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and compare them with the previous readings. Rotate the measured
connections each quarter. Repair those that have increased 20 percent in
resistance.
connections each quarter. Repair those that have increased 20 percent in
resistance.
C. Annually
C. Annually
Record the resistance of all the connections as in step A above and compare
them with the previous readings. Repair those that have increased 20
percent in resistance.
them with the previous readings. Repair those that have increased 20
percent in resistance.
D. During Discharge
D. During Discharge
Connection integrity may be checked with an accurate IR camera.
Temperature of the higher resistance connections will be noticeably higher
and should be repaired.
Temperature of the higher resistance connections will be noticeably higher
and should be repaired.
5.10
5.10 INTERNAL RESISTANCE
INTERNAL RESISTANCE
Internal resistance is a good indication of the state of charge and substitutes
for specific gravity readings taken on flooded, lead-acid type cells.
for specific gravity readings taken on flooded, lead-acid type cells.
Measuring the internal resistance of a module monitors the two main failure
modes--grid corrosion and dryout. The manufacturer's literature will list
the normal expected values. This test should not be done until after the
connection resistances of the cells are checked and repaired as in 5.9 above.
Elevated connection resistance will appear as internal resistance and make
cells appear faulty. Internal resistance can be checked as follows:
modes--grid corrosion and dryout. The manufacturer's literature will list
the normal expected values. This test should not be done until after the
connection resistances of the cells are checked and repaired as in 5.9 above.
Elevated connection resistance will appear as internal resistance and make
cells appear faulty. Internal resistance can be checked as follows:
1. While the battery is fully charged and operating on float, check and
record voltage and current for the cell being tested.
2. Apply a normal load across the cell.
3. Again check and record the voltage and current.
4. The internal resistance can then be calculated by dividing the change in
3. Again check and record the voltage and current.
4. The internal resistance can then be calculated by dividing the change in
voltage by the change in current.
Commercial test sets are available to measure internal resistance, which
saves time and effort. Consider purchasing a test set if maintaining more
than one VRLA battery.
saves time and effort. Consider purchasing a test set if maintaining more
than one VRLA battery.
A. Upon Installation
A. Upon Installation
After the battery has reached equilibrium (1 to 3 days) on float, perform the
internal resistance check on each cell/module and record the results on
form POM-134B as a baseline for future comparisons.
internal resistance check on each cell/module and record the results on
form POM-134B as a baseline for future comparisons.
B.
B. Quarterly
Quarterly
Perform the internal resistance check on each cell and compare the results
with the initial records. Changes in the internal resistance of 20 percent or
greater should be considered significant. Contact the battery manufacturer
with the initial records. Changes in the internal resistance of 20 percent or
greater should be considered significant. Contact the battery manufacturer