage is estimated and calculated at a constant time when the current value is zero. Using this open circuit voltage value, the current battery capacity is calculated from a simple function of the open circuit voltage value and the battery capacity. In an electric vehicle, such current measurements are zero only when the vehicle is started or when the vehicle is stopped in a traffic jam or stopped at a signal. These zero current measurements rarely occur, and in some cases are rare. Therefore, the total number of measured data is not enough as the basic data of the continuous capacity meter which responds continuously, but this kind of rare measured data shows the actual battery capacity under certain circumstances as described below. It can be used to provide an accurately measured reference point for another basic capacity meter which has the disadvantage of deviating from the value of.

The second basic remaining capacity detection method used in this application is a remaining capacity calculation method based on the principle of a coulometer. The coulometer type remaining capacity meter integrates the current flowing from the battery, and periodically subtracts the calculated integrated consumption capacity from the value of the battery capacity calculated or measured in advance.
As a well-known characteristic of a battery, there is a phenomenon that when the used current increases, the consumed capacity increases more than the increased current. In the present invention, in order to correct this, the Peukert's relation is used to correct the integrated current to perform integration and deduction. Temperature correction is also necessary and implemented. The coulometric remaining capacity meter using the deduction of the accumulated consumption capacity can accurately determine the actual battery capacity as long as the remaining capacity value at the start of the deduction process is accurate. The exact remaining capacity value at the start of deduction, ie the reference point, is provided by the open-circuit voltage-based remaining capacity meter which functions when the current is zero.

The present invention not only continuously provides an accurate value of the battery capacity, but also adjusts the capacity change with the aging of the battery by using the two types of remaining capacity meters. Peukert regardless of battery aging
The coulometer part of the remaining capacity meter, which uses the formula to calculate the current and temperature corrected integrated capacity values, will continue to be accurate.

Since the integrated capacitance is accurate in this way, this value can be used to correct a simple function representing the relationship between the open circuit voltage and the remaining capacitance in the first method. The value of the battery capacity is initially determined, for example, when starting an electric vehicle.
It is measured and calculated by the part of the capacitance calculation method by the open circuit voltage. If the vehicle then travels a certain distance, during which the current goes to zero for only a short time, the second open circuit voltage measurement is not performed. During this time, the remaining capacity is continuously updated using the coulometer part of the capacity meter. The vehicle stops, for example at a signal, at which time a new open circuit voltage measurement is obtained. The difference in battery capacity due to the difference between the two open circuit voltage measurements and the coulometric accumulated capacity between the two open circuit voltage measurement times should be equal if the battery does not age. When the battery capacity changes with time, the integrated capacity value between the two reference points by the coulometer is used to adjust the function indicating the relationship between the open circuit voltage and the capacity in the first method. As a result of the adjustment in these two complementary methods, there is a complete numerical match until the need for the next adjustment is detected and executed.

