MXPA97006517A - Lead acid battery maintenance free, regulated by valve, proof of fu - Google Patents

Abstract

The present invention relates to a maintenance-free, valve-regulated lead-acid battery comprising a receptacle, at least one plate compartment in the receptacle, each of said compartments containing plates and electrolyte, an electrolyte absorbing chamber in said receptacle for each of said compartments, each said chamber having a ventilation to the atmosphere, and a pressure regulating valve associated with each compartment, to release the gas pressure inside that compartment, each of said valves having a water side down which communicates with an entrance to a respective one of said chambers, each said chamber containing an inert, electrolyte absorbing material, permeable to gas, said absorbent material being placed between said inlet and said ventilation of said chamber so that the gas released through the downstream side of said valve flow through said absorbent material when passing into said vent, the contact path of said gas within said absorbent material being sufficiently long so that substantially all of the droplets of said electrolyte entrained in said liberated gas are absorbed by said material and are not carried out of said ventilation

Description

LEAD-FREE LEAD ACID BATTERY, REGULATED BY VALVE, LEAK-PROOF Field of the Invention This invention relates to lead-acid batteries of the maintenance-free, valve-regulated type, and more particularly to a means for preventing leakage of electrolytes through the pressure regulating valves of such a battery. BACKGROUND A lead acid battery has positive lead plates, negative lead oxide plates, and an electrolyte which is a solution of sulfuric acid and distilled water. The plates and the plate separator material between them are installed in plate packs in plate compartments. During charging, and especially if there is an overload, some of the water content of the electrolyte will be hydrolyzed in its component hydrogen and oxygen gases. The maintenance-free, valve-regulated type batteries are constructed so that the idyllized gases are recombined under pressure internally within the battery receptacle to re-form water, so that water is not normally lost. Since if you do not lose water, the batteries are "maintenance free". However, under certain conditions the electrolyte can escape, even from a maintenance-free, valve-regulated battery. While the battery is being charged, and particularly if it is being overcharged, internal gas generation can take place in such a high proportion that it exceeds the ratio at which the battery can internally recombine hydrogen and oxygen to re-form water. Under such conditions, the internal gas pressure rises and must be released from the receptacle. Pressure relief valves are built into the battery, often one for each plate compartment, in order to regulate the internal pressure in that compartment and prevent it from becoming excessive. The pressure relief valves are normally closed and open to release the pressure exceeding a predetermined maximum. When ventilation occurs, the gas released through the valve can carry droplets of the sulfuric acid electrolyte with it, so that the electrolyte is released along with the gas. The leakage of the electrolyte of sulfuric acid from the battery is highly undesirable: it can quickly corrode the electrical connections of the battery or attack the adjacent electrical circuitry. The problem of electrolyte leakage is more likely to arise through a pressure regulating valve when the battery is used in an application in which it is not oriented in a vertical position, such as when the battery is on its side or inverted . This arises, for example, when the battery is used in a portable light or as backup power for exit or emergency lighting. An emergency light is often mounted on the wall or ceiling of a room, in such a position that the battery tilts 90% from the vertical or even reverses. Normally, emergency lighting batteries are in a floating or standby condition in which only a small or slow enough charge is given to keep them at full charge without gas ventilation. However, if there is an external power failure, the battery may have to provide power for a prolonged period and may be extremely discharged. If a highly discharged battery is recharged at high current, the internal gas pressure from the dissociated water molecules tends to rise rapidly and the pressure relief valves can open. If the battery is on its side and particularly if it is in an inverted position, the valves will most likely be covered by liquid electrolyte. The release of gas through the valve can carry electrolyte out with it, and lead to the precisely noted problems.

