JP2003178808A - Manufacturing method of battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a battery pack wherein the battery pack, in which the original performance of the storage battery can be faithfully reproduced, can be manufactured with a superior reliability, while its production efficiency is enhanced. <P>SOLUTION: The manufactured plural storage batteries are divided into a storage battery group with a smaller capacity or a smaller positive electrode weight, and into a storage battery group with a larger capacity according to the boundary value decided by a distribution of its capacity or the positive electrode weight and specifications of the battery pack, and at an arranged position of sensors and/or a safety element for charging control decided by an arrangement of a unit cell and a structure of the battery, pack the storage battery extracted from the storage battery group with the smaller capacity or the smaller positive electrode weight is arranged, and at the remained position, the storage battery extracted from the storage battery group of the larger capacity of the larger positive electrode weight is arranged. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to manufacturing an assembled battery constituted by electrically connecting a plurality of storage batteries in a highly reliable manner according to the characteristics of each storage battery, and at the same time, to improve its production efficiency. The present invention relates to a method of manufacturing a battery pack that can be used.

[0002]

2. Related Background Art Conventionally used storage batteries include alkaline storage batteries such as nickel-cadmium batteries and nickel-hydrogen batteries, lead storage batteries, and lithium storage batteries for which high energy density is drawing attention. An assembled battery mounted on various mobile devices is usually configured by connecting a plurality of the above-mentioned storage batteries in series and / or in parallel. Since the battery capacity of the assembled battery determines the operating time of the device in which the assembled battery is mounted, the number of storage batteries forming the assembled battery is determined according to the specifications of the device. In the equipment, the discharge end voltage of the assembled battery is set according to the number of assembled batteries,
The battery pack that reaches the cut-off voltage is prohibited from being discharged.

The discharge end voltage Vend is set as follows in the case of an alkaline storage battery, for example. That is, when the number of groups of battery rows each including a plurality of storage batteries connected in series is up to 6, the terminal voltage of each storage battery is set to Vcel.
l, where n is the number of series-connected storage batteries forming a battery array, Vend = Vcell × n × 1.0 (1) is set. When the number of battery groups is 7 or more, Vend = Vcell * (n-1) * 1.2 (2) is set.

When the above-mentioned final voltage is not set in the device or the set value is inappropriate, the storage battery forming the assembled battery is over-discharged. On the other hand, in an assembled battery with a low battery capacity, due to the variations in the capacities of the plurality of batteries that make up the assembled battery, the remaining battery with the low remaining battery capacity is forcibly discharged from the other batteries and repolarized. Sometimes. If the phenomenon of reversal caused by this over-discharging is repeated, the performance of the storage battery deteriorates, which in turn deteriorates the performance of the assembled battery. This phenomenon becomes a particularly serious problem in lead-acid batteries and lithium-ion batteries.
Therefore, in order to avoid phenomena such as over-discharge and reversal,
As described above, it has been necessary to give consideration to each battery row, and thus the assembled battery, to maintain an appropriate discharge end voltage in accordance with the characteristics of the storage battery.

[0005]

However, due to the recent high functionality of devices and the expansion of their uses, even in devices for which the final voltage of the assembled battery is appropriately set, it is considered that the assembled battery is caused by overdischarge or reversal phenomenon. Performance deterioration of the.
It is considered that this cause is affected by various electronic circuits built in the device. That is, when the capacity of the battery pack is exhausted by the use of the device and the final voltage is reached, the device stops operating, and therefore the battery pack should not be over-discharged. However, depending on the device, a holding current and a leakage current, though minute, flow in the memory of various information and the electronic circuit for operation standby even after the operation is stopped. As a result, when the device is left for a long time, the battery pack is over-discharged during that time. At this time, the battery having a low capacity in the battery pack is forcibly discharged and repolarized due to the remaining capacity of the other battery.

When the reversal phenomenon due to overdischarge is repeated in this manner, the performance of the storage battery gradually deteriorates, and at the same time, the performance of the assembled battery also deteriorates. The performance deteriorated in this way may be significantly lower than the original performance expected of the assembled battery. As a result, the operating time of the device is shortened, or the number of times the device can be repeatedly used is small, which causes a decrease in reliability of the assembled battery itself.

