DE2704314A1 - BATTERY WITH CIRCULATING ELECTROLYTE - Google Patents

Description

Dfpi.-i.in. Peter-C. Sroka Dr. Ing. Ernst Stratmann

Po.enlanwäl * 27043H

4 Düsseldorf 1 ■ Schadowplatz 9

Düsseldorf, February 1, 1977

Westinghouse Electric Corporation
Pittsburgh / Pa.y V. St. A.

Circulating electrolyte battery

The invention relates to circulating electrolyte batteries.

Secondary electrical storage cells, which operate at high rates of charge and discharge, require some cooling method, to prevent overheating. This is especially true for applications in electric vehicles where a large number of interconnected cells and a close-packed arrangement may be required. A solution is to use the electrolyte as a heat exchange medium through the cell, into a cooling reservoir and from there back to the cell.

This solution was recognized in US Pat. No. 400,215, according to which a supply tube for the electrolyte at the bottom a galvanic battery was arranged. This caused fresh electrolyte to flow from the bottom of each cell stack to the top and passed around the electrodes. U.S. Patent 3,666,561 discloses a zinc-air battery in which a Circulation of electrolyte through a series of electric battery cells is provided. The electrolyte circuit was

709333/0829

Telephone (O? 11) 35 08 ^ S Tnlerjramme Custopat

_ ₂ _ 27043U. u

realized by pumping electrolyte into the bottom of each cell. Flows from an electrolyte chamber the electrolyte goes up through each cell and is removed from the top of each cell via outlet tubes. The electrode stack or assembly is not sealed from the container, so that electrolyte around one of the three plates can flow around each cell, and oxygen gas is introduced into the electrolyte circulation system around the reduce internal battery current.

A cooling system with circulating electrolytes is necessary for a battery, and not all of the problems associated with such systems have been resolved to date. Almost all housings for secondary electrical storage cells consist of metal, glass, rubber or plastic boxes. Stacks of cells are inserted into the boxes and then a cover is attached. When the electrolyte through If the cell stack is to be circulated for cooling purposes, conventional box and electrode stack designs have proven as unsatisfactory.

Problems associated with circulating electrolyte systems are: Cooling of each cell when charged and / or discharge to use high current rates; Hermetically sealed connections between the connections, the Inlet and outlet tubes and the container walls; Encapsulation and sealing of cell stacks so that the electrolyte is forced to flow through this cell stack as it flows from the inlet to the outlet of the housing; Maintenance the electrolyte level; Control of the specific gravity of the electrolyte and its uniformity; collection and disposal of explosive hydrogen and oxygen gases at a location where appropriate safety precautions can be taken; Simplification of the system so that cell size changes can be achieved easily and cheaply can.

709833 / 0P29

To solve all of these problems, the battery must have the following properties: It must be leak-proof, since the electrolyte circulates under pressure, all cell housings and connection connections must be extremely tight; it there must be a low pressure drop so that the circulation pump can be kept small, this also serves the prevention of leaks and increases operational safety; high resistance in the electrolyte connections between the cells to make the self-discharge as small as possible; uniform pressure drop in all cells so that they are relative to one another can be connected in parallel and still ensure a uniform flow of electrolyte through each cell is; and, most importantly, uniform electrolyte flow through the cell cross-section so that all of the battery plates a sufficient electrolyte flow is obtained and it is ensured that the electrolyte through the cell stack instead of flowing around it, so that the most effective cooling is achieved during charging.

The object of the invention is to provide a circulating electrolyte battery in which the above Problems are solved.

The solution of the invention is done by the features of the main claim.

A circulating electrolyte battery according to the invention thus consists of at least one cell that contains a structure or set of electrode plates, as well as electrolyte cooling devices, which contain the electrolyte and are spaced from the cell; furthermore electrolyte pumping equipment, which are connected to the cooling devices, as well as electrolyte circulation devices, the one Establish a connection between the pump devices and the cell and from the cell to the cooling devices. Essential is also that the front and edge sides of the stack assembly are sealed and that at least one channel in

709833/0829

-Jt-

. 6th

at least one electrode plate is provided in each stack representing approximately 0.5 to 10% of the electrode plate surface so that the pumped electrolyte only flows through the channel in the stack.

