JP3177405B2 - Secondary battery charge / discharge control method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A secondary battery capable of being repeatedly charged and discharged is provided with a full charge detecting means and a discharging detecting means in order to prevent overcharge and overdischarge. As the full charge detection means, a voltage detection method for detecting the battery voltage of the secondary battery, a −ΔV detection method for detecting that the voltage of the secondary battery has decreased by a predetermined voltage from the peak voltage, and a battery temperature of the secondary battery A temperature detection method and the like for detection are already known.

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

[0004]

By the way, secondary batteries are 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 are not completely the same in all the unit cells, and some variation occurs.

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

Accordingly, an object of the present invention is to provide a charge / discharge control method and apparatus for charging / discharging while preventing overcharge and overdischarge of a secondary battery.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling the charging and discharging of a secondary battery comprising a plurality of unit cells , wherein the amount of electricity of the secondary battery is 30% to 90%.
The charging and discharging of the secondary battery is performed within the range described above.

Further, the present invention is a charge / discharge control device for a secondary battery, which is a combination of a plurality of unit cells, wherein the charge switch controls charging of the secondary battery, and controls 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 calculating an electric quantity of the secondary battery by integrating the charging current and the discharging current. And condition determining means for controlling the charge switch and the discharge switch based on the calculated amount of electricity of the secondary battery. The condition determining means determines that the calculated amount of electricity of the secondary battery is Prepare
Charge and discharge of the secondary battery within the range of 30% to 90% of the amount of electricity
The charge switch and the discharge switch are turned on and off so that power is supplied .

[0009]

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

Therefore, in the present invention, the charging current and the discharging current are calculated by calculating the charging current and the discharging current to control the charging and discharging of the secondary battery. That is, while the secondary battery is being charged, the charging current of the secondary battery is detected and integrated (added).
%, The charging switch is turned off to interrupt charging of the secondary battery. On the other hand, when discharging the secondary battery, the discharge current of the secondary battery is detected and integrated (subtracted). When the amount of electricity remaining in the secondary battery reaches 30%, the discharge switch is turned off to turn off the secondary battery. Cut off the discharge.

[0011]

FIG. 1 shows an embodiment of the present invention, in which 1 is a charging power source composed of a solar cell, and 2 is a plurality (4 in this embodiment).
), A load driven by the secondary battery 2, 4 a charging power source 1 and a secondary battery 2
, A charging switch consisting of a relay switch inserted between the secondary battery 2 and the load 3, a discharge switch consisting of a relay switch inserted between the secondary battery 2 and the load 3, and 6 being connected in series with the secondary battery 2. , A current detection resistor for detecting a charge current and a discharge current of the secondary battery 2, a temperature detection element 7 for detecting a battery temperature of the secondary battery 2, an electric quantity 8, a battery voltage, a battery temperature, etc. of the secondary battery 2. Is a control circuit that controls the ON / OFF of the charge switch 4 and the discharge switch 5 based on.

FIG. 2 shows the details of the control circuit 8.
1 is a battery voltage detecting means for detecting the battery voltage of the secondary battery 2, and 12 and 13 are a first amplifier and a second amplifier for amplifying the voltage generated across the current detection resistor 6. When a charging current flows through the secondary battery 2, the first amplifier 12 generates a voltage proportional to the voltage across the current detection resistor 6. Conversely, when a discharging current flows through the secondary battery 2, the second 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 current detection means for detecting a charging current and a discharging current of the secondary battery 2.

Reference numeral 14 denotes an electric signal for calculating an amount of charge and an amount of discharge of the secondary battery 2 by multiplying output signals from the first amplifier 12 and the second amplifier 13, that is, a charge current or a discharge current by a predetermined time. The amount calculating means 15 adds the calculated amount of electricity when the secondary battery 2 is charged, based on the calculation result of the amount of electricity calculating means 14, and calculates the amount of electricity when the secondary battery 2 is discharged. This is an electric quantity integrating means for integrating the electric quantity of the secondary battery by subtracting the electric quantity, and the integration result of the electric quantity integrating means 15 indicates the calculated electric quantity 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 amount-of-electricity integrating unit 15, and displays the calculated amount of electricity of the secondary battery 2 using an LED or the like.

