JPH07274408A - Charging time estimating device for secondary battery - Google Patents

Abstract

PURPOSE:To accurately estimate time required for fully charging a secondary battery under charging, in a charge controller for secondary batteries having capacities approximately equal to open-time battery voltages. CONSTITUTION:Under the control of a charge control part 16, a charging time calculating part 17 obtains an estimated time t1 up to a changeover to a constant-voltage charge mode, by using a first function determined beforehand from a measured voltage of the battery under constant-current charging and a measured charging current and a battery voltage to change over to a constant- voltage charge mode, when a secondary battery 11 is being constant-current- charged. Next an estimated time t2 up to full charging after the changeover to constant-voltage charging is obtained by using a second function determined beforehand from the charging current in cource of the constant-current charging. And an estimated time required for fully charging the secondary battery under charging is obtained by adding these estimated times t1 and t2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charging time predicting device for predicting the charging time of a secondary battery whose open-circuit battery voltage is substantially equal to the battery capacity.

[0002]

2. Description of the Related Art As information processing equipment such as personal computers, portable types that are small, lightweight and easy to carry have become popular. This type of portable type information processing device is capable of being driven by a rechargeable battery (secondary battery), and various measures have been taken to charge the battery or to drive only the battery. In addition, various measures have been taken to predict the operating time and the charging time when the battery is used.

A conventional technique for predicting the charging time required for a conventional fully charged battery-powered portable computer as described above will be described with reference to FIG. Conventionally, this type of conventional technology for predicting the charging time required for full charge has been realized for a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery that does not have the characteristic that the battery voltage is proportional to the battery capacity.

In the case of a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery that does not have the characteristic that the battery voltage is proportional to the battery capacity, in order to predict the time until the battery is fully charged, it is necessary to temporarily charge the battery before starting charging. , It was necessary to discharge.

FIG. 6 is a block diagram showing a conventional structure. In FIG. 6, reference numeral 21 is a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery. A battery voltage measuring unit 22 measures the battery voltage of the secondary battery 21. A current measuring unit 23 measures a charging current and a discharging current of the secondary battery 21.

Reference numeral 24 is a charging on / off switch interposed in the charging path of the secondary battery 21, and turns on / off the charging of the secondary battery 21. Reference numeral 25 is a discharge on / off switch interposed in the discharge path of the secondary battery 21, and turns on / off the discharge of the secondary battery 21.

Reference numeral 26 is a power source for charging the secondary battery 21 with a constant current. Reference numeral 27 is a load that consumes electric power from the secondary battery 21. 28 is a battery voltage measuring unit 22 and a current measuring unit 23
It is a processing unit that controls charging / discharging of the secondary battery 21 in accordance with each measured value such as.

In FIG. 6, the discharge switch 25 is turned on and the electric power of the secondary battery 21 is consumed by the load 27 to discharge the secondary battery 21. The battery voltage of the secondary battery 21 being discharged is measured by the voltage measuring unit 22,
When the battery voltage reaches the normal discharge limit voltage of the secondary battery (hereinafter referred to as final discharge final voltage), the discharge switch 25 is turned off.
The discharge of the secondary battery 21 is stopped by setting it to F.

The remaining capacity of the secondary battery 21 at this time is 0%.
And After the discharge is completed, the charging switch 24 is turned on to start charging the secondary battery 21. When charging starts, the current measuring unit 23 measures the charging current of the secondary battery 21, and the measured current value is input to the processing unit 28. The processing unit 28 then performs a process of predicting the charging time until full charge.

In this process, the charge amount of the secondary battery 21 from the start of charging is calculated from the charging current value input from the current measuring unit 23. By subtracting the amount of charge to be charged from the battery capacity (remaining capacity 100%) of the secondary battery 21 that is known in advance, the amount of charge to be charged until the remaining capacity reaches 100% (charge quantity a) is found.

The time ta is calculated by dividing the charge amount a by the charging current value input from the current measuring unit 23. The calculated time ta corresponds to the charging time required for full charge.

However, the above-mentioned conventional structure has the following problems. 1) If the battery capacity of the secondary battery is not known in advance, the charging time cannot be predicted.

2) It is impossible to predict the charging time until the battery is fully charged unless the battery is discharged to 0% before the start of charging. 3) Since the true value of the battery capacity differs for each battery, it is not possible to accurately predict the charging time until the battery is fully charged.