The electrolyte can flow through several interconnected cells of a battery and a reservoir, which has a cooling mechanism contains, are circulated by means of pumping devices. Any heat exchange means can be used in order to cool the electrolyte, for example cooling water, the cooling coils present in the reservoir is passed through. The electrolyte is circulated at a rate sufficient to maintain the during the various To remove heat generated by charge or discharge rates. The reservoir and the pump are on the cells of the battery attached with quick release connectors so that the battery can be discharged with or without a reservoir and pump. The electrolyte level and specific gravity are maintained by adding water to the reservoir is used to maintain a constant height mirror. The battery can be connected to the reservoir through barrier venting devices vented, allowing explosive hydrogen and oxygen gases to escape.

The foregoing features can be specifically implemented in a circulating electrolyte battery that incorporates the has the following characteristics:

a) The cell electrodes of each arrangement are tightly attached and encapsulated in a molded battery housing, preferably with the help of a sealing epoxy resin filler, which is attached to the housing walls, the connections and adheres to inlet and outlet tubes for the electrolyte, providing an effective hermetic seal delivers to all of these bodies.

709833/0829

27043U

b) Low and uniform pressure drop from cell to cell and uniform flow of electrolyte through the Cell structure is achieved in that channels are provided in the plates, for example by cutting or pressing in narrow slots in the plates. The channels are spaced apart on the one hand to achieve effective cooling and on the other hand not more than 10% of the plate surface to take.

c) The electrolyte is forced through these channels and not around the periphery of the cell assemblies to flow around by providing a tight fit between the stacking surfaces and the wide front housing walls and by the space between the stacking edges and the narrow edges of the housing walls with a suitable sealing filler material is filled. The filler material can be made from a large number of materials can be selected, e.g. B. be a liquid, curable plastic resin or rubber, or else from materials foamed in place or from materials that have been foamed beforehand be cut to size, insist.

d) High electrical. Resistance in the electrolyte connection network was achieved through the use of long inlet and outlet tubes. The inlet tube extends preferably from the top to the bottom of the cell, while the outlet tube is preferably in shape a spiral is provided at the bottom of the cell. The branches connecting the cells to one another are located which is preferably located above the cells, which makes it possible for the electrolyte to run back into the cells to leave if the circulation is interrupted. This latter feature reduces the electrical path between the cells on the conductivity of the electrolyte film, which adheres to the pipe walls.

709833/0829

-t- 270A3H

The flow of electrolyte through the system can be summarized as follows: reservoir; Pump; Battery junction; Cell inlet manifolds; Cell electrolyte inlet tubes; Cell reservoirs; Feedthrough channels in sealed cell structures; Cell electrolyte outlet tubes; Cell outlet manifold; Battery junction; and from there on to the reservoir to cool down.

This improved cell stack electrolyte flow system offers many advantages over previously known systems, in particular the following:

a) Effective cooling of the battery structures enables the use of higher charging rates, reduced to these Way the loading time. In a typical charge / discharge cycle at a C / 2 rate, the temperature stays between 30 and 35 C with existing circulation, while without circulation the temperatures exceed values of 70 C. which would seriously affect the battery life.

b) The tightness of the system eliminates many safety hazards, such as spills and spraying, which could lead to short-circuit paths to ground and potential failure.

c) The parallel flow arrangement with the associated piping ensures that each cell in correct Maintained in a manner that prevents failure due to overfill or underfill and due to unsuitable specific gravity of the electrolyte.

d) The piping also ensures a safe gas treatment and offers itself in an advantageous manner to Elimination of the hydrogen and oxygen gases generated during the charge.

709833 / 0R? 9

_ _r _ 270A3U '5.

The invention is explained in more detail below on the basis of exemplary embodiments which are shown in the drawings.

It shows:

Fig. 1 is a perspective view of a battery unit with circulating electrolyte, the five in series includes interconnected battery cells;

FIG. 2 shows a partially sectioned plan view of the battery unit of FIG. 1;

3 shows a side view of the battery unit of FIG. 2, partially in section along the line III-III;

Fig. 4 is a cross-sectional view of the battery unit of Figure 2 along the section line IV-IV, wherein a Electrode plate, which shows channels arranged at a distance from one another, placed in a container is, furthermore, inlet manifold, cell electrolyte inlet pipe, cell reservoir and cell electrolyte outlet pipe;

Fig. 5 is a cross-section of the plate stack of an embodiment of a cell, the sealed Electrode plate sides and edges and the channels with the plate stack are shown, the for a uniform flow of the electrolyte through the stack instead of a flow around the Pile worries; and

Fig. 6 is a schematic view of an arrangement of battery packs used by an electrolyte circulation system is fed, with associated electrolyte cooling reservoir and pump.

