JPH0878061A - Charge control device for sealed battery - Google Patents

Abstract

PURPOSE: To charge a battery neither too much nor too little whether the battery is new one or not or the like by combining the detection of sealed reaction with switching voltage setting responding to a detection result so as to conduct specified action. CONSTITUTION: Constant current charge by means of a current I1 is executed at first. When a battery voltage reaches a switching voltage V1 , the constant current charge by means of a weaker current I2 is executed. When the battery voltage reaches a switching voltage V2 , the constant current charge by means of a further weaker current I3 is executed. The charge is terminated for instance after the lapse of a predetermined time. When the capacity of the battery is assumed to be C, the current I1 is about 0.2 to 0.3C, the current I2 is about 0.1C, the I3 is about 0.05C, and a constant current charge current by means of the current I3 continues 5 hours for instance. The current I3 is desirable to be set to such a value that an oxygen recycle reaction in the battery with an adequate electrolyte amount is conducted sufficiently so as not to exhaust gas outward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger for charging a sealed battery such as a lead-sealed battery with multi-stage constant current, and more particularly to a charge control device for the charger.

[0002]

2. Description of the Related Art Batteries such as lead batteries are used as a power source for electric vehicles. In order for the electric vehicle to continue running, the battery must be charged at a predetermined frequency. Several methods have been proposed as battery charging methods,
For example, Japanese Utility Model Publication No. 4-93454 discloses an example of multi-stage constant current charging.

In this prior art, first, constant current charging (first stage) is executed with a relatively large current value. When the battery voltage rises with the progress of charging and reaches an inflection point (predetermined switching voltage), constant current charging (second stage) is executed with a smaller current value. The second stage constant current charging is
The constant current charging of the first stage is ended after the lapse of time or a time determined according to the electrolyte temperature. By adopting such a method, gas generation in the battery can be suppressed.

[0004]

However, such a charging method is not suitable for a sealed battery. For example, in a lead-acid sealed battery, oxygen generated in the positive electrode during charging is reacted with lead in the negative electrode and finally returned to water (oxygen recycling reaction) so that gas is not discharged to the outside. However, it is not the case that this lead-oxygen recycling reaction is sufficiently performed in any lead-sealed battery. For example, in a new battery, the amount of electrolyte is generally larger than an appropriate amount, so that oxygen gas is generated from the positive electrode and hydrogen gas is generated from the negative electrode and is discharged to the outside. In this way, the lead-sealed battery in which the amount of the electrolyte is not optimized and the lead-sealed battery which is optimized as a result of being used properly have different voltages during charging. Therefore, if the constant current charging of that stage is terminated because the voltage of the battery has risen to a predetermined switching voltage, excess or deficiency will occur in charging.

The present invention has been made to solve the above problems, and pays attention to the sealed reaction in a sealed battery such as a lead sealed battery to determine whether the battery is new or not. The aim is to realize charging without excess or deficiency.

[0006]

In order to achieve such an object, the present invention is to charge a sealed battery with a constant current, and when the voltage of the sealed battery reaches a predetermined switching voltage, a smaller current value is set. In a charging control device for charging a sealed battery with a constant current, means for detecting a sealed reaction in the sealed battery, and high if it can be considered that the sealed reaction has not occurred, and low if it can be considered that it has occurred. Means for setting the switching voltage according to the detection result.

The present invention is characterized in that the sealing result is detected from the voltage of the sealed battery at the end of the previous charging, or from the amount of electrolytic solution or the specific gravity of the electrolytic solution of the sealed battery.

[0008]

In the present invention, in multi-stage constant current charging of a sealed battery, the presence or absence of a sealed reaction (for example, oxygen recycling reaction) in the sealed battery is first detected, and if the sealed reaction does not occur, the switching voltage is high. , If it is reached, it will be set low. In general, a sealed battery in which a sealed reaction does not occur has a high battery voltage (saturation voltage) at the end of multi-stage charging, and thus a low switching voltage may cause insufficient charging. On the other hand, since the saturation voltage of the sealed battery in which the sealing reaction occurs is low, overcharge may occur if the switching voltage is high. In the present invention, the switching voltage is set high when the sealing reaction does not occur, such as when the battery is new, and is set lower when it is not.
Therefore, in the present invention, sufficient charging is realized regardless of whether the battery is new or not.

