JP2002236155A - Battery remaining capacity calculation method - Google Patents

Abstract

(57) [Summary] [Problem] To accurately calculate the remaining capacity even in a deteriorated battery. Calculate the remaining capacity at the end of discharge more accurately. A remaining battery capacity calculation method calculates a remaining capacity of a battery by subtracting a discharging capacity from a charging capacity of the battery, and calculates a remaining rate by a ratio between the calculated remaining capacity and a learning capacity. When the battery is discharged and the voltage drops to the discharge alarm voltage, the battery is charged until it is fully charged, and the charge capacity from the state where the battery voltage has dropped to the discharge alarm voltage until it is fully charged is calculated and the auxiliary charge is performed. The discharge alarm capacity (R), which is the remaining capacity of the battery when discharged to the discharge alarm voltage,
The value obtained by adding the supplementary charge capacity (CCadd) to (Clow) is defined as the new learning capacity (FCCnew) of the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a remaining capacity of a battery, and more particularly to a method for accurately calculating a remaining capacity while correcting a learning capacity with a charging capacity. In this specification, the learning capacity means the corrected full charge capacity of the battery.

[0002]

2. Description of the Related Art At present, in a battery mounted on a laptop microcomputer or the like, it is necessary to accurately calculate the remaining capacity of the battery and provide it to the microcomputer as battery information in a charged / discharged use state. This is because the power of the microcomputer cannot be turned off during use, and it is necessary to turn off the power after performing a predetermined operation and terminating the software. In order to use the battery in this state, it is necessary to output an alarm to the microcomputer when the remaining capacity of the battery is reduced and the remaining usage time is close to the time for performing the end operation. After the alarm is input to the microcomputer, the operation of ending the software can be performed, and then the power can be turned off.

It is important for a battery used as a power source of electric equipment to accurately calculate the remaining capacity at the end of discharge. If the remaining capacity is not normally displayed at the end of discharge and overdischarge occurs in a very short time from the alarm alarm, electrical equipment such as microcomputers cannot be terminated normally, or the remaining usage time for shaving machines etc. If the character is incorrect, it cannot be used without complete shaving.

[0004]

In order to accurately calculate the remaining capacity at the end of discharge, the conventional method evaluates discharge characteristics finely based on temperature and charge / discharge rate and stores battery characteristics as parameters. , The remaining capacity is calculated based on these. However, in the conventional method, the remaining capacity can be accurately calculated when the battery is in a new state. However, as the battery deteriorates, the remaining capacity cannot be calculated accurately. In particular, the remaining capacity at the end of discharge cannot be calculated accurately. was there.

[0005] The present invention has been developed for the purpose of solving such a drawback. An important object of the present invention is to accurately calculate the remaining capacity even in a deteriorated battery,
In particular, it is an object of the present invention to provide a remaining capacity calculation method capable of more accurately calculating the remaining capacity at the end of discharge.

[0006]

According to the battery remaining capacity calculation method of the present invention, the remaining capacity of the battery is calculated by subtracting the discharging capacity from the charging capacity of the battery, and the ratio of the calculated remaining capacity to the learning capacity is calculated. Calculate the survival rate. When the battery is discharged and the voltage drops to the discharge alarm voltage, the battery is charged until it is fully charged, and the charge capacity from the state where the battery voltage has dropped to the discharge alarm voltage until it is fully charged is calculated and supplemented. The capacity (CCadd), and the auxiliary charge capacity (CCa) is added to the discharge alarm capacity (RClow) which is the remaining amount of the battery in a state where the battery is discharged to the discharge alarm voltage.
dd) is added to the new learning capacity of the battery (FCCnew)
And

The battery remaining capacity is calculated by calculating a discharge capacity (DCmax) from a fully charged state until the battery voltage drops to a discharge alarm voltage, and calculating the calculated discharge capacity (DCma).
x) can be subtracted from the old learning capacity (FCCold) to calculate the discharge alarm capacity (RClow). Discharge capacity (D
Cmax) can be calculated in consideration of the discharge efficiency. The discharge efficiency is preferably specified by using temperature and discharge current as parameters. The discharge efficiency can be specified by using the temperature and the discharge current immediately before the battery voltage drops to the discharge alarm voltage as parameters. As for the discharge efficiency using the temperature and the discharge current as parameters, values for specifying the discharge efficiency are stored as a table, and the discharge efficiency can be specified from the stored table.

