Battery vent and pressure blowout relief frit

1. A lead acid battery cover adapted to seal an automotive vehicle battery casing having a design pressure maximum, the lead acid battery cover comprising:

a rigid, porous frit consisting of modified polytetrafluoroethylene, wherein the frit allows gases to escape while preventing liquid from escaping and acts as a blowout disk when a pressure within said automotive vehicle battery casing exceeds a predetermined pressure that blows said frit out of said lead acid battery cover, wherein the predetermined pressure is within 5% to 10% of the design pressure maximum of the automotive vehicle battery casing; and

restraining means for holding said frit in said lead acid battery cover until said predetermined pressure is exceeded,

wherein the modified polvtetrafluoroethylene comprises Polytetrafluoroethylene, from 1 wt % to 35 wt % PMMA and from 1 wt % to 7 wt % lubricant.

2. A lead acid battery cover according to claim 1 wherein said restraining means is an O-ring.

3. A lead acid battery cover according to claim 1 wherein said restraining means is a housing in which said frit is secured until said predetermined pressure is exceeded.

4. A lead acid battery cover according to claim 1 wherein said restraining means is a lip on said lead acid battery cover.

5. A lead acid battery cover adapted to seal an automotive vehicle battery casing having a design pressure maximum, the lead acid battery cover comprising:

a rigid, porous frit consisting of modified polytetrafluoroethylene, wherein the frit allows gases to escape while preventing liquid from escaping and acts as a blowout disk when a pressure within said automotive vehicle battery casing exceeds a predetermined pressure that blows said frit out of said lead acid battery cover, wherein the predetermined pressure is within 5% to 10% of the design pressure maximum of the automotive vehicle battery casing; and

an O-ring for holding said frit in said lead acid battery cover until said predetermined pressure is exceeded blowing said frit out of said lead acid battery cover,

wherein the modified polytetrafluoroethylene comprises polytetrafluoroethylene, from 1 wt % to 35 wt % PMMA and from 1 wt % to 7 wt % lubricant.

6. A battery cover according to claim 5 wherein said O-ring has a durometer between 70 and 80.

7. A lead acid battery cover according to claim 5 that comprises molded plastic.

8. A lead acid battery cover according to claim 6 wherein said molded plastic is polypropylene.

9. A lead acid battery cover adapted to seal an automotive vehicle battery casing having a design pressure maximum, the lead acid battery cover comprising:

a rigid, porous frit consisting of modified polytetrafluoroethylene, wherein the frit allows gases to escape while preventing liquid from escaping; and

a housing for holding said frit in said lead acid battery cover until a pressure within said battery casing exceeds a predetermined pressure that blows said frit out of said lead acid battery cover, wherein the predetermined pressure is within 5% to 10% of the design pressure maximum of the automotive vehicle battery casing,

wherein the modified polytetrafluoroethylene comprises polytetrafluoroethylene, from 1 wt % to 35 wt % PMMA and from 1 wt % to 7 wt % lubricant.

10. A lead acid battery cover according to claim 9 wherein the lead acid battery cover comprises a molded plastic.

11. A lead acid battery cover according to claim 10 wherein said molded plastic is polypropylene.

12. A lead acid battery cover for an automotive vehicle battery casing having a design pressure maximum the lead acid battery cover comprising:

a rigid, porous frit consisting of polytetrafluoroethylene, from 1 wt % to 35 wt % PMMA and from 1 wt % to 7 wt % lubricant, wherein the frit allows gases to escape while preventing liquid from escaping and acts as a blowout disk when a pressure within said automotive vehicle battery casing exceeds a predetermined pressure that blows said frit out of said lead acid battery cover, wherein the predetermined pressure is within 5% to 10% of the design pressure maximum of the automotive vehicle battery casing; and

a lip on said lead acid battery cover for holding said frit in said lead acid battery cover until a pressure within said automotive vehicle battery casing exceeds said predetermined pressure that blows said frit out of said lead acid battery cover.

13. A lead acid battery cover according to claim 12 that comprises molded plastic.

14. A lead acid battery cover according to claim 12 wherein said molded plastic is polypropylene.

15. A lead acid battery cover adapted to seal an automotive vehicle battery casing having a design pressure maximum, the lead acid battery cover comprising:

a cylindrical vent opening in said lead acid battery cover, and having a face in said cylindrical vent opening;

a rigid, porous frit consisting of modified polytetrafluoroethylene, wherein the frit allows gases to escape through said cylindrical vent opening while preventing liquids from escaping through said cylindrical vent opening seated on said face;

a groove in front of said frit containing an O-ring such that when a pressure within the automotive vehicle battery casing exceeds a predetermined pressure said frit is blown out of said cylindrical vent opening, wherein the predetermined pressure is within 5% to 10% of the design pressure maximum of the automotive vehicle battery casing,

wherein the modified polytetrafluoroethylene comprises polytetrafluoroethylene, from 1 wt % to 35 wt % PMMA and from 1 wt % to 7 wt % lubricant.

16. A method for making a lead acid battery, the method comprising:

providing a casing having a design pressure maximum,

providing a liquid within said casing, and

sealing the liquid within the lead acid battery with the lead acid battery cover of claim 1 .

17. A method for preventing the explosion of a lead acid battery, in the event of a pressure buildup, the method comprising:

sealing a lead acid battery casing comprising a liquid with the lead acid battery cover of claim 1 , wherein the casing has a design pressure maximum.