Finally, the output of the remaining capacity meter of the present invention uses the amount of use of the battery-operated device as a display unit so that the user can easily understand. The remaining battery capacity obviously does not predict the future distance. Therefore, in the present application, the display is performed by using an arbitrary value of the amount that can be used by the device per unit capacity of the battery. In the present invention, the device usable amount per unit battery capacity that is most likely to be actually used is selected as the arbitrary value. For example, in an electric vehicle with a fully charged 30Ah battery,
When the vehicle travels on a flat windless road at a maximum value of 60 km, the maximum usage amount per unit capacity of the battery is 2 km / Ah.
At this time, if the battery has a remaining capacity of 5 Ah, the display shows 10 km. As a practical matter, the user may not be able to run 10 km because the accelerator is not optimally controlled in terms of energy consumption and the terrain is uneven. However, the display output value decreases smoothly and monotonously as the battery capacity is consumed. As another example, if a laptop computer can operate with a fully charged 2Ah battery for up to 120 minutes, the maximum usage is 60 minutes / Ah. This is
If the remaining capacity of 0.25 Ah is left, the display device
It means to indicate minutes. In this manner, the present invention allows for easy and easy-to-understand information regarding device use to be obtained from the time the user first uses the battery-powered device.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments, the discharge characteristics of a battery, which is a known fact, will be described in order to facilitate understanding of the present invention. FIG. 2 shows the relationship between the terminal voltage and the discharge time when a fully charged sealed lead acid battery having a nominal capacity of 30 Ah was discharged at a constant current until the end of discharge. As shown, the voltage gradually decreases over most of the discharge period and then sharply when the available capacity is exhausted. The battery capacity in this discharge state is obtained by multiplying the discharge current and the elapsed time until the voltage suddenly drops. Discharge time as the discharge current increases to decreases as Peukert formula (I ⁿ t = C). Where I
Is the discharge current, n is greater than 1 depending on the battery type, and C is a constant. Discharge duration (minutes)
And the discharge current (A) are shown in FIG. 3 in a double logarithmic table. From the linear regression equation of the data in this figure, the values of n and c are 1.31
3 and 3.386 × 10 ³ . Since the time until the end of discharge decreases as the discharge current increases, the capacity also naturally decreases. If a fully charged battery is discharged with several different constant currents, the capacity will also change according to the above function. FIG. 4 shows the relationship between the discharge current value and the dischargeable capacity of a 30 Ah nominal capacity battery. Furthermore, the capacity of the battery in constant current discharge gradually changes as the number of cycles increases. It is well known that the capacity generally decreases as the number of cycles increases. 28 Ah
An example of such variation in a nominal capacity sealed lead-acid battery is shown in FIG. Finally, FIG. 6 shows the relationship between the open circuit voltage and the remaining capacity of a 30 Ah nominal capacity battery at an early cycle life. The relationship between the state of charge and the open circuit voltage is given by the following equation for this battery.

Remaining capacity = 20.685 × (open circuit voltage-11.7) If 30Ah nominal capacity battery is 28Ah as shown in FIG.
If it changes over time like a nominal capacity battery,
The coefficient of 0.685 first increases to a maximum and then decreases monotonically with battery cycles.

(Embodiment 1) FIG. 1 is a circuit configuration diagram of an embodiment for realizing the battery remaining capacity meter of the present invention. Reference numerals 1 and 2 are detection circuits for the battery terminal voltage and discharge current, respectively. Specifically, the method of detecting the terminal voltage by resistance division is simple. Further, the detection of the discharge current includes a method using a shunt resistor connected in series with the load of the battery, a method using a current sensor using a Hall element, and any method is possible. The current detection part of the device is arranged such that only the discharge current is measured as a positive value, at which time no reverse current or charging current is measured. Three
Is a battery temperature detection circuit. The AC components of the detected terminal voltage and discharge current are removed by the low pass filters 4 and 5. This is because the discharge characteristics of the battery are dominated by the phenomenon of diffusion of the electrolyte, which is a very slow change,
This depends on the average discharge current value. The signal from which the AC component has been removed and the temperature detection signal are converted into digital signals by the A / D converter 9 through the sample hold circuits 6, 7 and 8, respectively. The following various program steps are stored in ROM (read-only memory) 11
And the remaining capacity of the battery is calculated.

1) A function relating the open circuit voltage to the battery capacity defined by the lowest drive current for a battery driven device.

2) A Peukert function that determines the consumed capacity integrated over time.

Various constants necessary for calculation are also stored in the ROM. The indicating device microcomputer 10 reads the terminal voltage value, the discharge current value, and the battery temperature converted into digital signals, executes the program command from the ROM 11 to calculate the remaining capacity value, and 2 according to the calculated remaining capacity value.
The value data is output to the latch circuit 12. Binary data is, for example, data decoded for driving the pointing device. The latch circuit 12 holds the previous data until the new data is sent from the microcomputer 10. The indicator device 13 indicates the remaining capacity value by the data held in the latch circuit 12.

The circuit configuration described above is merely an example. For example, instead of the low pass filters 4 and 5, a digital low pass filter can be used for the data read by the microcomputer 10, and the sample hold circuit 6 can be used. As for 7 and 8, it is possible to use one sample hold circuit in time division. If a D / A converter is used, an analog voltmeter can be used as the indicating device. Further, it is not the intention of the inventor to limit the output display means to the above-mentioned embodiment.

