JPH08331770A - Method and apparatus for charging/discharging secondary battery - Google Patents

Abstract

PURPOSE: To prevent the overcharge and excessive discharge of a secondary battery by charging/discharging the secondary battery, in the range between a charge- permissible electric quality smaller than the electric quality of the upper charge limit of the secondary battery and a discharge-permissible electric quality larger than the electric quality of the lower discharge limit of the secondary battery. CONSTITUTION: Charged and discharged quantities of electricity of a secondary battery 2 are calculated by the accumulation processing of charging and discharge currents, and the charge and discharge of the secondary battery 2 are controlled. Namely, during the charging of the secondary battery 2, the charging current of the secondary battery 2 is detected and accumulated (added), and a charging switch 4 is turned off and the charging of the secondary battery 2 is interrupted, when the quantity of electricity which the secondary battery 2 has reaches 90% (a charge-permissible quantity of electricity). When the secondary battery 2 is discharged, the discharge current of the secondary battery 2 is detected and accumulated (subtracted). A discharging switch 5 is turned off and the discharge of the secondary battery 2 is interrupted, when the quantity of electricity remaining in the secondary battery 2 becomes 30% (a discharge-permissible quantity of electricity).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging / discharging control method and device for preventing overcharge and overdischarge of a secondary battery and charging / discharging.

[0002]

2. Description of the Related Art A rechargeable battery which can be repeatedly charged and discharged is provided with a full charge detecting means and a discharge detecting means in order to prevent overcharge and overdischarge thereof. The full charge detection means includes a voltage detection method that detects the battery voltage of the secondary battery, a -ΔV detection method that detects that the voltage of the secondary battery has dropped from the peak voltage by a predetermined voltage, and a battery temperature of the secondary battery. A temperature detecting method for detecting is already known.

Further, as the discharge detecting means, a method of detecting the battery voltage of the secondary battery is well known.

[0004]

By the way, the secondary battery is often used in combination by electrically connecting a plurality of unit cells in series or in parallel. In such a case, the capacity of each unit cell and the temperature distribution of each unit cell due to charging / discharging do not become completely the same state in all the unit cells, and some variations occur.

Therefore, from the viewpoint of the entire secondary battery, there seems to be no problem, but some of the unit cells are overcharged or overdischarged, resulting in deterioration of the entire secondary battery. There is a fear.

Therefore, an object of the present invention is to provide a charging / discharging control method and device for preventing overcharge and overdischarge of a secondary battery and charging / discharging.

[0007]

SUMMARY OF THE INVENTION The present invention is a charge / discharge control method for a secondary battery, which comprises a plurality of unit cells combined together,
Charge and discharge of the secondary battery is performed within a range of charge allowable electricity amount smaller than the charge upper limit electricity amount of the secondary battery and discharge allowable electricity amount larger than the discharge lower limit electricity amount of the secondary battery. .

Furthermore, the present invention is a charge / discharge control device for a secondary battery comprising a combination of a plurality of unit cells, the charge switch controlling the charging of the secondary battery and the discharge of the secondary battery. A discharge switch, a charging / discharging current detecting means for detecting a charging current and a discharging current of the secondary battery, and an electric quantity integrating means for integrating the charging current and the discharging current to calculate an electric quantity of the secondary battery. A condition determining means for controlling the charging switch and the discharging switch based on the calculated electricity amount of the secondary battery, the condition determining means is configured such that the calculated electricity amount of the secondary battery is the charge of the secondary battery. It is determined that the charge allowable amount of electricity smaller than the upper limit amount of electricity and the discharge allowable amount of electricity greater than the discharge lower limit amount of electricity of the secondary battery are reached, and the charging switch and the discharge switch are turned off respectively. It is an.

[0009]

According to the present invention, the secondary battery is not charged and discharged with the entire amount of electricity originally possessed, but a range with a margin,
For example, charging / discharging is performed in the range of 30% to 90%.

