Stationary battery separators

1 Stationary Battery Separators As already mentioned, at the beginning 

In the second half of the 1960s, at the same time but independently, three basically different plastic separators were developed. One was the polyethylene separator [16] already referred to in starter batteries, used only rarely in stationary batteries, but successful in traction batteries. The others were the microporous phenoHc resin separator (DARAK) [18] and a microporous PVC separator [19], both of which became accepted as the standard separation for stationary batteries. They are distinguished by high porosity (about 70%) and thus very low electrical resistance and very low acid displacement, both important criteria for stationary batteries. 

---

Mn02 in KOH 118 standard profiles, separators 262 starter battery separators 252 f, 258 f starter light ignition (SLI) batteries 2 stationary battery separators 254... 

The range of microfiber glass mat separators offered by the leading producers are presented in Sec. 9.2.3.3 with typical data in connection with their predominant application in sealed stationary batteries. 

Stationary batteries serve predominantly as an emergency power supply, i.e., they are on continuous standby in order to be discharged for brief periods and sometimes deeply, up to 100 percent of nominal capacity, in the rare case of need. The following profile of requirements for the separator thus arises very low electrical resistance, low acid displacement, no leaching of substances harmful to float-... 

The production process for polyethylene separators (Sec. 9.2.2.1) as well as the characteristic properties (see Sec. 9.2.2.1 and 9.2.3.1) have already been described in detail above. Deviating therefrom, the desire for low acid displacement has to be added for separators in open stationary batteries. This can be met either by decreasing the backweb thickness or by increasing the porosity the latter, however, is at the expense of separator stability. 

The production process and the principal properties of this system have been described in detail in the section on traction battery separators (see Sec. 9.2.3.1). The outstanding properties, such as excellent porosity (70 percent) and resulting very low acid displacement and electrical resistance, come into full effect when applied in open stationary batteries. Due to the good inherent stiffness the backweb may even be reduced to 0.4 mm, reducing acid displacement and electrical... 

Since the early days of using PVC separators in stationary batteries, there has been a discussion about the generation of harmful substances caused by elevated temperatures or other catalytic influences, a release of chloride ions could occur which, oxidized to perchlorate ions, form soluble lead salts resulting in enhanced positive grid corrosion. Since this effect proceeds by self-acceleration, the surrounding conditions such as temperature and the proneness of alloys to corrosion as well as the quality of the PVC have to be taken carefully into account. 

Sintered PVC separators for open stationary batteries are produced in the same way as the corresponding starter battery version (Sec. 9.2.2.2). Their brittleness and thus difficult processability are disadvantages, as is their relatively low porosity the concerns about release of chloride ions and subsequent increased corrosion are to be considered here as well. On the other hand,... 

Comparative Evaluation of Separators for Open Stationary Batteries... 

Table 12 shows the physicochemical data of separators used in open stationary batteries. Since the emphasis is on low acid displacement, low electrical resistance, and high chemical stability, the phenolic resin-resorcinol separator is understandably the preferred system, even though polyethylene separators, especially at low backweb, are frequently used. For large electrode spacing and consequently high separation thickness, microporous as well as sintered... 

Table 12. Separators for flooded lead-acid stationary batteries...

Valve designs used in stationary batteries have proven to be satisfactory for VRLA automotive batteries, and valves with an ethylene-propylene-diene polymethylene (EPDM, an artificial rubber) lip packing appear to be particularly well suited. Most European vehicle manufacturers demand a separate valve for each cell and, for all valve outlets, a joint gas-collecting duct with a flame arrestor... 

In the manufacture of AGM separator materials for VRLA batteries, the thickness is quoted (measured) under a controlled standard pressure of 10 kPa. To improve the separator contact with the plates, the plate groups (active blocks) are compressed so as to reduce the separator thickness by about 25%. In tall stationary batteries, this compression is sustained by fastening the active blocks (plate groups) with polymer tapes before inserting them into the battery container. 

Those applications in which the secondary battery is discharged (similar in use to a primary battery) and recharged after use, either in the equipment in which it was discharged or separately. Secondary batteries are used in this manner for convenience, for cost savings (as they can be recharged rather than replaced), or for power drains beyond the capability of primary batteries. Most consumer electronics, electric-vehicle, traction, industrial truck, and some stationary battery applications fall in this category. 

---