Further, in the remaining capacity calculating method, the discharge alarm voltage can be changed using the temperature and the discharge current as parameters. The discharge alarm voltage that is changed using the temperature and the discharge current as parameters can be stored as a table and specified from the stored table.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a remaining capacity calculation method for embodying the technical idea of the present invention, and the present invention does not specify the remaining capacity calculation method in the following method.

FIG. 1 is a circuit diagram of a battery pack used in the remaining capacity calculation method of the present invention. This battery pack includes a battery 1 and
A current / voltage converter 2 for converting a charge / discharge current into a voltage;
A voltage detector 3 for detecting the voltage of the battery 1, a temperature detector 4 for detecting the ambient temperature of the battery 1, and a current / voltage converter 2
An A / D converter 11 for converting an analog signal, which is an output signal of the A / D converter, into a digital signal; an A / D converter 12 for converting an analog signal output from the voltage detector 3 into a digital signal; An A / D converter 13 for converting an output signal of
An accumulator 5 for calculating the output signal of the A / D converter 11 to accumulate the charge / discharge current or power; a remaining capacity calculator 6 for calculating the remaining capacity of the battery 1 from the output of the accumulator 5;
A low-battery detector 7 for comparing the output voltage of the D converter 12 with a stored set voltage, and an A / D converter 11
A timer 8 for determining the sampling periods of the samplings 13 to 13, a leaving deterioration cycle deterioration determining unit 9 for the battery 1, and a communication processing unit 10 for transmitting battery information by SMBus to an electric device using the battery 1 as a power supply.

The battery 1 is a lithium ion secondary battery or a nickel-hydrogen battery. However, the battery 1 can be any rechargeable battery such as a nickel-cadmium battery. Battery 1 has one or more secondary batteries connected in series or in parallel.

Although not shown, a current / voltage converter 2 for converting a charge / discharge current of the battery 1 into a voltage includes a current detection resistor connected in series with the battery, and a voltage generated at both ends of the current detection resistor. And an amplifier that amplifies the signal. Since the current detection resistor generates a voltage proportional to the current flowing through the battery 1, the current can be detected by the voltage. The amplifier is +
An operational amplifier that can amplify a negative signal, and distinguishes a charging current and a discharging current by +-of an output voltage. An analog signal which is an output signal of the current / voltage converter 2 is output to the A / D converter 11
Is converted into a digital signal. This digital signal is output to the integrating unit 5, the communication processing unit 10, and the LowBattery detecting unit 7.

The voltage detector 3 detects the voltage of the battery 1. The detection signal is converted into a voltage signal of a digital signal by the A / D converter 12 and output to the Low Battery detection unit 7. The LowBattery detection unit 7 outputs a discharge alarm signal when the battery voltage drops to the discharge alarm voltage, and outputs a discharge end voltage signal when the battery voltage drops to the discharge end voltage (EV) when the discharge proceeds further. The voltage is output to the calculation unit 6, and the voltage of the battery 1 is changed to an overdischarge voltage (OverDischarge).
When the voltage drops to a low level, an overdischarge voltage signal is output. The temperature detector 4 detects the ambient temperature of the battery 1. The detection signal is
The converted temperature digital signal is converted into a digital signal by the A / D converter 13,
The output is output to the accumulating unit 5, the neglected deterioration cycle deterioration determining unit 9, and the communication processing unit 10.

The accumulator 5 calculates the current signal input from the A / D converter 11 to calculate the remaining amount of the battery 1.
The remaining amount is calculated as an integrated current value (Ah) by subtracting the discharge capacity from the charge capacity of the battery 1. The charge capacity is calculated as an integrated value of the charge current of the battery 1 or by multiplying the integrated value by the charge efficiency. The discharge capacity is calculated in consideration of the integrated value of the discharge current or the discharge efficiency. The integrating unit 5 can also calculate the remaining amount based on the integrated value (Wh) of the power instead of the integration of the current. The integrated value of the power is calculated by subtracting the discharge power from the charge power. The power is converted into a current signal input from the A / D converter 11 by the A / D converter 1.
The calculation is performed by multiplying the voltage input from step 2.

