Buick LeSabre 1965 Service Manual page 579

ELECTRICAL SYSTEMS
BATTERY TESTING 1 0 - 9
Figure 10-3—Light Load Test
volts, battery should be charged
before returning car to owner.
NOTE: If any battery found to be
"good" by Light Load Test does
not perform satisfactorily in sub-
sequent service, it should again
be tested by the Light Load Test
and if it still tests "good", it
should be removed from car and
tested as outlined under F u l l
Charge Hydrometer Test. See
paragraph 10-10.
1 0 - 1 0 FULL CHARGE
HYDROMETER TEST
OF BATTERY AND
USE OF HYDRO-
METER
a. Full Charge Hydrometer
Test
The full charge hydrometer test
should be used on any battery
originally found to be "good" by
the Light Load Test, but has since
failed to perform satisfactorily in
service and which s t i l l tests
"good" by the Light Load Test.
IMPORTANT: The full charge
hydrometer test is not valid un-
less battery has been tested and
found to be "good" by the Light
Load Test.
1. Fully charge battery as de-
scribed under slow-charging (par.
10-12, subpar. a).
NOTE: H y d r o m e t e r reading
taken on partially charged bat-
teries are unreliable for this test.
2. Measure specific gravity, of
electrolyte in each cell and com-
pare readings with the following:
(a) If cell readings range between
1.230 and 1.310, the battery is
ready for use. All it needed was a
full charge. Any variation in the
specific gravity between cells
within this range does not indicate
a defective battery.
(b) If any cell reads less than
1.230 and:
(1) Battery has been in service
3 months or less, battery is good
but it has been improperly filled
with electrolyte or water and will
give poor performance. To cor-
rect this condition, empty t h e
electrolyte from any cell reading
less than 1.230 and refill with
1.265 specific gravity battery
grade electrolyte. The battery is
now ready for use.
(2) Battery has been in service
more than 3 months, it should be
replaced.
(c) If any cells read above 1.310
battery may be returned to serv-
ice. However, specific gravities
above 1.310 are harmful to bat-
tery and will cause early failure.
Such high readings are caused by
improper addition of electrolyte.
Adjusting the specific gravity will
not correct the damage that has
been done by h i g h s p e c i f i c
gravity.
b. Use of Hydometer
The hydrometer measures t h e
percentage of sulphuric acid in
the battery electrolyte in terms of
specific gravity. As a battery
drops from a charged to a dis-
charged condition, the acid leaves
the solution and enters the plates,
causing a decrease in specific
gravity of electrolyte. With a hy-
drometer, an indication of the
concentration of the electrolyte is
obtained.
The specific gravity of the elec-
trolyte varies not only with the
percentage of acid in the liquid,
it also varies with temperature.
As temperature increases, the
electrolyte expands so that the
specific gravity is reduced. As
temperature drops, the electrolyte
contacts so that the specific grav-
ity increases. Unless these vari-
ations in specific gravity a r e
taken into account, the specific
gravity obtained by the hydrom-
eter may not give a true indi-
cation of the concentration of acid
in the electrolyte.
Correction can be made for tem-
perature by adding .004, usually
referred to as 4 "points of grav-
ity", to the hydrometer reading
for every 10°F. that the elec-
trolyte is above 80° F. or sub-
tracting .004 for every 10° F. that
electrolyte is below 80° F. Figure
10-4 shows the exact correction
figure to use for any temperature
above or below 80° F., the three
steps used in obtaining the cor-
rected or true specific gravity,
and two examples showing how it
is figured.
When using a hydrometer, observe
the following points:
1. Hydrometer must be clean, in-
side and out, to insure an accurate
reading.
2. Hydrometer readings m u s t
never be taken immediately after
TAKE TEMPERATURE
l o
°
OF ELECTROLYTE
WITH THERMOMETER »o«
TAKE SP. GR. OF
ELECTROLYTE
WITH HYDROMETER
EXAMPLE
TEMPERATURE
HYDROMETER
READING
CORRECTION
(a 120° F.
TRUE SPECIFIC
GRAVITY
CHANGE HYDROMETER
READING BY AMOUNT
SHOWN ON THIS SIDE
OPPOSITE THE
ELECTROLYTE
TEMPERATURE
-Oi« EXAMPLE. B:
-OlO TEMPERATURE = 0° F.
HYDROMETER
READING = 1.230
CORRECTION
<5. 0 ° F . = - . 0 3 2
-.O2«
T R U E
SPECIFIC
GRAVITY = 1.198
-.031
Figure 10-4—Specific Gravity
Temperature Correction Scale