Therefore, in the present invention, the charge current integration process and the discharge current integration process are performed to calculate the charge electricity amount and the discharge electricity amount of the secondary battery and control the charge and discharge of the secondary battery. That is, during charging of the secondary battery, the charging current of the secondary battery is detected and integrated (added), and the result is 90
When it reaches%, the charge switch is turned off to interrupt the charging of the secondary battery. On the other hand, when the secondary battery is discharged, the discharge current of the secondary battery is detected and integrated (subtracted), and when the amount of electricity remaining in the secondary battery reaches 30%, the discharge switch is turned off and the secondary battery is discharged. Cut off the discharge.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which 1 is a charging power source composed of a solar cell, 2 is a plurality of power sources (4 in this embodiment).
(0) nickel-cadmium batteries are stacked and electrically connected in series to a secondary battery, 3 is a load driven by the secondary battery 2, and 4 is a charging power source 1 and a secondary battery 2.
Is a charge switch composed of a relay switch interposed between and, 5 is a discharge switch composed of a relay switch interposed between the secondary battery 2 and the load 3, and 6 is connected in series with the secondary battery 2. , A current detection resistor for detecting a charging current and a discharging current of the secondary battery 2, 7 a temperature detecting element for detecting a battery temperature of the secondary battery 2, 8 an electric quantity of the secondary battery 2, a battery voltage, a battery temperature, etc. Is a control circuit for controlling on / off of the charging switch 4 and the discharging switch 5 based on the above.

FIG. 2 shows the details of the control circuit 8.
Reference numeral 1 is a battery voltage detection means for detecting the battery voltage of the secondary battery 2, and 12 and 13 are a first amplification amplifier and a second amplification amplifier for amplifying the voltage generated across the current detection resistor 6. When the charging current flows in the secondary battery 2, the first amplification amplifier 12 generates a voltage proportional to the voltage across the current detection resistor 6, and conversely, when the discharging current flows in the secondary battery 2, the second amplification amplifier 13 Generates a voltage proportional to the voltage across the current detection resistor 6. That is, the first amplification amplifier 12 and the second amplification amplifier 13 constitute a current detection unit that detects the charging current and the discharging current of the secondary battery 2.

Numeral 14 is an electric power for calculating the amount of charge electricity and the amount of discharge electricity of the secondary battery 2 by multiplying the output signals from the first amplification amplifier 12 and the second amplification amplifier 13, that is, the charging current or discharging current by a predetermined time. The quantity calculating means 15 adds the calculated quantity of electricity when the secondary battery 2 is charged, based on the calculation result of the quantity of electricity calculating means 14, and calculates it when the secondary battery 2 is discharging. The amount of electricity of the secondary battery is integrated by subtracting the amount of electricity, and the result of integration by the amount of electricity integration unit 15 indicates the calculated amount of electricity of the secondary battery 2. . Reference numeral 16 denotes a display unit that displays the amount of electricity of the secondary battery 2 processed by the electricity amount accumulating unit 15, and displays the calculated amount of electricity of the secondary battery 2 by using an LED or the like.

Further, 17 is a battery temperature detecting means for receiving a signal from the temperature detecting element 7 to detect the battery temperature of the secondary battery 2, and 18 is an integration result of the electricity quantity integrating means 15, a battery voltage detecting means 11 and a battery. The condition determining means outputs a charge control signal CHG and a discharge control signal DIS for controlling ON / OFF of the charge switch 4 and the discharge switch 5 based on the detection result of the temperature detection means 17.

In the control circuit 8, the electric quantity calculating means 14, the electric quantity integrating means 15 and the condition judging means 18 are
It may be configured by a microcomputer.

First, the outline of the present invention will be described. In the secondary battery 2 in which unit cells composed of 40 nickel-cadmium batteries are stacked, the variation in the electric quantity of each unit cell,
There is a possibility that some of the unit cells may be overcharged or overdischarged due to the variation in temperature distribution due to charge / discharge, and as a result, the secondary battery 2 as a whole is deteriorated.

Therefore, according to the present invention, the secondary battery 2 is
The secondary battery 2 is charged and discharged between 30% and 90% of the original amount of electricity. To this end, according to the present invention, the charge current amount and the discharge current amount of the secondary battery 2 are calculated by performing the charge current integration process and the discharge current integration process to charge and discharge the secondary battery 2. Control.
That is, during charging of the secondary battery 2, the charging current of the secondary battery 2 is detected and integrated (added), and when the amount of electricity of the secondary battery 2 reaches 90%, the charging switch 4 is turned on. The charging of the secondary battery 2 is cut off by turning it off. On the other hand, when the secondary battery 2 is discharged, the discharge current of the secondary battery 2 is detected and integrated (subtracted).
Then, when the amount of electricity remaining in the secondary battery 2 reaches 30%, the discharge switch 4 is turned off to interrupt the discharge of the secondary battery 2.

