BATTERIES 7
en-59
7.11 SPECIFIC GRAVITY (62801 ONLY) ____________________________________________
The normal specific gravity readings for a fully charged
battery should be between 1.250 and 1.280 after
correcting for temperature.
Check the specific gravity after the batteries have been
charged and before adding water to the cells
It is possible to purchase a combination hydrometer-
thermometer which measures both specific gravity and
the electrolyte temperature, otherwise use a standard
hydrometer and a separate battery thermometer.
Temperature is important when measuring specific
gravity and test results must be corrected to compensate
for temperature differences. To compensate for different
temperatures, subtract one point (0.001) from the
measured reading for every 3° F (1.7° C) below 80° F
(26.7° C) or add one point (0.001) from the measured
reading for every 3° F above 80° F.
EXAMPLE: A reading of 1.282 taken at 65° F (18.3°
C) is compensated for temperature to 1.277 (1.282
minus five points (0.005) equals 1.277).
If low specific gravity readings are found:
1. Make sure the cells you checked have a sufficient
electrolyte level.
2. Check all battery connections for tightness and
corrosion. A non metallic grease or protective spray
may be applied to the connections to inhibit further
corrosion
3. Check for cracked or damaged battery case.
4. Check for broken or frayed battery cables.
If the hydrometer reading varies 30 points (0.030) or
more, it may indicate an aging or defective battery. Mark
the cells with low specific gravity readings. Check
electrolyte levels and recharge the batteries.
Take another gravity reading from all of the cells. If the
hydrometer reading varies by more than 30 points
(0.030) between two cells in the same battery, and the
electrolyte level is not low, it is a bad cell and the battery
should be replaced.
If one of the batteries have been found defective, mark
the bad battery and recharge with the bad battery still in
place. Once the batteries are charged, replace the
defective battery with a fully charged one (either a new
battery or one of equal age.
7.12 END OF CHARGE VOLTAGE TEST (62801 ONLY)________________________________
This test is made using a voltmeter, also on fully charged
batteries and with the charger connected. Check end of
charge voltage whenever LDU displays less than 50 VDC
immediately after a full charge.
1. Verify the batteries have been fully charged. Restart
the charger by disconnecting the AC cord from the
wall and reconnecting it.
2. After 15 minutes (with the charger still running)
measure the individual battery voltages using a volt-
ohm meter. Place the Black probe on the Negative
(–) terminal of the battery and the Red probe on the
Positive (+) terminal. Record all readings for the
batteries.
a. A fully charged battery should have a voltage
reading between 9.3 and 10.4 volts.
b. A reading of less than 9.3 volts from every
battery indicates they are all nearing the end of
their working life.
c. If one battery has a reading of less than 9.3 volts
or varies by more than 0.5 volts from the other
batteries, check the specific gravity reading and/
or perform a battery discharge test.
Below 80° (26.7° C) Above 80° (26.7° C)
° F° CSubtract° F° C Add
77 25 0.001 83 28.3 0.001
74 23.3 0.002 86 30 0.002
71 21.6 0.003 89 31.6 0.003
68 20 0.004 92 33.3 0.004
65 18.3 0.005 95 35 0.005
62 16.6 0.006 98 36.6 0.006
59 15 0.007 101 38.3 0.007
56 13.3 0.008 104 40 0.008
53 11.6 0.009 107 41.6 0.009
50 10 0.010 110 43.3 0.010
47 8.3 0.011 113 45 0.011
44 6.6 0.012 116 46.6 0.012
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