A typical flow chart of the programmed function steps executed in the microcomputer part of the battery state of charge meter described in claim 1 is shown in FIG. As can be seen from FIG. 7, the remaining capacity is continuously calculated from the start of driving the battery-operated device until it stops. The program has two branches. The left branch (open circuit voltage branch) operates when the current value is zero during the entire fixed time t _SET , and calculates a new value of the battery capacity (in other words, new capacity). The main branch on the right side (coulometer branch) operates when a current of zero or more flows in the discharge direction, and calculates the consumed capacity (hereinafter referred to as Δ capacity) by integrating the current with respect to time.
The new value of the battery capacity (in other words, the new capacity) is calculated by subtracting the Δ capacity from the current value of the battery capacity.

A schematic flowchart of the branch on the left side of FIG. 7 is shown on the upper side of FIG. A more detailed flow chart of the program steps in this open circuit voltage branch is shown in FIG.
Shown below. In the first step after entering this branch, the memory space in the microcomputer is initialized in order to accumulate the voltage-time data pair (V _N , t _N ) that is continuously measured for a certain time t _SET . Do. In the next step, one data pair is measured and stored in memory space. next,
A condition is determined whether the battery current value is zero and the elapsed time has not reached t _SET . If the current remains zero for a period of time t _SET , the voltage and time data pairs are fully stored and stored in memory space and provided for subsequent calculations. If the current value becomes a non-zero value before reaching t _SET , No is selected even in the next condition judgment unit (elapsed t ≧ t _SET ?) And the calculation is performed with the open circuit voltage branch without updating the value of the battery capacity. Get out of. If the current continues to be zero for the entire period until reaching t _SET , the next condition judgment unit (elapsed t ≧ t _SET ?)
S is selected to fit an exponential function to the voltage and time data pairs stored in memory space. The shape of the fitted exponential function is V = Alog
(T) + B. Here, A and B are constants. In the next step, a time value of 10 ³ seconds or more is V = Alog (t)
Substitute in + B to obtain a V _OCV value that closely approximates the open circuit voltage.

In the final step of this branch, this open circuit voltage value is substituted into an equation representing the relationship between the open circuit voltage defined by the minimum current that can drive the battery-powered device and the battery capacity. This formula is generally expressed as capacitance = M [a + bV
_OCV + c (V _OCV ) ² +. ． ． ], A, b,
c, etc. are constants. Also, in this example, M is a constant. However, M can be treated as a variable that changes with repeated use if useful information about the change in battery capacity with repeated use can be obtained. The new capacity is capacity = M [a + bV _OCV + c (V _OCV ).
² +. ． ． ], The value is stored in an appropriate register and displayed by the display circuit described above.

Then, the open circuit voltage branch is exited and the process proceeds to the main routine of the program.

A schematic flowchart of the branch on the right side in FIG. 7 is shown on the upper side of FIG. A more detailed flowchart of the program steps in this coulometer branch is shown at the bottom of FIG. In the first step after entering this branch,
The average current i and the temperature T during a fixed measurement time interval Δt are measured. The measured temperature T is the Peukert equation Δt ₂ = Δt ₁ (i ₁ /
i ₂₎ is used to calculate the index n used in the ^n. The function of temperature to calculate the index n is the general formula n = A +
Β (T) + Γ (T ² ) +. ． ． It is represented by. Α, Β,
Γ, etc. are constants. Next, using the Peukert formula, a correction Δt corresponding to the time interval elapsed while the battery was discharged at the lowest available current for the drive device is calculated.
The lowest usable current for a battery-powered device is defined as standard i, and the above general Peukert equation is used to calculate as follows.

Correction Δt = Δt (i / standard i) ^{n In the} next step, the correction Δt is quadratic by temperature using a temperature correction function with the temperature when the battery capacity is measured and defined as a reference. Make a correction. The function for calculating the new correction Δt is represented by the following general formula.

New correction Δt = correction Δt + α (T-standard T) + β (T
-Standard T) ² + γ (T-Standard T) ³ +. ． ． Where α, β, γ, etc. are constants. That is, new correction △
t corresponds to the time interval elapsed between discharging the battery at 1) the lowest available current for the power device and 2) the reference temperature at which the battery capacity was measured and defined. In the next step, the lowest usable current (standard i) and the time interval at which the current and temperature corrections were performed (new correction Δ
By multiplying by t), the consumed capacity (Δ capacity) integrated at a constant measurement interval is calculated. In the final step of this branch, the Δ capacity is subtracted from the existing battery capacity to obtain the new capacity, which is then stored in the appropriate display register by the display circuit described above. The branch of the coulometer is completed and the program moves to the main routine of the program. The program is again in the initial step. Return to.

