Electric accumulator batteries

Details Electric accumulator batteries Electric accumulator batteries

2002-09-26

2004-02-17

Tso, Edward H. (Department: 2838)

Electricity: battery or capacitor charging or discharging

Cell or battery charger structure

For battery pack

C429S177000

Reexamination Certificate

active

06693408

ABSTRACT:

FIELD OF THE INVENTION
The present invention refers to a lead-acid type electric accumulator battery which can be used for the traction of electric vehicles, for feeding networks in the stationary service, although it is preferably of those used in the starting, lighting and ignition of vehicles and comprises a recipient internally subdivided into cells in which the positive and negative plates, a separator and electrolyte are housed, the recipient closing by means of a lid through which the current tap terminals protrude and which has openings facing the cells which close by means of stoppers incorporating a valve for controlling the gas outlet.
More specifically, the battery of the invention is applicable to batteries flooded with acid electrolyte, although it is preferably of the gas recombination type.
Even more specifically, the battery of the invention refers to one of the type of bound plates forming a spiral, separated by a micro-fiberglass absorbent retainer.
BACKGROUND OF THE INVENTION
The gas recombination system in lead-acid batteries is known. Spanish patent application numbers 9701689 dated Jul. 30, 1997, 9902310 dated Oct. 20, 1999 and 200001486 dated Jun. 13, 2000 can be cited as examples, in which the progressive advance in this gas recombination technique is disclosed.
In this type of battery, the incorporation of filling materials in the separators is known, such as disclosed in patents ES 2,087,023 and EP 0680105.
The arrangement of regulating valves of the internal pressure of the cells of the battery is also known, as disclosed in patent ES 2134149 and Spanish patent application numbers 9902310 and 200001486.
The art continues to advance in the manufacturing of recombinant lead-acid batteries, such that the manufacturing and use means have been depurated, especially including the means for assisting in the recombination, for the purpose of minimizing the outward release of gases and more importantly, including as priority the safety systems used in order to prevent the effects of a possible outward release of gases, which constitutes the two largest objectives disclosed in the present invention.
It is known that the gas recombinant system in lead-acid batteries consists of introducing into such batteries the means capable of driving the gases generated by the positive plates constituting the battery anodes and that are released towards the negative plates, and that these means be suitable so as to permit and facilitate that these gases can react on the negative electrode surface.
In the general functioning of a lead-acid battery, oxygen gas is released from the anodes or positive plates and hydrogen gas is released from the negative plates. The evolution of these gases is much greater in the charge operation than in that of discharge or in standstill.
The intense production of gases in the plates of a battery being charged occurs in the positive plates before in the negative plates due to the difference of the electrode voltage necessary for the evolution of both gases, oxygen and hydrogen, which serves as a base for achieving the recombination of the oxygen gas released by the positive plates, as long as a means is interposed which efficiently drives it towards the negative plate surface.
The active material of the negative plates of the lead-acid battery is of spongy lead, very oxygen absorbent, with which it reacts initially forming lead oxide, according to the equation:
2Pb+O
2
=2PbO
The lead oxide formed in this manner on the negative plate surface is very unstable since, in the presence of the sulfuric acid integrating the battery electrolyte, it immediately forms the corresponding lead sulfate, according to the equation:
PbO+H
2
SO
4
=PbSO
4
+H
2
O
The lead sulfate is a compound which has the feature of reducing the voltage of the negative plates electrode in direct proportion to the content and therefore slows or prevents the release of hydrogen while these plates charge.
It is for the reasons above that the recombination of gases inside the cells of the battery functions, but it must be understood that the entire recombinant system depends on two important technical grounds:
The first of the two important technical grounds is that the oxygen must be driven from the positive plates to the surface of the negative plates, due to which suitable means must be used, generally special separators and/or electrolytes which open canals or conduits through which the circulation of the oxygen in its movement between plates is propitiated or facilitated.
The second technical ground is that the internal pressure generated in the cell by the gases or fumes released inside must be regulated so as to permit the outward escape of any possible excess of pressure of the gases or fumes, but at the same time constantly preventing the entrance of atmospheric air inside the cells, since the oxygen of the entering air would react with the negative active material and would deteriorate the recombinant system.
In reference to the first technical ground, the battery of the invention can incorporate different means tending to immobilize the electrolyte and to canalize the oxygen and direct it towards the negative plates; the electrolyte immobilization is essential in recombinant batteries as it facilitates the passage of gases through it and moreover, the “clean” or ecological objective is achieved because no acid would be leaked even if a battery should break; a different way to achieve the electrolyte immobilization is that of making it solid, forming a gel, although in the battery of the invention, which is preferably of the helical plates type, an element is incorporated which adapts to such spiral, serving as a plate separator, which in turn is an electrolyte immobilization means by absorbing this electrolyte in the pores of the separator means, which at the same time is an ideal oxygen carrying means, and which is basically a micro-fiberglass mattress mixed with a percentage of plastic micro-fibers whose total content can range between 10 and 50%.
It has been observed that the higher the percentage of plastic fibers contained in the material of the micro-fiberglass separator, the greater the physical resistance of the separator against breaking by traction and/or piercing, achieving with this a better separator effect between the electrodes or plates of a different sign, which should never touch for the purpose of preventing the short circuit between them.
It has also been observed that the ease of the passage of oxygen from the positive plates towards the negative ones is aided by the decrease of the percentage of plastic fibers in the separator material to limits being those previously indicated, from 10 to 50%, values which depend not only on the rated thickness of the separator, but especially on the compression coefficient to which the assembly of the elements integrated by the cells are subjected to.
It has also been observed that the micro-fibers composing the separator must not be entwined in the orthodox manner, that is to say fiber bundles aligned in parallel lines and perpendicularly crossing them with other bundles, but rather they must be freely mixed, without forming bundles and mixing between them, such that the sulfuric acid is immobile by being absorbed in such fibers and especially the microscopic gas bubbles find capillary paths whose winding feature precisely aids in its passing through thereof.
Lastly, it has been observed that a direct relationship exists between the dimension of the micro-fibers and the maximum dimension of the pores formed in the separator, such that a smaller maximum pore diameter corresponds to a shorter fiber length; this fact is of vital importance in recombinant batteries, as the tendency of forming lead sulfate depositions is known in pores of greater than 22 microns in diameter, depositions that can be transformed into lead dendrites when charging the batteries and that could electrically connect the consecutive plates, producing what is generally called a micro-short circuit, ruining the b

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