Lead acid storage battery

Abstract: A lead acid storage battery comprises a group of electrode plates (4,5), wherein a negative plate (4) is enclosed in an enveloped separator (1) joined together at both its edges (3) by welding or mechanical sealing and a glass mat (6) is separately provided between the separator (1) and a positive plate (5), the glass mat (6) having a width at least equal to the width of the separator (1) except both its edges (3).

Description: The present invention concerns improving the performance of lead acid storage batteries. So far, lead acid storage batteries each comprised a stack of a positive plate or plates and a negative plate or plates with a separator plate or plates located therebetween. Used to this end were separators provided with glass mats, now generally referred to as a planar type of separator. Other types of separator, recently introduced in the art, have been made of such synthetic resins as polyethylene. Owing to their thinness, the polyethylene separators have the merits of being lower in electrical resistance and better in oxidation resistance than the conventional separators. In use, the polyethylene separator, shown at 1 in Figure 5, is longitudinally folded together with a glass mat 2 pre-laminated thereon, defining an envelope. The envelope is then joined together at both its edges 3 by welding or mechanical seals. However, if the glass mat should extend to the welds 3, welding or mechanical sealing would be unfeasible. For this reason, a glass mat smaller in width than the welds 3 of the separator, i.e. a glass mat having a width such that its widthwise edges do not reach the welds 3 is now used in combination with the separator 1. In Figure 5, reference numeral 4 stands for a negative plate enclosed in the enveloped separator 1 and 5 stands for a positive plate. With such a narrow glass mat, however, the positive plate 5 would be curved into contact with the polyethylene separator as depicted in Figure 6, while the lead acid storage battery is used under severe conditions, deteriorating due to oxidation. At this portion shown at IS, there will be a short-circuit between the positive and negative plates 5 and 4. With the foregoing in mind, an object of the present invention is to extend the service life of a lead acid storage battery constructed with an enveloped separator made of polyethylene or other synthetic resin. Accordingly, the present invention consists in a lead acid storage battery comprising a group of electrode plates, wherein a negative plate is enclosed in an enveloped separator joined together at both its edges by welding or mechanical sealing and a glass mat is separately provided between said separator and a positive plate, characterised in that said glass mat extends between at least the whole surfaces of said positive and negative plates and has a width at least equal to the difference between the width of the enveloped separator including its welded or mechanically sealed edges and the width of said welded or mechanically sealed edges. In one embodiment of this invention, the glass mat may be equal in width to the width of the enveloped separator including its welded or mechanically sealed edges. By locating the glass mat according to this invention, it is unlikely that in use, the positive plate may be curved into contact with the negative plate, whereby the service life of the positive plate can be increased. The invention will be described, by examples, with reference to the drawings, wherein:- Figure 1 shows one embodiment of the lead acid storage battery according to this invention, (a) and (b) being top and front views, respectively; Figure 2 shows another embodiment of the lead acid storage battery according to this invention, (a) and (b) being top and front views, respectively; Figure 3 is an illustration of what condition the first embodiment is in after use; Figure 4 is an illustration of what condition the second embodiment is in after use; Figure 5 shows a conventional lead acid storage battery, (a) and (b) being top and front views, respectively; Figure 6 is an illustration of what condition the conventional example is in after use; and Figure 7 is characteristic curves showing how the voltages of the instant and conventional batteries vary at 30 seconds during endurance test. Referring first to Figure 1, there is shown one battery A 1 according to this invention, with a glass mat 6 located in it. As illustrated, the glass mat 6 having a width equal to that of a polyethylene enveloped separator 1 is separately provided between the separator 6 and a positive plate 5. Referring then to Figure 2, there is shown another battery A 2 according to this invention, with a glass mat 7 located in it. The glass mat 7 having a width smaller than the polyethylene enveloped separator 1 by the magnitude of both its edges 3 to be joined together is separately provided between the separator 1 and a positive plate 5. With the instant batteries A 1 and A 2 , there is no possibility of a short-circuit between positive and negative plates 4 and 5. This is because, as illustrated in Figures 3 and 4, the glass mats 6 and 7 are located all over the surfaces of the positive and negative plates 4 and 5, even when the positive plates 5 are curved while they are used under severe conditions. In what follows, the instant batteries will be compared in terms of service life with a conventional battery B in which, as shown in Figure 5, the glass mats are integrally placed over a polyethylene enveloped separator except both its edges, all having a capacity of 12V, 5HR and 48Ah. Endurance test was performed at 75c with charging at 14.8 V for 10 minutes and discharging at 25 A for 4 minutes. Figure 7 shows how the discharge voltages of the batteries vary at 30 seconds. It can be seen from Figure 7 that the instant batteries A 1 and A 2 show a 50% increase in terms of service life, as compared with the conventional battery B. Thus, the present invention is effective for extending the service life of batteries.

Claims: A lead acid storage battery comprising a group of electrode plates (4, 5), wherein a negative plate (4) is enclosed in an enveloped separator (1) joined together at both its edges (3) by welding or mechanical sealing and a glass mat (6;7) is separately provided between said separator (1) and a positive plate (5), characterised in that said glass mat (6;7) extends between at least the whole surfaces of said positive and negative plates (4, 5) and has a width at least equal to the difference between the width of the enveloped separator (1) including its welded or mechanically sealed edges (3) and the width of said welded or mechanically sealed edges (3). A lead acid storage battery as claimed in claim 1, wherein said glass mat (6;7) is equal in width to the width of the enveloped separator (1) including its welded or mechanically sealed edges (3).

Inventors: HIKAWA HIDEKI, MORIMOTO YOSHINARI, YAMAGUSHI OSAMU, HIKAWA, HIDEKI, MORIMOTO, YOSHINARI, YAMAGUSHI, OSAMU, HIKAWA, HIDEKI C/O SHIN-KOBE ELECTRIC MACHINERY CO, MORIMOTO, YOSHINARI C/O SHIN-KOBE ELECTRIC CO. LTD, YAMAGUSHI, OSAMU C/O SHIN-KOBE ELECTR. MACH. CO.
Applicants: SHIN KOBE ELECTRIC MACHINERY, SHIN-KOBE ELECTRIC MACHINERY CO LTD
Application year: 1991
Main classification: H01M2
IPC codes: H01M2, H01M10