In the present invention, the presence or absence of the sealed reaction is detected, for example, from the voltage of the sealed battery at the end of the previous charging, that is, the saturation voltage. As a result, the present invention can be realized without adding a new sensor, that is, only with the battery voltage sensor provided conventionally. Of course, the presence or absence of the closed reaction may be detected by directly detecting the amount of electrolyte or the specific gravity of the electrolyte. In this case, the switching voltage can be set more accurately, and the saturation voltage at the end of the previous charge must be stored. Disappears.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the construction of an apparatus suitable for carrying out each embodiment of the present invention. The battery 1 shown in this figure is a lead-sealed battery and is also a drive power source for an electric vehicle. The discharge output of the battery 1 is converted into an alternating current by the inverter 2 and supplied to the alternating current motor 3 which is the drive source of the vehicle. The charger 4 is a charger that charges the battery 1 according to a command or the like. The charging control circuit 5 controls the output current of the charger 4, that is, the charging current of the battery 1 according to a predetermined multi-step constant current charging method. The current sensor 6 detects the current of the battery 1,
The detected value is supplied to the charge control circuit 5 for performing constant current charging. Further, the specific gravity sensor 7 detects the electrolytic solution specific gravity of the battery 1 and supplies the detected value to the charge control circuit 5. The specific gravity sensor 7 is not necessary when carrying out the first embodiment.

FIG. 2 shows the principle of charge control in the present invention. The procedure shown in this figure is an example of three-stage constant current charging. That is, in this figure, first, the current I ₁
Constant current charging is performed, and when the voltage of the battery 1 reaches the switching voltage V ₁ , constant current charging is performed by the smaller current I _2, and when the voltage of the battery 1 reaches the switching voltage V ₂ , a smaller current I _{3 is performed.} The constant current charging is performed, and the charging is finished when a predetermined time elapses. If the capacity of the battery 1 is C, the current I ₁ is, for example, about 0.2 to 0.3 C, and the current I _{2 is}
Is about 0.1 C and the current I ₃ is about 0.05 C, and constant current charging with the current I ₃ is continued for 5 hours, for example. The current I ₃ is preferably set to a value such that the oxygen recycling reaction is sufficiently carried out in a battery having an appropriate amount of electrolyte and gas is not discharged to the outside.

In the present invention, the switching voltage V ₂ is changed according to the amount of the electrolytic solution of the battery 1. That is, the value of increasing the switching voltage V ₂ when an equal amount of the electrolytic solution is new is high, for example, set to V _{2 a,} if the electrolyte amount is small switching voltage V
₂ is set to a lower value, for example, V _2b . As described above, by setting the switching voltage V ₂ according to the amount of the electrolytic solution, it is possible to prevent the battery 1 from being overcharged or deficient. Specifically, when the amount of electrolyte is large and therefore the voltage (saturation voltage) at the end of the third-stage constant current charging is as high as V _b (B), the switching voltage V ₂ is set to V _2a and charging is performed. prevent deficiency, if the saturation voltage electrolyte volume is small therefore, for example, V _a and lower (a), is prevented overcharge by setting the switching voltage V ₂ to V _2b.

FIG. 3 shows a flow of operations of the charge control circuit 5 in the first embodiment of the present invention. In this embodiment, the stored switching voltages V ₁ and V ₂ are read (100), and then constant current charging with the current I ₁ is executed (102). When the voltage of the battery 1 reaches the switching voltage V ₁ (104, 106), constant current charging with a smaller current I ₂ is executed (108). When the voltage of the battery 1 reaches the switching voltage V ₂ (110, 112), a smaller current I ₃
The constant current charging by is executed, and at the same time, the built-in charging end timer is set to 5 hours (114). When the timer counts up (116, 118), the charging control circuit 5 ends charging (120). At that time, the voltage V _B of the battery 1 at the end of charging is detected by the charging control circuit 5,
The value of the switching voltage V ₂ to be used at the next charging is calculated by the following formula (122). The calculation result is the charge control circuit 5
It is stored internally (124).

