JPH0544783B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a recovery charging method using alternate charging and discharging in a prismatic sealed lead acid battery. Prior art and its problems Sealed lead-acid batteries include a type in which a pole group consisting of a thin electrode and a separator is spirally wound and inserted into a cylindrical battery case, such as the one seen in U.S. Pat. No. 3,862,861. , and one in which the electrode group is inserted into a conventional box-shaped battery case. The former has a cylindrical shape and can also use a metal case as an exterior can, so it has a high pressure resistance of 2 to 3
It can withstand high internal pressures such as Kg/ ^cm2 . Therefore, it is possible to charge with a large current that can cause such an internal pressure, and recovery charging can be performed in a short time. The rest is a box-shaped battery case, which is made of synthetic resin and has low pressure resistance, so it cannot maintain the internal pressure of the battery as high as a cylindrical battery. Therefore, the safety valve used in this battery is set at a low value, such as 1 kg/cm ² or less. On the other hand, the electrode plates used in prismatic batteries are
Since the cylindrical shape is generally thicker than the cylindrical shape, the charging current density is also higher, and therefore the oxygen gas absorption efficiency at the negative electrode is also lower in the prismatic shape. It takes a long time to charge a prismatic sealed lead-acid battery, and it takes about 5 hours at the shortest time, making it very difficult to use when using a portable device, that is, when using alternating charging and discharging. Compared to sealed Ni-Cd batteries and the aforementioned cylindrical sealed lead-acid batteries, which can be charged for a short period of time within 1 hour or 30 minutes, prismatic sealed lead-acid batteries are suitable for applications that require alternate charging and discharging. This is one of the major problems that we have. Purpose of the Invention The purpose of the present invention is to provide a method for charging a prismatic sealed lead-acid battery in a short time. The present invention provides a method that enables charging within one hour, or within 30 minutes depending on the conditions, without causing problems such as runaway. Structure of the Invention In order to achieve the above object, the present invention provides a charging method applied to a prismatic sealed lead-acid battery, in which the maximum current in the constant current part is set to 2 to 4 times the nominal capacity of the battery, and then the voltage in the constant voltage part is set to 2 to 4 times the nominal capacity of the battery. This is a charging method that sets the voltage from 2.40V to 2.55V per single battery cell.
Moreover, the charging circuit is cut off at the automatically set charging time within one hour. In addition, a safety protection circuit is provided so that the charging circuit becomes conductive when the temperature of the storage battery is 40°C or less before charging of the prismatic sealed lead acid battery starts. Examples of prismatic sealed lead-acid batteries to which the charging method of the present invention can be applied include those in which the electrolyte is held within a separator formed into a sheet shape mainly made of glass fiber of 1 micron or less and an electrode plate active material;
There are two types: one in which this electrolyte is made into a dilute gel, and one in which the electrolyte is in the form of a conventional gel. However, since it has a small internal resistance and generates little heat, it is optimal. At the same time, the lead-acid battery's straps and connections between cells must be made securely so that they will not melt due to large currents. Examples Example 1 As a separator, a sheet-like material formed by randomly intertwining 90 wt% of 0.8 micron glass fibers and 10 wt% of 11 micron glass fibers was used. A fully charged prismatic sealed lead-acid battery with a nominal capacity of 4AH and 6V was prepared. This battery was discharged at 0.25C (1A) to a final voltage of 5.10V. The discharge duration was 3 hours and 24 minutes, and the capacity at 0.25C was 3.40AH. This battery has a maximum current of 2.5C (10A), 7.50V
When constant current and constant voltage charging was performed for one hour at a constant voltage, the results shown in FIG. 1 were obtained. Note that the battery temperature at the start of charging was 20°C. Next, when the charged battery was discharged under the same conditions as above,
The discharge capacity at 0.25C was 3.40AH, and it was completely charged to its original state. The total cumulative charging capacity in this charging is 3.75AH, and charging starts.
After 30 minutes, it was charged to 3.5AH. The battery reached a maximum temperature of 38°C approximately 33 minutes after charging started. The change in battery weight before and after charging was less than 0.01 g, indicating that the sealing reaction was occurring smoothly. Example 2 Using a battery with the same configuration as Example 1, the maximum current,
Constant current and constant voltage charging was performed by changing the set voltage and charging time. Charging was performed in an air bath at 30°C. The capacity recovery rate after charging (capacity after charging/capacity before charging), the temperature rise due to charging, and the resulting swelling of the battery case were measured, and the results shown in Table 1 were obtained. In the table, ○ marks indicate that the capacity recovery rate is sufficient and there is no bulging of the battery case, △ mark indicates that the battery case has bulged (and includes cases that are about to cause thermal runaway), and × mark indicates the capacity. Indicates an insufficient recovery rate of 90% or less.

[Table] From the above results, when the maximum current is 1C, charging time of 30 minutes is insufficient for charging, and it is necessary to charge for 1 hour. Also, when the maximum current is 5C, short-time charging is possible, but the battery case is easily deformed due to intense heat generation. It can be seen that the maximum current should be set to 2 to 4C when considering short-time charging performance and safety against forgetting to turn off the battery. Regarding the set voltage, 2.30V/cell cannot charge the battery sufficiently in any case. At 2.60V/cell, heat generation and associated thermal runaway are about to occur after one hour. In order to secure charging and consider safety,
It should be set to 2.40 to 2.55V/cell, but for safety reasons, considering actual variations in the set voltage due to charger manufacturing, variations in battery voltage due to temperature, and a drop in the charging end voltage due to battery fluid loss. 2.45～
Should be set to 2.50V/cell. According to our experience, in this type of sealed lead-acid battery, when the gas absorption efficiency is close to 100%, the battery temperature exceeds 55℃ and the set voltage is
If the voltage is higher than 2.50V/cell, thermal runaway will lead to self-destruction, which is extremely dangerous. Therefore, the battery temperature at the start of charging should be kept at about 40° C. or lower, and in applications where the battery temperature becomes high, the set voltage should be set particularly low. Set the charging time to 1 hour or less, and set the charging circuit to automatically shut off after the set time. Also, by detecting the battery temperature, the battery temperature can be
A safer charging method is provided by providing a protection circuit that allows the charging circuit to conduct at temperatures below 40°C. Effects of the Invention As described above, the charging method of the present invention reduces the heat of the battery case of a prismatic sealed lead-acid battery by setting the charging current to 2 to 4 C and setting the set voltage to 2.40 to 2.55 V/cell. 1 without the inevitable swelling and violent thermal expansion associated with deformation.
It can be charged within 30 minutes under optimal conditions. Therefore, this type of prismatic sealed lead-acid battery, which has been limited so far, can be used for alternate charging and discharging applications, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a charging method according to the present invention.

Claims (1)

[Claims] 1. Two times (2C) to four times (4C) the battery nominal capacity (C)
Battery voltage is 2.40V to 2.55V per single cell at a constant current of
2.40V~ per single cell after charging until
Charge with a constant voltage of 2.55V and let the charging current drop,
A method for charging a sealed prismatic lead-acid battery, characterized in that the charging circuit is automatically cut off one hour after the start of charging. 2. The method for charging a prismatic sealed lead-acid battery according to claim 1, further comprising a safety protection circuit that shuts off the charging circuit when the battery temperature exceeds 40°C.