Primary battery system

A battery system (10,110) wherein an electrolyte solution of lithium hydroxide dissolved in seawater is circulated through a battery cartridge (11,111). The system is placed under pressure. A portion of the electrolyte mixture is discharged from the system through a suitable pressure regulating valve (20) while concurrently, fresh seawater is delivered into the system as by a pressurizing pump (17). The increased pressure acts to increase the density of the gaseous portion of the ejected gas liquid mixture, reduce the volume of the gaseous portion of the ejected gas-liquid mixture, thereby reducing the total volume of the ejected mixture, and reduce the ratio of gas volume to liquid volume in the system as well as the ejected gas-liquid mixture.

DESCRIPTION 
1. Technical Field 
This invention relates to metal-water electrochemical cells and in 
particular to means for controlling the electrolyte composition in such 
cells. 
2. Background Art 
One well-known form of metal-water electrochemical cell comprises a 
lithium/silver oxide cell. The electrolyte in such a cell comprises a 
solution of lithium hydroxide in water. In one marine application of such 
a cell, the lithium hydroxide is dissolved in seawater. 
The power developed by the cell is a function of several variables, such as 
temperature, electrolyte velocity, electrode area, electrode spacer 
configuration, voltage, gas-liquid volume ratio, and lithium hydroxide 
concentration in the electrolyte. Thus, by suitably controlling the amount 
of dissolved lithium hydroxide to desired varying values, while 
controlling the remaining variables to nearly constant values, variable 
power output may be obtained. 
In the operation of such a cell, lithium hydroxide is generated as a 
by-product of the electrochemistry, thus changing the concentration of 
lithium hydroxide in the electrolyte. To control the concentration of 
lithium hydroxide in the circulated electrolyte, a portion of the 
electrolyte circulated from the cell having an increased lithium hydroxide 
concentration is discharged and replaced with water, which, in the marine 
application discussed above, is seawater. 
The control of the lithium hydroxide in such an application is complicated 
by the fact that another by-product of the electrochemistry of the cell is 
hydrogen gas. The hydrogen does not dissolve in the electrolyte to any 
great extent but forms a distributed mixture therein, tending to 
pressurize the system. 
It has been conventional in such systems to separate the hydrogen gas from 
the electrolyte prior to ejection of a portion of the electrolyte having 
the increased concentration of lithium hydroxide. Such hydrogen gas 
separation subsystems are relatively expensive, bulky, and require 
undesirable energy consumption in the operation of the battery system. 
DISCLOSURE OF INVENTION 
The present invention comprehends an improved battery system which 
eliminates the need for separation of the gaseous by-product produced in 
the electrolyte as a result of the electrochemistry of the cell by 
controlling the pressurization of the system as a function of the rate of 
discharge of the electrolyte suitable for maintaining the desired lithium 
hydroxide concentration for the desired power output. 
In the illustrated embodiment, the system is caused to have a sufficient 
hydrogen gas pressure so as to provide a desired small gas-to-electrolyte 
volume ratio, permitting the use of a circulation pump of conventional 
design. The invention comprehends that the maintained hydrogen gas 
pressure is less than a preselected pressure so as to avoid the need for 
bulky and heavy structures in containing the pressurized hydrogen gas. It 
has been found that the provision of means to effect the desired 
pressurizing of the system permits the gas-to-electrolyte volume ratio in 
the system reservoir to rise at a decreasing rate so that during the 
normal operation of the battery system, the gas-to-electrolyte volume 
ratio in the reservoir becomes effectively constant at a pressure less 
than a preselected maximum. 
The invention comprehends providing pressure regulating means for 
discharging the electrolyte from the reservoir as an incident of the 
pressure thereof exceeding the preselected operating pressure. 
The invention further comprehends the provision of pressure control means 
permitting the pressure condition of the electrolyte to cause an increase 
in the density of the gaseous component in the electrolyte, resulting in a 
reduced ratio of the gaseous component volume to the liquid component 
volume of the gas-electrolyte mixture. 
The invention broadly comprehends the provision in a battery system 
including a battery cartridge producing a gaseous by-product and a solute 
by-product in a circulated electrolyte liquid as an incident of 
electrochemical operation thereof, of pressurizing means for placing the 
electrolyte mixture under a preselected pressure, and replacing a portion 
of the pressurized electrolyte mixture with water. The pressure is 
preselected to cause the ratio of the volume of gaseous by-product to 
volume of the liquid component to be reduced, thereby reducing the volume 
of the portion of the mixture being discharged, and, upon replacement of 
the ejected mixture with water, permitting the electrolyte mixture 
provided to the battery cartridge to have a desired solute concentration 
and gas-to-liquid volume ratio, for desired operation of the battery. 
