JPH1198697A - Method and device for charge control for secondary battery of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge control device for the secondary battery of an electric vehicle by which overcharging and undercharging of the secondary battery can be avoided. SOLUTION: An operation device 6a calculates discharging capacity from he total discharge value and the regenerative charge value of a battery 1, until it is charged in accordance with a formula: (discharge capacit) = (total discharge value) - (regenerative charge value) and calculates an optimum charge value according to a formula: (optimum charge value) = (discharge capacity) ×1.05. If an accumulated charge value in the charging state reaches an optimum charge value, a control device 6 controls a charger 7 so as to discontinue the charging. By controlling the charge such as this, the charge corresponding to the state of the battery can be executed, so that the overcharging and the undercharging can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control method and a charge control device for a secondary battery for an electric vehicle.

[0002]

A lead-acid battery is an example of a battery for an electric vehicle. When charging the lead-acid battery for an electric vehicle, a constant current / constant voltage charge control is generally performed. Used. At this time, the constant voltage charging time is set based on the battery temperature at the time of transition from constant current charging to constant voltage charging regardless of the amount of battery discharge at the start of charging. However, since the optimal charge amount at the time of charging depends on the discharge amount of the battery, the charge amount when charging up to the set charging time becomes insufficient or excessive with respect to the optimal charge amount. There was a risk of overcharging.

An object of the present invention is to provide a charge control method and a charge control device for a secondary battery for an electric vehicle, which can avoid overcharging or insufficient charging of the secondary battery.

[0004]

Means for Solving the Problems The invention of claim 1 is applied to a charge control method for a secondary battery for an electric vehicle, and calculates the following formula (5) from the total discharge amount and the regenerative charge amount before charging the battery.

[Equation 5] (Discharge capacity) = (Total discharge amount)-(Regenerative charge amount) The discharge capacity calculated by (5) is obtained, and the optimum charge amount is calculated based on the calculated battery discharge capacity. The charging is stopped when the integrated charging amount obtained during charging reaches the optimum charging amount. According to a second aspect of the present invention, in the charge control method according to the first aspect, the secondary battery is a lead-acid battery. According to a third aspect of the present invention, in the charge control method according to the second aspect, the optimal charge amount is calculated by the following equation (6).

(Optimal charge amount) = (discharge capacity) × 1.05 (6) According to a fourth aspect of the present invention, in the charge control method according to any one of the first to third aspects, the charge control pattern is Any one of the following (a) to (c). (A) Constant-current / constant-voltage charging control (b) Constant-current / constant-voltage / constant-current charging control (c) Constant-power / constant-voltage charging control In connection with FIG. The invention according to Item 5 is a charge control device for a lead-acid battery pack for an electric vehicle, which is based on the following formula (7) based on the total discharge amount and regenerative charge amount before the battery 1 is charged.

(Discharge capacity) = (total discharge amount) − (regenerative charge amount) The optimum charge amount is calculated based on the discharge capacity calculated by the following equation (8).

[Equation 8] (Optimal charge amount) = (discharge capacity) × 1.05 (8) and an arithmetic unit 6a for calculating the charge amount and stopping the charge when the integrated charge amount during charging reaches the optimum charge amount. Battery 1
The above-mentioned object is achieved by providing a control device 6 for controlling a charger 7 for charging the battery.

[0005]

As described above, according to the first to fifth aspects of the present invention, the optimum charge amount is calculated based on the discharge capacity calculated from the total discharge amount and the regenerative charge amount of the battery. Since the charging is stopped when the obtained integrated charging amount reaches the optimum charging amount, charging corresponding to the battery state can be performed, and overcharging or insufficient charging of the battery can be avoided. According to the invention of claim 3, in the lead-acid battery, by setting the optimum charge amount to 1.05 times the calculated discharge capacity, the battery life can be improved as compared with the conventional charge control method. it can.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easier to understand. However, the present invention is not limited to the embodiment.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is a block diagram illustrating a configuration of a traveling drive mechanism of the electric vehicle. The battery 1 supplies DC power to the inverter 2, and the inverter 2 converts DC power into AC power and supplies power to the motor 3 that generates running energy. At the time of regeneration, the traveling energy of the vehicle is inversely converted into electric energy via the motor 3 and the inverter 2, and the battery 1 is charged and the vehicle is subjected to regenerative braking. The voltage sensor 4 detects a voltage V across the battery 1, and the current sensor 5 detects a current I flowing through the battery 1.
Is detected. 6 is an inverter 2 based on the voltage V and the current I detected by the voltage sensor 4 and the current sensor 5.
This is a control device that performs output control, regenerative control, and the like, and includes a calculation unit 6a and a storage unit 6b. The battery 1 is a lead-acid battery in which a plurality of module batteries C1 to Cn are connected in series.