The device constructed as described above was connected to a scooter equipped with a battery having a capacity of 30 Ah when fully charged. The battery is not fully charged with a sealed lead acid battery. The scale of the display device indicates, for example, 30 Ah in a fully charged state, 15 Ah in a half state, and 0 Ah in an empty state. At the start of the scooter, the battery capacity was 21 Ah calculated by the open circuit voltage branch of the program.

The vehicle continued to run for about 20 km, during which the displayed value gradually stabilized and decreased to 9 Ah. The scooter was stopped and the battery was partially charged for about 1 hour. After removing the battery from the charger, the car was run again on the scooter. The battery capacity after charging was 18 Ah. While the vehicle continued to run for about 20 km, the display gradually decreased to 4 Ah. When you stop the vehicle,
During that time, the program broke open circuit voltage. At that time, the display output was still 4 Ah. The battery was removed from the vehicle, and a discharge test was performed on a specially designed battery charge / discharge characteristic measuring device in the laboratory. The actual remaining capacity confirmed in the laboratory was 4.3 Ah. This indicates that the constants stored in ROM and used in the program were suitable for this type of battery.

(Embodiment 2) The same circuit configuration of the battery remaining capacity meter as that shown in FIG. 1 of Embodiment 1 is used for this embodiment. FIG. 10 shows a typical flowchart of a program executed by the microcomputer portion of the battery remaining capacity meter according to the second aspect. As can be seen in FIG. 10, capacity is continuously measured from the time the battery powered device discloses operation until the end of operation of the device. 3 for the program
The left branch (open circuit voltage branch) having two branches operates when the current value is zero during the entire fixed period t _SET , and calculates a new value of the battery capacity (in other words, a new capacity). In the lower part of the open circuit voltage branch, two adjacent battery capacity calculation values in time series are compared and it is determined whether or not the calculated values have decreased. If the capacity value decreases, these two values are stored, the flag (FLAG) becomes 1, and the right branch of the program is instructed to analyze these two values. The main routine (coulometer branch) in the center operates when the discharge current has a positive value other than zero, and integrates the current with respect to time to calculate the consumed capacity Δ capacity. Then, a new value of the battery capacity (in other words, a new capacity) is calculated by subtracting the Δ capacity from the battery capacity value so far. In the coulometer branch of the program, the consumed capacity and capacity between two battery capacity measurement times that are adjacent and decrease in time series calculated by the open circuit voltage branch
_SUB is integrated over time. The right branch (normalized branch) is activated when the current value is positive and not zero and the signal FLAG indicates the presence of data and the right branch is ready for analysis. In the standardization branch, the capacity difference between two battery capacity values that are adjacent and decreased in time series calculated by the open circuit voltage method, and the consumed capacity and the capacity _SUB integrated with respect to time between adjacent measurement times are calculated. Compare. The accumulated consumption capacity, that is, the value of the capacity _{S UB} is used as a basis for adjusting the calculation function of the battery capacity value in the open circuit voltage branch of the program. As a result, the two methods are numerically consistent.

The program steps executed by the microcomputer part of the battery remaining capacity meter according to claim 2 will be described in more detail. As can be seen from FIG. 10, after the battery-powered device starts operating, 1) program signal variables, FLAG, 2) subtotal consumption capacity accumulated over time, capacity _SUB , 3) voltage value, V _OLD are saved. Initialize the memory space in the microcomputer. All of these three values are set to zero during the initialization process. In the next step, it is judged whether the current is zero or not. If the current is zero, the program enters the open circuit voltage branch. The first two steps of this branch are described in the description of Embodiment 1 with reference to FIGS. If the current value changes to a non-zero value before reaching t _SET , the first conditional statement in this branch will determine NO, and the open circuit voltage branch will exit without changing the battery capacity value. However, if the current continues to be zero for a fixed time t _SET , then a new value for the battery capacity (in other words, a new value for the battery capacity) is obtained by the relation between the battery capacity and the open circuit voltage defined by the lowest available current for the battery-powered device. Capacity).

