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TP-6804 1/15 71Section 5 Scheduled Maintenance
5.8.3 Checking Specific Gravity
Use abattery hydrometer tocheck the specific gravityof
the electrolyte in each battery cell. While holding the
hydrometervertically,read thenumber onthe glassbulb
at the top of the electrolyte level or the number adjacent
to the pointer. If the hydrometer used does not have a
correction table, use the correction factors in
Figure 5-13. Determine specific gravity and electrolyte
temperature of battery cells. Locate temperature in
Figure 5-13 and adjust the specific gravity by the
amount shown.
The batteryis fullycharged if thespecific gravity is1.260
at an electrolyte temperature of 80F (26.7C). The
differencebetween specific gravities of each cell should
not exceed 0.01. Charge the battery if the specific
gravity is below 1.215 at an electrolyte temperature of
80F (26.7C). See Figure 5-11.
Specific Gravity,
Corrected to
80F (26.7C)
Battery
Condition
Below 1.215 Needs charging
1.260 Fully charged
Figure 5-11 Specific Gravity Interpretation
Some battery testers have four or five beads in the test
tube. Draw electrolyte into the tube as performed with
the battery hydrometer described previously. Use the
manufacturer’s instructions. Figure 5-12 interprets
typical test results.
Number of Floating Beads
Battery
Condition
5 Overcharged
4 Fully charged
3 Good charge
1or2 Low charge
0 Dead battery
Figure 5-12 Bead-Type Test Interpretation
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
-- 12.2
-- 6.7
-- 1.1
4.4
10
21.1
26.7
32.2
37.8
43.3
48.9
54.4
60.0
65.6
71.1
15.6
+ .032
+ .030
+ .028
+ .026
+ .024
+ .022
+ .020
+ .018
+ .016
+ .014
+ .012
+ .010
+ .008
+ .006
+ .004
+ .002
0
-- .002
-- .004
-- . 006
-- .008
-- .010
-- .012
-- .014
-- .016
-- .018
-- .020
-- .022
-- .024
-- .026
-- .028
C F
EXAMPLE NO. 1—
Temperature below 80
F (26.7C)
Hydrometer Reading 1.250
Acid Temperature 20
F(--6.7C)
Subtract .024 Specific Gravity
Corrected Specific Gravity is 1.226
1.250 -- .024 = 1.226
EXAMPLE NO. 2—
Temperature above 80
F (26.7C)
Hydrometer Reading 1.235
Acid Temperature 100
F (37.8C)
Add .008 Specific Gravity
Corrected Specific Gravity is
1.243
1.235 + .008 = 1.243
Thetemperature correctionamountsto about.004(4 points)of
specific gravity for each 10F(5.5C) change in temperature.
Correction
1-787
Tempera-
ture
Figure 5-13 Specific Gravity Temperature Correction