JPH1175327A - Charging of battery unit and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger for battery unit which can conduct efficient charging up to a full charging condition with battery temperature restrained lower than a prescribed limit. SOLUTION: This charger is provided with a plurality of blower fans 4 for cooling a battery unit 1 constituted of a plurality of secondary batteries 2, and a control circuit 11 for adjusting the air volume of the blower fans 4. The control circuit 11 leads out fan air volume at which battery temperature will not exceed its prescribed limit by estimating the battery temperature at charging completion with the fan air volume used as a parameter, and outputs its results as the optimum output of the blower fan 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method and apparatus for charging a secondary battery such as a nickel-metal hydride battery, and more particularly to a method for forcibly cooling a secondary battery during charging with an optimum cooling power. It is an object of the present invention to provide a charging method and an apparatus that reliably prevent the battery temperature at the end of charging from exceeding a predetermined limit value.

[0002]

2. Description of the Related Art In recent years, as a DC power supply for electric vehicles such as electric vehicles and AV equipment, battery packs in which a plurality of secondary batteries such as nickel-metal hydride batteries are combined in series or in parallel have been used. When charging the battery, a dedicated charging device is used. For example, in charging a nickel-metal hydride battery, charging is performed until a fully charged state by supplying a constant charging current for a predetermined time.

Generally, a secondary battery generates heat as it is charged and discharged.
Particularly in nickel-hydrogen batteries, the temperature rise during charging is remarkable, and if the battery temperature exceeds the limit value, the charging reaction hardly progresses. Therefore, the assembled battery is forcibly cooled by a blower fan during charging. ing. At this time, in order to keep the power consumption of the blower fan as low as possible, a temperature sensor is attached to the secondary battery to monitor the battery temperature during charging, and the airflow of the blower fan increases stepwise as the battery temperature rises A control method is adopted for causing the control to be performed.

[0004]

However, in the conventional charge control system, even when a fan flow rate is set in accordance with the battery temperature at the time of rapid charging with a large current, in particular, the cooling effect by the air blowing takes time. There is a risk that the battery temperature will rise sharply and exceed the limit value due to a considerable delay. When the battery temperature exceeds the limit value, the charging is forcibly stopped, so that the charging cannot be performed until the battery is fully charged. It is an object of the present invention to provide a method and an apparatus for charging a battery unit that can efficiently charge a battery to a fully charged state while keeping the battery temperature below a predetermined limit value.

[0005]

According to a method of charging a battery unit according to the present invention, a battery temperature at the time of completion of charging is estimated by using a degree of cooling of the battery unit as a parameter, and the battery temperature exceeds a predetermined limit value. It is characterized in that the battery unit is charged while the battery unit is cooled based on the cooling degree obtained by deriving the cooling degree without the failure.

[0006] The rate of temperature rise of each secondary battery due to charging includes the amount of heat generated per unit time of the battery, the degree of forced cooling (cooling amount per unit time), the heat transfer coefficient of the battery, the heat capacity of the battery, and the Determined by surface area. Here, the calorific value per unit time of the battery, the heat transfer coefficient of the battery, the heat capacity of the battery, and the surface area of the battery are known values determined by the specifications and charging conditions of the battery. The change (battery temperature characteristic) can be obtained by calculation using the degree of forced cooling as a parameter. Also, the time required for charging can be calculated from the charging conditions. Therefore, if the degree of cooling is specified, the battery temperature at the time when charging is completed (end of charging) can be estimated. From this result, it is possible to determine the degree of cooling as an optimal (minimum) value at which the end-of-charge temperature does not exceed a predetermined limit value. In the case of a battery pack, its heat transfer coefficient can be determined, for example, as an average value of the heat transfer coefficient of each battery.

In the charging method of the present invention, first, the degree of cooling at which the end-of-charge temperature does not exceed a predetermined limit value is determined, and then the degree of cooling is set as the cooling power for the battery unit. Charge while cooling the unit. As a result, the temperature of the battery during charging rises in accordance with the battery temperature characteristics, and there is no possibility that the terminal charging temperature of the battery exceeds a predetermined limit value. Of course, power consumption for cooling is minimized.