It is known to filter gas and electrolyte released from a non-maintenance-free, valve regulated battery for the purpose of removing the electrolyte as shown in British Patent No. 791,139 and US Patent No. 2,331,450 to Baum. The filters contain electrolyte neutralizing compounds such as sodium carbonate which reacts with the electrolyte to form a harmless salt, while allowing the gas to escape through a vent. However, the salt produced by the neutralization tends to clog the filter and eventually prevents the release of the gas, and therefore requires periodic cleaning. In a valve regulated battery, it is desirable to provide a means for separating the electrolyte droplets from the ventilated gas without at the same time creating salts or otherwise restricting gas release, and without significantly or undesirably increasing the internal pressure in the battery. BRIEF DESCRIPTION OF THE INVENTION In accordance with this invention, a maintenance-free, valve-regulated battery is provided, wherein the gas and any electrolyte entrained therein are vented through the pressure release valve to an exactly adjacent chamber that It contains a porous material, electrolyte absorber, permeable to gas, which absorbs and retains the electrolyte but allows the ventilated gas to escape. The electrolyte is absorbed and retained as electrolyte, - that is, it is not neutralized. The electrolyte is absorbed in part by passing the gas over the surface of the absorbent medium, which is placed between the inlet to the chamber containing the absorbent, and the ventilation thereof. The volume of the absorbing medium is most preferably sufficient to absorb all the electrolyte present in the respective plate chamber. Preferably, an electrolyte absorbing chamber is provided separately for each plate compartment so that each chamber has to absorb only a fraction of the total amount of electrolyte. The electrolyte absorbing chambers are preferably installed to externally enclose or enclose the sides of the respective plate compartments. In this way, if a plate compartment were to break, the electrolyte would tend to leak into one of the surrounding chambers that contains the absorbent, and would be retained there without leaking to the outside of the battery. In order to establish the smallest possible total volume of the receptacle, the absorbent chambers are preferably triangular in cross section, their long sides being formed by the side walls of the plate compartments. In this way, the side walls of the plate compartments are angled, instead of being parallel, to the outer walls of the receptacle. The electrolyte chambers protect and insulate the corners and side walls of the impact plate or rupture damage compartments. DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a battery in which a preferred form of the invention is incorporated; Figure 2 is a disassembled partial perspective view of the battery of Figure 1, showing the upper part and the inner cover of the battery; Figure 3 is a view similar to Figure 2 but illustrating the inner cover and the lower housing of the battery; Figure 4 is a cross section taken on line 4-4 of Figure 2; and Figure 5 is a cross section taken on line 5-5 of Figure 1. DETAILED DESCRIPTION In a preferred embodiment of the invention, as shown in the figures, a valve regulated lead acid battery generally designated by 10 is contained within a receptacle comprising a lower housing 12, an inner cover 14 and a part upper or upper cover 16. Lower housing 12 contains one or more side-by-side plate compartments 18, which are generally rectangular in horizontal cross section. In the preferred embodiment shown, there are three plate compartments 18a, b, and c, and three corresponding electrolyte absorber chambers 20a, b, and c, respectively, each chamber 20 receiving ventilated gas from a different plate compartment 18 (FIG. 5) . The chambers 20 are preferably installed externally of and around the group of plate compartments, on the sides of the housing 12 so that the chambers 20 almost completely enclose the side walls of the group of plate compartments. Preferably, the chambers 20 are approximately triangular as seen in horizontal cross-section (FIG. 5), with the corners rounded between their shorter sides, and installed so that the longer side is adjacent to the vertical wall (lateral) of a plate compartment. For purposes of symmetry, if there are three plate compartments, a fourth chamber or simulated chamber 21 can be provided, so that preferably one chamber 20 or 21 is provided on each side face of the approximately square sectioned housing, one on each side of the compartments. of plate. Observed in cross section, the plate compartments form a square that is rotated or angled within what is in effect a larger square defined by the electrolyte absorbing chambers 20 and 21 around them. The electrolyte retention chambers 20 can extend substantially to the same total height as the plate compartments (see Figure 4), but are quite thin in dimension perpendicular to the side walls of the plate compartments. In each plate compartment 18 a plate pack 19 is placed comprising one or more positive plates 23 and negative plates 25, separated by separators 27. The nature of the plate packages can be conventional and is known per se. All positive plates in each plate compartment are electrically connected together and towards an external positive post, similarly, the negative plates are electrically connected to an external negative post. Each plate compartment contains an electrolyte 28 comprising sulfuric acid dissolved in water. During at least the recharging portion of the battery operation cycle there is free or unabsorbed liquid electrolyte 28 within each plate compartment. The lower housing 12 is closed and sealed by an inner cover 14 which, as can be seen in figures 3 and 4, is configured on its lower surface with depending grooved ridges or ribs 30 corresponding to, and receiving, the upper edges of the partitions defining the respective compartments and chambers 18, 20, and 21. The ribs 30 of the inner cover 14 are sealed to the partitions of the housing 14 by epoxy resin or ultrasonic seal so that the electrolyte can not leak out of a compartment 18 on the edge of the internal partition towards an adjacent compartment. As seen in Figures 2 and 4, the inner cover 14 is mounted on the pressure relief valves 33 by the respective plate compartments 18a, b, and e. Each valve 33 has a body in the form of a short straight tube 35 that opens downwardly through the inner cover 14 to the respective plate compartment below it, and contains a spring-sectioned elastic valve member in U, inverted, 37 that fits snugly over the upper end of the tube 35. The valve member 37 is made of a non-reactive elastic material, and normally closes the tube 35 to contain the pressure in the chamber 18 below it. This is derived downwardly on the tube (towards a closed position) by a projection 39 projecting from the upper cover 16 above it. As can be seen in figure 2, the projection 39 can be in the form of a "+", so as to hold only a portion of the upper surface of the valve member 37. When the pressure of the gas under the valve member in the plate chamber exceeds a predetermined value (preferably about 2.5 psi), this raises the valve member 37 upwards in the areas between the arms of the projection 39 and the gas escapes through the upper part of the tube 35 and descending between the edge of the valve member and the outer surface of the tube 35. It is noted that although the opening of the valve thus created may be very small, the external inflow of gas may carry electrolyte droplets drawn out with it through the valve, as shown in FIG. shown by the arrows 40. The upper part 16 has ribs 42 on its lower surface intercorresponding and sealing the grooves 44 at the upper edges of the partitions on the upper part. upper surface of the inner cover 14, and thereby separates each valve 33 from the others and creates valve compartments 45. The ribs 42 are sealed to the slots 44 preferably by thermal welding or epoxy resin after the battery has been assembled . Exactly adjacent to each pressure relief valve 33 in its respective valve compartment 45 is an inlet opening 46 through the inner cover 14 which provides communication from the valve compartment 45 to the respective electrolyte absorber chamber 20 a , b, or c. Ventilation 47 (FIGS. 1 and 4) is provided in the outer side wall, preferably in the rounded corner of each chamber 20. As is apparent from FIG. 3, the electrolyte absorbing chambers 20 a, b, and c are preferably elongated vertically, but narrow in the dimension towards the vertical central axis of the receptacle. Each contains a porous, gas permeable material, 50 which is highly absorbent of sulfuric acid electrolyte. A preferred material for this purpose is a sheet-borosilicate microfiber plush microfiber plush separating material having a weight per unit surface area in the range of about 130 gm / m2 or more. It does not need to be packed or packed in its chamber, and not tightly or completely fill the interior volume of the chamber between the inlet 46 and the vent 47. There may be a flow space on the surface of the absorbent material from the inlet to the inside. ventilation, as well as flow passages through the plush like in a filter.