This formula is of a general type capacity = M [a + bV
_OCV + c (V _OCV ) ² +. ． ． ], Where a, b,
c and the like are constants. In this example, M is a variable adjusted in the standardization branch that standardizes the battery capacity that changes with repeated use. The new capacity is capacity = M [a + b
V _OCV + c (V _OCV ) ² +. ． ． ] Then this value is stored by the display circuit in the appropriate register for display in the same manner as described in Example 1.

The new capacity is expressed as capacity = M [a + bV _OCV + c (V
_OCV ) ² +. ． ． ] The next step after calculation from is the condition determination step. The voltage value V _OLD accumulated in the memory space is capacity = M [a + bV _OCV + c
(V _OCV ) ² +. ． ． If] or less voltage V _OCV that is assigned to, 1) the value of V _OCV is stored as a new V _OLD, 2) accumulated was consumed capacity, subtotals capacity _SUB is initialized to a zero value, 3) The open circuit voltage branch moves to the main routine of the program. If the voltage value V _OLD is greater than V _OCV , the signal variable FLAG is changed to 1 to indicate that there is data to analyze for the standardized branch of the program, and the open circuit voltage branch goes to the main routine of the program. . The condition determining step in which the signal variable FLAG becomes 1 means that two battery capacity values that are adjacent and decreasing in time series are measured by the open circuit voltage method. The higher of the two values is calculated by the value stored in _VOLD . The lower value is calculated by the current V _OCV .

If the current changes from a zero value to a non-zero value, No is selected in the conditional judgment statement at the beginning of the program, and the program is the main routine in the center (coulometer branch).
to go into. If the signal variable FLAG is equal to zero, the coulometer branch moves to the main routine having the same program steps as in the first embodiment described with reference to FIGS. The only difference is the final step. There, the program calculates the integrated subtotal, the capacity _SUB , of the consumed capacity different from the current battery capacity. Subtotal of total consumption capacity, capacity _{S UB,} is the consumption capacity, Δ capacity, which is gradually integrated over time,
It is calculated by adding to the current value of the capacity _SUB stored in the memory space. After the completion of this process, the calculation is performed at the condition judgment step (current = 0) at the head of the coulometer branch.
? ) Return to.

When the signal variable FLAG becomes 1 after shifting to the central main routine of the program, the main routine is exited and the process moves to the right branch (standardized branch). As mentioned above, the fact that the signal variable FLAG is equal to 1 means that adjacent and decreasing battery capacity values in the two time series were measured by the open circuit voltage method and stored in the memory space. When the signal variable FLAG equals 1,
It also means that the current value of the capacity _SUB is determined during the measurement interval between the adjacent and decreasing battery capacity values in the two time series. The first step in this standardization branch is to make the sum of the consumed capacity, the capacity _SUB , equal to the difference between two continuously decreasing current battery capacity values obtained by the open circuit voltage method. Performs the calculation of the new value of. This is mathematically expressed as follows.

Capacity _SUB = M [a + bV _OLD + c (V _OLD ) ² +
...]-M [a + bV _OCV + c (V _OCV ) ² + ...] M can be easily obtained by rearranging this equation. New M
The value of is used to calculate the battery capacity (in other words, the new capacity).

New capacity = M [a + bV _OCV + c (V _OCV ) ² +. ． ． ] At this point in the program, the two methods are numerically consistent. At the end of this branch, the variables in the program are reinitialized as follows. That is, 1) the value of V _OCV is accumulated in V _OLD , 2) the signal variable FLAG is reset to zero, and 3) the consumption capacity accumulated over time and the subtotal of the capacity _SUB are reset to zero. The standardization branch is
After that, the process ends and shifts to the program main routine.

The device constructed as described above was connected to a scooter equipped with a battery having a capacity of 30 Ah when fully charged. The battery is not fully charged with a sealed lead acid battery. The scale of the display device indicates, for example, 30 Ah in a fully charged state, 15 Ah in a half state, and 0 Ah in an empty state. At the start of the scooter, the battery capacity was calculated to be 26 Ah by the open circuit voltage branch of the program.