[0008] A charging device according to the present invention includes cooling means for forcibly cooling the battery unit from the outside, and cooling adjusting means for adjusting the output of the cooling means. The cooling adjusting means charges the output of the cooling means as a parameter. By estimating the battery temperature at the time of completion, the output of the cooling means in which the battery temperature does not exceed a predetermined limit value is derived, and the result is set as the optimum output for the cooling means.

In the above-described charging apparatus of the present invention, by setting the optimum output to the cooling means by the cooling adjusting means, the cooling means is operated at the optimum output, and the battery unit is charged while being forcibly cooled. You.

In a specific configuration, the cooling adjustment means includes: an environmental temperature measuring means for measuring a temperature of an environment in which the battery unit is installed; a battery temperature measuring means for measuring a temperature of the battery unit; Based on battery temperature,
First operation processing means for deriving a battery temperature characteristic representing a change in the battery temperature during charging using the output of the cooling means as a parameter and the charging time as a variable, and, based on the derived battery temperature characteristic, A second arithmetic processing means for deriving an output of the cooling means such that the battery temperature does not exceed a predetermined limit value and setting the result as an optimum output to the cooling means.

In this specific configuration, the measured values of the environmental temperature and the battery temperature at the start of charging are used for deriving the battery temperature characteristic by the first arithmetic processing means, and the time change of the battery temperature is determined by the output of the cooling means. Is calculated as a parameter.
Based on the result, the second arithmetic processing unit estimates the end-of-charge temperature of the battery, and derives an output of the cooling unit such that the estimated temperature does not exceed a predetermined limit value.

In a specific configuration, the cooling means is a blower fan installed toward the battery unit. First
The arithmetic processing unit derives a heat transfer coefficient at a specific fan air flow based on a relationship between a preset fan air flow and a heat transfer coefficient of the battery unit, and derives a battery temperature characteristic based on the result. The second arithmetic processing means determines that the battery temperature at the time of completion of charging exceeds a predetermined limit value while changing the fan air volume to be specified when the first arithmetic processing means derives the battery temperature characteristic by a fixed amount. Search for the output of no cooling means.

In this specific configuration, cool air is supplied from the blower fan to the battery unit to cool the battery unit. Here, the relationship between the fan air volume and the heat transfer coefficient of the battery unit has been experimentally obtained in advance. Therefore, the first
The arithmetic processing means derives a heat transfer coefficient at a specific fan airflow based on the relationship. Thereafter, the second arithmetic processing means changes the fan airflow required for deriving the battery temperature characteristics by the first arithmetic processing means by a fixed amount at a time, and completes the charging based on the battery temperature characteristics derived by the first arithmetic processing means. The battery temperature at the time is estimated, and the minimum fan airflow at which the battery temperature does not exceed a predetermined limit value is determined.

In a more specific configuration, the cooling adjusting means includes fine adjusting means for finely adjusting the output of the cooling means in accordance with the deviation of the battery temperature from the battery temperature characteristic derived by the first arithmetic processing means. .

In this specific configuration, the battery temperature during charging is measured by the battery temperature measuring means, and the output of the cooling means is finely adjusted so that the deviation of the measured value from the battery temperature characteristics becomes zero. As a result, the battery temperature changes with high accuracy according to the battery temperature characteristics, and the final battery temperature is accurately adjusted.

[0016]

According to the charging method and apparatus according to the present invention, the battery can be efficiently charged with an optimum cooling power so that the terminal charging temperature of the battery does not exceed the limit value.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention applied to a nickel-hydrogen battery assembled battery will be specifically described with reference to the drawings. FIG. 2 shows a battery unit in which the present invention is to be implemented.
The appearance of (1) is shown, in which a plurality of nickel-hydrogen rechargeable batteries (2) are arranged with a predetermined gap therebetween, and are held together by a frame (3) in this state. , Each plus terminal and minus terminal are connected in series with each other. The frame (3) has a plurality of blower fans for forcibly cooling the plurality of secondary batteries (2).
(4) is attached.