Further, reference numeral 17 denotes a battery temperature detecting means for detecting a battery temperature of the secondary battery 2 by receiving a signal from the temperature detecting element 7, and 18 an integration result of the electric quantity integrating means 15, a battery voltage detecting means 11 and a battery. This is a condition determining means for outputting 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 detecting 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
It may be constituted by a microcomputer.

First, the outline of the present invention will be described. In a secondary battery 2 in which unit cells each composed of 40 nickel cadmium cells are stacked, variations in the amount of electricity of each unit cell,
Due to variations in the temperature distribution due to charge and discharge, some of the cells may be overcharged or overdischarged, and as a result, the entire secondary battery 2 will be deteriorated.

Therefore, according to the present invention, the secondary battery 2 is
The battery is charged and discharged between 30% and 90% of the amount of electricity originally provided in the secondary battery 2. For this purpose, according to the present invention, the charge electric current and the discharge electric charge of the secondary battery 2 are calculated by performing the charge current integration process and the discharge current integration process, and the charge and discharge of the secondary battery 2 are performed. Control.
That is, while the secondary battery 2 is being charged, the charging current of the secondary battery 2 is detected and integrated (added). When the amount of electricity of the secondary battery 2 reaches 90%, the charging switch 4 is turned on. Turn off to cut off charging of the secondary battery 2. 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 shut off the discharge of the secondary battery 2.

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

Furthermore, when the charging and discharging of the secondary battery 2 are repeatedly performed, the secondary battery 2 calculated by the self-discharge of each unit cell of the secondary battery 2, the variation in the amount of electricity of the unit cell, the thermal effect, or the like. An error occurs between the amount of charged electricity or the amount of discharged electricity and the actual amount 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. It is to prevent.

Hereinafter, the specific operation of the present invention will be described with reference to the operation flowcharts of FIGS. First, in step S1, an initial value of the circuit is set. The initial value to be set includes the original fully charged amount of electricity of the secondary battery 2 and the charging efficiency. In step S2, the charge switch 4 and the discharge switch 5 are turned on, and the charge flag and the discharge flag are turned on.

In step S3, the battery voltage detecting means 11, the first amplifier 12, and the second 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
Battery temperature is detected. In steps S4 and S5, when the current of the secondary battery 2 is detected, it is determined whether the current is a charging current or a discharging current. If the current is the charging current, in step S6, the first
Based on the output of the amplifier 12,
, The amount of charge electricity is calculated. On the other hand, if the current is the discharge current, the amount of discharge electricity is calculated by the amount-of-electricity calculation means 14 based on the output of the second amplifier 13 in step S7.

In step S8, the electric quantity integrating means 1
5, the integration of the amount of charge or the amount of discharge is performed. When the secondary battery 2 is charged, the amount of charged electricity is added, and when discharged, the amount of charge 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 charge flag is not ON (that is, the charge switch 4 is off, and the
Is only discharged) in step S10.
In, it is determined whether the calculated amount of electricity of the secondary battery 2 is 80% or less. Then, when it is determined that the charge is not more than 80% (that is, it is determined that the rechargeable battery 2 is not immediately overcharged even when 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 charge flag is already ON, then 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 off and the secondary battery 2 is only charged),
In step S14, the calculated amount of electricity of the secondary battery 2 is 4
It is determined whether it is 0% or more. Then, when it is determined that it is not more than 40% (that is, it is determined that overdischarging does not immediately occur even when the secondary battery 2 is discharged), the discharge switch 5 is turned on in steps S15 and S16. And the discharge flag is turned ON.