Thus, broadly under a specific steady operation condition, the mass flow 
rate of the ejected gas and the mass flow rate of the ejected electrolyte 
remain substantially steady since the electro-chemical reaction is 
substantially steady. The effects of the increased system pressure as to 
increase the density of the gaseous portion of the ejected gas-liquid 
mixture, reduce the volume of the gaseous portion of the ejected 
gas-liquid mixture, thereby reducing the total volume of the ejected 
mixture, and reduce the ratio of gas volume to liquid volume in the system 
as well as the ejected gas-liquid mixture. 
The battery electrolyte control system of the present invention is 
extremely simple and economical of construction while yet providing 
improved efficiency, size and weight reduction, and reliability.

BEST MODE FOR CARRYING OUT THE INVENTION 
In the illustrative embodiment of the invention as disclosed in the 
drawing, a battery system generally designated 10 is shown to comprise a 
primary battery system having a battery cartridge 11 disposed in a battery 
cartridge zone 12 within a housing 13. The housing is provided with a 
divider wall 14 separating zone 12 from a reservoir chamber 15. 
In the illustrated embodiment, battery cartridge 11 comprises a 
lithium/silver oxide battery cartridge utilizing an electrolyte comprising 
an aqueous solution of lithium hydroxide. In the illustrative system, 
water is introduced into the electrolyte from the surrounding ambient 
seawater 16. 
Water is drawn into reservoir 15 by means of a pump 17 having an inlet 18 
opening to the ambient seawater, and an outlet 19 opening to the reservoir 
15. The invention comprehends the pressurizing of the electrolyte in the 
reservoir and, in the illustrative embodiment, a pump 17 is provided for 
producing pressure in the reservoir chamber 15 greater than the ambient 
pressure. 
The pressure in chamber 15 is desirably maintained at the preselected 
elevated pressure, such as approximately 25 psi absolute to 3500 psi 
absolute, and preferably in the range of approximately 100 psi absolute to 
1000 psi absolute, by a suitable pressure regulating valve 20. As shown, 
the valve is connected through an inlet 21 to the reservoir chamber 15 and 
through an outlet 22 to exteriorly of the housing 13. 
As will be obvious to those skilled in the art, the valve inlet could also 
be connected to other locations within the electrolyte circulation path, 
such as to battery cartridge discharge 26, thermostatic bypass valve 
discharge 29, heat exchanger paths 30 through 31, heat exchanger discharge 
32, or circulation pump discharge 25. 
Circulation of electrolyte from reservoir 15 through the battery cartridge 
11 and back to the reservoir 15 is effected by means of a main pump 23 
having an inlet 24 opening to the reservoir chamber 15. An outlet 25 of 
the pump 23 is connected to one side of the battery cartridge 11 for 
delivering the electrolyte through the battery to outlet 26 thereof 
extending through the divider wall 14 to thermostat bypass valve 27. In 
the illustrated embodiment, the thermostat valve is located in reservoir 
15, as seen in FIG. 1, it being obvious to those skilled in the art that 
the thermostat valve can be provided at other suitable locations in the 
electrolyte circulation path. 
The thermostat valve is selectively operable to deliver the returned 
electrolyte through a first outlet 28 directly to the reservoir chamber 
15, or through second outlet 29 to a heat exchanger 30 providing heat 
exchange between the electrolyte circulated therethrough and the ambient 
seawater 16 through the housing 13. As will be obvious to those skilled in 
the art, the heat exchange may be provided at any desired location in the 
electrolyte circulation path. 
As further shown in FIG. 1, the heat exchanging means includes a second 
portion 31 also providing heat exchange between the electrolyte flowed 
therethrough and the ambient seawater 16 through the housing 13, with the 
outlet 32 of the heat exchanger portion 31 opening into the reservoir 
chamber 15. 
In the battery system 10 illustrated in FIG. 1, divider wall 14 is provided 
with suitable openings 33 providing communication between reservoir 
chamber 15 and zone 12 exteriorly of the battery cartridge 11 so as to 
place both the reservoir and zone 12 at substantially equal pressure. 
In a modified form of the invention, as illustrated in FIG. 2, a battery 
system generally designated 110 is similar to battery system 10, but is 
provided with a dividing wall 114 which is imperforate so as to 
effectively maintain the pressure in reservoir chamber 115 selectively 
different from the pressure in zone 112 surrounding the battery cartridge 
111. The discharge conduit 125 from the main pump 123 includes a first 
outlet 134 opening to zone 112 and a second outlet 135 opening to the 
battery cartridge 111. Thus, zone 112 and the inlet to the battery 
cartridge are placed under equal pressures. In all other respects, battery 
system 110 is similar to and functions similar to battery system 10. 
