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ENGINE—ELECTRICAL 6Y-5
BATTERY TESTING PROCEDURES
Testing procedures are used to determine whether the
Battery is (1) good and usable, (2) requires recharging or
(3) should be replaced. Analysis of Battery conditions can
be accomplished, by performing a visual inspection,
Instrument Test, and the full charge hydrometer test.
1. VISUAL INSPECTION
The first step in testing the Battery should be a visual
inspection, which very often will save time and expense
in determining Battery condition.
• Check the outside of the Battery for a broken or
cracked case or a broken or cracked cover. If any
damage is evident, the Battery should be replaced.
« Note the electrolyte level. Levels that are too low or
too high may cause poor performance, as covered in
the section entitled "Periodic Servicing".
o Check for loose cable connections, and for evidence
of corrosion as covered in section entitled ' 'Periodic
Servicing". Correct as required before proceeding
with tests.
2. INSTRUMENT TEST
A number of suppliers have approved testing equipment
available. These testers have a programmed test proce-
dure consisting of a series of timed discharge and
charge events, requiring approximately 2 to 3 minutes,
that will determine the condition of the Battery with a
high degree of accuracy. When using these testers, the
procedure
recommended by the tester
manufacturer
should be followed. Batteries should not be charged prior
to testing as doing so may alter the test results. If a
tester is not available for testing, the "Specific Gravity
Cell Comparison Test" may be used or an alternate
method, but with a sacrifice in testing accuracy.
3. FULL CHARGE HYDROMETER TEST
This test should be used only on Batteries which test
good with testing equipment or "Specific Gravity Cell
Comparison Test" but which subsequently fail in service.
• Remove the Battery from the vehicle, and adjust the
electrolyte level as necessary, by adding colorless,
odorless, drinking water.
• Fully charge the Battery at the Slow Charging rate
as covered in the section entitled "Battery Charg-
ing".
• Measure the specific gravity of the electrolyte in
each cell and interpret as follows:
Hydrometer Reading Less Than 1.230—Full charge
hydrometer readings less than 1.230 corrected for
temperature indicate the Battery is defective and
should be replaced.
Hydrometer Readings Above 1.310—Full charge hy-
drometer readings above 1.310 corrected for tem-
perature indicate that the cells have been improperly
filled (activation) or improperly serviced.
Poor
service and short Battery life will result.
SPECIFIC GRAVITY READINGS
A hydrometer can be used to measure the specific
gravity of the electrolyte in each cell.
The hydrometer measures the 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. An indication of the concentration of the
electrolyte is obtained with a hydrometer.
When using a hydrometer, observe the following points:
1. Hydrometer must be clean, inside and out, to insure
an accurate reading.
2. Hydrometer readings must never be taken immedi-
ately after water has been added. The water must be
thoroughly mixed with the electrolyte by charging for
at least 15 minutes at a rate high enough to cause
vigorous gassing.
3. If hydrometer has built-in thermometer, draw liquid
into it several times to insure correct temperature
before taking reading.
4. Hold hydrometer vertically and draw in just enough
liquid from battery cell so that float is free floating.
Hold hydrometer at eye level so that float is vertical
and free of outer tube, then take reading at surface of
liquid. Disregard the curvature where the liquid
rises against float stem due to surface tension.
5. Avoid dropping battery fluid on car or clothing as it
is extremely corrosive. Any fluid that drops should
be washed off immediately with baking soda solution.
The specific gravity of the electrolyte varies not only
with the percentage of acid in the liquid but also with
temperature. As temperature increases, the electrolyte
expands so that the specific gravity is reduced. As
temperature drops, the electrolyte contracts so that the
specific gravity increases. Unless these variations in
specific gravity are taken into account, the specific
gravity obtained by the hydrometer may not give a true
indication of the concentration of acid in the electrolyte.
A fully charged Battery will have a specific gravity
reading of approximately 1.270 at an electrolyte temper-
ature of 80°F. If the electrolyte temperature is above or
below 80°F, additions or subtractions must be made in
order to obtain a hydrometer reading corrected to the
80°F standard.
For every 10° above 80°F, add four
specific gravity points (.004) to the hydrometer reading.
Example: A hydrometer reading of 1.260 at 110°F would
be 1.272 corrected to 80°F, indicating a fully charged
Battery. For every 10° below 80°F, subtract four points
(.004) from the reading. Example: A hydrometer reading
of 1.272 at 0°F would be 1.240 corrected to 80°F, indi-
cating a partially charged Battery.
Specific Gravity Cell Comparison Test—This test may
be used when a instrument tester is not available. To
perform this test measure the specific gravity of each
cell, regardless of state of charge, and interpret the
results as follows:
• If specific gravity readings show a difference be-
tween the highest and lowest cell of .050 (50 points)
or more, the Battery is defective and should be
replaced.
INSTALLING BATTERIES
To install a Battery properly, it is important to ob-
serve the following precautions:
• Connect grounded terminal of Battery last to avoid
short circuits which may damage the electrical
system.
CHEVROLET CHASSIS SERVICE MANUAL
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