When charging the battery 1, as shown in FIG. 3, a charger 7 provided separately from the electric vehicle is provided.
Will be charged by. The charging by the charger 7 is performed by the controller 6.
The control is performed based on the discharge capacity, the current I, and the voltage V of the battery 1 stored in the storage unit 6b.

Next, a charging control method according to the present embodiment will be described. FIG. 4 is a diagram showing changes in the current I and the voltage V during charging when control is performed in the charge pattern of “constant current-constant voltage-constant current”, and the vertical axis represents the current value and the voltage value. , The horizontal axis represents time t. As shown in FIG. 4, constant-current charging is started with a constant current I0, and when the charging voltage reaches a predetermined value V1, the operation shifts to constant-voltage charging.
When the charging becomes constant voltage, the current I decreases to a predetermined current value I1.
When it becomes, charging is performed again with a constant current.

FIG. 1 is a flowchart showing the charging control by the control device 6, and the control operation will be described with reference to this flowchart. The flowchart of FIG. 1 starts when the charging operation by the charger 7 is started. In step S1, based on the discharge capacity of the battery 1 stored in the storage unit 6b of the control device 6 in advance, the optimum charge amount is calculated by the following equation (9).

(Optimal charge amount) = (discharge capacity) × 1.05 (9) Here, the discharge capacity of the equation (9) is calculated by the following equation (1)
0) and stored in the storage unit 6b. In addition,
The total discharge amount and the regenerative charge amount in Expression (10) are calculated by current integration (Ah) based on the current I during traveling.

(Discharge capacity) = (total discharge amount) − (regenerative charge amount) (10)

When the optimum charge amount has been calculated in step S1, the process proceeds to step S2 to start charging. Next, step S3 is a step of judging whether or not the integrated charge value after the start of charging is equal to or more than the optimum charge amount calculated in step S1, and if it is equal to or more than the optimum charge amount, the process proceeds to step S4, where the charge is performed. A charging stop signal is transmitted to the container 7 to stop charging. Thus, charging of the battery 1 is completed.

As described above, in the charge control method of the present embodiment, the discharge capacity of the battery 1 is actually obtained, and 1.05 times the discharge capacity is set as the optimum charge amount, and the charge is performed at the optimum charge amount. Since it is stopped, there are the following advantages. First, in the present embodiment, since the discharge capacity of the battery 1 is actually obtained and the optimal charge amount is set based on the discharge capacity, the following effects are obtained. Improves battery life Prevents thermal runaway phenomenon Suppresses charging irregularities in module batteries Prevents overcharging and reduces charging time

[0013] Regarding the battery life, there is a close relationship between the charge amount and the battery life, and the lead-acid battery has the longest life when the charge amount is approximately 1.05 times the discharge capacity. Was confirmed by experiments. FIG. 5 qualitatively shows the relationship between the charge amount and the battery life obtained by the experiment, and the horizontal axis represents (charge amount) / (discharge capacity) in%.

FIGS. 6A and 6B are diagrams for explaining the thermal runaway phenomenon. FIG. 6A is a diagram conceptually showing a cycle of the thermal runaway. FIG. 6B is a diagram showing the battery temperature Tb and the charging current when the phenomenon occurs. I is a diagram showing changes in charging voltage V. FIG. When the battery deteriorates, the internal resistance increases, and accordingly, the heat generation increases and the battery temperature rises. When the battery temperature rises, the current value that reaches the hydrogen generation potential (the potential at which lead sulfate in the active material of the battery is almost charged and electrolysis of water in the electrolyte occurs) increases,
The charge receiving current increases. By repeating this circulation, a thermal escape phenomenon occurs. Conventionally, the constant voltage charging time is set regardless of the discharge capacity of the battery. Therefore, in the case of overcharging, there is a possibility that the above-mentioned thermal runaway phenomenon may occur, and this is shown in FIG. As described above, there has been a problem that the battery temperature and the charging current rapidly increase during the constant voltage charging, and the deterioration of the battery is accelerated. However, in the present embodiment, charging is stopped when the charged amount reaches 1.05 times the discharge capacity, so that overcharging can be prevented, and the occurrence of such a thermal escape phenomenon can be prevented. Can be suppressed. As a result, battery deterioration can be suppressed.

