4.2
Separation
Separation between plates is
provided by injection molded plastic
separator grids, integrating both plate
edge insulation and plate separation.
By providing a large spacing
between the positive and negative
plates and a generous quantity
of electrolyte between plates, good
electrolyte circulation and gas
dissipation are provided, and there
is no stratification of the electrolyte
as found with lead acid batteries.
4.3
Electrolyte
The electrolyte used in the block
battery, which is a solution of
potassium hydroxide and lithium
hydroxide, is optimized to give the
best combination of performance, life,
energy efficiency and a wide
temperature range.
The concentration of the standard
electrolyte is such as to allow the cell
to be operated down to temperature
extremes as low as -20°C and as
high as +60°C. This allows the very
high temperature fluctuation found in
certain regions to be accommodated.
For very low temperatures a special
high density electrolyte can be used.
It is an important consideration of the
block battery, and indeed all nickel-
cadmium batteries, that the electrolyte
does not change during charge and
discharge. It retains its ability to
transfer ions between the cell plates,
irrespective of the charge level.
In most applications the electrolyte
will retain its effectiveness for the life
of the battery and will never need
replacing. However, under certain
conditions, such as extended use in
high temperature situations, the
electrolyte can become carbonated.
If this occurs the battery performance
can be improved by replacing the
electrolyte (see section 11.4).
The standard electrolyte used for
the first fill in cells (see 10.5
Discharged and empty cells)
is E22 and for replacement in
service is E13.
4.4
Terminal pillars
Short terminal pillars are welded
to the plate bus bars using a well
established and proven method.
These posts are manufactured from
steel bar, internally threaded for
bolting on connectors and nickel
plated.
The sealing between the cover
and the terminal is provided by
a compressed visco-elastic sealing
surface held in place by compression
lock washers. This assembly
is designed to provide satisfactory
sealing throughout the life of
the product.
4.5
Venting system
The block battery is fitted with a
special flame arresting flip top vent
to give an effective and safe venting
system.
4.6
Cell container
The battery is built up using
well-proven block battery construction.
The tough polypropylene containers
are welded together by heat sealing.
8
BlockBat 3/11/98 10:11 Page 11
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