JPH1197073A - Method for charging sealed lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve charge and discharge cycle life characteristics of a battery group by measuring the oxygen concentration around the outside of a charging storage battery, controlling of the decrease of charging current or the drop of charging voltage, or stopping charging, and suitably charging the battery group with a simple method in which many storage batteries are connected in series,. SOLUTION: A battery group in which twenty four battery modules each of which has parallel connected six storage batteries and has electric capacity of 60 Ah (standardized capacity) are connected in series is put in a housing container and covered with a hood. A hole is provided on a part of the hood, and an oxygen concentration meter is attached to the part. Therefore, charging is started at the constant current of 20 A while the oxygen concentration is measured for each minute, and charging current is decreased to one third when, the oxygen concentration reaches 25%. The oxygen concentration is once decreased and then increased. When the oxygen concentration again reaches 25%, the charging current is again decreased to one third. The operation is repeated, and charging is finished at the time when about eight hours pass from the start of charging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a sealed lead-acid battery.

[0002]

2. Description of the Related Art A sealed lead-acid battery has a configuration in which oxygen gas generated by electrolysis of an electrolytic solution at a positive electrode is charged and reacted at a negative electrode during charging, thereby returning the oxygen gas to water and preventing a decrease in the electrolytic solution. ing. However, if the battery is charged with a large current after the full charge state, the oxygen gas generation rate at the anode exceeds the oxygen gas absorption reaction rate at the cathode, and the internal pressure of the battery increases. Since the battery case material of the sealed lead-acid battery is usually made of plastic, the battery may be ruptured when the internal pressure of the battery increases, and a gas release valve is attached to the sealed lead-acid battery to avoid this. When the gas release valve is activated,
As a matter of course, the electrolyte decreases, and the sealed lead-acid battery reaches its end of life early. Therefore, it is an important subject to control charging so that the gas release valve is not operated as much as possible. In particular, when the sealed lead-acid battery is the driving power source of the electric vehicle, the required voltage is very high, and thus a plurality of batteries are connected in series and used. For example, in case of 144V specification, 7
A series connection of two batteries requires a series connection of 144 batteries for the 288V specification. Conventionally, when charging a group of a large number of serially connected batteries, the battery voltage of a representative battery (pilot battery) or a representative battery module is monitored. The reason for this is that it is difficult to monitor the state of all individual batteries in terms of cost. When the voltage of the pilot battery reaches a predetermined value during charging,
Control is performed such that the supply of the charging current is stopped or the charging current value is reduced.

[0003]

However, the pilot battery is merely a representative of a large number of batteries, and monitoring its state does not necessarily accurately monitor the state of the entire series-connected battery group. Naturally, as the number of batteries connected in series increases, variations in the state of individual batteries tend to increase. Therefore, at the time of charging, even if the voltage of the pilot battery has not reached the predetermined value, the voltages of the other batteries have already exceeded the predetermined value, the internal pressure of the battery has increased, and oxygen gas has been continuously discharged out of the battery. It is possible. This phenomenon can occur both when the battery is charged at a constant current and at a constant voltage. Oxygen gas is released out of the battery, the electrolyte decreases, and if even one battery that reaches the end of its life early is in a battery group connected in series, the entire battery group becomes unusable. In other words, batteries that can still be used are wasted. The problem to be solved by the present invention is not limited to a single sealed lead-acid battery, and a battery group in which a large number of sealed lead-acid batteries are connected in series is appropriately charged by a simple method, and the charge / discharge cycle life of the battery group is reduced. The purpose is to improve the characteristics.

[0004]

Means for Solving the Problems To solve the above-mentioned problems, a method for charging a sealed lead-acid battery according to the present invention measures the oxygen concentration around the outside of the sealed lead-acid battery in a rechargeable battery, and determines the oxygen concentration. When the predetermined value is reached, at least one of the control of the reduction of the charging current and the reduction of the charging voltage is performed, or the charging is stopped. By using the oxygen concentration around the outside of the sealed lead-acid battery measured by an oxygen sensor or the like as an index for charge control, it is possible to easily detect that there is a battery generating oxygen gas due to excessive charging. Therefore, it is possible to take measures such as stopping charging or reducing the charging current before the battery in which the oxygen gas is generated is seriously damaged. Thereby, the charge / discharge cycle life characteristics of the battery group can be improved.

