FR2654263A1 - LEAD ACCUMULATOR BATTERY, PARTICULARLY FOR STARTING MOTOR VEHICLE ENDOTHERMIC ENGINES. - Google Patents

Abstract

In a lead accumulator battery of the gas recombination type, usable particularly for the start-up of endothermic engines of motor vehicles, the porous separators (10) impregnated with acid electrolyte interposed between the electrodes (6, 8) have pores of equivalent diameters between 10 and 50 microns, preferably between 10 and 30 microns, and the acid electrolyte is present in an amount such that said pores are substantially all saturated with the electrolyte itself.

Description

The present invention relates to a lead storage battery,

  particularly intended for installation on board a vehicle

  automobile to start the latter.

  One of the main problems facing the designer of the battery project for motor vehicles relates to the resistance to leakage of sulfuric acid, whether in the form of drops or sweat, or in the form of vapor. In addition, the size and structure of the batteries must meet the ever increasing number of conditions posed by the design needs of the motor vehicle. Indeed, the engine space, where the batteries are generally installed, is more and more limited because of the complexity of the installations and because of the aerodynamic shape of the hood, imposed by the penetration coefficient which must have the lowest possible value This imposes limits on the dimensions of the battery particularly in the direction of the height C ' this is why the level of acid approaching the battery cover makes it difficult to produce through openings. These openings, even provided with a labyrinth, are subjected to liquid engorgement, particularly under the action of tremors and accelerations during the movement of the vehicle. In addition, this enclosed liquid can be pushed outwards due to the pressure of the gases which develop, particularly while the vehicle is moving, that is to say under load-voltage condition

constant of the alternator.

  As the reliability of a modern battery requires an absolute absence of leaks, even small, of sulfuric acid, different solutions have been adopted, which nevertheless involve

  significant increases in the cost of batteries.

  In the case of free acid batteries, a solution is constituted by a labyrinth cover, preferably made with juxtaposed parts. The design of this solution is complex and expensive and furthermore, it often requires two heat-sealing stations in the

battery mounting line.

  An ideal solution to the problem is provided by the batteries operating according to the oxygen recombination system, as described in the

US-A-3,862,861.

  This system involves the absorption of the acid in separating elements made up of felt in microfibers of glass, resistant to the anodic environment and to sulfuric acid and therefore relatively expensive. In addition, the system requires check valves. of gases which must be placed on the elements of the accumulator to prevent the access of oxygen from the air The receptacles, which must withstand pressures and depressions, must have more rigid walls than usual. The amount of acid must be as small as possible to leave media for the diffusion of oxygen passing from the positive plate to the negative plate. Therefore, the thermal capacity of the assembly is lower than that of the normal battery. with free acid and this makes the battery even more sensitive to the heat given off by the engine, especially since the film absorbed on the microfibers evaporates more easily

  since it is distributed over large areas.

  Due to the problems set out above, the object of the present invention is to provide a battery of the gas recombination type which is particularly suitable for installation on board a motor vehicle, the manufacture of which is substantially less expensive than that of

  traditional recombination batteries.

  The invention originates from the examination of the service conditions in which a battery is required to start up; these conditions differ greatly from those for which batteries are sold at

  fixed installation of the gas recombination type.

  In the latter type of use, the battery is constantly charged (that is to say in "buffer" or conservation battery), parallel to the generator which is maintained at a constant voltage chosen in a timely manner. recombination efficiency close to 100% to avoid that in operation, there is consumption of water by electrolysis and drying

drums.

  Operation on board the vehicle, on the other hand, involves fairly reduced recharging times compared to the total time. Recharging time can range from 2 to 5% on motor vehicles, up to 20 to 40% on commercial vehicles with long journeys During the rest of the time, the open circuit battery is subject to minimal pressure drop and development

minimum gaseous.

  The object of the invention is therefore constituted by a lead storage battery comprising a plurality of cells each including at least one positive electrode and at least one negative electrode between which a porous separator made of an absorbent fibrous material is interposed impregnated with acid electrolyte, which battery is characterized in that said separator has pores of equivalent diameters between 10 and 50 microns and in that the acid electrolyte is present in an amount such that said pores are substantially

  all saturated with the electrolyte itself.

  In the battery according to the invention, during recharging, the developed gas can therefore make its way through said metals or pores to

  reach the negative electrode where it recombines.

  Thanks to these characteristics, the battery according to the invention operates on a principle of partial gas recombination in which the acid is however substantially immobilized, and this allows the use of more economical means than those imposed by a high efficiency system.

of recombination.

  Advantages and additional characteristics of the storage battery according to the invention will become more clearly apparent from

  the description below with reference to

  attached drawings, provided by way of nonlimiting example, o: Figure 1 is a perspective view of a battery according to the invention; and Figure 2 is a partial sectional view along

line II-II of Figure 2.

  With reference to the figures, a battery, designated as a whole by the reference 1, comprises an external envelope 2 defining a cavity 4 inside which are housed a plurality of positive electrode plates and

  negative, designated 6 and 8 respectively.