The decrease in the reliability of the assembled battery due to the reversal phenomenon due to such over-discharge becomes more remarkable as the number of storage batteries constituting the assembled battery increases, particularly as the number of storage batteries connected in series increases. The damage is terrible. Further, in order to avoid the reversal phenomenon due to this over-discharge on the device side, complicated control is required, which causes a problem such as an increase in the price of the device. The present invention has been made in consideration of such a problem, and an object thereof is a battery pack which can faithfully reproduce the original performance of a storage battery and which can be manufactured with high reliability and high production efficiency. It is to provide a manufacturing method of.

[0008]

In order to achieve the above-mentioned object, a method for manufacturing an assembled battery according to the present invention is a method for manufacturing an assembled battery in which a plurality of storage batteries are conductively connected to each other. The storage battery is divided into a storage battery group having a small capacity and a storage battery group having a large capacity according to a boundary value determined based on the distribution of the capacity and specifications of the assembled battery, and is determined by the arrangement of the unit cells and the structure of the assembled battery. A storage battery extracted from the above-mentioned storage battery group having a small capacity is arranged at the position where the sensors and / or safety elements for charge control are arranged, and a storage battery extracted from the storage battery group having a large capacity is arranged at the remaining position. It is characterized by that.

Alternatively, the plurality of manufactured storage batteries are divided into a storage battery group having a small positive electrode weight and a storage battery group having a large positive electrode weight according to a boundary value determined based on the distribution of the positive electrode weight and the specification of the assembled battery. A storage battery extracted from the small storage battery group is arranged at a position for arranging sensors and / or safety elements for charge control determined by the arrangement of batteries and the structure of the assembled battery, and the remaining position is provided with the above It is characterized in that storage batteries extracted from a heavy storage battery group are arranged.

A storage battery selected from a storage battery group having a low capacity or a storage battery group having a small positive electrode weight is selected at a position where various sensors for controlling charge / discharge of the assembled battery and safety elements for safety measures are provided. By arranging such a storage battery, it is possible to reliably monitor the performance of a storage battery having a low capacity or a storage battery having a small positive electrode weight, which is a major factor influencing the performance of the assembled battery. In the remaining position, a storage battery selected from a storage battery group with a high capacity or a storage battery selected from a storage battery group with a large positive electrode weight is placed, so that the manufactured storage batteries can be used without waste and a plurality of assembled batteries can be used. Can be manufactured with high production efficiency.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Generally, communication equipment, OA equipment, AV
When constructing an assembled battery used in portable equipment such as equipment, in addition to a plurality of storage batteries, safety elements such as a thermostat, a fuse, and a polyswitch are incorporated for the purpose of ensuring safety and protecting the circuit. Further, as one of the charging control methods for performing rapid charging, a sensor such as a thermistor may be incorporated to detect the temperature of the battery. The installation positions of such sensors and safety elements are almost determined by the arrangement of a plurality of storage batteries and the structure of the assembled battery, but in general, they are often determined as the positions where the temperature easily rises. In other words, the installation positions of the sensors and the safety elements are not determined in consideration of variations in the performance of the individual storage batteries, but are determined exclusively according to the arrangement of the storage batteries and the structure of the assembled battery. Therefore, the above-mentioned over-discharge phenomenon cannot be avoided.

Therefore, in the assembled battery according to the present invention, a storage battery having a low capacity or a storage battery having a small positive electrode weight is arranged at a position where sensors and safety elements are provided. In such a storage battery having a low capacity or a storage battery having a small positive electrode weight, the charging is completed at the earliest, and the temperature rise of the battery occurs earliest. For this reason, when controlling charging by using a charging control method that detects voltage during charging or a charging control method that detects a rise in battery temperature, the amount of charge is regulated by a storage battery with a low capacity or a storage battery with a small positive electrode weight. Therefore, the other storage batteries are charged by the same amount as the storage battery having the low capacity or the storage battery having the small positive electrode weight. Therefore, after this, when the assembled battery is discharged, the discharge capacity of each storage battery becomes the same discharge amount regardless of the original capacity of each battery. Therefore, even when the above-mentioned over-discharge phenomenon of the assembled battery occurs, the discharge capacities of the respective storage batteries are uniform, so that no storage battery that undergoes reversal due to over-discharge occurs.