When the vehicle was continuously driven for about 30 km, the displayed value gradually decreased to 9 Ah during that time. The scooter was stopped and the battery was partially charged for about 2 hours. After removing the battery from the charger, the car was run again on the scooter. The battery capacity after charging was 24 Ah. While the vehicle continued to run for about 20 km continuously, the display gradually decreased to 6 Ah during that time. When the vehicle was stopped, the program broke open circuit voltage in the meantime. At that time, the display output was still 6 Ah.
The battery was removed from the vehicle, and a discharge test was performed on a specially designed battery charge / discharge characteristic measuring device in the laboratory. The actual remaining capacity confirmed in the laboratory was 6.1 Ah. This indicates that the constants stored in ROM and used in the program were suitable for this type of battery.

The scooter was then run for several months under normal conditions and the same tests as above were repeated. The fully charged battery capacity was reduced to 25 Ah. At the beginning of the second test, the capacitance was measured as 23 Ah by the open circuit voltage part of the program.

When the vehicle was continuously driven for about 10 km, the displayed value gradually decreased to 17 Ah during that time. When the vehicle was stopped, the program broke open circuit voltage in the meantime. At that time, the display output remained at 17 Ah. The battery was removed from the vehicle, and a discharge test was performed on a specially designed battery charge / discharge characteristic measuring device in the laboratory. The actual remaining capacity confirmed in the laboratory is 16.
It was 9 Ah. This is the R used in the program
It means that the constants stored in the OM fit the battery well and that the standardized branch of the program worked as expected.

(Example 3) An apparatus constructed according to the general specifications described in Example 1 was connected to an electric scooter equipped with a battery having a full charge capacity of 30 Ah. The scooter ran on a windless test truck at different constant speeds and measured the maximum usable capacity per unit battery capacity. After several times, a maximum usable amount per unit capacity of 1.93 km / Ah was obtained at a constant speed of 32 km / hour. For a fully charged battery of 30 Ah, this rate corresponds to a maximum usable capacity of 57.9 km. In order to make the display device easy to understand, the maximum display scale is set to 60 km, although it is a distance that cannot be actually obtained. And half the scale is 30km
At the final point (empty state), it becomes 0 km. An additional calculation step is added to the program executed by the microcomputer of the battery remaining capacity meter of the first embodiment, and the calculated capacity value and new capacity are multiplied by 1.93 km / Ah. In this way, the display device shows the maximum remaining usage amount that is easy for the user to understand.

A fully charged battery at the time of starting the doctor has a display value of 57 km on the remaining capacity meter. When the vehicle traveled continuously in the city for 20 km, the displayed value steadily decreased to 29 km during that time. The reduction of the battery capacity (travelable distance) by the remaining capacity meter is 28 km (57-29 = 2).
It was 8), but the actual distance traveled was 20 km. The reason for this difference in value is that the driving conditions in urban areas are not optimal for maximizing battery usage. Move the scooter to the test truck and move at a constant speed of 32
I ran for an additional 40 minutes at km / h. During this time, the displayed value steadily decreased to 8 km. This 21km reduction in remaining usable capacity was predictable as the vehicle was operated under full battery capacity usage. For the use of two forms, city driving and test truck driving,
The display device operated steadily and smoothly, and the output value did not drop suddenly.

[0044]

As described above, the present application is an open circuit voltage type battery remaining capacity meter that functions only when the current value is zero for a certain period of time, and continuously when the current is a positive value instead of zero in the discharging direction. By combining the beneficial features of the coulometer type battery remaining capacity meter that functions as described above, it is possible to provide a single battery remaining capacity meter that cancels out the disadvantages of both and also has the advantages of both.

Further, the battery remaining capacity meter includes a simple means for compensating the aging of the battery. Finally, it includes means for converting the output of the battery capacity meter into a value representing the actual remaining usage of the battery-powered device. The converted output is displayed in the form of distance or kilometers for electric vehicles and in the form of time of use for portable computers.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a battery remaining capacity meter according to the present invention.

FIG. 2 is a diagram showing a constant current discharge characteristic of a battery.

FIG. 3 is a diagram showing a relationship between a common logarithm of a discharge current and a common logarithm of a discharge duration time.

FIG. 4 is a diagram showing a relationship between a discharge current value and a dischargeable capacity.