[0014]

As described above, in the conventional charging time predicting means for the secondary battery, the charging time cannot be predicted unless the battery capacity of the secondary battery is known in advance. It is not possible to predict the charge time until full charge unless the battery is discharged to 0% before starting. Accurately predict the charge time until full charge because the true value of the battery capacity differs for each battery. However, there are various problems such as the inability to perform the above.

The present invention has been made in view of the above situation,
When charging a secondary battery whose open-circuit battery voltage is almost equal to the battery capacity, a secondary battery charge time prediction device that can always accurately predict the charge time until full charge for each secondary battery The purpose is to provide.

[0016]

According to the present invention, there is provided a voltage measuring unit for measuring a battery voltage of a secondary battery, a current measuring unit for measuring a charging current of the secondary battery, and constant current charging / constant voltage charging. A means for determining the charging mode, predicting the charging time for each charging mode from the measured battery voltage value and charging current value, and calculating the time until full charge is provided, and Realize a mechanism to accurately predict the charging time.

[0017]

When the secondary battery is charged in the constant current mode, the battery voltage and charging current during constant current charging and the battery voltage for switching to the constant voltage charging mode are set to the first predetermined value.
The predicted time t1 until switching to constant voltage charging is obtained using the function of. Next, the predicted time t2 from the switching to the constant voltage charging until the full charging is obtained from the charging current during the constant current charging using a predetermined second function. By adding the estimated times t1 and t2, the estimated time until the secondary battery being charged is fully charged is obtained. As a result, it is possible to accurately predict the charging time until the secondary battery is fully charged.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment i of the present invention. In the figure, 11 is a lithium secondary battery. A voltage measuring unit 12 measures the battery voltage of the lithium secondary battery 11. A current measuring unit 13 measures the charging / discharging current of the lithium secondary battery 11.

Reference numeral 14 is a switch interposed in the charging path of the lithium secondary battery 11 to turn on / off the charging of the lithium secondary battery 11. Reference numeral 15 denotes a constant voltage / constant current power supply unit, which supplies electric power for charging the lithium secondary battery 11 with a constant current / constant voltage.

Reference numeral 16 denotes a charge control unit, which controls the switch 14 to turn on / off the charge of the lithium secondary battery 11. Also, the voltage measuring unit 12 and the current measuring unit 13
Then, each measured value is input to detect the full charge of the lithium secondary battery 11.

Reference numeral 17 denotes a charging time calculation unit, which receives information on the charging current and the battery voltage of the lithium secondary battery 11 from the charging control unit 16 and calculates the charging time until the lithium secondary battery 11 is fully charged. To do. This calculation means will be described later.

The operation of the charging time predicting apparatus in the above embodiment will now be described with reference to the flow chart shown in FIG. 2 and the characteristic diagrams shown in FIGS. In describing the operation of the embodiment of the present invention, charging of the lithium secondary battery will be described.

Charging of a lithium secondary battery is generally performed by
Charging is performed by constant voltage / constant current charging. A constant voltage / constant current power supply is used as a power supply source. The constant voltage / constant current power supply has a constant current (I
When the battery voltage reaches Vo, the constant current charging mode is switched to the constant voltage charging mode, and the power is supplied at the constant voltage (Vo).

When the battery voltage of the lithium secondary battery is lower than Vo, the lithium secondary battery is charged with a constant current. As the charging progresses, the battery voltage of the lithium secondary battery rises, and when the battery voltage reaches Vo, the charging state shifts from constant current charging to constant voltage charging. After shifting to constant voltage charging, the charging current of the lithium secondary battery decreases, and when it reaches a certain current value or less, the charging is stopped as a full charge.

The charging characteristics of the lithium secondary battery at this time are shown in FIG. The operation of the above embodiment will be described below with reference to the flow chart shown in FIG. 2 and the characteristic diagrams shown in FIGS.

In charging the lithium secondary battery 11, the battery voltage of the lithium secondary battery 11 is measured by the voltage measuring unit 12. The battery voltage data measured by the voltage measuring unit 12 is sent to the charging control unit 16.

The charging control unit 16 judges from the transmitted battery voltage whether or not there is no problem in starting charging, and when it is judged that there is no problem in starting charging, the switch 14
Is turned on to start charging the lithium secondary battery 11.

After the start of charging, the charging control unit 16 determines whether the lithium secondary battery 11 is charged in the constant current charging mode based on the data from the voltage measuring unit 12 and the current measuring unit 13.
Determine if the battery is charged in constant voltage charging mode.