Further, in the present invention, the charging switch 4
Is once turned off and then returned to the on state when the amount of electricity remaining in the secondary battery 2 becomes 80% or less as the secondary battery 2 is discharged. Further, the discharge switch 5 is once turned off and then returned to the on state when the amount of electricity of the secondary battery 2 becomes 40% or more as the secondary battery 2 is charged. .

Further, when the secondary battery 2 is repeatedly charged and discharged, the secondary battery calculated by the self-discharge of the individual cells of the secondary battery 2, the variation in the amount of electricity of the cells, the thermal influence, or the like. An error will occur between the charged or discharged quantity of electricity and the actual quantity of electricity of the secondary battery 2. Therefore, in the present invention, the calculated amount of electricity of the secondary battery 2 is appropriately corrected based on the battery temperature and the battery voltage of the secondary battery 2, and the overcharge and overdischarge of the secondary battery 2 due to such an error are performed. Is to prevent.

The specific operation of the present invention will be described below with reference to the operation flowcharts of FIGS. First, in step S1, the initial value of the circuit is set. The initial values to be set include the original full-charged electricity amount of the secondary battery 2 and charging efficiency. In step S2, the charging switch 4 and the discharging switch 5 are turned on, and the charging flag and the discharging flag are turned on.

In step S3, the battery voltage detecting means 11, the first amplifying amplifier 12 and the second amplifying amplifier 1
3 and the battery temperature detecting means 17, respectively, the voltage of the secondary battery 2, the charging current or the discharging current, and the secondary battery 2
The battery temperature of is detected. When the current of the secondary battery 2 is detected in steps S4 and S5, it is determined whether the current is the charging current or the discharging current. If it is the charging current, in step S6, the first
Based on the output of the amplification amplifier 12, the electric quantity calculation means 14
Thus, the amount of charge electricity is calculated. On the other hand, when it is the discharge current, in step S7, the discharged electricity quantity is calculated by the electricity quantity calculation means 14 based on the output of the second amplification amplifier 13.

In step S8, the electricity quantity integrating means 1
5, the charge electricity amount or the discharge electricity amount is integrated. When the secondary battery 2 is charged, the charge electricity amount is added, and when it is discharged, it is subtracted. Thereby, the amount of electricity of the secondary battery 2 is calculated. Then, the process proceeds to step S9 in FIG.

In step S9, the charging flag is turned on.
Is determined. The charging flag is not ON (that is, the charging switch 4 is OFF, and the secondary battery 2
Is only discharged), step S10
At, it is determined whether the calculated electricity amount of the secondary battery 2 is 80% or less. Then, when it is determined that it is 80% or less (that is, it is determined that overcharging does not occur immediately even if the secondary battery 2 is charged), the charging switch 4 is turned on in steps S11 and S12. , The charging flag is turned on.

If it is determined in step S9 that the charging flag is already ON, in step S13,
It is determined whether the discharge flag is ON. When the discharge flag is not ON (that is, the discharge switch 5 is in the OFF state, and the secondary battery 2 is only charged),
In step S14, the calculated electricity quantity of the secondary battery 2 is 4
It is determined whether it is 0% or more. Then, if it is determined to be 40% or less (that is, it is determined that the secondary battery 2 is not discharged immediately even if discharged), the discharge switch 5 is turned on in steps S15 and S16. The discharge flag is turned on.

Next, step S17 shown in FIG. 5 (at this time,
(The charge switch 4 and the discharge switch 5 are both in the ON state), it is determined whether the calculated amount of electricity of the secondary battery 2 is 90% or more. If so, steps S18 and S1 are performed to prevent overcharge of the secondary battery 2.
In 9, the charge switch 4 is turned off and the charge flag is also turned off, and the process returns to step S3.

If it is determined in step S17 that the calculated amount of electricity of the secondary battery 2 is not 90% or more, step S20
In, it is determined whether the battery temperature of the secondary battery 2 is within the normal range (for example, 60 degrees or less). if,
If the normal range is exceeded, an error occurs between the calculated amount of electricity of the secondary battery 2 and the actual amount of electricity of the secondary battery 2, and the secondary battery 2 is already fully charged. Is. At that time, the process first resets the calculated amount of electricity of the secondary battery 2 to 100% in step S21, then turns off the charging switch 4 and the charging flag in steps S22 and S23, and the process proceeds to step S3. Return.

When the battery temperature of the secondary battery 2 is within the normal range, it is determined in step S24 whether the calculated amount of electricity of the secondary battery 2 is 30% or less. If it is 30% or less, in steps S25 and S26, the discharge switch 5 is turned off and the discharge flag is also turned off in order to prevent overdischarge of the secondary battery 2, and the process is performed in step S25.
Return to 3.

