Using A Hydrometer; Fig. 30 Hydrometer Temperature Correction - Cushman Titan 36V Owner's Manual And Service Manual

Read all of Manual to become thoroughly familiar with this vehicle. Pay particular attention to all Notes, Cautions and Warnings
To prevent battery explosion that could result in
severe personal injury or death, never insert a
metal thermometer into a battery. Use a
hydrometer with a built in thermometer that is
designed for testing batteries.
Specific gravity is the measurement of a liquid
that is compared to a baseline. The baseline is
water which is assigned a base number of
1.000. The concentration of sulfuric acid to
water in a new golf car battery is 1.280 which
means that the electrolyte weighs 1.280 times
the weight of the same volume of water. A fully
charged battery will test at 1.275 - 1.280 while a
discharged battery will read in the 1.140 range.
Do not perform a hydrometer test on a battery that has just
been watered. The battery must go through at least one charge
and discharge cycle in order to permit the water to adequately
mix with the electrolyte.
The temperature of the electrolyte is important since the
hydrometer reading must be corrected to 80° F (27° C).
High quality hydrometers are equipped with an internal
thermometer that will measure the temperature of the
electrolyte and will include a conversion scale to correct
the float reading. It is important to recognize that the
electrolyte temperature is significantly different from the
ambient temperature if the vehicle has been operated.

Using A Hydrometer

1. Draw electrolyte into the hydrometer several times to
permit the thermometer to adjust to the electrolyte
temperature and note the reading. Examine the color
of the electrolyte. A brown or gray coloration indicates
a problem with the battery and is a sign that the bat-
tery is nearing the end of its life.
2. Draw the minimum quantity of electrolyte into the
hydrometer to permit the float to float freely without
contacting the top or bottom of the cylinder.
3. Hold the hydrometer in a vertical position at eye level
and note the reading where the electrolyte meets the
scale on the float.
4. Add or subtract four points (.004) to the reading for
every 10° F (6°C) the electrolyte temperature is
above or below 80° F (27° C). Adjust the reading to
conform with the electrolyte temperature, e.g., if the
OPERATION AND SERVICE INFORMATION
reading indicates a specific gravity of 1.250 and the
electrolyte temperature is 90° F (32° C), add four
points (.004) to the 1.250 which gives a corrected
reading of 1.254. Similarly if the temperature was 70°
F (21° C), subtract four points (.004) from the 1.250
to give a corrected reading of 1.246 (Ref Fig. 30 on
page 25).
5. Test each cell and note the readings (corrected to 80°
F or 27° C). A variation of fifty points between any two
cell readings (example 1.250 - 1.200) indicates a
problem with the low reading cell(s).
As a battery ages the specific gravity of the electrolyte
will decrease at full charge. This is not a reason to
replace the battery, providing all cells are within fifty
points of each other.
Since the hydrometer test is in response to a vehicle
exhibiting a performance problem, the vehicle should be
recharged and the test repeated. If the results indicate a
weak cell, the battery or batteries should be removed
and replaced with a good battery of the same brand, type
and approximate age.
Owner's Manual and Service Guide
Electrolyte
Temperature
° F ° C
160 71.1
+.032
+.030
150 65.6 +.028
+.026
140 60.0
+.024
+.022
130 54.4
+.020
+.018
120 48.9
+.016
+.014
110 43.3
+.012
+.010
100 37.8
+.008
+.006
90 32.2
+.004
+.002
80 26.7
0
–.002
70 21.1
–.004
–.006
60 15.6
–.008
–.010
50 10.0
–.012
–.014
40 4.4
–.016
–.018
30 -1.1
–.020
–.022
20 -6.7
–.024
–.026
–.028
10 -12.1
Ref Htc 1

Fig. 30 Hydrometer Temperature Correction

EXAMPLE #1:
Electrolyte Temperature
Above 80°F (27°C)
Electrolyte temperature
90° F (32° C)
Hydrometer reading 1.250
1.250 + .004 = 1.254
corrected specific gravity
EXAMPLE #2:
Electrolyte Temperature
Below 80°F (27 °C)
Electrolyte temperature
70° F (21° C)
Hydrometer reading 1.250
1.250 - .004 = 1.246
corrected specific gravity
Page 25