The charging device of the present invention shown in FIG. 1 is connected to the plus terminal (14) and the minus terminal (15) of the battery unit (1). The charging device includes a charging circuit (12) that converts AC 100V AC power supplied from an AC power supply (13) into DC power and outputs the DC power, and the DC power from the charging circuit (12) is supplied to a battery unit ( 1) is supplied as power for charging, and a control circuit (11) comprising a microcomputer and D
Power is supplied to the C / DC converter (10) as operating power.
The positive and negative output terminals of the DC / DC converter (10) are connected to a motor (41) to drive each of the blower fans (4).
Connected to

The battery unit (1) includes a plurality of secondary batteries.
Battery temperature sensor for measuring the temperature at the representative point of (2)
(5) is pasted. In addition, an environmental temperature sensor (6) for measuring the temperature (outside air temperature) of the environment in which the battery unit (1) is installed is arranged near the battery unit (1). As the temperature sensors (5) and (6), a thermocouple or a thermistor can be adopted. Both temperature sensors
(5) and (6) are connected to a temperature detection circuit (9) via amplifiers (7) and (8), whereby the battery temperature and the environmental temperature are detected. The output terminal of the temperature detection circuit (9) is connected to the control circuit (11), and the detection data of the battery temperature and the ambient temperature is transmitted to the control circuit (1).
Supplied to 1).

In the charging device for the battery unit (1), the optimum fan airflow of the blower fan (4) is determined by the arithmetic processing of the control circuit (11) to be described later, and each secondary battery (2) is determined based on the optimum fan airflow. ) Is cooled while the charging circuit (12)
A constant charging current is supplied to the battery unit (1) for a predetermined time, and each secondary battery (2) is charged.

FIGS. 3 to 5 show the operation processing procedure of the control circuit (11). First, in step S1 of FIG.
A charging current value corresponding to the selected charging speed is taken in from charging current values set in advance according to one or a plurality of types of charging speeds. Next, in step S2, a charging time t _e required for full charging is calculated based on the taken charging current value, and a heat generation amount Q per unit time of the secondary battery is calculated.
Is calculated.

Subsequently, in step S3, the environmental temperature To and the battery temperature (initial temperature) T are taken in from the environmental temperature sensor (6) and the battery temperature sensor (5), and in step S4, the optimum fan air volume is determined. I do.

FIG. 4 shows a procedure for determining the optimum fan air flow. In step S41, the fan air flow is first set to 0, and in step S42, the heat transfer coefficient of each battery is derived. . In deriving the heat transfer coefficient,
As shown in FIG. 6, the relationship between the heat transfer coefficient of each battery constituting the battery unit and the fan airflow rate is experimentally obtained in advance and functioned, and the heat transfer coefficient Ui at a specific fan airflow W for each battery. Can be derived. Here, the heat transfer coefficient means a total heat transfer coefficient or a heat transmission coefficient including heat transfer by heat radiation in addition to convection heat transfer. Can be considered.

Next, in step S43 of FIG. 4, a battery temperature curve is estimated based on the following equation (1). Here, C is the heat capacity of one battery, T is the battery temperature, t is the charging time, Q is the amount of heat generated per unit time of one battery, U is the heat transfer coefficient of the battery, A is the surface area of one battery, To is the ambient temperature.

[0025]

## EQU1 ## C × dT / dt = Q-UA (T-To)

Equation 1 indicates that the amount of heat stored in the battery per unit time per unit time (left side) is equal to the difference between the amount of heat generated by the battery (first term on the right side) and the amount of cooling (first thermodynamics).
Law). In the present embodiment, the average value of the heat transfer coefficients Ui of the respective batteries obtained in step S42 is adopted as the heat transfer coefficient U of Equation 1.

In equation (1), the heat capacity C of the battery, the calorific value Q, the heat transfer coefficient U, and the surface area A of the battery are known values, and the environmental temperature To and the initial temperature of the battery are obtained as measurement data. It is possible to solve the differential equation of
As a result, the fan air volume can be set as a parameter as shown in FIG.
(W ₀ , W ₁ , W ₂ , W ₃ ...) Can be used to calculate the change over time (battery temperature curve) of the battery pond temperature T.

