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TP-6200 10/12 151Section 3 Scheduled Maintenance
3.11.3 Specific Gravity Check
Use a battery hydrometer to check the specific gravity of
the electrolyte in each battery cell of batteries with filler
caps. Holding the hydrometer vertically, read the
number on the glass bulb at the top of the electrolyte
level or the number adjacent to the pointer. If the
hydrometer used does not have a correction table,
consult Figure 3-20. Determine the specific gravity and
electrolyte temperature of the battery cells. Locate the
temperature in Figure 3-20 and correct the specific
gravity by the amount shown. The battery is fully
charged if the specific gravity i s 1.260 at an electrolyte
temperature of 26.7_C(80_F). Maintain the specific
gravities between cells within ±0.01 of each other.
Charge the battery if the specific gravity is below 1.215
at an electrolyte temperature of 26.7_C(80_F).
Note: Some battery testers have four or five beads in a
test tube. Draw electrolyte into the tube as with
the battery hydrometer described in this section
or use the manufacturer ’s instructions. Use
Figure 3-21 to interpret typical test results.
3.11.4 Charge Battery
Use a battery charger to maintain a fully charged battery
when the generator set is used in a standby application.
The engine battery-charging alternator charges the
battery while the generator set is running.
Note: If the generator set is in a temporary prime power
application in which the generator set has periods
of inactivity, the controller circuitry may drain the
battery. If there is no power source for a battery
charger, place the controller in the prime power
mode, if equipped, or disconnect the battery from
the generator set.
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 26.7
°C(80°F)
Hydrometer Reading 1.250
Acid Temperature --6.7
°C(20°F)
Subtract .024 Specific Gravity
Corrected Specific Gravity is 1.226
1.250 -- .024 = 1.226
Example No. 2
Temperature above 26.7
°C(80°F)
Hydrometer Reading 1.235
Acid Temperature 37.8
°C (100°F)
Add .008 Specific Gravity
Corrected Specific Gravity is
1.243
1.235 + .008 = 1.243
The temperature correction amounts to about .004 (4 points) of
specific gravity for each 5.5°C(10°F) change in temperature.
Correction
1-787
Figure 3-20 Specific Gravity Temperature Correction
Number of Floating Beads Battery Condition
5 Overcharged
4 Fully charged
3 A good charge
1or2 A low charge
0 A dead battery
Figure 3-21 Bead-Type Test Interpretation