Hydrometer; Using A Hydrometer - Cushman Shuttle 2 Service Manual

BATTERIES AND CHARGING
Read all of Section B and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
B
A cost effective way to identify a poorly performing bat-
tery is to use a hydrometer to identify a battery in a set
with a lower than normal specific gravity. Once the par-
ticular cell or cells that are the problem are identified, the
suspect battery can be removed and replaced. At this
point there is nothing that can be done to salvage the
battery; however, the individual battery should be
replaced with a good battery of the same brand, type
and approximate age.

Hydrometer

A hydrometer (P/N 50900-G1) is used to test the state of
charge of a battery cell (Ref. Fig. 7). This is performed
by measuring the density of the electrolyte, which is
accomplished by measuring the specific gravity of the
electrolyte. The greater the concentration of sulfuric
acid, the more dense the electrolyte becomes. The
higher the density, the higher the state of charge.
Bulb
32
28
Add to Float
24
20
Reading
16
12
8
4
0
4
8
12
16
20
Subtract
24
from Float
28
Reading
32
36
Thermometer
Fig. 7 Hydrometer
To prevent a 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.
Page L-6
Float
Cylinder
1100
1125
1150
1200
1225
1250
1275
1300
32
28
24
20
16
12
8
4
0
4
8
12
16
20
24
28
32
36
Weight
Repair and Service Manual
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 bat-
tery 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 ade-
quately 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 inter-
nal thermometer that will measure the temperature of
1100 the electrolyte and will include a conversion scale to cor-
1125 rect the float reading. It is important to recognize that the
1150 electrolyte temperature is significantly different from the
1175 ambient temperature if the vehicle has been operated.
1200

Using A Hydrometer

1225
1250
1. Draw electrolyte into the hydrometer several times to
1275
permit the thermometer to adjust to the electrolyte
1300
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 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. 8).
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
NOTICE