709833/0829

270431A

- <β -

'40 -

In Figure 1 of the drawings, a battery unit or a battery module 10 is shown with its associated dimensions, these dimensions are very dependent on the battery application. The battery module, the at least one Cell contains, can consist of a housing 11, which makes up, for example, a metal, rubber or plastic box. This cell 12 is housed in its own housing or container which has flat front and side walls. The battery module housing 11 is not absolutely necessary, since the various cells are exclusively through the cell outlet branch 13 and the cell inlet manifold 14 could be held together, shown in parallel arrangement are. The cells could also be held together between the connecting pieces 15 by means of electrical connections will. Of course, any retaining or clamping device can be used to hold the separated cells together, such as a U-shaped base plate, as shown in the drawing under reference number 17, this U-shaped bottom plate would be used without the battery module housing.

Figure 2 shows a plan view of the battery module with connecting pieces 15. The coiled cell electrolyte outlet tube 21, which is attached to the opening 22, is also shown the cell outlet manifold 13 is attached. The cell electrolyte inlet tube is shown at 23. Figure 3 shows also the position of these tubes within the cell, the electrolyte inlet tube being shown at 30 at the bottom of the cell is.

FIG. 4 shows a cross section through a preferably cell 12 of the invention. Cell electrolyte circulation devices, tubular cell inlet manifold 14 and cell outlet manifold 13 are preferably in parallel intended. These electrolyte circulation devices are preferably connected to one another above the cells, to enable the electrolyte to fail in the event of the

709833/0829

270A3H

- 9 -

Ή,

Circulation back into the cells. This diminishes the electrical path between cells, when the electrolyte is not circulating, on the conductivity of the electrolyte film, which adheres to the walls of the branch pipe.

The tubes of the inlet and outlet manifolds have a relatively large internal cross-section. This represents one low flow resistance and reduces the pressure drop across the cell, which is necessary to increase the pressure decrease that for sufficient electrolyte flow is needed. Cell inlet and cell outlet branch tubes are long in length for high electrical resistance when the tubes are filled with electrolyte, which is necessary to prevent the current leakage path from the cell Zoom out cell.

Preferably, the electrolyte is pumped up through the electrode assembly so that those generated during charging Oxygen and hydrogen gases can be easily vented to the cooling reservoir without causing a dangerous pressure build-up forms. In the cell shown in Figure 4, the electrolyte flows from junction 14 at the top of the Cell housing to the bottom of the cell structure by means of the cell electrolyte inlet tube 23. The cell electrolyte inlet tube 23 extends from the top of the electrode assembly down along a corner of the battery cell between the corner sides of the structure and the corner wall of the cell housing. The tube then bends around the bottom of the assembly and extends into the cell bottom reservoir 40. The cell assembly, which consists of a series of alternating positive and negative electrode plates, one of which at 41 may rest on blocks of plastic, rubber, or foam to form the bottom reservoir 40.

Thus, the electrolyte flowing into the cell housing will fill the bottom electrolyte reservoir, that of the blocks or other suitable structural support means

709833/0 8 29

will. The electrolyte is then forced to flow upward through the channels in the electrode plates.

In Figure 5 is a cross-sectional top view of electrode plate 41 and other alternating positive and negative Plates which make up one type of cell electrode assembly 50 are shown. The channels 4 3 can thereby be produced be that narrow slots are cut in the electrode plates, or that the plates are embossed, so that they form narrow channels in themselves, or by any other suitable means.

The cross-section of the channels can be circular as shown, but can also be square or any other Have cross-section. The channels need not be provided on both the positive and negative plates are as shown, but can, for example, only be embossed on the positive or only on the negative plates so that channels would only appear on every other disk.

The channels should not extend through the electrode as this will affect the conductivity of the plate would decrease. The channel area can make up approximately 0.5 to 10% of the plate front area. If the channels are more than make up about 10% of the plate area, there is a severe loss of active material with an associated reduction the battery efficiency. There are usually 1 to 6 channels per plate for good electrolyte circulation and Battery cooling sufficient.

