JPH0574197B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an improvement in a charging method for a sealed lead-acid battery. Conventional technology Problems with conventional sealed lead-acid battery chargers include:
It has the ability to charge batteries that have been left unattended after being over-discharged (hereinafter referred to as "over-discharged batteries"). This is because the internal resistance of the overdischarged battery is high, making it difficult for charging current to flow. In particular, for cathode absorption type sealed lead-acid batteries, a method is often used in which charging is performed using a minute current (hereinafter referred to as "trickle charging") after detecting the voltage at the end of charging. When an over-discharged battery is charged with this type of charger, the internal resistance of the over-discharged battery is high, so the charging voltage rises immediately after charging starts and the battery enters trickle charging, resulting in almost no charge.
As one of the ways to overcome this drawback, the patent application
As described in No. 16196, there is a method of applying an AC voltage to an over-discharged battery or reverse charging it, and then performing regular charging to restore the battery. Problems to be Solved by the Invention When the above charging method is applied to an actual charger, the conditions for determining that the current flowing in the charging and discharging directions are equal or close to it in order to switch to regular charging There is a problem that in some cases, recovery may not be possible. As a condition for switching reverse charging, the simplest method is to apply an alternating current voltage or keep the reverse charging time constant. However, with this method, recovery performance is poor for over-discharged batteries with extremely high internal resistance, and when the internal resistance is relatively low, the charging time increases and charging There are adverse effects such as increased heat generation and deterioration of life characteristics after recovery. An example of this is shown below. The battery used was a 4V, 4Vh sealed lead-acid battery. Charging characteristics when the reverse charging time is 60 minutes are shown in FIGS. 4 and 5. Figure 4 shows that the internal resistance is approximately
Charging characteristics of a 300Ω over-discharged battery. Figure 5 shows the charging characteristics when the internal resistance is about 1600Ω. If the internal resistance is about 300Ω, normal charging will begin after reverse charging, but if the internal resistance is high, about 1600Ω, the battery will enter trickle charging early after returning to normal charging and will not be charged. Table 1 shows the maximum battery surface temperature when an overdischarged battery with an internal resistance of approximately 300Ω is used and the reverse charging time is varied. Obviously, the longer the reverse charging time is, the more heat is generated.

[Table] Figure 6 shows the cycle life characteristics of an over-discharged battery that recovered after 60 minutes of reverse charging. Over-discharged battery A, which has an internal resistance of about 10Ω, has been reverse-charged more than necessary, so the internal resistance has decreased to about 10Ω.
Compared to battery B, which was left over-discharged at 300Ω, the capacity decreased faster, and its life span was approximately 150 cycles. From these facts, when performing reverse charging to recover, it is considered preferable to perform reverse charging according to the internal resistance of the overdischarged battery. Means for Solving the Problems In view of the above-mentioned problems, the present invention reversely charges an over-discharged battery according to its internal resistance, so that the AC voltage component included in the charging voltage is Focusing on the fact that the higher the resistance, the higher the resistance, when charging a battery that has been left over-discharged, reverse charging is repeated for a certain period of time until the AC voltage component included in the charging voltage drops below a certain value. The feature is that the battery can be returned to charging. Function: It is possible to perform reverse charging according to the internal resistance of an over-discharged battery. This applies the fact that when the internal resistance of an over-discharged battery is high, the AC voltage component included in the charging voltage (always a positive value) becomes large. Reverse charging is performed in accordance with the internal resistance by repeatedly performing reverse charging until the AC voltage component included in the voltage falls below a certain value. Embodiment FIG. 1 is a block diagram of a charger used in the present invention. During normal charging, trickle charging starts after detecting the voltage at the end of charging. When the voltage detecting section 1 detects the voltage at the end of charging, the control section 2 operates and controls the current control section 3 to perform trickle charging using the resistor 4. enter. In the case of charging an over-discharged battery, the AC voltage component generated in the sealed lead-acid battery 5 is applied to the resistor 7 through the capacitor 6 . This alternating current voltage becomes an input to an alternating current voltage detecting section 8, and if it exceeds a certain value, a timer 9 is operated. The timer 9 causes a current to flow through the coil 10 of the relay for a certain period of time to switch the contacts 11 of the relay, and also operates the control section 2 to flow a reverse charging current. With such an operation, reverse charging is repeated until the AC component included in the charging voltage falls below a certain value, and normal charging can begin. Charging characteristics when using a 4V, 4Ah sealed lead acid battery are shown in Figures 2 and 3. The detection voltage at the end of charging is 4.9V, the timer setting axis is 15 (min), and the AC component detection voltage is 1.0V ^pp . Figure 2 shows the charging characteristics when the internal resistance is approximately 1600Ω, and normal charging is started after 6 times of reverse charging. Figure 3 shows the charging characteristics when the internal resistance is approximately 50Ω, and normal charging begins after one reverse charge. In this way, reverse charging could be repeated depending on the internal resistance from high to low internal resistance. Note that 12 is a diode, and 13 is a transformer rectifier. Effects of the Invention As described above, according to the present invention, reverse charging can be performed depending on the internal resistance, so it has great industrial value, such as making it easy to charge a normal battery or a battery that has been left over-discharged. It is what it is.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the charger used in the present invention, FIGS. 2 and 3 are characteristic curve diagrams showing charging characteristics when the charger in FIG. 1 is used, and FIG. 4 5 is a characteristic curve diagram showing charging characteristics when reverse charging time is constant, and FIG. 6 is a characteristic curve diagram showing cycle life characteristics after reverse charging recovery. 1 is a voltage detection section, 3 is a current control section, 5 is a sealed lead acid battery, and 8 is an AC voltage detection section.

Claims (1)

[Claims] 1. At the start of normal charging, if the AC voltage component included in the charging voltage exceeds a certain value, an operation is performed to flow a current in the opposite direction to the normal one for a certain period of time until the AC voltage component becomes below the certain value. A method for charging a sealed lead-acid battery, which is characterized by returning to normal charging after repeating up to 30 seconds.