| Battery Application & Technology
The simplest method for the construction of
lead-acid battery electrodes is the plant plate, named
after the inventor of the lead-acid battery. A plant plate
is merely a flat plate composed
of pure lead. Since the capacity of a lead-acid battery is
proportional to the surface area
of the electrodes that is exposed to the electrolyte,
various schemes are employed to increase
the surface area of the electrodes per unit volume or
weight. Plant plates are grooved
or perforated to increase their surface area. A typical
plant plate is shown below.
Plate
The most commonly used method to increase
surface area is to make the active material into a paste
that acts like a sponge where the electrolyte fills all the
pores. The paste, or active material,
is mounted into a frame or grid structure that mechanically
supports it and serves as the
electrical conductor carrying the current during both the
charge and discharge cycle. The most
commonly used plate today is the pasted plate, also known as
the flat plate. This grid structure
is a lattice-work that resembles the cross section of a
honeycomb, with the paste filling
all of the rectangular windows on the structure. The picture
below shows a typical construction of
a pasted plate grid. The flat plate construction is used as
the negative electrode plate in almost
all cases, and serves as the positive plate in most standby
applications.
Pasted Grid plate
Positive electrodes are usually of pasted
plate or tubular construction. Tubular electrodes are
popular positive plates for
heavy cycling applications. This construction uses a frame
structure consisting of a
series of vertical spines connected to a common bus. The
paste is held in
micro-porous, non-conductive tubes which are placed over the
individual spines. A simplified
view of tubular plate construction is shown in below.
Regardless of the plate type
used, the capacity of any battery is increased by adding
multiple plates in parallel.
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