In step S44 of FIG. 4, the terminal charging temperature Te is derived from the battery temperature curve. Here, the charging end temperature, a battery temperature at the charging time t _e has passed required full charge. Then, in a step S45, it is determined whether or not the end-of-charging temperature Te is equal to or lower than a predetermined limit value Tmax (for example, 45 ° C.). After increasing by the value ΔW, the process returns to step S42, and similarly, the end-of-charge temperature Te is derived, and the comparison with the predetermined limit value Tmax is repeated.

When the end-of-charging temperature Te falls below the predetermined limit value Tmax due to the increase in the air volume, and the determination in step S45 is YES, the process proceeds to step S47 to output the fan air volume W at that time. I do.

As a result, a drive control signal corresponding to the fan airflow W is supplied to the DC / DC converter (10) in FIG.
A drive current for the motor (41) is generated. Thus, the blower fan (4) is driven to rotate, and a fan airflow W is obtained. Then, in step S5 of FIG.
After the charging for (1) is started, fine adjustment of the fan air volume is performed in step S6.

FIG. 5 shows a procedure for finely adjusting the fan air flow. After the environmental temperature To and the battery temperature T are fetched in step S71, the process proceeds to step S72.
Then, a deviation ΔT of the battery temperature T from the battery temperature curve is calculated based on the battery temperature curve at the fan air volume at that time. Subsequently, in step S73, the temperature deviation ΔT
Is determined to be greater than or equal to the predetermined limit value ΔTlimit, and if no, the process proceeds to step S77 to maintain the fan airflow at that time.

If the answer is YES in step S73, the process proceeds to step S74 to determine whether or not the temperature deviation ΔT is a positive value. If the temperature difference ΔT is a positive value, the process proceeds to step S75. While the air volume W is increased by a predetermined minute amount ΔW ′, if the air volume W is a negative value, the air volume W is increased in step S76.
Is reduced by a predetermined minute amount ΔW ′, and then the step S7 is performed.
At 7, the fan airflow W is output. As a result, the fan airflow is increased or decreased, and the fan airflow is finely adjusted according to the temperature deviation ΔT.

Next, in step S7 of FIG. 3, it is determined whether the battery temperature T exceeds a predetermined limit value Tmax or a predetermined charging time has elapsed.
Return to the fine adjustment of the fan air volume. Thereafter, when the determination is yes in step S7, the charging is terminated in step S8.

FIG. 8 is a graph comparing the change in battery temperature (battery of the present invention) when charging is performed by the above-described charging device of the present invention with the change in temperature (battery for comparison) by a conventional temperature control method. . For both the battery of the present invention and the battery for comparison, a battery unit composed of ten nickel-metal hydride batteries was configured as a battery unit. The voltage of the battery unit is 12 V, the rated capacity is 100 Ah, and the charging rate is 20 A (0.2
C). The charging time required for full charging was set to be 30 minutes longer than the charging time up to the rated capacity of 5 hours.

In charging the battery of the present invention, the procedure shown in FIGS. 3 and 4 was employed with the fine adjustment of the fan air volume shown in FIG. 5 stopped, and the charging was stopped when the battery temperature exceeded 45 ° C. . On the other hand, in charging the comparative battery, the fan airflow was increased when the battery temperature exceeded 35 ° C, and the charging was stopped when the battery temperature exceeded 45 ° C.

As is clear from FIG. 8, in the comparative battery, the battery temperature exceeds 45 ° C. before the elapse of 5 hours, and the battery is forcibly stopped charging without reaching the rated capacity. On the other hand, in the battery of the present invention, the battery temperature does not exceed 45 ° C. by charging for 5 hours and 30 minutes, and after being charged to 110 Ah exceeding the rated capacity, the charging is forcibly stopped after a predetermined time has elapsed. I have.

FIG. 9 shows a change in battery temperature (battery of the present invention) when the fan air volume fine adjustment shown in FIG. 5 is executed in the charging method using the charging device of the present invention. This is a comparison with the change in the battery temperature (comparative battery; the battery of the present invention in FIG. 8). As is clear from FIG. 9, in the comparative example battery, the charging time was 5 hours to
During a period of 5 hours and 30 minutes, the battery temperature reaches a predetermined limit value (45
(° C.), but in the battery of the present invention, the battery temperature is suppressed to 40 ° C. or less even when the charging time is 5 hours to 5 hours and 30 minutes.