In the end, the reliability of the assembled battery, which depends on the discharge performance and the like, depends on the performance of the battery having a low capacity in which the sensors are installed or the battery having a small positive electrode weight. It is possible to avoid a decrease in reliability due to the extreme phenomenon. In other words, it is possible to provide a highly reliable assembled battery that reproduces the original performance of a single battery. Explaining the method for manufacturing the assembled battery according to the present invention, first, in the present invention, the plurality of manufactured storage batteries are divided into a storage battery group having a large battery capacity and a battery group having a small battery capacity according to the battery capacities. It starts from that. Alternatively, it is started by dividing a plurality of manufactured storage batteries into a storage battery group having a large positive electrode weight (large) and a battery group having a small positive electrode weight (small) according to the weight of the positive electrode.

The selection of the storage battery according to the battery capacity or the weight of the positive electrode will be described below. It is assumed that the battery capacities or the positive electrode weights of a plurality of storage batteries exhibit a nearly normal distribution. Then, according to a certain boundary value P, the storage battery is divided into a group L having a large battery capacity or a positive electrode weight and a group S having a small positive electrode weight. At this time, it can be said that the battery capacity or the positive electrode weight of the storage battery selected from the small group S is always smaller than the battery capacity or the positive electrode weight of the storage battery selected from the large group L.

On the other hand, the area under the normal distribution curve (total number of storage batteries) is the area AL of the large group L depending on the boundary value P.
And the area AS of the small group S can be divided into two. As a result, the following equation is established. AL: AS = [number of groups L]: [number of groups S] (3) That is, 2 by the area ratio divided by a certain boundary value P.
It can be seen that the ratio of the numbers of the two groups L and S can be determined. Conversely speaking, a certain boundary value P can be determined by designating the ratio of the numbers of the two groups L and S.

FIG. 1 shows a schematic diagram of the standard normal distribution. The total area under the normal distribution curve is equal to 1. The relationship between the variable z and the area under the standard normal distribution curve from z = 0 to a positive value of z indicated by diagonal lines in FIG. 1 is statistically obtained. Using the relationship table, the value of the variable z for the area ratio to be divided into two is calculated. Then, in the case of the present invention, the following relationships are generally established.

[Number of groups S having small capacity / weight] <[Number of groups L having large capacity / weight] [Boundary value P] <[Average value X] Therefore, the variable z shows a negative value. Since the total area has symmetry with z = 0 as an axis, z corresponding to the ratio of the numbers of the groups S having a small capacity or small weight and the boundary value P at that time are obtained by the following formula.

[Area corresponding to z] = 0.5- [Ratio of number of groups S having small capacity / small weight] (4) [boundary value P] = [average value X] −z × [standard deviation S] ] (5) By doing so, the storage batteries can be selected in an optimum number ratio according to the specifications of various assembled batteries and the number of constituent batteries and the number of sensors and safety elements. Therefore, it is possible to manufacture the assembled battery with high production efficiency without wasting the storage battery.

[0019]

EXAMPLE The present invention will be described in detail below with reference to Example 1. As Example 1 according to the present invention, a case of an eight-series assembled battery used in a portable liquid crystal television will be described in detail. Nickel-cadmium batteries having a known AA size and a nominal capacity of 800 mAh were manufactured, and these storage batteries were initially charged and discharged, and then completely discharged to an end voltage of 1.0 V, and the battery capacities of the respective batteries were measured. At this time, the values of 100 battery capacities were randomly extracted, and the average value X and standard deviation S of those battery capacities were determined.

In the specification of the battery pack, one temperature sensor for charging control and one resettable thermostat as a safety element are provided. In this case, in order to arrange batteries having small capacities at these two locations, the capacity of the manufactured storage batteries may be selected in a ratio of [group S having small capacity]: [group L having large capacity] = 2: 6. . Therefore, [0.25] is substituted into the above-mentioned formula (4) so that the ratio of the group S having a small capacity is 25%, and the value of the variable z corresponding to the area 0.25 is obtained from the relation table. At this time, the variable z corresponding to the closest value in the relation table was [0.67]. This z
The boundary value P was obtained by substituting the value of Eq.
Using this boundary value P, the total number of batteries was selected into two groups, a small group S having a capacity of less than the P value and a large group L having a capacity of the P value or more. Then, two storage batteries arbitrarily selected from the small capacity group S are arranged at the positions of the temperature sensor and the thermostat of the assembled battery, and six batteries arbitrarily selected from the large capacity group L are arranged at the remaining positions, An assembled battery A according to the present invention was produced.

