Traction Battery Separators

Polyethylene Phenol-separators formaldehyde-resorcinol separators 

PVC Rubber Microfiber separators separators glass mat separators 

In Europe, with the economic upswing after 1950, forklifts with batteries came into use - a development which met less acceptance in the U S A for various reasons, among them low fuel cost. In this appHcation rubber separators and microporous PVC (Porvic I) were finally able to replace wood veneers, until from around 1975 they again met strong competitors in the new separators aheady mentioned made of phenolic resin (DARAK), PVC, and mainly polyethylene (Daramic). Today this market is dominated by the polyethylene separator, as is shown in Table 11.4. The annual growth of this market is 2-3%, but with large fluctuation based on prevailing economic conditions. 

Sealed batteries have made little entry into this market with heavy cycling service, since the lead-calcium alloys required for these versions tend toward premature capacity loss, a phenomenon intensively investigated in recent years and possibly 

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It can be stated generally that requirements for traction battery separators in respect to mechanical properties and chemical stability are considerably higher than for starter battery separators. This is due to the fact that a forklift battery is typically... 

A detailed description of the production process and the properties of polyethylene separators can be found in Sec. 9.2.2.1, so only the modifications, which are important for traction battery separators are covered here. 

Further details are given in the systems comparison under Comparative Evaluation of Traction Battery Separators , below. 

Polyethylene separators offer the best balanced property spectrum excellent mechanical and chemical stability as well as good values for acid availability and electrical resistance have established their breakthrough to be the leading traction battery separator. Rubber separators, phenolic resin-resorcinol separators, and mi-croporous PVC separators are more difficult to handle than polyethylene separators their lack of flexibility does not allow folding into sleeves or use in a meandering assembly in addition they are more expensive. 

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... 

It can be stated generally that requirements for traction battery separators in respect to mechanical properties and chemical stability are considerably higher than those for starter battery separators. This is due to the fact that a forklift battery is typically operated for about 40 000-50 000 h in charge-discharge service, whereas a starter battery for only about 2000 h. The requirements for electrical resistance are lower because of the typically lower current densities for traction batteries. These differences are of course reflected in the design of modem traction battery separator material. 

Comparative Evaluation of the Traction Battery Separators Which separator properties are important for use in traction batteries For this aspect primarily the highly predominant application, namely forklift traction batteries, is to be considered chemical resistance against attacks by acid and oxidation, mechanical stability for problem-free assembly, stiffness to counteract overexpansion of the negative active material, and low acid displacement are particularly desirable. Delay in antimony poisoning, absence or near-absence of oily deposits in the cells, and - last but not least - a low electrical resistance complete the requirement profile. 

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