JP2000048865A - Battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide at low cost a method for constituting a battery system having high reliability and safety. SOLUTION: In this battery system having a set battery in which a plurality of secondary batteries are connected, two sets of strings in which (a) pieces of sodium-sulfur secondary batteries are connected in line are connected to each other in parallel to from a set, (c) sets of blocks in which (b) sets of the sets are connected in line are connected to each other in parallel to constitute a unit, a terminal for monitoring voltage is provided for each module in which (d) sets of units are connected in line, and plural sets of modules are connected to constitute the set battery. (a) and (b) indicate integers of 2 or more, and (c) and (d) indicate integers 1 or more. Therefore, a battery system having high reliability and safety can be constituted at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery system in which a plurality of secondary batteries are connected and used.
Batteries suitable for power storage, power supply system, power supply system, emergency power supply system when power supply from power company is stopped, mobile power supply system, power supply system for electric vehicle, etc. It is about the system.

[0002]

2. Description of the Related Art In a conventional battery system, for example, 1997
As described in 242 to 243, first, several batteries are connected in series to form a string, a plurality of sets of the strings are connected in parallel to form a block, and a plurality of sets of the blocks are connected in series. The module is housed in an insulated container.

Further, Japanese Patent Application No. 8-2417005 discloses an assembled battery in which a plurality of single parallel connection sets which do not include a serial connection portion are connected in series with a non-aqueous secondary battery.

[0004]

SUMMARY OF THE INVENTION When a module such as that described in the 1997 Institute of Electrical and Electronics Engineers, Power and Energy Division, page 242-243 is adopted, one battery inside the module is damaged and the electromotive force is reduced or If it reaches zero, the imbalance in voltage between the strings connected in parallel causes an excessive current to flow through the string containing the damaged battery, and the excess current may damage even a healthy battery. Was high. Therefore, in the conventional method, it is necessary to take measures such as inserting a current fuse for each string to prevent a chain damage of the battery. Further, a large number of such current fuses are required because they are required for each string, and this has resulted in a significant cost burden on the system.

[0005] Further, in Japanese Patent Application No. 8-2417005, when a single product not including a series connection part is connected in parallel, a failure occurs in a single battery and the electromotive force is lost. Cause a big problem. That is, when the electromotive force of a single battery during normal operation is 1 V, the resistance of the battery is 1 mΩ, and the electromotive force of the failed battery is 0 V and the resistance is 1 mΩ, 500 A or more from the normally operating battery to the failed battery There was a danger that excessive current would flow.

That is, in the above-described conventional technology, there is a danger that an extremely large current flows inside the circuit when a failure occurs in the battery. Alternatively, in order to protect the excessive current, a mechanism for protecting the excessive current is required for each string, so that there is a problem that the cost burden is large.

An object of the present invention is to prevent an excessive current from flowing by a proper battery connection method.

[0008]

A feature of the present invention is that two sets of strings in which a number of rechargeable batteries are connected in series are connected in parallel to form a set, and a block in which b sets are connected in series is formed. c units are connected in parallel to form a unit, and d units are connected in series to form a module (a and b are integers of 2 or more, c and c are integers of 1 or more).

Here, more desirably, the number a of series connected batteries in the string, the number b of sets connected in series, and the number d of units connected in series are expressed by the following formula (1) in order to avoid overcharge destruction of the batteries. ) And (3), and are selected to satisfy the constraints (2) and (3) in order to avoid over-discharge breakdown of the battery. Is preferably selected so as to satisfy the equations (1), (2) and (3). The block number c is an integer of 1 or more.

[Vc (charge) −Eocv] × [n−1] + Vc (charge) <Vb (charge) Equation (1) [Vc (discharge) −Eocv] × [n−1] + Vc (discharge)> Vb (discharge) Expression (2) a × b × d ≦ n Expression (3) where Vc (charge) is an overcharge protection voltage for one of the secondary batteries, and Vc (discharge) is an expression of the secondary battery. Vc (charge): overcharge breakdown voltage for one secondary battery, Vc (discharge): overcharge breakdown voltage for one secondary battery, Eocv: end of charge at operating temperature Is the equilibrium electromotive force. In a battery system in which a large number of batteries are connected and used, economical operation cannot be performed in an operation in which the entire battery system is immediately stopped when one of the constituent batteries fails. Therefore, it is necessary that the battery system as a whole can operate satisfactorily even when several batteries have failed. Therefore, it is necessary that the operation of the module can be continued to the extent that one battery inside the module has failed.

As will be described later in the section of the embodiment of the invention, as can be seen from the operation results of the modules No. 1 and No. 4 of Comparative Example 1 and the modules No. 5 and No. 8 of Example 1, When the minimum number a of series connected batteries is 7 or less, the battery connected in series with the failed battery is not discharged at all, so that a ≧ 8 from the viewpoint of the efficiency of the entire battery system. preferable.

When a ≧ 8, according to the conventional method,
Modules No. 2 and No. 2 of Comparative Example 1 From FIG. 3, it can be seen that the current flowing through the string including the failed battery becomes extremely large, and there is a high risk of causing further battery failure. Therefore, in the conventional battery connection method, in order to prevent a chain of battery failure, it is necessary to prevent a chain of battery failure due to an excessive current by incorporating a current fuse for each string. On the other hand, according to the present invention, the module No. As can be seen from the results of Nos. 6 and 7, since no excessive current flows in any of the batteries, there is no need to incorporate a current fuse, which is a great cost advantage.

The voltage between the positive terminal and the negative terminal of the battery is equal to or higher than the overdischarge breakdown voltage Vb (discharge),
If the voltage is not kept below b (charge), the battery will be abnormal. Therefore, when operating the battery system, it is necessary to monitor the battery voltage. However, if the voltage of all batteries is 1
It is not realistic from a cost standpoint to monitor books one by one. On the other hand, however, even if a large number of batteries are collected and the battery voltage is monitored, accurate voltage monitoring cannot be performed. Therefore, Equations (1) and (2) must be satisfied between the number n of series batteries in a unit for monitoring the voltage and the protection voltage for judging to stop the operation for protecting the batteries.

The operating temperature of the sodium-sulfur secondary battery is 3
Since the temperature is 00 ° C. or higher, the operation is performed by storing the module units in a heat insulating container. Therefore, it is difficult to take out the voltage terminal for monitoring the voltage of the battery from the inside of the heat insulating container to the outside. Therefore, it is preferable to measure the battery voltage by providing a voltage measurement terminal for each module.

Although the present invention is particularly suitable for a sodium-sulfur secondary battery, it works equally well for other secondary batteries.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, comparative examples and examples for illustrating the present invention in detail will be shown.

Comparative Example 1 1736 sodium-sulfur batteries having the structure shown in FIG. 1 were manufactured. The material of the solid electrolyte tube 1 is β ″ -alumina, the positive electrode container 3, the negative electrode container 4, the negative electrode cap 7, the positive electrode cap 11, and the material of the protective tube 20 are SUS3.
The material of 10S, safety tube 6, positive electrode terminal 12, negative electrode terminal 13, and cartridge 21 was aluminum metal. Argon gas is sealed in the upper space P1 of the cartridge 21 to push out sodium inside the cartridge.
The outer diameter of the protection tube 20 is 1 mm smaller than the inner diameter of the solid electrolyte tube 1, the outer diameter of the safety tube 6 is 0.4 mm smaller than the inner diameter of the protection tube 20, and the outer diameter of the cartridge 21 is 0.2 mm smaller than the inner diameter of the safety tube 6. I made it smaller. One 0.14 mm diameter hole was drilled at the bottom of the cartridge for the supply of liquid sodium. It also has an α-alumina ring 2 for positive and negative electrode insulation, sodium as a negative electrode active material 5, sulfur as a positive electrode active material 9, carbon as a positive electrode conductive material 10, and a protective tube 20. Sodium as the negative electrode active material 5 and sulfur as the positive electrode active material 9 cause the battery to operate in a molten state (about 3
00 ° C to about 350 ° C). The heights of the respective liquid levels are indicated by L1, L2, and L3, respectively, in the figure. The space above L2 is indicated as P2. The carbon that is the positive electrode conductive material 10 is generally in a felt shape, but can take various forms.

A module was manufactured using these batteries. Module No. 1 first forms a string by connecting six batteries in series to form a string, connects 14 sets of the strings in parallel to form a block, and stores the four sets of blocks connected in series in an insulated container. did. FIG. 2 shows a circuit diagram of the module No. 1. Module No. 2 forms a string by connecting eight batteries in series first to form a string, and connects 14 sets of strings in parallel to form a block. The four sets of blocks are connected in series in an insulated container. did. Module No. 3 was constructed by first connecting 10 batteries in series to form a string, connecting 14 sets of the strings in parallel to form a block, and connecting the 4 sets of blocks in series to form a module. Module No. 4 forms a string by first connecting seven batteries in series to form a string, connecting 14 sets of strings in parallel to form a block, and storing the four sets of blocks connected in series in an insulated container. did. The batteries in each module were destroyed one by one in advance so that the electromotive force of the batteries became zero, and then the temperature of the batteries was raised to 330 ° C. and maintained at that temperature. Prepare a current extraction terminal and a voltage terminal for monitoring the module voltage at both ends of the module, connect the current terminal and the inverter, and control the charge and discharge with the control device while monitoring the module voltage with the voltage terminal. Was.

A charge / discharge test was performed on these modules. The discharge current is 420 A, the charge current is 330 A, and the module voltage is 1.6 × 24 V for module No. 1, 1.6 × 32 V for module No. 2, 1.6 × 40 V for module No. 3, and 1.6 × 40 V for module No. 4 stops discharging when it reaches 1.6 × 28 V, and the module voltage is 2.2 × 24 V for module No. 1 and 2.2 × for module No. 2
The charging was stopped when the voltage reached 32 V, the module No. 3 reached 2.2 × 40 V, and the module No. 4 reached 2.2 × 28 V.

FIG. 3 (a) shows the time change of the current flowing through the broken battery of the module No. 1. In FIG. 3B,
6 shows a time change of a current flowing through a broken battery of module No. 2. FIG. 3 (c) shows the time change of the current flowing through the battery of module No. 3 that has been destroyed.

From FIG. 3A, in the module No. 1,
It can be seen that no current flows through the broken battery and its string. This means that the other five batteries in the string other than the broken battery are not working at all. Such a situation is undesirable because it significantly reduces the efficiency of the module. Module N
The measurement result of No. 4 was the same as that of Module No. 1.

As can be seen from FIG. 3B, in module No. 2, the value of the current flowing through the string containing the destroyed battery continued to increase until just before the end of the discharge, and a maximum current of 102 A flowed. When the current flows evenly through all the strings, the current value is 30 A, which is more than three times that value.

As can be seen from FIG. 3 (c), in module No. 3, the value of the current flowing through the string containing the destroyed battery continues to increase until immediately before the end of the discharge, and a maximum of 98 A
Current flows, and this value reaches more than three times the normal current value. Such an excessive current not only accelerates the deterioration of the batteries in the strings, but also causes a rise in the temperature due to the Joule heat of those batteries, which may lead to a serious accident in some cases. Usually, in order to avoid such a danger, a current fuse is incorporated for each string.

As described above, when a battery pack made by simply connecting a secondary battery in series-parallel-series connection is charged and discharged, serious damage to the entire system occurs if one of the battery packs is broken. There is a possibility that the influence may be exerted, and in order to avoid the influence, it is necessary to incorporate a protection mechanism such as a current fuse for each string, thereby causing a problem that the system cost is greatly increased.

Example 1 1736 batteries which were the same as those used in Comparative Example 1 were prepared, and a module was manufactured using these batteries.

FIG. 4 is a circuit diagram of the module No. 5.
Module No. 5 first connects six batteries in series to form a string, connects two sets of strings in parallel to form a set, and connects the two sets in series to form a block; Seven sets of the blocks were connected in parallel to form a unit, and one set of the units was housed in a heat insulating container as one module.

In module No. 6, a string is formed by first connecting eight batteries in series to form a string, two sets of the strings are connected in parallel to form a set, and the two sets are connected in series to form a block. Then, seven sets of the blocks were connected in parallel to form a unit, and one set of the units was housed in a heat insulating container as one module. Module No.
Reference numeral 7 first connects 10 batteries in series to form a string, connects two sets of strings in parallel to form a set, and connects the two sets in series to form a block. 7 units are connected in parallel to form a unit,
One set of the units was housed in a heat insulating container as one module. Module No. Reference numeral 8 first connects seven batteries in series to form a string, connects two sets of strings in parallel to form a set, and connects the two sets in series to form a block. Seven units are connected in parallel to form a unit, and one unit
The module was housed in an insulated container.

The battery in each module is destroyed one by one in advance so that the electromotive force of the battery becomes zero, and then the temperature of the battery is raised to 330 ° C.
It was kept at that temperature. Prepare a current extraction terminal and a voltage terminal for monitoring the module voltage at both ends of the module, connect the current terminal and the inverter, charge the control device while monitoring the module voltage with the voltage terminal,
Discharge control was performed. Charge and discharge tests of these modules were performed. The test conditions were the same as in Comparative Example 1, the discharge current was 420 A, the charge current was 330 A, the module voltage was 1.6 × 24 V for module No. 5, and the module No. 6
1.6 × 32V, module No.7 1.6 × 40V,
The module No. 8 stops discharging when the voltage reaches 1.6 × 28 V, and the module voltage reaches 2.2 × 28 V.
× 24V, 2.2 × 32V for module No. 6, 2.2 × 40V for module No. 7, 2.2 for module No. 8
The charging was stopped when the voltage reached × 28V.

FIG. 5A shows the time change of the current flowing through the broken battery of the module No. 5, and FIG. 5B shows the time change of the current flowing through the broken battery of the module No. 6. c) shows the time change of the current flowing through the broken battery of module No. 7.

As shown in FIG. 3A, in module No. 5,
It can be seen that no current flows in the broken battery and its string as in Comparative Example 1. This means that the other five batteries in the string other than the broken battery are not working at all. Such a situation is undesirable because it significantly reduces the efficiency of the module. The measurement result of module No. 8 was the same as that of module No. 5.

As can be seen from FIG. 3 (b), in module No. 6, the value of the current flowing through the string containing the destroyed battery continues to increase until just before the end of discharge, as in Comparative Example 1. Only flowed. When the current flows evenly through all the strings, the current value is 30 A, which is less than twice the current value.

As can be seen from FIG. 3 (c), in module No. 7, the value of the current flowing through the string containing the destroyed battery continued to increase until just before the end of discharge, as in Comparative Example 1. But only 57A of current flowed.
As described above, according to the present invention, even when charging and discharging are performed in a state including a damaged battery, an excessive current can be prevented from flowing through the battery, and a safe assembled battery and a battery system can be constructed.

As described above, by comparing Example 1 with Comparative Example 1, the module according to the embodiment of the present invention has:
It can be seen that even when a damaged battery is generated in the module, an excessive current can be suppressed from flowing. This means that according to the embodiment of the present invention, no safety mechanism against excessive current is required. In other words, according to the embodiment of the present invention, it can be understood that a NAS battery system having performance and safety comparable to those of the related art can be realized at low cost.

Comparative Example 2 Sixteen types of modules were manufactured using batteries having the same specifications as those used in Comparative Example 1. In the module, a battery was first connected in series to form a string, a set of strings c was connected in parallel to form a block, and a set of blocks d connected in series was housed in a heat insulating container. The batteries in each module were destroyed one by one in advance so that the electromotive force of the batteries became zero, and then the temperature of the batteries was raised to 330 ° C. and maintained at that temperature.

The charge / discharge test of these modules was performed. The test conditions were the same as in Comparative Example 1, and the discharge current was 30 A ×
c, the charging current is 24 A × c, and the module voltage is 1.
Discharging was stopped when the voltage reached 6 × a × dV, and charging was stopped when the module voltage reached 2.2 × a × dV.

Table 1 shows the maximum value of the current flowing through the broken battery in each module. String parallel number c is 3
In the case of (1), the maximum current value increases, but in other cases, the maximum current value is about 90 to 100 A in any of the modules regardless of the values of a, c, and d.

[0037]

[Table 1]

Example 2 Sixteen types of modules were manufactured using batteries having the same specifications as those used in Comparative Example 1. In the module, a battery is first connected in series to form a string, two sets of the strings are connected in parallel to form a set, and the set b is connected in series to form a block. c sets are connected in parallel to form a set,
A set of the sets connected in series was housed in a heat insulating container as a module. The batteries in each module were destroyed one by one in advance so that the electromotive force of the batteries became zero, and then the temperature of the batteries was raised to 330 ° C. and maintained at that temperature.

The charge / discharge test of these modules was performed. The test conditions were the same as in Comparative Example 1, and the discharge current was 30 A ×
2 × c, the charging current is 24 A × 2 × c, and when the module voltage reaches 1.6 × a × b × dV, the discharge is stopped, and the module voltage reaches 2.2 × a × b × dV. When you stop charging.

Table 2 shows the maximum value of the current flowing through the broken battery in each module. It can be seen that the maximum current value is about 50 to 60 A in any of the modules.

[0041]

[Table 2]

As described above, by comparing Example 2 with Comparative Example 2, the module according to the embodiment of the present invention has:
It can be seen that no matter how the number of batteries in the module is selected, it is possible to prevent an excessive current from flowing even when a damaged battery occurs in the module. This means that according to the invention, no safety mechanism against excessive currents is required. That is, according to the embodiment of the present invention,
It can be seen that a NAS battery system of the same performance and safety as the conventional one can be realized at low cost. As described above, as can be seen from the examples and the comparative examples, it is understood that the present invention makes it possible to construct a safe and low-cost battery system. In the examples and comparative examples of the present invention, examples using a sodium-sulfur secondary battery are shown. However, the same applies in principle to any type of secondary battery. It is also applicable to secondary batteries.

A power storage system can be constructed by including a battery system having the modules described above, an AC / DC converter for converting DC to AC and AC to DC, and a control unit for controlling these. The battery system is connected to a power supply via an AC / DC converter. In addition, the battery system is connected to the load via the AC / DC converter. The battery system and the AC / DC converter are connected to the control unit by a signal line or wirelessly. As the control unit, a dedicated microprocessor, a general-purpose computer, or a personal computer can be used.

[0044]

According to the present invention, a highly reliable and safe battery system can be constructed at low cost.

[Brief description of the drawings]

FIG. 1 shows Example 1 and Comparative Example 1 for explaining the present invention.
The figure showing the structure of the sodium-sulfur battery used for (1).

FIG. 2 is a diagram illustrating a circuit of a module manufactured in Comparative Example 1 for explaining the present invention.

FIG. 3 is a diagram illustrating an operation result of a module manufactured in Comparative Example 1 for explaining the present invention.

FIG. 4 is a diagram illustrating a circuit of a module manufactured in Example 1 for describing the present invention.

FIG. 5 is a diagram illustrating an operation result of the module manufactured in Example 1 for explaining the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte tube, 2 ... Alpha-alumina ring for positive / negative electrode insulation, 3 ... Positive container, 4 ... Negative container, 5 ... Negative electrode active material, 6
... Safety tube, 7 ... Negative electrode cap, 9 ... Positive electrode active material, 10 ...
Positive electrode conductive material, 11: positive electrode cap, 12: positive electrode terminal, 1
3: negative electrode terminal, 20: protective tube, 21: cartridge.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/00 302 H02J 7/00 302D 7/02 7/02 J F term (Reference) 5G003 BA02 FA08 5H022 AA09 AA14 BB27 CC06 KK00 KK01 5H029 AJ12 AK05 AL13 AM15 BJ02 DJ00 HJ00 HJ16 HJ18 5H030 AA06 AS01 BB01 BB21 DD06 FF21 FF43 FF44

