Catalyst design for VRLA batteries
A catalyst device for use with battery cells to recombine oxygen and hydrogen gas and thereby improve the performance and life of such cells. The catalyst device has the ability to filter out catalyst poisons and control the temperature of the recombination reactions. A container houses the catalyst within a chamber. A catalyst poison filter is provided in the chamber with the catalyst. The movement of gas and vapor to and from the chamber is controlled by a microporous section of the device. The pore size is chosen to allow gas and vapor to pass, but not liquids, and to also prevent a flame from passing through. Within these parameters the pore size can also be chosen to control and or limit the amount of gas that can pass through to the catalyst in a given time period. Preferably, the microporous section is formed as a disc that seals an opening in the chamber. The filter material is then placed as a layer between the catalyst and the opening such that the poison in the gas must pass through the filter material before reaching the catalyst.
1. A valve regulated lead acid (VRLA) battery cell comprising:
a sealed housing;
a positive electrode positioned in the housing;
a negative electrode positioned in the housing in spaced relationship from the positive electrode;
an electrolyte in said housing in contact with said positive and negative electrodes;
a gas space within said housing in which oxygen and hydrogen gas collects;
a pressure relief valve which allows gas to escape from the housing and which prevents oxygen gas from outside the housing from entering said housing;
a catalyst device which includes a container having a container wall and which defines an internal chamber, said catalyst device including a catalyst arranged within said internal chamber and which is capable of reacting oxygen gas and hydrogen gas to form water vapor, said catalyst device being arranged such that said catalyst is in fluid communication with said gas space and isolated from said oxygen gas outside of said housing; and
a micro-porous section having pores through which said oxygen gas and hydrogen gas can pass into said internal chamber from outside of said container, said micro-porous section being capable of preventing liquid water from passing there through, said device being configured such that all fluid communication between said outside of said internal chamber and said internal chamber is by passage through said micro-porous section; and wherein at least one of the pore size, planar surface area and thickness of said micro-porous section is selected to control the amount or rate at which said oxygen and hydrogen gases can pass into said internal chamber to control the heat generated by the catalytic combination of said oxygen and hydrogen gases.
2. A battery cell in accordance with claim 1 wherein said micro-porous section is arranged in at least a portion of said container wall.
3. A battery cell in accordance with claim 1 wherein said micro-porous section has pores ranging in size between 1 and 40 microns.
4. A battery cell in accordance with claim 1 wherein said container is impervious to gas and water and has an opening to said chamber through which said fluid communication takes place, and wherein said micro-porous section comprises a micro-porous hydrophobic member arranged to seal said opening and which allows said hydrogen and oxygen gas to pass there through and which prevents liquid water from passing there through.
5. A battery cell in accordance with claim 1 wherein said container is made of a plastic material and is attached to a flange capable of being attached to said pressure relief valve.
6. A battery cell in accordance with claim 1 wherein said catalyst device further comprises a catalyst poison filter arranged within said chamber to remove at least a portion of catalyst poisons in said oxygen and hydrogen gas.
7. A battery cell in accordance with claim 2 wherein said poison filter comprises potassium.
8. A device for use with a VRLA battery which battery has a housing defining an internal and an external environment, said device comprising:
a catalyst container having a container wall and defining an internal chamber;
a catalyst arranged within said chamber, said catalyst capable of reacting oxygen gas and hydrogen gas to form water vapor;
a micro-porous section having pores through which said oxygen gas and hydrogen gas can pass into said internal chamber from outside of said container, said micro-porous section being capable of preventing liquid water from passing therethrough, said device being configured such that all fluid communication between said outside of said internal chamber and said internal chamber is by passage through said micro-porous section; and wherein at least one of the pore size, planar surface area and thickness of said micro-porous section is selected to control the amount or rate at which said oxygen and hydrogen gases can pass into said internal chamber to control the heat generated by the catalytic combination of said oxygen and hydrogen gases; and
a pressure relief valve which allows gas to escape from the battery and which prevents gas from the external environment from entering the battery, said catalyst container being attached to said pressure relief valve;
said container being arranged such that said catalyst is capable of receiving said hydrogen and oxygen gases through said micro-porous section from said internal environment of said battery and not from said external environment when said device is in combination with said battery.
9. A device in accordance with claim 8 wherein said catalyst container is attached to said pressure relief valve by a flanged connection.
10. A catalyst device for combining gases within a storage battery; comprising:
a catalyst capable of reacting oxygen gas and hydrogen gas to form water vapor;
a catalyst container within which said catalyst is disposed, said container being impervious to gas and water and having an opening which is the only path for fluid communication between an outside of said container and catalyst; and
a micro-porous member disposed to close said opening so as to control said fluid communication through said opening, said micro-porous member having pores through which said oxygen and hydrogen gases and water vapor can pass but through which liquid water cannot pass, wherein at least one of the pore size, planar surface area and thickness of said micro-porous member is selected to control the amount or rate at which said oxygen and hydrogen gases can pass through said micro-porous member to said catalyst so as to control the rate of the catalytic combination of said oxygen and hydrogen gases.
11. A catalyst device for combining gases within a storage battery in accordance with claim 10 wherein said container is cylindrical, and said opening comprises a single opening disposed at an end of said container.
12. A VRLA battery having a catalyst device in accordance with claim 10 , said battery comprising:
a sealed housing defining an internal environment within said housing and an external environment outside said housing;
an electrolyte disposed in said housing;
positive and negative plates disposed in said housing and in contact with said electrolyte;
a gas space in said internal environment in which said oxygen and hydrogen gases collect;
a pressure relief valve which prevents gas from said external environment from entering said internal environment; and
wherein said catalyst device is arranged so that said catalyst is in fluid communication with only said gas space.
13. The device of claim 11 in combination with a storage battery that has a housing defining an internal and external environment, wherein said container is arranged such that said catalyst is capable of receiving said hydrogen and oxygen gases from said internal environment of said battery and not from said external environment when said device is in combination with said battery.
14. A device for combining gases within a storage battery; comprising:
a catalyst container having a container wall and defining an internal chamber;
a catalyst arranged within said chamber, said catalyst capable of reacting oxygen gas and hydrogen gas to form water vapor;
a micro-porous section having pores through which said oxygen gas and hydrogen gas can pass from outside of said internal container into said internal chamber, said micro-porous section being capable of preventing liquid water from passing there through, said device being configured such that all fluid communication between said outside of said internal chamber and said internal chamber is by passage through said micro-porous section; and wherein at least one of the pore size, planar surface area and thickness of said micro-porous section is selected to control the amount or rate at which said oxygen and hydrogen gases can pass into said internal chamber to control the heat generated by the catalytic combination of said oxygen and hydrogen gases.
15. A device in accordance with claim 14 wherein said micro-porous section is arranged in at least a portion of said container wall.
16. A device in accordance with claim 14 wherein said container comprises a plastics material.
17. A device in accordance with claim 14 wherein said micro-porous section has pores ranging in size between 1 and 40 microns.
18. A device in accordance with claim 14 wherein said container wall is substantially non-porous to gas and liquid and said container has an opening to said chamber through which all fluid communication between said outside of said internal chamber and said internal chamber takes place, and wherein said micro-porous section comprises a micro-porous hydrophobic member arranged in relation to said opening such that all fluid communication between said outside of said internal chamber and said internal chamber passes through said micro-porous member.
19. A device in accordance with claim 14 further comprising a pressure relief valve.
20. A device in accordance with claim 14 wherein said container is made of a plastic material and is attached to a flange capable of attaching to a pressure relief valve.