Page 329 - Handbook of Battery Materials

11.2 Separators for Lead–Acid Storage Batteries 299

Table 11.4 World lead–acid traction battery production 1997 (million watt-hour, estimate).

Polyethylene Phenol– PVC Rubber Microfiber Total
separators formaldehyde– separators separators glass mat
resorcinol separators
separators

USA–Canada 4150 80 50 350 150 4780
Europe 3700 800 1100 950 50 6600
Asia–Pacific 950 150 500 900 50 2550
Latin America 20 50 50 100 – 220
Total (million Wh) 8820 1080 1700 2300 250 14 150
(%) 62.3 7.6 12.0 16.3 1.8 100.0

In Europe, with the economic upswing after 1950, forklifts with batteries came
into use – a development which met less acceptance in the USA for various reasons,
among them low fuel cost. In this application 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 already 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
close to a solution.

11.2.1.3.3 Electrical Vehicle Battery Separators Although electric vehicles are
only a special application for traction batteries, the general interest in them may
justify their own separate section.
Electric vehicles are around only in a few surviving niches, electric baggage
carts at German railway stations, postal delivery trucks, and milk delivery vans
in the UK being the best-known examples. Based on a growing consciousness of
decreasing natural resources and especially on the oil crisis around 1970 there were
intensive efforts to develop electric propulsion further, but they focused mainly
on high-energy battery systems such as sodium–sulfur. The serious difference in
energy density between a fuel tank of around 12 000 Wh kg −1 and the batteries
of 30−40 Wh kg −1 actually available was insurmountable; even when considering
all efficiencies involved, there remains a factor in the order of magnitude of 100;
the electric vehicle returned to the background. Only since about 1990, prompted
by the California Clean Air Act and by considerable research grants from the US
Advanced Battery Consortium (USABC) – a joint activity mainly of the three major
US car manufacturers – have increased efforts on electric vehicles been resumed.