[0005] The charge control method of the present invention is not necessarily a technique applicable only to a battery group in which a plurality of sealed lead-acid batteries are connected in series. Naturally, the present invention can be applied to charging a single sealed lead-acid battery.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of an embodiment of the present invention will be described below. A battery group in which 24 battery modules each having an electric capacity of 60 Ah (standard capacity) in which six sealed lead storage batteries are connected in parallel is produced. The battery group is stored in a storage container made of polypropylene, and is covered with a sheet (hood) made of polyethylene. It is desirable that the materials of the storage container and the hood are acid-resistant. Although there is almost no possibility that the electrolytic solution (sulfuric acid aqueous solution) is released from the sealed lead-acid battery, as described above, in this example, the emergency was taken into consideration. A hole for measuring oxygen concentration is provided in one place of the hood, and an oxygen concentration meter is attached to this hole. The oximeter used was an oximeter (model number CM-25ANL) manufactured by Riken Keiki. The charging control will be described in detail. First, charging is started at a constant current of 20 A while measuring the oxygen concentration at one minute intervals. Oxygen concentration is 2
After confirming that the volume reached 5 vol%, the charging current was reduced to 1 /
3 and continue charging. The oxygen concentration once decreases and then increases. Oxygen concentration is 25vol again
% After confirming that the charging current has reached
(That is, 1/9 of the initial value), and charging is continued.
This operation is repeated, and charging ends when eight hours have elapsed from the start of charging.

[0007] The charge control of the present embodiment may be automated by software or the like, or may be performed manually. Each charge control condition can be changed without departing from the spirit of the present invention. In this example, the constant current charging is adopted, but for example, a constant voltage charging may be adopted. Further, in this example, the charging current is reduced when the oxygen concentration reaches a predetermined value. However, a method of stopping charging may be employed.

[0008]

EXAMPLES Two battery groups described in the embodiment of the present invention were prepared. For one battery group, as detailed above,
The charging method of the present invention was applied. The other battery group was charged while controlling an appropriate sealed lead-acid battery as a pilot battery. More specifically, 2
The charging was started at a constant current of 0 A, and after confirming that the battery voltage of the pilot battery reached 2.5 V, the charging current was increased to 1
/ 3 and continue charging. The battery voltage once decreases and then increases. After confirming again that the battery voltage has reached 2.5 V, the charging current is further reduced to 1/3 (that is, 1/9 of the initial value) to continue charging. This operation is repeated, and charging ends when eight hours have elapsed from the start of charging. The value of 2.5V is not too high. It was confirmed by another experiment that the set value of 2.5 V did not significantly damage the life characteristics of the sealed lead storage battery.

After each of the two battery groups was charged by the above-described charging method, the battery group was discharged at a constant current of 20 A until the terminal voltage of the battery group reached 40.8 V (average 1.7 V / cell). A charge / discharge cycle life test was performed on the two battery groups under the above charge / discharge conditions. In this test, the life is determined when the discharge capacity reaches 60% of the initial value. As a result, the battery group to which the conventional charging method controlled by the pilot battery was applied reached its life after about 500 charging / discharging operations, whereas the battery group to which the charging method of the present invention was applied was 80 cells.
The service life was not reached even if the charge and discharge were performed 0 times or more.

[0010]

According to the present invention, a battery group in which a number of sealed lead-acid batteries are connected in series can be properly charged by a simple method, and the charge / discharge cycle life characteristics of the battery group can be improved. .

Claims (2)

[Claims] An oxygen concentration around the outside of a sealed lead-acid battery in a rechargeable battery is measured, and when the oxygen concentration reaches a predetermined value, at least one control of a reduction in charging current and a reduction in charging voltage is performed. Or charging is stopped, wherein the charging is stopped. 2. The method for charging a sealed lead-acid battery according to claim 1, wherein a plurality of sealed lead-acid batteries are connected in series.