[0015]

## EQU1 ## V ₂ = K ₁ · (V _B −V ₀ ) + K ₂ where K ₁ , K ₂ , V ₀ : constant By such an operation, the switching voltage V ₂ is added without adding the specific gravity sensor 7 or the like. Can be set to an appropriate value to prevent excess or deficiency of charging. That is, as shown in FIG. 2, since the amount of the electrolytic solution appears as the level of the saturation voltage, the switching voltage V ₂ should be set by the above equation, that is, according to the difference between the saturation voltage and the constant V _0. As a result, charge switching can be executed in accordance with the amount of electrolytic solution so that neither overcharge nor undercharge occurs. Of course, not only the switching voltage V ₂ but also the switching voltage V ₁ may be changed, or only the switching voltage V ₁ may be changed. It is not limited to three-step constant current charging.

FIG. 4 shows an operation flow of the charge control circuit 5 in the second embodiment of the present invention. In this embodiment, first, the specific gravity sensor 7 detects the specific gravity of the electrolytic solution (126), and based on this, the switching voltages V ₁ and V ₂ are determined (126). The arithmetic expressions of the switching voltages V ₁ and V ₂ are
The expression in parentheses in the above expression may be replaced with the difference between the detected value of the electrolyte specific gravity and the appropriate amount. Then, steps 102 to 118 are executed, and the charging ends (120).

[0017] By this operation, without storing the switching voltage V ₁ and V _2, the excess and deficiency of setting the switching voltage V ₁ and V ₂ to an appropriate value charging can be prevented. At that time, since the specific gravity of the electrolytic solution is directly detected, there are fewer error factors than in the first embodiment, and accurate setting is possible. Note that only the switching voltage V ₁ or only the switching voltage V ₂ may be changed, and the invention is not limited to the three-stage constant current charging.

[0018]

As described above, according to the present invention,
In multi-stage constant current charging of a sealed battery, the sealed reaction in the sealed battery is first detected, and the switching voltage is set high if it cannot be considered that the sealed reaction has not occurred, and set low if it can be considered. It is possible to realize proper charging regardless of whether the product is new or not.

Further, according to the present invention, the presence or absence of the closed reaction is detected from the saturation voltage at the end of the previous charging, so that the above effect can be obtained without adding a new sensor. Further, according to the present invention, since the presence or absence of the closed reaction is detected by the direct detection of the amount of electrolyte or the specific gravity of the electrolyte, more accurate switching voltage setting becomes possible and the saturation voltage at the end of the previous charge is stored. The processing can be simplified by eliminating the need for

[Brief description of drawings]

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

FIG. 2 is a timing chart showing the principle of charge control in the present invention.

FIG. 3 is a flowchart showing the operation of the charge control circuit in the first embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of a charge control circuit according to the second embodiment of the present invention.

[Explanation of symbols] 1 battery 2 inverter 3 motor 4 charger 5 charging control circuit 6 current sensor 7 specific gravity sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Kobayashi 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (3)

[Claims] 1. A charging control device for charging a sealed battery with a constant current and, when the voltage of the sealed battery reaches a predetermined switching voltage, charging the sealed battery with a constant current at a smaller current value. A means for detecting the reaction, and a means for setting the switching voltage according to the detection result so that it is high if it can be considered that the closed reaction has not occurred and low if it can be considered that the closed reaction has not occurred. Charge control device. 2. The charging control device according to claim 1, wherein
A charging control device characterized by detecting a sealed reaction from the voltage of a sealed battery at the end of the previous charging. 3. The charging control device according to claim 1, wherein
A charging control device, which detects a sealed reaction from the amount of electrolytic solution or the specific gravity of electrolytic solution of a sealed battery.