ELECTRICAL
EQUIPMENT
Keep the current constant by varying
the series resistance of the circuit or
the generator output.
This
charge
shmdd not be
brokm
by
long
rest
periods.
If, however, the temperature of any
cell rises above the permissible
maxi-
mum quoted in Para.
2
(d),
the charge
must be interrupted until the tem-
perature has fallen at least 10°F. below
that figure. Throughout the charge,
the electrolyte must be kept level with
the top of the separators by the addition
of acid solution of the same specific
gravity as the original filling-in acid,
until specific gravity and voltage read-
ings have remained constant for five
successive hourly readings. If the
charge is continued beyond that point,
top up with distilled water.
At the end of the charge carefully check
the specific gravity in each cell to
ensure that, when corrected to
60°F.,
it lies within the specified limits. If
any cell requires adjustment, some of
the electrolyte must be siphoned off
and replaced either by distilled water
or by acid of the strength originally
used for filling-in, depending on
whether the specific gravity is too high
or too low. Continue the charge for an
hour or so to ensure adequate
mixing of
the electrolyte and again check the
specific gravity readings. If necessary,
repeat the adjustment process until the
desired reading is obtained in each cell.
Finaliy, allow the battery to cool, and
siphon off any electrolyte above the
tops of the separators.
5.
PREPARING GTZ
"DRY-
CHARGED
"
BATTERIES
FOR
SER-
VICE
"
Dry-charged
"
batteries are supplied
without electrolyte but
with
the plates in a
charged condition. No
initial
charging is
required.
When they are required for service it is
only necessary to fill each cell with sulphuric
acid of the correct specific gravity. No
initial charging is required. This pro-
cedure ensures that there is no deterioration
of the efficiency of the battery during the
storage period before the battery is required
for use.
(a) Preparation of Electrolyte
The electrolyte is prepared by mixing
together distilled water and concen-
trated sulphuric acid,
usually
of specific
gravity 1.835. This mixing must be
carried out in a lead-lined
tank
or a
glass or earthenware vessel. The acid
must be added slowly to the water
while the mixture is stirred with a
glass rod. NEVER ADD THE
WATER TO THE ACID, as the
resulting chemical reaction may cause
violent and dangerous spurting of the
concentrated acid.
The total quantity of electrolyte needed
to
fill
the battery
can
be
calculated by
reference to para.
2
(a).
The specific gravity of the filling
electrolyte depends on the climate in
which the battery is to be used. If the
temperature of the battery and its
surroundings will not normally rise
above 90°F.
(32"C.), electrolyte of
specific gravity 1.270 is required. El-
ectrolyte of this
specific gravity is
prepared by adding 1 part (by volume)
of 1.835 specific gravity sulphuric acid
to 2.8 parts of distilled water.
On the other hand, in tropical climates
where the
temperature may frequently
rise above 90°F., the electrolyte should
be of specific gravity 1.210, and is
prepared by adding 1 part of 1.835
acid to
4
parts of distilled water.
N.B.-All specific gravity
figures
are
given for an electrolyte temperature
of WF., which is adopted as a
reference temperature. Hydrometer
readings taken at other temperatures
can
be corrected to this reference
temperature as follows
:-
For every 5°F. BELOW 60°F.,
DEDUCT .W2 from the observed
reading to obtain true reading at
60°F. For every 5°F. ABOVE 60°F.,
ADD .W2 to the observed reading
to obtain true reading at 60°F.
Heat is roduced by the mixture of
acid an
‘l'
water, and the electrolyte
should
be
allowed to
cool
before
pouring
it into the battery.
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