BATTERY WITH GEL BLANKET BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a valve regulated absorbed glass mat lead-acid Electric storage battery which incorporates a gel blanket on top of the battery plates.

2. Description of the Prior Art Lead-acid batteries, designated valve regulated, lead-acid (VRLA), are built with either gelled or absorbed electrolyte. In both designs, the gasses that are generated by the electrochemical charging processes are recombined within the battery cells. The absorbed glass mat (AGM) battery design uses separator material that absorbs the electrolyte.

The gelled battery design uses a mixture of silicon dioxide with the sulfuric acid to produce a semi-solid, gelled electrolyte.

The AGM batteries are typically designed so that the separator material is less than 100% saturated with the electrolyte. This is done to promote gas recombination reactions as discussed. These batteries are therefore"acid starved"meaning there is no excess of electrolyte in the cells, as is the case with conventional flooded lead-acid batteries. For proper discharge and charge reactions to take place, it is important that the acid balance be maintained in the separators.

These maintenance free batteries are acid starved, so that it is important that the proper acid balance be maintained in the separators, particularly during high rate discharge, such as occurs in hybrid vehicle applications. There have been numerous patents issued for acid starved batteries, which all have headspace above the battery plates and separators, which headspace is an air space, and may contain oxygen and other gases released from the separators and electrodes during high rate discharge, recharge. The gases released are corrosive and may affect the oxygen recombination process and integrity of the internal connectors. Examples of such batteries are illustrated in U. S. Patent Nos. 3,776, 779; 5,035, 966; 3, 930, 881 ; 4,414, 302; 5,091, 275; 4,317, 872, and 5,376, 479. Patent No.

5,376, 479 has a gel added to the space surrounding the sides and bottom of the electrodes, but the space above them is empty.

The invention is directed to a valve regulated lead-acid absorbed glass mat battery where a gel electrolyte is added to the battery above the separators, where it encapsulates the plate lugs, straps and inter-weld parts providing a protective barrier to cathodic corrosion, a heat sink, and also reducing the resistance of the battery.

SUMMARY OF THE INVENTION This invention relates to a valve regulated absorbed glass mat lead- acid electric storage battery, which has a gel blanket inside the battery covering the tops of the plates, the separators, the plate lugs, straps and/or inter-cell weld parts.

The principal object of the invention is to provide an absorbed glass mat battery that has a gel blanket in the top headspace of the battery.

A further object of the invention is to provide a battery which has improved short duration high rate performance.

A further object of the invention is to provide a battery which provides benefits to the life of the internal components.

A further object of the invention is to provide a battery which has an improved product life cycle.

A further object of the invention is to provide a battery which is simple to construct, sturdy and reliable in operation.

Other objects and advantageous features of the invention will be apparent from the description and claims.

DESCRIPTION OF THE DRAWINGS The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part hereof in which: FIG. la is a cutaway view of an absorbed glass mat battery incorporating the gel blanket of the invention.

FIG. lb is a cutaway view of an absorbed glass mat battery incorporating the gel blanket of the invention.

FIG. 2 is a graph of the high rate discharge performance of a battery constructed in accordance with the invention.

FIG. 3 is a graph depicting the effect of a gel blanket on the internal resistance of the battery, compared to an AGM battery without the gel blanket during high rate discharges.

FIG. 4 is a graph comparing the capacity and cycle life of a battery constructed in accordance with the invention, and FIG. 5 is a graph showing the lower internal resistance of a battery constructed in accordance with the invention.

It should, of course, be understood that the description and drawings herein are merely illustrative and that various modifications and changes can be made in the structures disclosed without departing from the spirit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS When referring to the preferred embodiments, certain terminology will be utilized for the sake of clarity. Use of such terminology is intended to encompass not only the described embodiments, but also technical equivalents which operate and function in substantially the same way to bring about the same result.

Referring now more particularly to the drawings and FIG. la and lb thereof, a battery 10 incorporating the invention is therein illustrated. The battery 10 includes an outer casing 11, open at the top and closed off by a cover 12. The cover 12 has a plurality of valves therein (not shown) for controlled ventilation. A plurality of plates 14 and 15 are provided with absorbed glass mat separators 16 (AGM) between them. The plates 14 and 15, and separators 16 are of well known type. The glass mat separators 16 preferably consist of micro fibers with possibly some synthetic colloidal silica particles and a sulfate salt. A liquid electrolyte (not shown) is provided of well known type, which is added to the battery and absorbed by the separators 16 to the desired saturation percentage.

The battery 10 is also provided with plate lugs 17, straps 18 and inter-weld parts (not shown) which connect the plates 14,15 together, and are also connected to posts 18 (one being illustrated).

Two production methods are preferably used to form the plates 14, 15 of the battery 10. In the first or one step process, the plates are formed in the casing 11, the separators 16 are inserted between them, and electrolyte is added after finishing the plates, with electrolyte added or removed after activation to provide the desired mat saturation percentage.

A gel material is added to the batteries after activation, and forms a gel blanket 20 on top of the plates, 14,15 separators 16, plate lugs 17, straps 18, and inter-weld parts (not shown).

In the second process the plates 14,15 are formed individually in tanks, washed and dried, and then assembled in the casing 11. After assembly electrolyte is added and the battery is activated. Gel material is added to the batteries after activation of the battery 10 and covers the top of the plates 14,15, separators 16, plate lugs 17, straps 18 and inter-weld parts (not shown) and forms a gel blanket 20.

The gel material is prepared by mixing colloidal, fumed, or granular silicon dioxide with sulfuric acid in the range of 1,200 to 1,400 specific gravity, and then added to the battery 10. The colloidal, fumed or granular silica in the gel blanket is S I (, in the weight percentage range of about 5% to 15%. The gel material after being added to the battery 10"sets up"into a viscous material with the consistency of petroleum jelly and forms the gel blanket 20. After the addition of the gel blanket 20 the batteries are finished using the normal process.

Referring to FIGS. 2-5 graphs of tests of an (AGM) battery are shown wherein the battery was constructed using the described gel blanket, and tested against an (AGM) battery without a gel blanket. The tests disclosed that the AGM battery with gel blanket provided more power at the start, where many applications require a high rate discharge. The AGM battery with gel blanket also ran longer, and had less internal resistance.

It will thus be seen that improved batteries have been provided with which the objects of the invention are achieved.