A. Charging operation in constant current charging mode When the lithium secondary battery 11 is charged in the constant current charging mode, the battery voltage of the lithium secondary battery 11 is measured by the voltage measuring unit 12 during charging, and the charging current is calculated. Is measured by the current measuring unit 13. The data of each measured value is supplied to the charge controller 16 (steps S1 and S2 in FIG. 2).

The charging control unit 16 confirms that the lithium secondary battery 11 is being charged with a constant current, and the charging time calculation unit 1
Start 7 The charging time calculation unit 17 is the charging control unit 1
Under the control of 6, the battery voltage (V that switches from the constant current charging state to the constant voltage charging state according to the measured battery voltage Va).
Predict the charging time to reach o). This predicted time is set to t1 (steps S3 to S6 in FIG. 2).

The prediction of the time t1 is performed as follows. The charging characteristics of the lithium secondary battery are as shown in FIG. 3, and the charging voltage and time during the constant current charging period can be expressed as shown in FIG.

From FIG. 4, the charging time t is the battery voltage V
And a function of the charging current I during constant current charging. This function will be represented as tc (V, I). From the battery voltage Va and the charging current Im during constant current charging, the time ta (= tc (Va, I) is calculated by the above function tc (V, I).
m)) is obtained (step S4 in FIG. 2).

The charging current Im and the constant voltage value V during the constant current
From o, the time tb (=
tc (Vo, Im)) is calculated (step S5 in FIG. 2).
). From these ta and tb, the time t1 until the lithium secondary battery being charged at the constant current is switched to the constant voltage charging can be obtained by [t1 = tb-ta] (step S6 in FIG. 2).

Furthermore, the charging time (Im) measured by the current measuring unit 13 is used to predict the charging time from the transition to constant voltage charging to full charge. This predicted time is set to t2 (steps S9 to S11 in FIG. 2).

The prediction of t2 is performed as follows. The charging characteristics of the lithium secondary battery are as shown in FIG. 3, and the charging voltage and time during the constant voltage charging period can be expressed as shown in FIG.

From FIG. 5, it can be seen that the charging time t is a function of the charging current I. This function will be referred to as tv (I). From the charging current Im during constant current charging, the time ta ′ (= tv (Im)) is calculated by the above function tv (I).
Is required (step S9 in FIG. 2).

From the charging current Ib for detecting full charge,
By the above function tv (I), time tb ′ (= tv (I
b)) is obtained (step S10 in FIG. 2). This ta
From ', tb', the charging time t2 from the constant current charging to the constant voltage charging until the full charge is [t2 = tb '
-Ta '] (step S11 in FIG. 2).

Therefore, each predicted time t1, t
The total t3 (= t1 + t2) of 2 is the time until the lithium secondary battery 11 being charged is fully charged (step S12 in FIG. 2).

B. Charging Operation in Constant Voltage Charging Mode The operation when the lithium secondary battery 11 is charged in the constant voltage charging mode will be described below.

The charging characteristics of the lithium secondary battery are as shown in FIG. 3, and the charging voltage and time during the constant voltage charging period can be expressed as shown in FIG. From FIG. 5, it can be seen that the charging time t is a function of the charging current I. This function will be referred to as tv (I).

Under the control of the charging control unit 16, the charging time calculation unit 17 calculates the charging time from the charging current (In) during constant voltage charging measured by the current measuring unit 13 to the full charge during constant voltage charging. Predict (steps S7 to S11 in FIG. 2).

At this time, since the time t1 from the constant current charging to the constant voltage charging is not relevant, [t1 = 0] is set, and the charging current In during constant voltage charging measured by the current measuring unit 13 is calculated as above. By the function tv (I), the time ta
'(= Tv (In)) is obtained (step S7 in FIG. 2).
~ S9).

From the charging current Ib for detecting full charge,
By the above function tv (I), time tb ′ (= tv (I
b)) is obtained (step S10 in FIG. 2). This ta
From ', tb', the charging time t2 until full charge during constant voltage charging is obtained by [t2 = tb'-ta '] (step S11 in FIG. 2).

Thus, the predicted time t1 until switching to constant voltage charging and the predicted time t2 until full charging after switching to constant voltage charging are obtained, and from these values, the predicted charging time of the secondary battery is obtained. With this configuration, it is possible to always accurately predict the charging time until the secondary battery is fully charged.

