DAF LF45, LF55 Series. Manual — part 350
5
LF45/55 series
Inspection of batteries
BATTERIES
4-1
4. INSPECTION OF BATTERIES
4.1 VISUAL INSPECTION
-
A white dividing line at
1
/
3
of the plate height
(this can be seen through transparent
battery boxes) indicates that the battery has
been allowed to remain in a seriously
discharged condition.
-
If the electrolyte is brown and the battery
consumes a lot of fluid, this indicates that
the battery is overcharged.
-
If the electrolyte is turbid and milky and the
cells have a white deposit, the battery has
become damaged due to insufficient
charging (deep discharge).
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BATTERIES
Inspection of batteries
LF45/55 series
4-2
4.2 INSPECTION OF THE CHARGING CONDITION
Relative density
-
The charging and discharging of the battery
leads to a chemical reaction in the battery,
which involves sulphuric acid. The sulphuric
acid concentration drops as the battery
discharges.
The concentration, measured as relative
density (kg/dm
3
), is a useful yardstick for
determining the charging condition of the
battery.
-
An acidimeter can be used to check the
charging condition.
Relative density at 27_C in kg/dm
3
Charged battery
: 1.28
Half-charged battery
: 1.20
Discharged battery
: 1.10
-
Measurement corrections are necessary if
temperatures are significantly lower or
higher. For every 10_C of lower
temperature, subtract 0.007 points from the
measured value. For each 10_C of higher
temperature, 0.007 points must be added.
In batteries in good condition, the relative
density must be the same in all the cells.
The maximum difference between the
highest and lowest relative density may not
exceed 0.03 kg/dm
3
.
Note:
If the relative density in one of the cells is much
lower than in the other cells, the cause may be
cell closure. If the relative density of two
adjacent cells is much lower than in the other
cells, this indicates a leak in the cell partition. In
both cases, the battery must be replaced.
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5
LF45/55 series
Inspection of batteries
BATTERIES
4-3
Voltage
-
The charging condition of the batteries can
also be measured using a sensitive,
preferably digital voltmeter. This method
can only be used 1 to 2 hours after full
completion of charging or discharging.
Measure the absolute rest voltage (the
positive and negative clamps must be
removed from the battery).
The charging condition of the battery can be
calculated using the formula: voltage per
cell = relative density (kg/dm
3
) + 0.84.
Example:
For a fully charged battery, the relative
density per cell is 1.28 kg/dm
3
. The voltage
per cell is therefore 1.28 + 0.84 = 2.12 V.
A 12 V battery has 6 cells. The total voltage
for a charged battery is 6 x 2.12 = 12.72 V.
The voltage of a half-charged battery is
approx. 12.24 V.
The voltage of a discharged battery is
approx. 11.75 V.
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5
BATTERIES
Inspection of batteries
LF45/55 series
4-4
4.3 INSPECTION USING A BATTERY TESTER
-
The general condition of the battery can be
checked quickly using a battery tester. For
this check, a load is applied to the battery
and then the discharge voltage at the
battery terminals is measured. The load
applied to the battery must be at least 3
times the capacity of the battery.
-
The rule of thumb is that the test can be
carried out when the battery is sufficiently
charged (relative density 1.25 -
1.28 kg/dm
3
).
At normal temperatures (10-20_C), the
charging voltage for a properly charged
battery must be 10 volts after 10 seconds.
In the case of a partially discharged battery
(relative density 1.25 kg/dm
3
), the reading
should be at least 9 volts.
It is important that the voltage be measured
directly at the battery terminals.
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200440
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