  According to the principle of hermetic batteries (S.L A) with oxygen recombination between each pair of positive and negative electrodes is interposed a porous separator 10 made of an absorbent fibrous material impregnated with a

acid electrolyte.

  According to a characteristic of the invention, each separator is made of a felt of synthetic fibers, resistant to the operating environment, which have a diameter typically greater than 10 microns and which define the méats or pores having an equivalent diameter generally between 10 and 50 microns, and preferably between 10 and 30 microns These fibers can be made of a relatively inexpensive material made of a resin chosen from the group consisting of polyolefin resins, vinyl resins, resins

  polyesters, terephthalic resins.

  The quantity of acid electrolyte present in the battery is such that the pores of the separator are substantially all saturated by the electrolyte, or in other words the quantity of electrolyte is present in an amount greater than that essential for total recombination, since, according to the principle of operation of the battery according to the invention, recombination is not necessary in the open circuit periods During recharging, the developed gas diffuses up to the lead sponge of the negative electrode and recombines, even if this only occurs in small proportions, by

  example between 30 and 50% of the amount of gas.

  Using the separators described above

  above, it is advantageous, for the duration and the reliability of the accumulator, to use additional protective diaphragms 12 made for example of a cellulose material, which will be interposed between a separator and the faces of each electrode, preferably of the negative electrode These diaphragms have pores having an equivalent diameter smaller than that of the pores of the separator and typically between 2

and 10 microns.

  In a battery mounting process using continuously produced electrode plates, for which the support of the active materials is represented by a grid of drawn lead alloy (expanded metal), this characteristic is already achieved, since the paste is spread by applying two thin cellulosic sheets to the plates In this case, the previously mentioned function will be performed by these diaphragms for which a

resistance to sulfuric acid.

  Thanks to the characteristics of the battery according to the invention, the assembly can be even more economical since, as indicated in the figure, it is not necessary to provide check valves, the access of oxygen from the air being prevented by the liquid The walls of the container can be thin, since they are not subjected to internal pressures and depressions In addition, the cover can be produced in a simple and economical manner, since it does not need '' prevent leaks from

  "waves" of acid, but only of vapor.

  The operation of the storage battery includes sufficient gas development for the on-board charging regimes. If grid electrodes made of an antimony-free alloy, such as Pb Ca and Pb Ca Sn, are used, resort to the introduction into the alloy for the grids of an adjuvant making it possible to obtain a moderate gas development For example, in the alloy for grids, silver can be used as adjuvants at a rate of 0.005 to 0 , 02% by weight or cobalt at a rate of 0.005 to 0.03% by weight In addition, adjuvants consisting of silver, cobalt, antimony, nickel salts can be introduced into the electrolyte (or into active materials) in an amount generally between 0.05 and 0.03% by weight, in order to increase the development of gas without significantly increasing the automatic discharge and water consumption The concentrations of the adjuvants in the electrolyte vary depending on the type of mounting of the electrodes and batteries and stay within the range of values indicated above. The optimal quantity can be evaluated after a few tests, by evaluating the water consumption by reference to the methodology defined by the standards of the International Electrotechnical Commission (95- 2 Starter Battery Methods of Test and corresponding IEC standards) The addition of additives must not increase consumption beyond the values indicated in international standards

  mentioned above (See point 5 8 of the Standards).

  Naturally, by retaining the principle of the invention, the embodiments and the starting details can be largely

  modified from description and

  illustrations without departing from the

scope of the present invention.

Claims (4)

  1 Lead-acid storage battery of the gas recombination type, usable particularly for the start-up of endothermic engines of motor vehicles, comprising a plurality of cells each including at least one positive electrode (6) and at least one negative electrode ( 8) between which is inserted a porous separator (10) made of an absorbent fibrous material impregnated with acid electrolyte, which battery is characterized in that said separator (10) has pores of equivalent diameters between 10 and 50 microns and in that the acid electrolyte is present in an amount such that said pores are substantially all saturated.   2 storage battery according to claim 1, characterized in that said separator pores have an equivalent diameter of 10 at 30 microns.   3 Accumulator battery according to   claims 1 or 2, characterized in that it   comprises a plurality of porous diaphragms each inserted between a separating element and the faces of at least the negative electrode, said diaphragms having pores of diameter   equivalent between 2 and 10 microns.   4 Storage battery according to any one   claims 1 to 3, characterized in that   said separator consists of fibers of a resin chosen from the group consisting of polyethylene, polyester, terephthalic resins and vinyl.   Storage battery according to any one   of claims 1 to 4, of the type comprising   antimony-free lead alloy electrodes, characterized in that the alloy constituting the electrodes comprises silver in a quantity ranging from 0.005 to 0.02% by weight or cobalt in an amount ranging from 0.005 to 0.03% weight. 6 Storage battery according to any one   of claims 1 to 4, of the type comprising   antimony-free lead alloy electrodes, characterized in that the acid electrolyte comprises a certain amount of a salt of a metal selected from the group of silver, cobalt, antimony, nickel and of their   mixtures in an amount of 0.005 to 0.03% by weight.