Further, the integrating unit 5 calculates the calculated residual rate (%)
Is corrected. When a signal indicating that the voltage of the battery 1 has dropped to the discharge alarm voltage is input from the A / D converter 12, the integrating unit 5 calculates the remaining rate (%) of the battery 1 as the remaining rate corresponding to the discharge alarm voltage. When a signal indicating that the battery voltage has dropped to the discharge end voltage due to the progress of discharge is input, the integrating unit 5 corrects the calculated remaining rate to zero. This is because when the battery voltage decreases to the discharge end voltage, the actual capacity of the battery 1 becomes zero.

The remaining capacity calculator 6 calculates the learning capacity (FCC), and calculates the remaining rate (%) of the battery 1 based on the calculated learning capacity (FCC) and the remaining amount. The remaining amount is calculated by the integrating unit 5. The remaining rate (%) of the battery 1 is represented by the remaining amount / learning capacity (FC).
It is calculated by the ratio of C).

The learning capacity (FCC) of the battery 1 is not constant but decreases as the battery 1 deteriorates. Therefore, the remaining capacity calculation unit 6 corrects the learning capacity (FCC) so that the calculated value matches the actual learning capacity (FCC) of the battery 1. The learning capacity (FCC) of the battery 1 is corrected by an integrated value when the battery 1 is charged. The learning capacity (FCC) is not corrected by the integrated value when the battery 1 is discharged. This is because the charging current is substantially constant while the discharging current fluctuates greatly, so that the integrated value of the charging current can calculate the learning capacity (FCC) with higher accuracy.

In order to realize this, the remaining capacity calculator 6 controls charging and discharging of the battery 1 and calculates a learning capacity (FCC). The remaining capacity calculator 6 outputs a control signal from the assembled battery to the charger or the electric device via the SMBus in order to control the charging and discharging of the battery 1. The control signal controls a charge switch (not shown) connected in series with the battery 1 to turn on and off, thereby controlling the state of charge of the battery 1.

When the battery 1 is discharged and the voltage drops to the discharge alarm voltage, the remaining capacity calculator 6 controls the battery 1 to continue charging until it is fully charged. When the battery 1 is charged while being connected to an electric device in an operating state, the charging current is set to be larger than the discharging current of the battery 1. The charge capacity from the state in which the battery voltage is reduced to the discharge alarm voltage to the time when the battery is fully charged is integrated by the integrating unit 5,
It is calculated as a supplementary charge capacity (CCadd).

Further, when the battery 1 is charged / discharged, the integrating unit 5 subtracts the discharge capacity from the charge capacity and calculates the remaining amount of the battery 1 when discharged to the discharge alarm voltage. ). Discharge alarm capacity (R
Clow) calculates the discharge capacity (DCmax) from the fully charged state until the voltage of the battery 1 drops to the discharge alarm voltage, and uses the calculated discharge capacity (DCmax) as the old learning capacity (FC
Cold). That is, the discharge alarm capacity (RClow) of the battery 1 is calculated by the following equation. Discharge alarm capacity (RClow) = old learning capacity (FCCold)-discharge capacity (DCmax)

Thus, the discharge alarm capacity (RClo)
When w) is calculated, a new learning capacity (FCCnew) is calculated by adding an auxiliary charge capacity (CCadd) which is a capacity from the discharge alarm voltage to a full charge. That is, the new learning capacity (FCCnew) is calculated by the following equation. New learning capacity (FCCnew) = supplementary charging capacity (CCadd)
+ Discharge alarm capacity (RClow)

When the new learning capacity (FCCnew) is calculated, the learning capacity (FCC) becomes the old learning capacity (FCCold).
To the new learning capacity (FCCnew). afterwards,
The remaining rate (%) is calculated based on the new learning capacity (FCCnew).

