Page 341 - Handbook of Battery Materials

11.2 Separators for Lead–Acid Storage Batteries 311

Table 11.8 Glass fiber leaf separators.

Brand name Backweb Electrical Porosity (%) Pore size Supplier
thickness resistance (average)
2
(mm) (mΩ cm ) (µm)
Axohm 10 G+ 0.70 65 85 27 Iydall Axohm [72]

2
and very low electrical resistance (65 m cm ). The battery performance meets
expectations: very good cold crank data attract attention, and the water loss is
comparable with that of PVC but exceeds that of cellulosic separators significantly;
the separator is not a cause of battery life limitation.
There is at present only one producer of this type of separator left; typical data
are shown in Table 11.8.

11.2.2.2.4 Leaf Separators with Attached Glass Mat Even though this version
is not a distinct type of separator, this section is dedicated to it. To all leaf-type
separators described, a glass mat can be applied on the side directed toward the
positive electrode, which is usually fixed by an adhesive coated onto the ribs (cf.
Figure 11.18). This raises the cost of the separator and is usually not required for
starter batteries used under normal service conditions, but it holds the positive
active mass better inside the electrode and thus prevents premature shedding. It
is especially important for batteries subject to severe vibrations or encountering
frequent deep discharges. Typical applications include construction machinery
batteries or the area bordering on cycling applications, such as marine batteries,
truck and off-road vehicle batteries, electric lawn mowers, golf carts, or other small
traction batteries.

11.2.2.2.5 ‘Japanese’ Separators The development of the starter battery in
Japan has taken an independent course (see Section 11.2.1.2), visibly expressed by
the separator’s thick glass mat and its lack of spacing ribs (cf. Figure 11.19). The
cellulosic backweb impregnated with phenolic resin, generally in use until around
1980 and largely identical to the separator of the same type already mentioned
has been completely replaced by thin (∼0.3 mm) fleece materials made of organic
fibers.
Since the glass mat supplies sufficient stiffness, high backweb thickness was no
longer needed! These fleeces are made of organic fibers (polyester and polypropy-
lene, as well as so-called ‘synthetic pulp,’ i.e., fibrillated polypropylene) on paper
machines.
The basic materials are sufficiently stable in sulfuric acid not to require the
expensive phenolic resin impregnation. Traces of adhesive are applied to hold
the glass mat in order to achieve the total thickness. This separation system may
be expensive to manufacture, a fact certainly largely balanced by savings in positive
active mass, but it also has some indisputable advantages.