Komatsu 930E-2 Shop Manual page 562

Corrosion creates resistance in the charging circuit
which causes undercharging and gradual starvation of
the battery.
NOTE: When washing batteries, make sure cell caps
are tight to prevent cleaning solution from entering the
cells.
Addition of acid will be necessary if considerable elec-
trolyte has been lost through spillage. Before adding
acid, make sure battery is fully charged. This is accom-
plished by putting the battery on charge and taking
hourly specific gravity readings on each cell. When all
the cells are gassing freely and three successive
hourly readings show no rise in specific gravity, the
battery is considered charged. Additional acid may
now be added. Continue charging for another hour and
again check specific gravity. Repeat the above proce-
dure until all cells indicate a specific gravity of 1.260-
1.265 corrected to 80°F (27°C).
NOTE: Use 1.400 strength sulphuric acid when mak-
ing specific gravity adjustments. Acid of higher
strength will attack the plates and separators before it
has a chance to diffuse into the solution.
If the temperature of the electrolyte is not reasonably
close to 80°F (27°C) when the specific gravity is taken,
temperature should be corrected to 80°F (27°C):
• For every 10°F (5°C) below 80°F (27°C), 0.004
should be SUBTRACTED from the specific gravity
reading.
• For every 10°F (5°C) above 80°F (27°C), 0.004
should be ADDED to the reading.
Idle batteries should not be allowed to stand unat-
tended. If equipment is to stand unused for more than
two weeks, the batteries should be removed and
placed in a cool, dry place where they may be checked
periodically and charged when necessary. Remem-
ber, all lead-acid batteries discharge slowly when not
in use. This self discharge takes place even though the
battery is not connected in a circuit and is more pro-
nounced in warm weather than in cold.
M13-2
The rate of self-discharge of a battery kept at 100°F
(38°C) is about six times that of a battery kept at 50°F
(19°C) and self-discharge of a battery kept at 80°F
(27°C) is about four times that one at 50°F (10°C).
Over a thirty day period, the average self-discharge
runs about 0.002 specific gravity per day at 80°F
(27°C).
To offset the results of self-discharge, idle batteries
should receive a booster charge (not a quick charge)
at least once every thirty days. Batteries allowed to
stand for long periods in a discharged condition are
attacked by a crystallization of the lead sulfate on the
plates. Such batteries are called sulfated and are, in
the majority of cases, irreparably damaged. In less
severe cases, the sulfated battery may be restored to
limited service by prolonged charging at a low rate
(approximately
An undercharged battery is extremely susceptible to
freezing when allowed to stand in cold weather.
The electrolyte of a battery in various stages of charge
will start to freeze at temperatures indicated in the
table.
The temperatures in table I indicate the points at which
the first ice crystals appear. Lower temperatures must
be reached for a solid freeze. Solid freezing of the
electrolyte may crack the battery case and damage the
positive plates. As will be noted, a
is in no danger of freezing, therefore, a
better is desirable, especially during winter weather.
Specific Gravity
Corrected to 80°F (27°C)
24VDC Electric Supply System
with 220 Amp. Niehoff Alternator
⁄
1
.
normal rate)
2
⁄
3
charged battery
4
Freezing
Temperature
Degrees
1.280 -90°F (-70°C)
1.250 -60°F (-54°C)
1.200 -16°F (-27°C)
1.150 +5°F (-15°C)
1.100 +19°F (-7°C)
TABLE I
⁄
3
charge or
4
M13002 2/99