As described above, according to the charging device of the present invention, the battery unit is efficiently charged to the fully charged state by setting the optimal fan airflow while keeping the end-of-charge temperature lower than the predetermined limit value. You can do it.

The configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims. For example, in the case where the battery unit is composed of a single secondary battery, as well as in the case where the battery unit is composed of a plurality of secondary batteries, in a configuration in which an individual blower fan is provided for each secondary battery, Also, it is possible to individually adjust the air volume of each blower fan by employing the charge control method of the present invention. In addition, it is also possible to install one blower fan for each of a plurality of secondary batteries, and to individually adjust the air volume of each blower fan.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a charging device according to the present invention.

FIG. 2 is a partially cutaway perspective view of a battery unit.

FIG. 3 is a flowchart showing a charge control procedure according to the present invention.

FIG. 4 is a flowchart illustrating a procedure for determining an optimal fan air volume.

FIG. 5 is a flowchart showing a procedure for finely adjusting a fan air volume.

FIG. 6 is a graph showing a relationship between a heat transfer coefficient and a fan air volume;

FIG. 7 is a graph showing a relationship between battery temperature and charging time using a fan airflow as a parameter.

FIG. 8 is a graph comparing a temperature change when a fine adjustment of a fan air volume is not performed with a conventional example.

FIG. 9 is a graph comparing the temperature change when the fan airflow is finely adjusted with the case where the fan airflow is not finely adjusted.

[Explanation of symbols]

 (1) Battery unit (2) Secondary battery (4) Blower fan (41) Motor (11) Control circuit (12) Charging device (13) AC power supply (14) Positive terminal (15) Negative terminal (5) Battery temperature Sensor (6) Environmental temperature sensor (9) Temperature detection circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Yoshinori Matsuura 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Katsuhiko Niiyama 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Ikuro Yonezu 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Pref. Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2 5-5, Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A charging method for charging a battery unit while externally forcibly cooling a battery unit composed of an aggregate of one or more secondary batteries, wherein charging is completed using a degree of cooling of the battery unit as a parameter. Estimate the battery temperature at the time, derive the degree of cooling such that the battery temperature does not exceed a predetermined limit value, and charge the battery unit while cooling the battery unit based on the degree of cooling obtained thereby. A method for charging a battery unit. 2. A charging device for charging a battery unit comprising an assembly of one or more secondary batteries, comprising: cooling means for forcibly cooling the battery unit from the outside; and cooling adjustment for adjusting the output of the cooling means. Means, and the cooling adjustment means comprises:
By estimating the battery temperature at the time of completion of charging by using the output of the cooling means as a parameter, the output of the cooling means such that the battery temperature does not exceed a predetermined limit value is derived,
A battery unit charging device, wherein the result is set as an optimum output to a cooling means. 3. The cooling adjusting means includes: an environmental temperature measuring means for measuring a temperature of an environment in which the battery unit is installed; a battery temperature measuring means for measuring a temperature of the battery unit; First operation processing means for deriving a battery temperature characteristic representing a change in battery temperature during charging using the output of the cooling means as a parameter and the charging time as a variable, based on the derived battery temperature characteristic, and completing the charging. 3. The charging device according to claim 2, further comprising a second arithmetic processing unit that derives an output of the cooling unit such that the battery temperature at the time does not exceed a predetermined limit value, and sets the result as an optimum output to the cooling unit. apparatus. 4. The cooling unit is a blower fan installed toward the battery unit, and the first arithmetic processing unit is configured to perform a process based on a relationship between a preset fan air volume and a heat transfer coefficient of the battery unit. A heat transfer coefficient at a specific fan airflow is derived, and a battery temperature characteristic is derived based on the result. The second arithmetic processing means includes a fan to be specified when the first arithmetic processing means derives the battery temperature characteristic. 4. The charging apparatus according to claim 3, wherein the output of the cooling means is searched for such that the battery temperature at the time of completion of charging does not exceed a predetermined limit value while changing the air volume at a constant rate. 5. The cooling adjustment means further comprises fine adjustment means for finely adjusting the output of the cooling means in accordance with a deviation of the battery temperature from the battery temperature characteristic derived by the first arithmetic processing means. The charging device according to claim 4.