Channels on one side of the plate are preferred, as shown in Figure 5, as this provides a strong electrode structure that requires minimal machining or pressing. Plate separators are not shown, made of continuous or perforated film of cellulose, polypropylene, nylon or other suitable insulation

709833/0 ^ 29

Materials could be made and placed between the panels or wrapped around each panel in a serpentine fashion could be. The separators should of course be compatible with the electrolyte. For sufficient For cooling, it is important that the electrolyte flows only along the channels between the electrode plates of the structure and not around the sides and edges of the structure, although minimal electrolyte penetration through the plates may occur.

In order to create a hermetic seal and to ensure that no electrolyte flows around the structure the spaces 44 between the corner sides of the structure 45 and the edge wall of the cell housing 46, see Figures 4 and 5, filled with a suitable sealant. The sealant can be a curable, liquid epoxy resin or another Plastic resin, but rubber or some other material, such as polypropylene foam or polyethylene foam are effective as a hermetic seal of the space 44, these materials are not chemically degraded by the electrolyte.

The sealing filler seals and encapsulates the side edge of the structure and the central part of the electrolyte inlet tube. The sealing agent is preferably curable at a temperature of approximately 25 ° C. Electrolyte flow between the wide front of the cell structure and the flat front cell housing walls can thereby be prevented that between the two surfaces shown in Figure 5 at 51 a precisely fitting and intimate contact is established. This arrangement results in a seal on the sides of the electrode assemblies, that is, the edge sides and the wide flat sides, but not the top and bottom of the structure .

709833 / Π829

The electrode plates that make up the structures of the cells are preferably made of flexible, porous plates of approximately 75 to 95% porosity consisting of diffusion-bonded metal fibers, such as nickel fibers, preferably but made of steel wool or nickel coated steel wool, see U.S. Patent 3,895,960. Other types of panels, for example Porous sintered nickel powder or cast porous nickel can be used, it has been found however, not as effective as sheets of expanded fiber metal. The fiber metal plates can during the "formation" expand and contract to obtain improved loading of active material.

The plates contain active battery material which is arranged within the pore volume of the plates and distributed on the material. For example, if an iron-nickel cell is to be manufactured, the active material of the positive electrode plates may comprise Mi (OH), with small effective amounts of Co (OH) as an activating additive. The negative electrode plates can comprise an iron oxide, for example FiO, Fe ₃ O ₃ , Fe ₃ O ₄ , Fe ₃ O ₃ ^ H ₂ O or mixtures thereof, with small effective amounts of sulfur-containing activating additives sintered onto or with the iron oxide are mixed as described in U.S. Patent 3,853. Of course, other types of positive and negative active materials and other additives can also be used.

Each electrode plate has an electrical lead nose that is generally spot welded to an embossed top area or otherwise attached. These lead noses 47 represent devices with which to the plates electrical contact is established. Terminal connection tracks 48 are attached to the lead noses around the positive and to electrically connect negative plates to the connection lugs 15.

709833/0829

Once the electrolyte through the channels 43 of the structure in the preferred embodiment of the invention upwards flows, it exits the cell through the cell electrolyte outlet tube 21 and the cell outlet manifold 13. The length of the cell electrolyte outlet tube 21 should preferably be increased in order to have a high electrical resistance in the Establish electrolyte pipe network, for example by using a helical or similar configuration as shown in FIGS. 2 and 4.

In all cases, the tubing in the cell and battery module, such as inlet and outlet pipes, should be used and branches are made of non-conductive pipe material, such as polypropylene, polyethylene, Polyvinyl chloride, acrylonitrile butadiene styrene, nylon, or any other type of plastic or rubber material made from the electrolyte are not attacked. These non-conductive tubes and branches can by means of suitable Adhesive can be attached, such as epoxy adhesive or polyvinyl chloride adhesive.

To ensure an escape of electrolyte through the electrolyte outlet pipe 21, the space 49 between the top the cell housing and the top of the outlet pipe inlet are filled with a suitable sealant, similar to that described above. This would also form the top of the cell housing. To such a To create top, a partition can be placed over the top of the bottom opening of the cell electrolyte outlet tube and sealant is sprayed or poured onto the partition to cover the top of the outlet tube, the Encapsulate top of inlet pipe and connections.