The above-described technique of the present invention can be applied not only to the charging mechanism of the lithium secondary battery but also to any device having another secondary battery whose open-circuit battery voltage is almost proportional to the remaining capacity of the battery.

[0046]

As described above in detail, according to the present invention, in the charging control device for the secondary battery, the battery voltage when opened is substantially equal to the battery capacity, until the battery being charged is fully charged. The time can be predicted accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of the above embodiment.

FIG. 3 is a diagram showing charging characteristics of a secondary battery to be charged in the above-mentioned embodiment.

FIG. 4 is a characteristic diagram showing the relationship between charging voltage and time during the constant current charging period of the above embodiment.

FIG. 5 is a characteristic diagram showing the relationship between charging current and time during the constant voltage charging period of the above embodiment.

FIG. 6 is a block diagram showing a configuration of a conventional secondary battery charging time prediction device.

[Explanation of symbols]

11 ... Lithium secondary battery, 12 ... Voltage measuring unit, 13 ... Current measuring unit, 14 ... Switch, 15 ... Constant voltage / constant current power supply unit, 16 ... Charging control unit, 17 ... Charging time calculating unit.

Claims (6)

[Claims] 1. A rechargeable battery charge control device in which the battery voltage when opened is approximately equal to the battery capacity, and means for measuring the rechargeable battery voltage and means for measuring the rechargeable battery charging current. A means for calculating the time until the secondary battery being charged is fully charged based on the measured battery voltage and charging current value, and the secondary battery being charged is fully charged. To predict the charging time of a secondary battery. 2. A charging control device for controlling constant current / constant voltage charging of a secondary battery, the battery voltage of which when opened is substantially equal to the battery capacity, means for measuring the battery voltage of the secondary battery, and the secondary battery. Means for measuring the charging current of the secondary battery, means for determining the charging mode of the secondary battery, and charging until the secondary battery is charged in the constant current mode until the measured battery voltage value switches to constant voltage charging. A means for predicting the time and predicting the charging time from the measured charging current value to full charge, and the charging current value measured when the secondary battery is charged in the constant voltage mode becomes full charge. And a means for predicting a charging time up to, and predicting the time until the secondary battery being charged is fully charged. 3. When the secondary battery is charged in the constant current mode, a predetermined first function is used from the battery voltage and charging current during constant current charging and the battery voltage switching to the constant voltage charging mode. Then, using the means for obtaining the predicted time t1 until switching to constant voltage charging and the second function predetermined from the charging current during constant current charging when the secondary battery is charged in the constant current mode. Means for obtaining a predicted time t2 until full charge after switching to constant voltage charging, and means for adding t2 to the predicted time t1 to obtain a predicted time until the secondary battery being charged is fully charged. The charging time predicting apparatus for a secondary battery according to claim 1, further comprising: 4. When the secondary battery is charged in a constant current mode, a battery voltage V during constant current charging is calculated by using a function tc (V, I) of a charging time t determined by a battery voltage V and a charging current I.
The time ta (= tc (Va, Im)) is obtained from a and the charging current Im by the above function tc (V, I), and the function is calculated from the charging current Im during constant current charging and the battery voltage Vo switching to the constant voltage charging mode. time tb by tc (V, I)
The charging time predicting device for a secondary battery according to claim 2 or 3, wherein (= tc (Vo, Im)) is obtained, and by subtracting ta from tb, a predicted time until switching to constant voltage charging is obtained. 5. When the secondary battery is charged in the constant current mode, the charging current Im during constant current charging is used by using the function tv (I) of the charging time t determined by the charging current I during constant voltage charging. From the above function tv (I) to the time ta '(=
tv (Im)), and charging current Ib for detecting full charge
From the above function tv (I) to time tb '(= tv
(Ib)) and subtracting tb 'from ta' to obtain a predicted time until full charge after switching to constant voltage charging. A charging time prediction device for a secondary battery according to claim 2 or 3 or 4. . 6. When the secondary battery is charged in the constant voltage mode, the charging current In during constant voltage charging is calculated by using the function tv (I) of the charging time t determined by the charging current I during constant voltage charging. From the above function tv (I) to the time ta '(=
tv (In)) is calculated and the charging current Ib for detecting full charge is obtained.
From the above function tv (I) to time tb '(= tv
(Ib)) is obtained, and the estimated time until full charge is obtained by subtracting tb 'from ta'.
Alternatively, the charging time prediction device for a secondary battery according to item 5.