On the other hand, as Comparative Example 1 of the product of the present invention, two batteries arbitrarily selected from the group L having a large capacity are arranged at the position of the temperature sensor and the thermostat of the battery pack, and the group having a small capacity is arranged at the remaining positions. Six batteries arbitrarily selected from both groups of S and a group L having a large capacity were arranged to prepare an assembled battery B of Comparative Example 1. These assembled batteries are charged under conditions of charge (current 1C, charge control of -ΔV detection or temperature detection), discharge conditions (constant resistance 1
It was subjected to cycle evaluation of 0Ω, connection 3 hours) and rest time (1 hour each after charging and discharging). The discharge condition for this cycle evaluation is a reproduction of the over-discharge phenomenon that assumes that the device does not have an appropriate final voltage set.If the batteries that make up the battery pack vary in capacity, at least one Is a harsh condition where there is always a reversing battery.

FIG. 2 shows the maintenance ratio of the duration until the terminal voltage of the assembled battery reaches 8.4 V with respect to the number of cycles. By the way, the terminal voltage of the assembled battery of 8.4V is the desired final voltage in the case of eight batteries in series, according to the formula (2) described above. As a result, the battery pack B had a reduction in the maintenance rate earlier than the battery pack A. After the cycle evaluation was completed in the discharged state of the assembled battery B, the storage batteries were separated one by one, and the open circuit voltage of each battery and the discharge time after the complete charge / discharge were measured. The results are shown in Table 1.

[0023]

[Table 1]

Next, another embodiment of the present invention will be described in detail with reference to the second embodiment. As Example 2 according to the present invention, a case of an eight-series assembled battery used in a portable liquid crystal television will be described in detail. Known AA size, nominal capacity 800mAh
The weight of the positive electrode used in this storage battery was measured when the nickel cadmium battery was manufactured. At this time randomly 1
The value of the weight of 00 positive electrodes was extracted, and the average value X and the standard deviation S of the weight of 100 positive electrodes were obtained.

According to the specification of the assembled battery of the present invention, one temperature sensor for charging control and one resettable thermostat as a safety element are installed. In this case, in order to arrange batteries having a small positive electrode weight at these two locations, the positive electrodes may be weight-sorted in a ratio of [small weight group S]: [large weight group L] = 2: 6. Then, [0.25] was substituted into the above-mentioned formula (4) so that the ratio of the group S having a small weight was 25%, and the value of the variable z corresponding to the area 0.25 was obtained from the relation table. At this time, the variable z corresponding to the closest value in the relation table was [0.67]. This z
The boundary value P was obtained by substituting the value of Eq.
Using this boundary value P, the total number of positive electrodes was divided into two groups, a small group S having a capacity less than the P value and a large group L having a capacity not less than the P value. These two groups are manufactured in different production lots, and each has a known AA size and a nominal capacity of 800 mAh of Ni / M.
An H battery was manufactured and subjected to predetermined initial charge / discharge. Next, two batteries arbitrarily selected from the group S having a small positive electrode weight are arranged at the positions of the temperature sensor and the thermostat of the assembled battery, and a battery 6 arbitrarily selected from the group L having a large positive electrode weight is arranged at the remaining positions.
The books were arranged and the assembled battery C according to the present invention was produced.

On the other hand, as Comparative Example 2 of the product of the present invention, two batteries arbitrarily selected from the group L having a large positive electrode weight are arranged at the positions of the temperature sensor and the thermostat of the assembled battery, and the remaining positions of the positive electrode are set. Six batteries arbitrarily selected from both the group S having a small weight and the group L having a large weight were arranged to prepare an assembled battery D of Comparative Example 2. These assembled batteries were subjected to cycle evaluation under charge conditions (current 1C, charge control for -ΔV detection or temperature detection), discharge conditions (constant resistance 10Ω, connection 3 hours), rest time (1 hour after charging and 1 hour after discharging). It was The discharge condition for this cycle evaluation is a reproduction of the over-discharge phenomenon that assumes that the device does not have an appropriate final voltage set.If the batteries that make up the battery pack vary in capacity, at least one Is a harsh condition where there is always a reversing battery.