According to FIG. 6, a battery is formed in that the cell inlet branches 14 and the outlet branches 13 are preferably connected in parallel to each other. To facilitate the construction of a high capacity battery,

709833 / D829

Several sets of cells, ie sets of battery modules 10 _f , are fastened in place, with all fluid flows running parallel to make the pressure required for the system as low as possible and to create uniform cooling from cell to cell. The battery modules can then be arranged to create a complete high performance battery system according to the voltage and space requirements for each particular application. 6 shows a high-performance battery which consists of three groups of three battery modules each. Each battery module contains five cells.

The modules are by means of shared battery manifold electrolyte circulation facilities 60 connected, the length and position of which depends on the battery construction. The battery branches can from the heat exchanger devices 61 and the electrolyte pump devices 62 by means of quick-release couplings 63 can be disconnected so that the high-performance battery can be discharged without a heat exchanger and pump can. The heat exchangers or cooling devices can comprise an electrolyte cooling reservoir 64, the cooling water cooling coils 65 contains. A radiator or other cooling device could be added to the system around the cooling coils to be supplemented or replaced by air cooling. The electrolyte is circulated by the pump at a rate that is effective removes the heat generated by the various charge and discharge rates.

The level of the electrolyte and its specific gravity are determined by adding water to the electrolyte in the Cooling reservoir 64 controlled by inlet 66 to maintain a constant level for the electrolyte in the cells. The battery system is vented to atmosphere, preferably at the reservoir, by any suitable means Measures such as barrier vents 67 made from a sintered ceramic barrier can exist and make hydrogen and oxygen possible,

709833/0 * 29

• A

to escape, but at the same time act as a flame and explosion barrier. A bladder tube extending from the opening in the reservoir into the bottom of an open container of water can also be used as a gas vent. The alkaline electrolyte used will generally consist of an aqueous solution of 10% to 35% KOH or NaOH, preferably with about 2 to 20 g Li (OH) ₂ per liter. No gases are added to the electrolyte.

example

High-capacity iron-nickel batteries similar to those of Figures 1 through 6 were constructed. The battery plates were Made from nickel-plated steel fibers that have been formed into plates. Fibers with the approximate dimensions 0.025 χ 0.05 χ 6.35 mm in length were made in the flexible, expandable fiber-metal plates used. The panels were then heated in a protective gas atmosphere and caused metal-to-metal diffusion bonds were formed at the fiber contact points. There was no melting of the fibers, so there was maximum pore volume was assured.

The "nickel" plates were then set to about 8% theoretical Density, 92% porosity, embossed and the "iron" plate body were embossed to 17% theoretical density, 83% porosity. Each nickel plate had two vertical impressions Channels 3.18 mm wide. The plate was approximately 165 mm wide and approximately 2.3 mm thick. The canals were about 2 now deep. The channels comprised approximately 4% of the surface of the plate. A layer of steel was then stamped onto the top part of the plates are spot welded to make electrical lead-nose connections as shown in Figure 4 at 47.

The iron active material comprised magnetic iron oxide particles. The magnetic iron oxide had a composition of about 79% Fe ₃ O ₃ , 22% FeO and 1% impurities. It

709833/0829

- in -

'49 *

Enough sulfur was used to make a sulfur to iron oxide ratio of about 0.1 to 10% of that of the sulfurized To create iron oxide. This additive helped keep the surface of the iron active material in the active state to keep.

The "iron" tablets were made with the sulfurized magnetic Loaded iron oxide by wet application method. These iron electrode plates were then sized and dried. They contained about 1.5 to about 1.9 sulfurized activated iron material.

They contained about 1.5 to about 1.9 g / cm plate volume

The nickel active material comprised nickel hydroxide doped with small amounts of cobalt hydroxide. The nickel plates were loaded by a "formation" impregnation process. The panels contained from about 0.9 to about 1.3 g / cm ^{3 of} active material. The "iron" and "nickel" plates were then ready for cell construction.

A battery module with the dimensions of approximately 178 mm width χ 254 mm depth χ 254 mm height, as shown in Figure 1, was used and comprised five cells. The cell housings, which were made of high-density polyethylene and were open at the top, were approximately 178 mm wide, 51 mm deep and 254 mm high. These housings would then contain the electrode assemblies.