By the way, the discharge capacity (DCma) from the fully charged state until the voltage of the battery 1 decreases to the discharge alarm voltage.
x) in the calculation of the discharge capacity (DCma) with higher accuracy
To calculate x), the discharge efficiency is taken into account. The discharge efficiency is specified using the ambient temperature of the battery 1 and the discharge current as parameters. The ambient temperature and discharge current are the temperature and discharge current immediately before the battery voltage drops to the discharge alarm voltage. The discharge efficiency using the ambient temperature of the battery 1 and the discharge current as parameters is stored in the memory as a table shown in FIG. The table in the figure specifies the discharge efficiency from the three temperatures and the four discharge currents. The discharge efficiency between the temperatures shown here and further between the discharge currents can be calculated by interpolation. it can. The discharge efficiency between the temperature and the current can be easily calculated by linear interpolation. The discharge efficiency in this figure is A,
B, C, and D are sequentially reduced in the range of 100 to 70%. The discharge efficiencies A to D are determined to be optimum values in consideration of the type of the battery 1.

The discharge alarm voltage is preferably specified as a voltage at which the remaining rate (%) of the battery 1 becomes 0 to 8%. When the discharge alarm voltage is set to a voltage at which the residual rate (%) becomes 0%,
It becomes equal to the discharge end voltage. When this voltage is set, a discharge alarm signal and a discharge end voltage signal are output together. Preferably, the discharge alarm voltage is set higher than the discharge end voltage, and the remaining rate (%) at the time when the discharge alarm voltage is reached is made larger than 0%.

Since the discharge alarm voltage changes depending on the temperature and the discharge current, the temperature and the discharge current are changed as parameters. The discharge alarm voltage having the temperature and the discharge current as parameters is stored in the memory as a table shown in FIG. 3, similarly to the discharge efficiency. The table in the figure shows three temperatures and
Although the discharge efficiency is specified from the four discharge currents, the discharge alarm voltage during the temperature shown here and also during the discharge current is:
It can be calculated by interpolation. The discharge alarm voltage between the temperature and the current can be easily calculated by linear interpolation. This figure shows the discharge alarm voltage of the lithium ion secondary battery 1 and A, B, C, and D are sequentially reduced in the range of 3.7 to 3.0 V. The discharge alarm voltages of A to D
Is determined to be the optimal value.

When the battery 1 is discharged and the voltage of the battery 1 becomes the discharge alarm voltage, a low-battery detection unit 7 outputs a discharge alarm signal to the remaining capacity calculation unit 6, and further discharge proceeds to a discharge end voltage. When the voltage drops, a discharge end voltage signal indicating that the discharge end voltage has been reached is output. Battery 1
Is fully charged, the voltage of the battery 1 rises to the full charge voltage, and this signal is output from the A / D converter 12 to the remaining capacity calculation unit 6.

The standing deterioration cycle deterioration judging unit 9 includes the battery 1
When the storage capacity is deteriorated by leaving it unused without using the learning capacity (F
CC) is reduced. The corrected learning capacity (F
CC) is output to the remaining capacity calculator 6.

The communication processing unit 10 calculates the remaining capacity calculated by the remaining capacity calculation unit 6, the battery voltage detected by the voltage detection unit 3,
The temperature detected by the temperature detection unit 4 is sent to the attached device by S
Transmit by MBus.

The above assembled battery performs the following operations in a state of being mounted on an electric device such as a microcomputer.
Transmit remaining capacity to electrical equipment. (1) When the battery 1 is discharged and the voltage of the battery 1 drops to the discharge alarm voltage, a discharge alarm signal is output. As shown in the table of FIG. 3, the discharge alarm voltage is detected by changing to a voltage specified by the ambient temperature of the battery 1 and the discharge current. When the battery 1 is discharged, the integrating unit 5
The discharge capacity (DCmax) from full charge is integrated. The discharge capacity (DCmax) is calculated in consideration of the discharge efficiency specified from the ambient temperature of the battery 1 and the discharge current. The calculated discharge capacity (DCmax) is the old learning capacity (FCCold)
, And the discharge alarm capacity (RClow) is calculated.

(2) When the voltage of the battery 1 drops to the discharge alarm voltage, charging of the battery 1 is started and the battery 1 is continuously charged until it is fully charged. The charge capacity from the discharge alarm voltage to the full charge is calculated as the auxiliary charge capacity (CCadd). The supplementary charge capacity (CCadd) is added to the discharge alarm capacity (RClow) calculated in the step (1), and the new learning capacity (F
CCnew) is calculated. After the new learning capacity (FCCnew) is calculated, the remaining rate (%) is calculated based on the new learning capacity (FCCnew). Survival rate(%)
Is calculated by the ratio of the remaining amount of the battery 1 / the new learning capacity (FCCnew). The remaining amount is calculated by subtracting the discharge capacity from the charge capacity.