FIG. 3 shows the maintenance ratio of the duration until the terminal voltage of the assembled battery reaches 8.4 V with respect to the number of cycles. By the way, the terminal voltage of the assembled battery of 8.4V is the desired final voltage in the case of eight batteries in series, according to the formula (2) described above. Then, the assembled battery D had a reduction in the maintenance rate earlier than the assembled battery C. After the cycle evaluation was completed in the discharged state of this assembled battery D, the batteries were separated into individual batteries and the open circuit voltage of each battery and the subsequent discharge time were measured. The results are shown in Table 2.

[0028]

[Table 2]

From Table 1, immediately after discharge in the assembled battery B,
It was found that there were batteries with low open circuit voltage and markedly reduced discharge duration. It is considered that the performance of these batteries deteriorated due to the reversal of polarity. It is considered that since the battery pack B relied on a battery having a large capacity for charge control, a battery having a smaller capacity than this battery was poled by the remaining capacity of the other battery having a larger capacity. On the other hand, in the assembled battery A, the charge control depends on the battery having the lowest capacity, and the discharge capacity becomes equal by the same charged amount of each battery, and it is considered that the reversal due to over-discharge could be avoided. To be That is, it is considered that the original performance of the unit cell is reproduced.

Further, from Table 2, it was found that there was a battery in which the open circuit voltage was low and the discharge duration was remarkably reduced immediately after discharging in the assembled battery D. It is considered that the performance of these batteries deteriorated due to the reversal of polarity. Since the charge control of the assembled battery D relied on a battery having a large positive electrode weight, that is, a battery having a large capacity, it is considered that a battery having a smaller positive electrode weight than this battery was reversed by the battery having the remaining capacity. It is considered that in the assembled battery C, the charge control depends on the battery having the smallest weight of the positive electrode, and the discharge capacities become equal as the charged amount of each battery becomes the same, so that the reversal due to over-discharge can be avoided. In other words, it is considered that the original performance of the unit cell was reproduced.

The present invention is not limited to nickel-cadmium batteries, but it can be easily predicted that the same effect can be obtained not only in alkaline storage batteries such as nickel-hydrogen batteries but also in storage batteries such as lead storage batteries and lithium storage batteries. . In particular, as the capacity becomes higher, the capacity variation of the storage battery tends to increase, so that the reversal phenomenon due to overdischarge becomes more serious. Therefore, it can be easily predicted that the effect of the present invention will be greater. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

[0032]

As described above, according to the present invention, it is possible to prevent the deterioration of reliability of the assembled battery due to the reversal phenomenon caused by over-discharge due to the assembled battery without depending on the specifications of various devices, and to improve the unit cell originally. Since the performance can be reproduced, it is possible to supply an assembled battery with high reliability and high industrial value. In addition, the assembled battery can be assembled without wasting the manufactured storage battery, and the production efficiency thereof can be sufficiently improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a standard normal distribution curve of a storage battery.

FIG. 2 is a cycle change diagram of the duration maintenance rate of the assembled batteries A and B.

FIG. 3 is a cycle change diagram of the duration maintenance rate of the assembled batteries C and D.

Claims (2)

[Claims] 1. A method of manufacturing an assembled battery, which is configured by conductively connecting a plurality of storage batteries, wherein the plurality of manufactured storage batteries are determined based on a distribution of their capacities and specifications of the assembled battery. According to the value, it is divided into a storage battery group with a small capacity and a storage battery group with a large capacity. A method of manufacturing an assembled battery, wherein a storage battery extracted from the storage battery group is arranged, and a storage battery extracted from the storage battery group having the large capacity is arranged at a remaining position. 2. A method of manufacturing an assembled battery, which is configured by conductively connecting a plurality of storage batteries, wherein the plurality of manufactured storage batteries are determined based on the distribution of the positive electrode weight and the specifications of the assembled battery. According to the boundary value, it is divided into a storage battery group with a small positive electrode weight and a storage battery group with a large positive electrode weight, and the above-mentioned weight is placed at the position where sensors and / or safety elements for charge control are determined by the arrangement of the unit cells and the structure of the battery pack A storage battery extracted from a small storage battery group is arranged, and a storage battery extracted from the heavy storage battery group is arranged at the remaining position.