During assembly, iron and nickel plates alternated stacked, with the plates isolated from each other by means of serpentine-like wound polypropylene separators whereupon the connection lugs, see 48 in Figure 4, were welded to the noses under inert gas, to provide facilities for making electrical connections to the panels. The cell structure, together with a polypropylene cell electrolyte inlet tube having an inner diameter of 4.76 mm, was then placed in the cell housing introduced where it is on top of two polyethylene

709833/0829

-Yf-

Blocks of foam rested that were approximately 25.4 mm wide χ 50.8 mm deep 15.9 mm high, see 42 in Figure

The inlet pipe ran down on the corner side of the structure next to the narrow edge wall of the cell container, bent over on the floor and continued below the cell structure. The inlet pipe ended roughly in the middle of the bottom reservoir, see the reference number 40 in FIG. 4, this reservoir being formed by the foam blocks 42 and the cell structure will. A groove was formed in the foam block through which the inlet tube passed so that the inlet tube around the bottom of the construction fit around.

This yielded cells with inserted electrode assemblies, which were held on the floor with the help of foam blocks and which had an electrolyte inlet tube that went into a reservoir located at the bottom of the cell was running. The space shown in Figure with 44 between edge sides of the structure and the 5 mm edge wall of the cell container was unfilled.

A viscous, room temperature curable epoxy resin was then poured from an injection gun into this space 44 between each edge side of the superstructures and each edge wall of the cell housing issued to act as a hermetic seal to work and encapsulate the assembly between the foam blocks and the top of the electrode assembly. Top and the bottom of the superstructure remained unsealed. This will force pumped electrolyte through from the bottom reservoir Plate channels 43 to flow to the top of the cell instead of going around the plates.

The top of the cell was then fitted with a polypropylene cell electrolyte outlet tube equipped with an inner diameter of 7.9 mm. This tube that in the drawings indicated at 21 has a spiral configuration. It starts just above the electrode assemblies under the Cell outlet branch and runs across the cell width,

709833/0829

winds around the cell electrolyte inlet tube, runs back over the cell and fits into the cell outlet manifold as shown in FIGS.

To form the lid of the cell, the cell electrolyte outlet tube is used held in place with polyvinyl chloride tape with the outlet opening straight at the Top of the cell structure is located. The tape has openings to the bottom part of the electrolyte outlet tube, the positive and negative connecting tabs and the top of the electrolyte inlet tube through. An upper one Reservoir volume is thus created between the tape and the top of the assemblies.

A viscous room temperature curable epoxy resin was then applied from an injection gun to the top of the Tape is dispensed to the top of the cell electrolyte outlet and inlet tubes and the intercell connector tabs encapsulate. Thus, the top of the cell is made of epoxy resin.

The iron plate in the superstructure was still in the unformed State. An electrolyte solution containing 25 wt% KOH and 15 g / l Li (OH) was poured into the cell and formation of the iron plates through a series of charge-discharge cycles.

The cells were then matched and electrically connected to one another to form a five-cell battery module. Four modules were then arranged in series and polyvinyl chloride cell inlet branches with an inner diameter of 12.7 mm and cell outlet branches with an inner diameter of 19.05 mm were attached to the cell electrolyte inlet tubes and cell electrolyte outlet tubes, respectively, by means of a room temperature curable epoxy resin adhesive . Each module was similar to the module shown in Figure 1, with branches 13 and 14 parallel on top

709833 / 0S29

270A3U

of cells were arranged. The modules were combined with one another in the manner shown in FIG. 6, however there were only four groups of modules, each group containing four interconnected battery modules and each Module had five cells. Overall, the result was a high-performance battery with a total of 16 modules or 80 cells.

Referring to Figure 6, the cell inlet manifolds 14 and outlet branches 13 to common polyvinyl chloride battery branches with 25 mm inner diameter and with flexible polyvinyl chloride hose and hose clamps were connected. The pump branches were with a 0.25 PS pump and an electrolyte reservoir 61 of 95 liters connected from polyvinyl chloride.

The reservoir had a closed lid and a ceramic one Flame barrier vent 66 to vent hydrogen or oxygen that is due in the electrolyte of battery charging may be present, as well as one Inlet 67 for adding water or electrolyte. The cooling coils 65 consisted of 6 mm long coiled Stainless steel tube with an inner diameter of 12.7 mm. Cold water was passed through the cooling coils, to cool the circulating electrolyte.