Next, step S17 shown in FIG.
When both the charge switch 4 and the discharge switch 5 are on), 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 the secondary battery 2 from being overcharged.
At 9, the charging switch 4 is turned off and the charging 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 a 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 rechargeable battery 2 and the actual amount of electricity of the rechargeable battery 2, and the rechargeable battery 2 is already in a fully charged state. It is. At that time, the process first resets the calculated amount of electricity of the secondary battery 2 to 100% in step S21, and then turns off the charge switch 4 and the charge flag in steps S22 and S23, and the process proceeds to step S3. Return.

If 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 not more than 30%, 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 proceeds to step S25.
Return to 3.

On the other hand, if the calculated amount of electricity 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 voltage is equal to or higher than the cell (the secondary battery 2 of the present embodiment has 40 unit cells connected in series, and the battery voltage of the secondary battery 2 is 44 V).

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 overdischarged. It is a case where 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 turns off 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 method of controlling charge and discharge of a secondary battery formed by combining a plurality of cells, the two
Within the range of 30% to 90% of the amount of electricity originally provided by the secondary battery
In the charge and discharge of the secondary battery, that is, the secondary battery
Charges and discharges over the range of all electricity originally provided
Rather, the charge / discharge is performed with sufficient margin, so even if there is some variation in the capacity of each unit or the temperature distribution of each unit due to charge / discharge, overcharge and overcharge of each unit Discharge can be reliably prevented, and the secondary battery can be charged and discharged.

[Brief description of the drawings]

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

FIG. 2 is a block circuit diagram showing a main part of an embodiment of the present invention in detail.

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

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

FIG. 5 is an operation flowchart showing one 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 Electric quantity calculation means 15 Electric quantity integration means 17 Battery temperature detection Means 18 Condition judgment means

Continuation of front page (56) References JP-A-7-274404 (JP, A) JP-A-8-140272 (JP, A) JP-A-6-176797 (JP, A) JP-A-6-90504 (JP) JP-A-6-78464 (JP, A) JP-A-5-316658 (JP, A) JP-A-5-316666 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H02J 7/10 H01M 10/44 H02J 7/00

Claims (4)

(57) [Claims] 1. A charge / discharge control method for a secondary battery comprising a plurality of unit cells , wherein the secondary battery is provided with
Charging / discharging the secondary battery within a range of 30% to 90% of the amount of electricity . 2. A charge / discharge control device for a secondary battery comprising a plurality of unit cells, comprising: a charge switch for controlling charging of the secondary battery; and a discharge switch for controlling discharge of the secondary battery. Charge / discharge current detecting means for detecting a charge current and a discharge current of the secondary battery; an electric quantity integrating means for calculating an electric quantity of the secondary battery by integrating the charge current and the discharge current; Condition determining means for controlling the charge switch and the discharge switch based on the calculated amount of electricity of the secondary battery. The condition determining means determines that the calculated amount of electricity of the secondary battery is an amount of electricity originally provided by the secondary battery. Of 30
% To 90% of the secondary battery.
A charging and discharging control device for a secondary battery, wherein the charging switch and the discharging switch are turned on and off , respectively. 3. The condition determining means determines that the calculated amount of electricity of the secondary battery is 90% of the amount of electricity originally provided by the secondary battery.
A smaller amount of charge restart electricity has been reached and the secondary
3. The secondary battery according to claim 2, wherein the battery determines that the discharge restart electricity amount is larger than 30% of the original electricity amount, and turns on the charge switch and the discharge switch, respectively. Charge and discharge control device. 4. A temperature detecting device for detecting a battery temperature of the secondary battery, and a voltage detecting device for detecting a battery voltage of the secondary battery, wherein the determining device determines that the battery temperature of the secondary battery is It is determined that the temperature has reached a temperature higher than an allowable range and that the battery voltage of the secondary battery has reached a voltage lower than an allowable range, and the charge switch and the discharge switch are respectively turned off. Item 2. A charge / discharge control device for a secondary battery according to Item 2.