BATTERIES AND CHARGING
Page H-6
Repair and Service Manual
Read all of Section B and this section before attempting any procedure. Pay particular attention to all Notes, Cautions and Warnings
Hydrometer
A hydrometer (P/N 50900-G1) is used to test the state of
charge of a battery cell (Ref Fig. 7 on page H-6). 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 sulfu-
ric acid, the more dense the electrolyte becomes. The
higher the density, the higher the state of charge.
To prevent a battery
explosion that could
result in severe per-
sonal injury or death, never insert a metal
thermometer into a battery. Use a hydrome-
ter 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 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 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 10F (6C) the electrolyte temperature is
above or below 80F (27C). 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 90F (32C), add four
points (.004) to the 1.250 which gives a corrected
reading of 1.254. Similarly if the temperature was
70F (21C), subtract four points (.004) from the
1.250 to give a corrected reading of 1.246 (Ref Fig. 8
on page H-7).
5. Test each cell and note the readings (corrected to
80 F or 27C). A variation of fifty points between
any two cell readings (example 1.250 - 1.200) indi-
cates 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
Fig. 7 Hydrometer
32
28
24
20
16
12
8
4
0
4
8
12
16
20
24
28
32
36
32
28
24
20
16
12
8
4
4
12
16
20
24
28
32
36
1100
1125
1150
1200
1225
1250
1275
1300
1100
1125
1150
1200
1225
1250
1275
1300
Add to Float
Reading
Subtract
from Float
Reading
Bulb
Cylinder
Float
Weight
Thermometer
1175
! !
To Next Page
Loading...
Need help?
General