It is important to note that escaping gas does not necessarily need to seep through the length of the absorber in order for the electrolyte to be absorbed. That is, the gas does not need to flow through the absorber either longitudinally or transversely. Actually, much of the effectiveness of this material in the absorption of gas droplets from the gas flow is that the contact of the droplets with the external surface of the sheet or plush is apparently effective for its absorption. The distance at which the gas flows over the surface of the plush from the inlet to the vent is preferably several times greater, for example, at least about 5 times larger, than the distance that it must flow transversely through the plush . This structure has been found to be extraordinarily effective in absorbing the electrolyte without the pressure drop that often accompanies filtration, and without the need for a neutralizing compound that could clog a filter material and render it ineffective, or at least cause a drop in undesirably high pressure in the flow through it. The volume of the electrolyte absorbing material should preferably be sufficient to absorb at least about 1/3, and most preferably virtually all, of the free electrolyte from the plate compartment it serves. In this way, if the battery 10 is ventilated while in an inverted position and all gases or free electrolyte will escape through the valve, the absorbent material must be large enough volumetric to absorb all the droplets contained in it. the gas, or the electrolyte itself. The absorber retains the electrolyte indefinitely within itself. Normally, the electrolyte is not drained or "muddy" in the chamber, which could, depending on the position, allow it to escape through the vent. Example a 4.0 amp per hour, 6 volt battery, having three plate compartments, each initially containing 30 electrolyte electrons, has three electrolyte absorbing compartments installed as shown in the drawings. Each compartment is 3.32"high x 0.64 wide x 2.10" long. Each compartment contains one or more pieces of separating terry material, "BG-16005 Hovosorb", made by Hollings orth & Vose Corp. The plush in each chamber was 0.095"thick x 3.20" high x 1.24"wide, its volume is sufficient to absorb virtually all the droplets and all the electrolyte not absorbed in the plate compartment. Slides into the camera from the top end of the camera before the top cover is applied and does not fill the camera, the internal dimensions of which are 3.32"high x 0.28" wide x 1.45"long. Having described the invention, what is claimed is:

