14
TT-855 12/93
Operation
Checking Specific Gravity (Lead-Acid Batteries)
Use a battery hydrometer to check the specific gravity of
the electrolyte in each battery cell. While holding the
hydrometer vertically, read the number on the glass bulb
at the top of the electrolyte level. The battery is fully
charged if the specific gravity is 1.260 at an electrolyte
temperature of 80
_
F (26.7
_
C). The difference between
specific gravities of each cell should not exceed 0.01.
The battery should be charged if the specific gravity is
below 1.215 at an electrolyte temperature of 80
_
F
(26.7
_
C). The temperature of the battery electrolyte
will affect the specific gravity reading and must be
taken into consideration when checking battery
specific gravity. If the hydrometer used does not
have a temperature correction table, use the one
shown in Figure 9.
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
(26.7
_
C)
Hydrometer Reading 1.250
Acid Temperature
20
_
F (6.7
_
C)
Subtract .024 Sp. Gravity
Corrected Sp. Gravity is 1.226
EXAMPLE NO. 2
Temperature above 80
_
F
(26.7
_
C)
Hydrometer Reading 1.235
Acid Temperature 100
_
F
(37.8
_
C)
Add .008 Sp. Gravity
Corrected Sp. Gravity is 1.243
The Temperature correction amounts to about .004 (4
“points”) of specific gravity for each 10
_
F (5.5
_
C) change in
temperature.
Correction
Figure 9. Specific Gravity Temperature Correction
Charging Nickel-Cadmium Batteries
Since charging recommendations vary between
manufacturers of nickel-cadmium batteries, specific
nickel-cadmium battery charging instructions are not
provided in this manual. Contact the manufacturer of the
nickel-cadmium battery for specific charging and
maintenance instructions. If the voltage setting
recommended by the battery manufacturer is different
from the battery charger’s factory setting, call battery
charger manufacturer for the procedure for properly
adjusting the battery charger.
