Columbia ParCar Expediter EX21-24A, Service Manual

Page: 80 / 94

Section 9
–
Battery and Battery Charge
r
1.250
– 1.270
100%
1.220
– 1.240
75%
1.190
– 1.210
50%
1.160
– 1.180
25%
Table 2
Specific Gravity vs. Action Required
SG Reading Action
Battery Cell 1 Cell 2 Cell 3
1 1.100 1.100 1.100 Charge & recheck
2 1.260 1.180 1.250
Cell 2 bad
– replace
battery
3 1.250 1.260 1.250 Good
4 1.190 1.170 1.120
Charge & recheck
Suspect cell 3
Table 3
If the difference between the highest and lowest cell is 0.050
(50 points) or more, the battery is nearing the end of its useful
life and should be replaced.
DISCHARGE (LOAD) TEST
The discharge, or load test, is the recommended method of
determining battery condition because it simulates electric
vehicle operation under controlled conditions. A 75 amp draw
is applied to the battery bank with a Load Tester. The time it
takes the battery bank to drop to 31.5 volts, along with
individual battery voltages, is used to determine battery
condition.
NOTICE: Use of automotive type of load tester is not
recommended and will offer inaccurate results.
Use an appropriate volt tester that gives voltage and
minutes of discharge.
TEST PREPARATION
The following preparations must be verified before discharged
load testing. Should any of the following recommendations not
be performed, results of testing will be inaccurate and
misleading.
▪
Batteries must receive a full charge before conducting
Discharge (Load) Test.
▪
Discharge (Load) Test must be performed within 18 hours
of charging.
▪
Vehicle must not be used, even for short runs, prior to
Discharge (Load) Test.
▪
Electrolyte level must be correct in all cells.
TEST PROCEDURE
Discharge Load Test must be performed in well
ventilated area.
1. Connect tester leads to battery bank.
2. Check and record electrolyte temperature of center cell of
each battery.
3. Turn tester on.
4. After 20-30 minutes, with tester on, check and record
individual battery voltages to the nearest 0.1 (1/10) volt.
All individual battery voltage readings must be made as
rapidly as possible to be accurate.
5. Allow tester to shut off automatically, and record time
elapsed from start of discharge.
Tester shutoff should occur at a battery voltage of 42v +/- 0.2v
(48 volt system) or 21v +/- 0.2v (24 volt system). Check
tester shutoff voltage periodically. This setting must be
accurate for a valid test.
RESULTS INTERPRETATION
1. Compare individual battery voltages recorded in step 4 of
Discharge (Load) Test Procedure and discard any battery
that is 0.2 (2/10) volt lower than the highest battery in bank.
If defective battery is found, recharge the entire bank for 12
hours. Then, replace the defective battery with a good fully
charged battery of the same brand and date code, if
possible. Equalize the bank by placing it on charge for an
additional three hours, then retest.
2. If all battery voltages are within 0.2 volts of each other,
compare discharge time from step 4 of Discharge (Load)
Test Procedure with minimum times in Temperature and
Time Table. Even if individual battery voltages are
satisfactory, but the discharge time fails to meet minimums
in Temperature and Time table, the entire battery bank
should be replaced.
DISCHARGE LOAD TEST: Temperature & Time