[0031]

The method for calculating the remaining capacity of a battery according to the present invention has the advantage that the remaining capacity can be accurately calculated even for a deteriorated battery. That is, the remaining capacity calculation method of the present invention calculates a supplementary charge capacity (CC) by fully charging a battery discharged to a discharge alarm voltage and calculating a charge capacity from the discharge alarm voltage to a full charge.
add) and the supplementary charge capacity (CCadd) to the discharge alarm capacity (RClow), which is the remaining amount of the battery discharged to the discharge alarm voltage.
Is set as the new learning capacity (FCCnew) of the battery. This remaining capacity calculation method is to add a supplementary charge capacity (CCadd) to a discharge alarm capacity (RClow), which is the remaining capacity of a battery at the end of discharging, and to obtain a new learning capacity (FCCne) of the battery.
Since w) is calculated, it is possible to realize a feature that, even in a deteriorated battery, the remaining capacity, particularly the remaining capacity at the end of discharge, can be calculated more accurately.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a battery pack used in a remaining capacity calculation method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a table of discharge efficiency using temperature and discharge current as parameters.

FIG. 3 is a diagram showing an example of a table of a discharge alarm voltage using temperature and discharge current as parameters.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Current / voltage conversion part 3 ... Voltage detection part 4 ... Temperature detection part 5 ... Integration part 6 ... Remaining capacity calculation part 7 ... LowBattery detection part 8 ... Timer 9 ... Leaving deterioration cycle deterioration judgment part 10 ... Communication processing Part 11: A / D converter 12: A / D converter 13: A / D converter

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kenji Kawaguchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Hideyuki Nagaya 2-chome, Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Toru Amatsuki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 2G016 CB12 CB21 CB22 CB32 CC01 CC04 CC05 CC06 CC10 CC16 CC23 CD02 CF06 5G003 BA01 DA07 EA05 GC05 5H030 AA08 AS20 FF22 FF42 FF44

Claims (8)

[Claims] 1. A method for calculating a remaining capacity of a battery by subtracting a discharging capacity from a charging capacity of the battery to calculate a remaining capacity of the battery, and calculating a remaining rate by a ratio of the calculated remaining capacity to a learning capacity. When the battery is discharged and the voltage drops to the discharge alarm voltage,
The battery is charged until it is fully charged, the charge capacity from when the battery voltage drops to the discharge alarm voltage until it is fully charged is calculated and used as the auxiliary charge capacity (CCadd), and the battery is discharged to the discharge alarm voltage And calculating a value obtained by adding the supplementary charge capacity (CCadd) to the discharge alarm capacity (RClow), which is the remaining amount of the battery, as a new learning capacity (FCCnew) of the battery. 2. Calculating a discharge capacity (DCmax) from a fully charged state until the battery voltage drops to a discharge alarm voltage, and calculating the calculated discharge capacity (DCmax) to an old learning capacity (FC).
2. The method according to claim 1, wherein the discharge warning capacity (RClow) is calculated by subtracting the discharge alarm capacity from the remaining capacity. 3. A discharge capacity (DCma) in consideration of discharge efficiency.
3. The method according to claim 2, wherein x) is calculated. 4. The method according to claim 3, wherein the discharge efficiency is specified using temperature and discharge current as parameters. 5. The battery remaining capacity calculation method according to claim 4, wherein the discharge efficiency is specified as parameters of the temperature and the discharge current immediately before the battery voltage drops to the discharge alarm voltage. 6. The method according to claim 4, wherein values for specifying the discharge efficiency are stored as a table using the temperature and the discharge current as parameters, and the discharge efficiency is specified from the stored table. 7. The method according to claim 1, wherein the discharge alarm voltage is changed using temperature and discharge current as parameters. 8. The method according to claim 7, wherein the discharge alarm voltage having the temperature and the discharge current as parameters is stored as a table, and the discharge alarm voltage is specified from the stored table.