FIG. 5 is a diagram showing a relationship between a cycle number and a dischargeable capacity.

FIG. 6 is a diagram showing a relationship between an open circuit discharge voltage and a dischargeable capacity.

FIG. 7 is a flowchart of program control (claim 1) in the microcomputer of the battery remaining capacity meter of the present invention.

FIG. 8 is a flowchart of program control (claim 3) in the microcomputer of the battery remaining capacity meter of the present invention.

FIG. 9 is a flowchart of program control (claim 4) in the microcomputer of the battery remaining capacity meter of the present invention.

FIG. 10 is a flowchart of program control (claim 2) in the microcomputer of the battery remaining capacity meter of the present invention.

[Explanation of symbols]

 1 Battery Terminal Voltage Detection Circuit 2 Battery Discharge Current Detection Circuit 3 Battery Temperature Detection Circuit 4,5 Low Pass Filter 6, 7, 8 Sample Hold 9 A / D Converter 10 Microcomputer 11 ROM 12 Latch 13 Indicator 14 LED Module

Claims (5)

[Claims] 1. A means for measuring a terminal voltage of a battery, a means for measuring a terminal current of a battery, a means for measuring a temperature of a battery, a means for calculating a remaining capacity from the voltage / current / temperature, and a calculation result stored therein. In a battery remaining capacity meter of a battery-powered device having means for displaying a calculation result, (1) when the current is zero for a certain period of time, an open circuit defined at a minimum operating current of the drive device from a measured voltage value. Remaining capacity is calculated using the relationship between voltage and capacity (2) If the current is flowing zero or more in the discharging direction of the battery, the consumed capacity should be integrated over time and subtracted from the current value of the remaining capacity of the battery. A battery remaining capacity meter characterized in that the means (1) and (2) for calculating the remaining capacity at the next moment are used complementarily. 2. Means for measuring the voltage of the battery, means for measuring the terminal current of the battery, means for measuring the temperature of the battery, means for calculating the remaining capacity from the voltage / current / temperature, and means for storing the calculation result. In a battery remaining capacity meter of a battery-powered device having means for displaying a calculation result, (1) when the current is zero for a certain period of time,
Calculate the remaining capacity from the measured voltage value by using the relationship between the open circuit voltage and the capacity defined at the minimum operating current of the driving device (2) If the current flows zero or more in the discharging direction of the battery, the consumed capacity is Is calculated and the remaining capacity at the next moment is calculated by subtracting from the current value of the remaining capacity of the battery, and the remaining capacity is calculated by complementarily using the means of (1) and (2). The capacity difference between the continuous binary remaining capacities obtained by the means of (1) can also be obtained by integrating the consumed capacity with respect to time using the method of (2). A battery remaining capacity meter characterized in that a function for calculating the present battery capacity value in the means (1) is adjusted by using the integrated consumed capacity so that the capacity calculation values by the two means are numerically identical. 3. The data calculation means according to claim 1 or 2, which functions when a current value is zero for a certain period of time. 1) Time and voltage data are accumulated in a memory device, and 2) Combination of accumulated time and voltage data. And 3) a means for calculating an open circuit voltage value for a time value of 10 ³ seconds or more using the logarithmic function.
The battery remaining capacity meter according to claim 2 or claim 3. 4. The data calculation means according to claim 1 or 2, which functions when a current flows in the discharge direction of a battery of zero or more, 1) measuring an average current and temperature for a certain period of time,
2) Calculate the time corresponding to the lowest usable current corrected by the current value using the Peukert formula that has an index corresponding to the measured temperature, and 3) Temperature correction with the temperature when the battery capacity is measured as the standard. Using the function, calculate the time corresponding to the lowest available current corrected by temperature,
4) The method according to claim 1 or 2, further comprising means for accumulating the consumption capacity at a certain time by multiplying the minimum usable current value at the standard temperature by a correction time depending on the current and the temperature. Battery remaining capacity meter. 5. During operation of the battery-operated device, the voltage and current and the temperature of the battery are continuously measured, the data is analyzed to calculate the existing battery capacity, and the value is the maximum drivable amount of the device per unit battery capacity. A battery remaining capacity meter characterized by calculating the maximum remaining usage amount by multiplying by and showing it to the indicating device.