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. A lead-free, valve-regulated maintenance acid battery comprising a receptacle, at least one plate compartment in the receptacle, each of said compartments containing plates and electrolyte, an electrolyte absorbing chamber in said receptacle for each of said compartments, each said chamber having a ventilation to the atmosphere, and a pressure regulating valve associated with each compartment, to release the gas pressure inside that compartment, each of said valves having a downstream side which is communicates with an entrance to a respective one of said chambers, each said chamber containing an inert, electrolyte absorbing material, permeable to gas, said absorbent material being placed between said inlet and said ventilation of said chamber so that the gas released through the Downstream side of said valve flows through said absorbent material upon passing to the said ventilation, the path of contact of said gas within said absorbent material being long enough so that substantially all droplets of said electrolyte entrained in said released gas are absorbed by said material and are not carried away from said ventilation. The battery according to claim 1, characterized in that the volume of said absorbent material in each chamber is sufficient to absorb at least about 1/3 of the volume of electrolyte in the respective plate compartment. The battery according to claim 1, characterized in that each of said inputs is at the upper end of the respective chamber. The battery according to claim 3, characterized in that said ventilation is in a side wall of the respective chamber, below the upper part of the absorbent material in that chamber. The battery according to claim 1, characterized in that said absorbent material is a sheet-shaped plush. The battery according to claim 5, characterized in that the gas released through each said valve, when flowing towards said ventilation, flows on the surface of said plush at a distance several times greater than that flowing through said plush. The battery according to claim 5, characterized in that there is a gas flow space from said inlet to said vent, between said plush and a wall of said chamber. The battery according to claim 1, characterized in that each of said valves and the respective chambers, the absorbent material and the ventilation associated with the chamber, are installed and sized to establish a pressure drop between the respective inlet and the vent, while the gas is being vented through said valve, which is less than the pressure at which the valve opens. The battery according to claim 1, characterized in that it has at least three plate compartments and at least three electrolyte absorbing chambers, and said chambers substantially surround the sides of said plate compartments. A lead-free, valve-regulated maintenance acid battery comprising a receptacle, at least three plate compartments in said receptacle, each said compartment containing plates and electrolyte, at least three electrolyte absorbing chambers in said receptacle, each of said chambers having a vent to the atmosphere, and a pressure regulating valve associated with each of said compartments for releasing the gas pressure within that compartment, each said valve having a downstream side communicating with an inlet to a respective one of said chambers, each said chamber containing an inert material, electrolyte absorbent, permeable to gas, said absorbent material placed between said inlet and said venting of said chamber so that the gas released through the downstream side of said valve flows through and onto said absorbent material upon passing said ventilation, said chambers surrounding substantially externally the sides of said plate compartments and thereby protecting said impact compartments and absorbing the electrolyte that could leak from them.