FIG. 7 is a diagram for explaining the charging variation of the module battery shown in FIG. 1, and shows the current I, the battery battery voltage V0, and the module battery voltages V1 and V2 when the battery pack is charged by constant power and constant voltage charging. . In FIG. 7, V0 represents the assembled battery voltage on a scale of 1/10.
Module battery voltages V1 and V2 correspond to module battery C, respectively.
1, C2. In FIG. 7, when comparing the module batteries C1 and C2, the module battery C1 having a lower voltage is obtained.
It can be seen that C1 has a lower sealed reaction efficiency than module battery C2. In the conventional charging control method, when a constant voltage charging time longer than an actually required constant voltage charging time is set, charging is performed in a state in which the sealed reaction efficiency varies, and a variation in charge amount occurs. However, according to the charging control method of the present embodiment, since charging is not performed more than necessary, the charging time in a state where the sealing reaction efficiency varies can be shorter than before, and the charging of the module batteries C1 to Cn can be performed. Variation in the amount can be suppressed.

Regarding the shortening of the charging time, in the conventional charging control method, a battery having a small discharge capacity tends to be set to a constant voltage charging time longer than an actually required time and to be overcharged. there were. However, according to the charging control method described above, such overcharging can be prevented, and the charging time can be reduced.

In addition to the above-described embodiment, a temperature sensor for detecting the battery temperature is provided as one of the measures for preventing the thermal runaway phenomenon, and charging is stopped when the battery temperature reaches a predetermined upper limit temperature. You may do it. Further, as the charge control pattern, control may be performed so that the charging is switched to the constant current charging before the charge amount of the battery becomes 1.05 times the discharge capacity. Furthermore, in the above-described embodiment, the charge pattern of “constant current / constant voltage / constant current” has been described as an example, but the present invention relates to the charge pattern of “constant current / constant voltage” and “constant power / constant voltage”. Can also be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a secondary battery 1 and a charging device used for charging the secondary battery.

FIG. 2 is a block diagram showing a configuration of a traveling drive mechanism of the electric vehicle.

FIG. 3 is a block diagram when a charger 7 is connected to the electric vehicle.

FIG. 4 is a diagram showing a charging pattern of constant current, constant voltage, and constant current.

FIG. 5 is a diagram illustrating an improvement in battery life.

6A and 6B are diagrams for explaining a thermal runaway phenomenon, in which FIG. 6A is a conceptual diagram of a thermal runaway cycle, and FIG. 6B is a diagram showing changes in battery temperature, charging current, and charging voltage when the phenomenon occurs.

FIG. 7 is a diagram illustrating charging variation of a module battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Inverter 3 Motor 4 Voltage sensor 5 Current sensor 6 Control device 6a Operation part 6b Storage part 7 Charger C1-Cn module battery

Claims (5)

[Claims] 1. A method for controlling the charging of a secondary battery for an electric vehicle, comprising the following formula (1): (discharge capacity) = (total discharge amount) ) − (Regenerative charge)… calculates the optimal charge based on the discharge capacity calculated in (1),
A charging control method for an electric vehicle secondary battery, wherein charging is stopped when the integrated charging amount during charging reaches the optimum charging amount. 2. The charge control method for an electric vehicle secondary battery according to claim 1, wherein the secondary battery is a lead-acid battery. 3. The charge control method according to claim 2, wherein the optimal charge amount is calculated by the following equation (2): (optimal charge amount) = (discharge capacity) × 1.05 (2) Charging control method for a secondary battery for an electric vehicle. 4. The charge control method according to claim 1, wherein the charge control pattern comprises: (a) constant current / constant voltage charge control; and (b) constant current / constant voltage / constant current charge control. c) Constant power / constant voltage charge control. A charge control method for a secondary battery for an electric vehicle, wherein the charge control method is any one of the following. 5. A charge control device for a lead-acid battery pack for an electric vehicle, comprising: a total discharge amount and a regenerative charge amount before the battery is charged, the following formula (3): (Total discharge amount)-(regenerative charge amount) An optimal charge amount is calculated based on the discharge capacity calculated by the following equation (4). (Equation 4) (optimal charge amount) = (discharge capacity) × 1. 05 ... (4) and a control device for controlling a charger for charging the battery so as to stop charging when the integrated charge amount during charging reaches the optimum charge amount. A charge control device for a lead-acid battery for an electric vehicle, comprising: