JPH03127467A - Perfect discharge device of zinc-bromine battery - Google Patents

Abstract

PURPOSE:To avoid the generation of an imperfect discharge by connecting discharge resistance units responding to the battery stacks by using multipole connector devices. CONSTITUTION:By connecting multipole connectors (CN) 72 and 78, exclusive discharge resistance units 74a, 74b,...74n-1 are connected to battery stacks 64a, 64b,...64n-1 respectively, and the stacks 64 and the resistance units 74 are made into the opposite condition one to one to perform the discharge operations independently with different discharge amounts respectively. As a result, even though the discharge capacities in the stacks 64 are uneven each other, the discharge operations are carried out until all the stacks finish the discharges. In such a way, only the service times of the stacks 64 up to the time the discharge is finished are different, but all the discharges can be completed finally, and an improper condition such as an imperfect discharge and a reverse charging can be avoided securely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a complete discharge control device for zinc-bromine batteries for electric vehicles, particularly for eliminating variations in the state of zinc electrodeposition between cells constituting a battery stack. The present invention relates to a complete discharge control device for a zinc-bromine battery.

[Prior art] Zinc-bromine batteries have been developed in which bromine, which has high solubility in electrolytes and excellent electrode reaction characteristics, is used as the positive electrode active material and zinc is used as the negative electrode active material. Due to its many advantages such as energy density, it is attracting attention as a driving source for electric vehicles, for example.

FIG. 3 shows the principle structure of a general zinc-bromine battery disclosed in Japanese Patent Application Laid-Open No. 57-199167.

An electrochemical reaction expressed by the following equation is performed between a positive electrode side reaction tank 14 in which a positive electrode 10 and a negative electrode 12 are disposed, and a negative electrode side reaction tank 16 via an electrolytic solution 18.

(Negative electrode) Z n"+ 2 e"" = ' Z n discharge (1) In such a zinc-bromine battery, a zinc bromide ZnBr2 aqueous solution is used as the electrolyte 18, and if necessary, a conductivity improvement agent, Bromine complexing agents, dendrite inhibitors, etc. are added.

At the time of charging, in the reaction tank 14.16, the above-mentioned formula 1 →
A charging reaction shown by is performed, and bromine B r
On the other hand, on the negative electrode 12 side, zinc Zn is precipitated, and a deposited layer of zinc is formed on the negative electrode 12.

Further, during discharging, a reaction opposite to that during charging is performed, which is indicated by -, and on the positive electrode 10 side, bromine Br2 is reduced and becomes bromine ions Br-, which are dissolved in the electrolytic solution 18, and on the negative electrode 12 side, zinc The deposited layer is oxidized to become zinc ions Zn2+ and dissolved in the electrolytic solution 18.

Here, the inside of the reaction tank 14.16 in which the electrical reaction is carried out is separated by a separator film 20 to prevent self-discharge due to bromine B r 2 generated during charging. It allows various ions in the electrolytic solution 18 to pass through, but blocks the passage of bromine B r 2 dissolved therein, thereby achieving a self-discharge prevention effect.

As the separator membrane 20, an ion-permeable membrane or a porous membrane is generally used, and the latter is preferable from the viewpoint of reducing the internal resistance of the battery.

The electrolyte circulation type battery as shown in the illustrated example includes a positive electrolyte storage tank 22 and a negative electrolyte storage tank 24 for storing energy obtained through a chemical reaction during charging.

The positive electrode side electrolyte storage tank 22 forms an electrolyte circulation path with the positive electrode side reaction tank 14 via piping 26, 28, and the positive electrode side reaction tank 14 is pumped by a pump 30 provided in the circulation path. The positive electrode side electrolyte 18a after the reaction in is sent to the storage tank 22, and the electrolyte 18a in the storage tank 22 is supplied to the reaction tank 14.

Here, if a bromine complexing agent is added to the electrolytic solution 18, the bromine B r 2 generated during charging is complexed and precipitated as a complex compound 32 insoluble in the electrolytic solution 18, and the complex compound 32 is sequentially precipitated and stored in a complex storage section 34 formed at the bottom of the storage layer 22.

Further, the complex storage section 34 and the pipe 28 are connected by a complex supply pipe 38 having a valve 36.
6 is normally kept open, and the complex compound 32 precipitated in the complex storage section 34 is sent to the positive electrode side reaction tank 14 via the pipe 28.

In addition, the negative electrode side electrolyte storage tank 24 similarly forms an electrolyte circulation path with the negative electrode side reaction tank 16 via piping 40, 42, and the negative electrode side reaction tank is operated by a pump 44 provided in the circulation path. The negative electrode side electrolyte 18b that has reacted in the 16 is stored t
At the same time, a new electrolytic solution 18b is supplied from the storage tank 24 to the reaction tank 16.

In this way, in the zinc-bromine battery, the electrolytic solution 18 is sufficiently stored in the storage tanks 22 and 24, and when charging using the stored electrolytic solution 18, the charging reaction shown in the first equation is carried out, and the complex storage section 32 is charged. A bromine complex compound is stored, a zinc precipitation tank is formed on the negative electrode 12, and electric power is stored.

FIG. 4 shows an exploded perspective view of a typical zinc-bromine battery stack formed using this principle.

This battery stack has a large number of electrode frames 48 and separator frames 50 stacked alternately, and both ends thereof are closed by end blocks 52 (only one is shown in the illustrated example).

Each electrode frame 48 has an electrode portion 48a forming a positive or negative electrode on its front and back surfaces, and the separator frame 5
One electrode part 48a of the electrode frame 48 located on both sides of the electrode frame 48 is configured to form a positive electrode, and the other electrode part 48 forms a negative electrode. On the other hand, the separator frame 52 carries a separator film 50a.

The space between one electrode section 48a and one side of the separator membrane 50a forms one reaction tank, and the space between the other side of the separator membrane 50a and the next electrode section 48a forms the other side reaction tank. These cells form cells, which are the basic functional units of the battery stack.

A supply side common manifold 53 and a discharge side common manifold 54 penetrate through all the cells including the end block 52 of this battery stack and communicate with the positive and negative side reaction tanks.
is formed.

Therefore, the electrolyte 18 supplied from each electrolyte storage tank is
Passing through each supply side common manifold 53, passing through a channel 50b formed in each separator frame 50, and a rectifying plate 50c formed at the connection part with the separator film 50a.
After being evenly introduced into each reaction tank and subjected to a predetermined chemical reaction, the discharge side supply manifold 5
4 and returns to the electrolyte storage tank again.

In the zinc-bromine battery constructed as described above, one cell has a voltage of about 1.6 to 1.8V, and the battery stack has a voltage of about 60V.
A stack of about 100 cells/stack is usually used.

However, a higher voltage may be required depending on the type of motor used as the load.

In this case, it is unavoidable that when the number of cells in one stack is increased, the shunt current also increases.

For this reason, a method is adopted in which multiple battery stacks are connected in series.

However, as multiple battery stacks are connected in this way and charging and discharging are repeated, the state of zinc electrodeposition on the surface of each stack electrode is disturbed, and this causes the separator film 2
This causes problems such as damage to the electrolyte 18 and deterioration of the quality of the electrolyte 18, resulting in a shortened battery life.

To deal with this problem, it is necessary to periodically perform a complete discharge to reduce the battery capacity to zero when the battery is not in use, and to consume the deposited zinc. No. 5 in Publication No. 144066, etc.
The circuit shown in the figure was used.

In the figure, both ends of a stack 56a, 56b, . . . , 56n of zinc-bromine batteries connected in series, which are installed in an electric vehicle and function as a power source for driving the vehicle, are connected to a load resistor 58 to perform a complete discharge action. be exposed.

[Problem to be Solved by the Invention] Here, when a complete discharge is performed using a circuit as shown in FIG. It is difficult to make them the same.

If this characteristic differs between stacks, the voltage of the entire battery system shown by the solid line in Figure 6 and the discharge current of the entire battery system shown by the two-dot chain line converge to O and appear to be completely complete. Even though the discharging action has ended, the - battery stack falls into an incompletely discharged state with remaining capacity as shown by the dashed line, and the other battery stacks are reversely charged and have a negative voltage. A situation may arise in which the voltage is applied.

Here, the above-mentioned reverse charging effect causes the generation of bromine on the negative electrode (zinc electrode) side, and during the next charging, the zinc deposited reacts with this bromine (self-discharge), causing a decrease in discharge capacity. cause. However, the battery stack that is reverse-charged is originally limited to batteries with lower discharge capacity, and as a result, the difference in capacity between the batteries further increases.

Therefore, in such a series connection discharge method, it is necessary to select and use only batteries with uniform characteristics.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a complete discharge device for zinc-bromine batteries that can reliably complete the discharge of all battery stacks without causing incomplete discharge or reverse charging. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention comprises a discharging resistor including a plurality of resistors corresponding to each battery stack, and each resistor corresponding to each battery stack is It is characterized in that it is equipped with multi-polar connector means that are connected in parallel, and that a discharge resistor is connected to each battery stack to prevent reverse charging.

[Function] Therefore, according to the present invention, each battery stack is individually connected to a discharge resistor by the multi-pole connector means when performing a complete discharge, so that each battery stack can be connected to a discharge resistor independently, regardless of the difference in discharge capacity between the stacks. Since the battery is discharged without any delay until the battery capacity is completely consumed with different discharge currents, there is no residual voltage in each individual stack even though the battery system consisting of multiple stacks has finished discharging. Occurrence of incomplete discharge such as reverse charging or reverse charging can be avoided.

[Examples] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the circuit configuration of the device of the present invention. In the figure, zinc-bromine cell stacks 54a, 64b.

..., 64n are connected in series, and terminals 66 and 68 at both ends thereof are connected to a normal load such as an electric vehicle motor (not shown).

In the illustrated example, between each battery stack 64,
Furthermore, intermediate terminals 7 Q a, 70 b, . . . 7
0n( is provided. During normal battery use (charging/discharging,
When the vehicle is running, etc.), these intermediate terminals 70 are open and connected to a multi-pole connector 72.

Each of the above components is installed in an electric vehicle. On the other hand, the complete discharge load resistor 74 installed outside the vehicle is divided into equal parts to the number of battery stacks 64 by intermediate terminals 76 a, 76 b, -, 76 n-1, and corresponding resistors 74 a, 74 b, . . . , 74n-1, and the other end of the intermediate terminal is connected to the multi-pole connector 78 on the other side.

As a result, by connecting both the connectors 72 and 78, each battery stack 64a, 64b, . . . , 6
A dedicated discharge resistor 74a is provided for every 4n-1.

74b, ..., 74n-1 will be connected,
With the battery stack 64 and the discharge resistor 74 in one-to-one correspondence, the discharge action proceeds independently with different discharge currents.

Note that it is preferable that the multipolar connectors 72 and 78 have a plug-outlet type structure, for example.

Therefore, even if the discharge capacity of each battery stack 64 is uneven, there is no effect, and the discharge operation is performed until each stack completes discharge without any problem.

As a result, the voltage and current of each battery stack 64 are
Each battery stack 64 exhibits a change over time as shown in the figure (the illustrated example shows a case of two batteries), and each battery stack 64 is able to complete discharging in the end, with only a difference in the usage time until completion of discharging. Inconvenient situations such as incomplete discharge and reverse charging can be reliably avoided.

[Effects of the Invention] As explained above, according to the present invention, since the discharge resistor corresponding to each battery stack is connected using the multi-pole connector means, the risk of complete discharge and reverse charging is eliminated from all battery stacks. Therefore, even battery stacks with slightly different discharge capacities can be applied to a series-connected battery system without any problem.

Furthermore, the tolerance level for differences in discharge capacity between batteries due to uneven zinc deposition during repeated charging and discharging is expanded.
The frequency of complete discharge work that must be performed periodically can be reduced.

Furthermore, it is possible to ensure complete discharge with the one-touch operation of connecting a multi-pole connector, so even if there is a difference in discharge capacity between battery stacks installed in a vehicle, unlike conventional methods, the batteries can be unloaded and each The troublesome effort of completing the discharge in stack order becomes unnecessary.

In addition, the present invention has the advantage of being extremely easy to adapt to, as it requires only a design change to add an intermediate terminal to a substantial conventional device.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of the device of the present invention, FIG. 2 is a graph showing the relationship between terminal voltage, discharge current, and discharge time of the device according to FIG. 1, and FIG. FIG. 4 is an exploded perspective view of the battery stack according to FIG. 3, FIG. 5 is a configuration diagram showing a conventional complete discharge device, and FIG. It is a graph figure which shows the relationship between the terminal voltage of the apparatus based on a figure, discharge current, and discharge time. 64...Battery stack 72゜78...Multi-pole connector means discharge resistor intermediate terminal

Claims (1)

[Claims] In a complete discharge device for a zinc-bromine battery that performs complete discharge by short-circuiting a plurality of battery stacks connected in series through a discharge resistor when the batteries are not in use, the discharge resistor corresponds to each battery stack. The battery comprises a plurality of resistors, and includes multi-polar connector means for simultaneously connecting each of the battery stacks and the corresponding resistors, and a discharge resistor is connected to each battery stack to prevent reverse charging. Features: Complete discharge device for zinc-bromine batteries.