The electrolyte solution used in the system contained 25% by weight KOH and 15 g / l Li (OH) ₃ . No gases were added to the electrolyte. The pump and reservoir were connected to the battery modules by means of cut-off valves in the common pump branches, so that the high-performance battery could be discharged without these components.

The assembled high-capacity battery was then charged on the test bench for several 3-hour and two-hour periods Discharge test cycles checked to determine capacity. The best results were about 17 kWh or

709833/0829

44 Wh / kg cell weight. The battery was then operated in several electric vehicles for more than 100 cycles.

The 80 cell (96 V) circulating electrolyte battery was charged at a rate of C / 2 (100 amps) Charged for 3 hours. The total electrolyte flow was 34 l / min, with an average pressure drop above that

Cell inlet-outlet junction of 0.35 kg / cm. The initial reservoir electrolyte temperature was 25 ° C. The temperature the battery after the full charge was 32 C. If no electrolyte circulation is provided during the charge the battery temperature rose above 70 C after a full charge, which affects the service life of the Electrodes and the separators is very disadvantageous.

The epoxy resin sealing system on the Corner sides of the panels in the structure and at the top of each cell as tight. A uniform and very efficient and effective cooling of the cells during charging was achieved. There was no adverse self-discharge determined by the electrical conductivity of the electrolyte-circulating pipe system. There was no excessive Increase in the pressure drop in the cell after 2,000 charge-discharge cycles. This shows that there are no blockages in the plate channels due to plate swelling or due to occurred from detached active material. The use of two channels per nickel plate, which is 4% of one side of the Nickel plate surface provided sufficient cooling for this system. There could be more channels until to 10% of the plate surface, where more cooling and less active material volume is required is.

Claims ι

709833/0829

Blank page

Claims (6)

P a t e η t a η s ρ r Ü c h e; λ .J battery with circulating electrolyte, consisting of at least one cell, which has a structure of electrode plates, with electrolyte cooling devices that contain electrolyte separately from the cell, with electrolyte pumping devices that are connected to the cooling devices, and with electrolyte Circulation devices leading from the pumping devices to the cell and from the cell to the cooling devices, characterized in that the front and edge sides of the structure (50) are sealed and that at least one channel (43) in at least one electrode plate (41) in each structure (50) is provided, the channel (43) making up 0.5 to 10% of the electrode plate surface, so that pumped electrolyte only flows through the channels (43) in the structure (50). 2. Battery according to claim 1, characterized in that the structure (50) within a cell housing (11) is arranged and at least one flat positive electrode plate and at least one flat negative electrode plate each plate containing active material on the flat surface and within of the pore volume of the plate is arranged distributed, and that an alkaline electrolyte is provided in the way is that it flows from the bottom to the top of the structure and that the channel (43) extends on the Surface of the electrode plate (41) is located and does not pass through this electrode plate (41). 3. Battery according to claim 2, characterized in that the plates (41) made of 75 to 95% porous metal fiber plates consist, with the negative plates active iron oxide material and the positive plates active Include nickel hydroxide material. 709833/0829 ORIGINAL INSPECTED -a *. 27043U 4. Battery according to claim 1, 2 or 3, characterized in that the plates (41) in each structure (50) one Separator have between them that the structure (50) is arranged within a cell housing (11) in such a way is that the front sides of the structure (50) of electrode plates (41) are in intimate contact with the cell housing (11) stand and that the edge sides of the structure (50) made of electrode plates (41) by means of a hardenable Sealing means are sealed to provide a hermetic seal between the sides of the structure (50) and to manufacture the cell housing (11). 5. Battery according to claim 4, characterized in that the channels (43) are pressed into the surface of the electrode plate (41) so that the sealant is an epoxy resin and that the cooling means comprise a reservoir (64) which has means (67) for venting hydrogen and contains oxygen gas from the electrolyte. 6. Battery according to one of claims 1 to 5, characterized in that that the electrolyte circulation devices have parallel inlet (13) and outlet devices (14), which are arranged on top of the battery cells (42) and from the pumping and cooling devices (62, 64) can be separated (63). ES / hs 3 709833/0829