INDUSTRIAL APPLICABILITY 
In one embodiment of the invention, the battery cartridge 11 comprised a 
lithium/silver oxide battery cartridge. Pump 17 comprised a positive 
displacement pump with a variable output capacity of approximately 0 gpm 
to 60 gpm, operating at approximately 2 gpm to 20 gpm when the battery is 
required to deliver full power, suitable to place the reservoir chamber at 
a pressure of approximately 100 psi absolute to 1000 psi absolute, and 
more specifically, in the illustrated embodiment, at a pressure of 
approximately 200 psi absolute to 800 psi absolute. The main pump 23 
provided a discharge of approximate 50 gpm to 500 gpm at full power, at a 
pressure differential of approximately 20 psi to 350 psi for providing the 
desired circulation of the electrolyte fluid. 
By maintaining the pressure in reservoir 15 at approximately 200 psi 
absolute, or greater, the hydrogen gas by-product by operation of the 
battery cartridge 11 was compressed in the electrolyte liquid so as to 
have a ratio to the lithium hydroxide by-product produced by operation of 
the battery cartridge suitable to permit the mixture of the elecyrolyte 
and compressed hydrogen gas to be discharged through valve 20 while 
maintaining the molarity or the lithium hydroxide in the electrolyte in 
reservoir 15 suitable to provide desired operation of the battery 
cartridge 11 when recirculated thereto by pump 23. 
It has been found that where the battery system is operated at a depth in 
the seawater of approximately 200' to 3,000' or more, sufficient pressure 
is produced by the ambient seawater to effect the desired compression of 
the hydrogen gas in reservoir 15. However, when the battery system is 
operated at lesser depths, the pump 17 and regulating valve 20 maintain a 
minimum pressure within the reservoir 15 sufficient to permit ejection of 
sufficient quantities of hydrogen gas, while maintaining a desired low 
gas-to-liquid volume ratio in the circulated fluid mixture, so as to 
permit continuing operation of the battery system as a primary battery 
system, with a portion of the recirculated electrolyte being continuously 
discharged by replacement with fresh seawater electrolyte through the 
inlet pump 17. 
Resultingly, the expensive and energy inefficient separation of hydrogen 
gas from the returned electrolyte is effectively eliminated by the 
improved simplified structure of the present invention providing improved 
efficiency and reliability in the operation of the primary battery system. 
The heat generated by operation of the battery cartridge is transmitted to 
the ambient seawater through the heat exchanger 30, 31, when necessary, 
under the control of thermostat valve 27. Where the temperature of the 
returned electrolyte mixture is below the setting of the thermostat valve, 
the mixture may be delivered directly back to the reservoir 15 through the 
outlet conduit 28 without the need for heat exchange. 
Where it is desired to maintain the pressure within the zone surrounding 
the battery cartridge substantially equal to the pressure at the battery 
cartridge inlet, the system 110 illustrated in FIG. 2 may be employed. 
To initiate operation of the battery, a measured amount of lithium 
hydroxide is dissolved in seawater with the solution then being introduced 
into the battery cartridge inlet. In one illustration embodiment, the 
starting solute was dry sodium hydroxide stored in the reservoir area. As 
will be obvious to those skilled in the art, other suitable start-up means 
may be utilized within the scope of the invention. 
In summary, the invention comprehends a novel battery system wherein the 
gaseous by-product generated by the battery cartridge in the 
electrochemical operation thereof is maintained in the fluid mixture at a 
preselected pressure so as to reduce the ratio of the volume of the 
gaseous component to the volume of the liquid component within the fluid 
mixture. Maintenance of the desired concentration of the solute is 
effected by introducing fresh solvent to replace a portion of the 
pressurized fluid which is discharged, thereby removing from the system a 
portion of the generated gaseous by-product and reducing the solute 
concentration to the desired level. The invention is advantageously 
adapted for use in a lithium/silver oxide battery system. 
The invention comprehends any modification of the disclosed system wherein 
pressurizing all or any part of the system, permitting the gas and 
electrolyte liquid to be ejected as a mixture, is desired. Thus, the 
invention is adapted for use wherein the recirculating electrolyte 
normally constitutes a gas/liquid mixture. 
The foregoing disclosure of specific embodiments is illustrative of the 
broad inventive concepts comprehended by the invention.