Claims (7)

[Claims] 1. A battery system having an assembled battery to which a plurality of secondary batteries are connected, wherein the assembled battery is formed by connecting two sets of strings each having a number of the secondary batteries connected in series. A unit is formed by forming a set, and connecting the b sets connected in series to the c sets in parallel to form a unit, and having a terminal for monitoring the voltage for each module connected in series to the d sets. A battery system comprising a plurality of modules connected to form an assembled battery (a and b)
Is an integer of 2 or more, and c and c are integers of 1 or more. A set is formed by connecting a set of a series of a rechargeable batteries in parallel to two sets to form a set, and a set of b sets connected in series to a set of c is connected in parallel to form a unit. d is connected in series to form a module. 2. The battery system according to claim 1, wherein a is an integer of 8 or more. 3. A battery system comprising an assembled battery in which a plurality of sodium-sulfur secondary batteries in which sodium and sulfur are disposed via a solid electrolyte are electrically connected, wherein the sodium constituting the assembled battery is provided. The overcharge protection voltage for one of the sulfur secondary batteries is Vc (charge), and the overdischarge protection voltage is V
When c (discharge), overcharge breakdown voltage is Vb (charge), overdischarge breakdown voltage is Vb (discharge), and equilibrium electromotive force at the end of charging at the operating temperature is Eocv, [Vc (charge) −Eocv] × [ n-1] + Vc (charge)
<Vb (charge) and [Vc (discharge) −Eocv] × [n−1] + Vc (disch
arge)> Vb (discharge) and positive integers n, a, b, d (a and b are 2 or more) satisfying a × b × d = n. A set is formed by connecting two sets of strings each having a battery connected in series in parallel to form a set, and connecting at least one set of blocks connected in series to set b in parallel to form a unit. A battery system comprising: a terminal for monitoring a voltage for each of d modules connected in series; and connecting a plurality of such modules to form an assembled battery. 4. A battery system comprising an assembled battery in which a plurality of sodium-sulfur secondary batteries in which sodium and sulfur are arranged via a solid electrolyte are electrically connected, wherein the sodium-sulfur forming the assembled battery is provided. The overcharge protection voltage for one of the sulfur secondary batteries is Vc (charge), and the overdischarge protection voltage is Vc
(discharge), the overcharge breakdown voltage is Vb (charge), the overdischarge breakdown voltage is Vb (discharge), and the equilibrium electromotive force at the end of charging at the operating temperature is Eocv. [Vc (charge) −Eocv] × [n -1] + Vc (charge)
<Vb (charge) and positive integers n, a, b, d (a and b are 2 or more) satisfying a × b × d = n, and the assembled battery is the sodium-sulfur secondary battery. Are connected in parallel to form two sets of a strings connected in series to form a set, and b sets of this set are connected in parallel to one or more sets of blocks connected in series to form a unit. A battery system comprising a terminal for monitoring a voltage for each module connected in series, and connecting a plurality of such modules to form an assembled battery. 5. A battery system having an assembled battery in which a plurality of sodium-sulfur secondary batteries in which sodium and sulfur are arranged via a solid electrolyte are electrically connected, wherein the assembled battery is a battery including the sodium-sulfur secondary battery. -A set of a string of sulfur secondary batteries connected in series is connected in parallel to form two sets,
A block is formed by connecting a set of b sets connected in series and a set of c sets are connected in parallel to form a unit. A terminal for monitoring voltage is provided for each module in which the set is connected in series to d sets. A battery system (a, b, c, and d are positive integers, and a and b are 2 or more). 6. A set in which two sets of strings in which a number of secondary batteries are connected in series are connected in parallel, a block in which b sets are connected in series, and a unit in which c sets of blocks are connected in parallel, A battery system (a and b) comprising: d sets of said units connected in series.
Is an integer of 2 or more, and c and c are integers of 1 or more. 7. A power storage system, comprising: the battery system according to claim 1; an AC / DC converter that converts DC to AC and AC to DC; and a control unit that controls these devices. .