Service manual

Groundsmaster 3280−D/3320Page 6 − 30Electrical System
B. Temperature correct each cell reading. For each
10
o
F (5.5
o
C) above 80
o
F (26.7
o
C) add 0.004 to the
specific gravity reading. For each 10
o
F (5.5
o
C) be-
low 80
o
F (26.7
o
C) subtract 0.004 from the specific
gravity reading.
Example: Cell Temperature 100
o
F
Cell Gravity 1.245
100
o
F minus 80
o
F equals 20
o
F
(37.7
o
C minus 26.7
o
C equals 11.0
o
C)
20
o
F multiply by 0.004/10
o
F equals 0.008
(11
o
C multiply by 0.004/5.5
o
C equals 0.008)
ADD (conversion above) 0.008
Correction to 80
o
F (26.7
o
C) 1.253
C. If the difference between the highest and lowest
cell specific gravity is 0.050 or greater or the lowest
cell specific gravity is less than 1.225, charge the bat-
tery. Charge at the recommended rate and time giv-
en in Charging or until all cells specific gravity is
1.225 or greater with the difference in specific gravity
between the highest and lowest cell less than 0.050.
If these charging conditions can not be met, replace
the battery.
3. Perform a high−discharge test with an adjustable
load tester.
This is one of the most reliable means of testing a battery
as it simulates the cold−cranking test. A commercial bat-
tery load tester is required to perform this test.
CAUTION
Follow the manufacturer’s instructions when us-
ing a battery load tester.
A. Check the voltage across the battery terminals
prior to testing the battery. If the voltage is less than
12.4 VDC, recharge the battery.
B. If the battery has been charged, apply a 150 amp
load for 15 seconds to remove the surface charge.
Use a battery load tester following the manufactur-
er’s instructions.
C. Make sure battery terminals are free of corrosion.
D. Measure the temperature of the center cell.
E. Connect a battery load tester to the battery termi-
nals following the manufacturer’s instructions.
Connect a digital multimeter to the battery terminals.
F. Apply a test load of one half the Cranking Perfor-
mance (see Battery Specifications) rating of the bat-
tery for 15 seconds.
G. Take a voltage reading at 15 seconds, then re-
move the load.
H. Using the table below, determine the minimum
voltage for the cell temperature reading:
Minimum
Voltage
Battery Electrolyte
Temperature
9.6 70
o
F (and up) 21.1
o
C (and up)
9.5 60
o
F 15.6
o
C
9.4 50
o
F 10.0
o
C
9.3 40
o
F 4.4
o
C
9.1 30
o
F −1.1
o
C
8.9 20
o
F −6.7
o
C
8.7 10
o
F −12.2
o
C
8.5 0
o
F −17.8
o
C
I. If the test voltage is below the minimum, replace
the battery. If the test voltage is at or above the mini-
mum, return the battery to service.
Charging
To minimize possible damage to the battery and allow
the battery to be fully charged, the slow charging meth-
od is presented here. This charging method can be ac-
complished with a constant current battery charger
which is available in most shops.
CAUTION
Follow the manufacturer’s instructions when us-
ing a battery charger.
NOTE: Using specific gravity of the battery cells is the
most accurate method of determining battery condition.
1. Determine the battery charge level from either its
specific gravity or open circuit voltage.
Battery Charge
Level
Specific
Gravity
Open Circuit
Voltage
100% 1.265 12.68
75% 1.225 12.45
50% 1.190 12.24
25% 1.155 12.06
0% 1.120 11.89