On the other hand, when the calculated electricity amount of the secondary battery 2 is not less than 30%, it is determined in step S27 whether the battery voltage of the secondary battery 2 is normal, specifically, the battery voltage is 1.1 V / It is determined whether or not the cell (the secondary battery 2 of this embodiment has 40 unit cells connected in series, so the battery voltage of the secondary battery 2 is 44 V) or more.

If the battery voltage is 44 V or less, an error occurs between the calculated amount of electricity of the secondary battery 2 and the actual amount of electricity of the secondary battery 2, and the secondary battery 2 is already over-discharged. This is the case when it is in a state. At that time, the process first resets the calculated amount of electricity of the secondary battery 2 to 10% in step S28, then turns off the discharge switch 5 and the discharge flag in steps S29 and S30, and the process proceeds to step S3. Return. If the battery voltage is normal, the process returns to step S3.

[0030]

According to the present invention, there is provided a charging / discharging control method for a secondary battery comprising a combination of a plurality of unit cells, the allowable charging electric amount being smaller than the charging upper limit electric amount of the secondary battery, and the secondary battery charging method. Since the secondary battery is charged / discharged within a range of discharge allowable electricity quantity that is larger than the discharge lower limit electricity quantity of the secondary battery, the capacity of each cell or the temperature distribution of each cell associated with charging / discharging will have some influence. Even if variations occur, it is possible to reliably prevent overcharging and overdischarging of each unit cell and charge and discharge the secondary battery.

[Brief description of drawings]

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

FIG. 2 is a block circuit diagram showing in detail the essential parts of one embodiment of the present invention.

FIG. 3 is an operation flowchart showing an embodiment of the present invention.

FIG. 4 is an operation flowchart showing an embodiment of the present invention.

FIG. 5 is an operation flowchart showing an embodiment of the present invention.

[Explanation of symbols]

 2 Secondary Battery 4 Charge Switch 5 Discharge Switch 6 Current Detection Resistor 7 Temperature Detection Element 8 Control Circuit 11 Battery Voltage Detection Means 12 First Amplification Amplifier 13 Second Amplification Amplifier 14 Electricity Quantity Calculation Means 15 Electricity Quantity Accumulation Means 17 Battery Temperature Detection Means 18 Condition judging means

Claims (4)

[Claims] 1. A charging / discharging control method for a secondary battery comprising a combination of a plurality of unit cells, wherein the allowable charging amount of electricity is smaller than the charging upper limit of electricity of the secondary battery and the discharging lower limit of electricity of the secondary battery. Within the range of discharge allowable electricity quantity that is larger than
A charging / discharging control method for a secondary battery, comprising charging / discharging the secondary battery. 2. A charging / discharging control device for a secondary battery, comprising a plurality of unit cells combined, comprising: a charging switch for controlling charging of the secondary battery; and a discharging switch for controlling discharging of the secondary battery. A charging / discharging current detecting means for detecting a charging current and a discharging current of the secondary battery; an electric quantity integrating means for integrating the charging current and the discharging current to calculate an electric quantity of the secondary battery; A condition determining means for controlling the charging switch and the discharging switch based on the calculated electricity quantity of the secondary battery, wherein the condition determining means is such that the calculated electricity quantity of the secondary battery is the charge upper limit electricity quantity of the secondary battery. To determine that the charge allowable amount of electricity is smaller than that and the discharge allowable amount of electricity is greater than the discharge lower limit amount of electricity of the secondary battery, and each of the charge switch and the discharge switch is turned off. To Characteristic secondary battery charge / discharge control device. 3. The condition determining means determines that the calculated electricity quantity of the secondary battery has reached a charge resumption electricity quantity smaller than the charge allowable electricity quantity, and a discharge resumption electricity quantity larger than the discharge allowable electricity quantity. 3. The charging / discharging control device for a secondary battery according to claim 2, wherein the charging switch and the discharging switch are each brought into a conductive state by determining that the charging amount has reached. 4. A temperature detecting means for detecting a battery temperature of the secondary battery, and a voltage detecting means for detecting a battery voltage of the secondary battery, wherein the determining means determines that the battery temperature of the secondary battery is It is determined that a temperature above an allowable range and a battery voltage of the secondary battery has reached a voltage below an allowable range, and each of the charge switch and the discharge switch is turned off. Item 2. A secondary battery charging / discharging control device.