Vertiv Alber Cellcorder CRT-400 User Manual page 142

Application Note CC–001
Surprisingly, the IEEE/ANSI VRLA P–1188 proposed standard is more liberal in this matter. It
recommends that from 25% to about 43%, the cell's manufacturer be contacted. Above 43%, a load test
be done ASAP. Actually, the standard is expressed in the reciprocal of internal resistance, conductance
(mhos.)
Data Anomalies
Another part of the battery literates' fantasy is also likely to be shattered: that all the data gathered for
the baseline, or test readings taken afterward, would fall reasonably close to any trend line. That is,
higher capacity cells will have uniformly lower internal resistances and lower capacity cells will have
proportionately higher internal resistances. Even cells fresh off of a tightly controlled production line fail
to completely conform with this expected behavior.
In the course of your own testing, you will find tested, high capacity cells with an unusually high internal
resistance. Similarly, there will be cells with the low internal resistance characteristic of a good cell that
would fail a capacity test. Unfortunately, the current state of the art does not permit impedance,
conductance, admittance or resistance testing to definitively identify the cells with anomalies–without
the assistance of a load test.
If you are fortunate to have large amounts of both capacity and corresponding internal resistance data,
developing a baseline should be no problem. When a program is just starting, or there are few cells of a
particular model, some educated "guess–timating" helps in sorting out data. If you need baseline data
try calling us or the cell's manufacturer.
Internal Resistance Test Frequency
The whole purpose of the internal resistance check is to determine whether a cell has deteriorated and
if so, how much and how fast. Logically, checks are done periodically. At least quarterly, check cells that
have exhibited signs of abnormality either from inspection or an earlier capacity, integrity or internal
resistance test.
Since neither specific gravity nor visual checks can be done on sealed cells, you would want to do much
more frequent testing than on vented cells. For that reason, it's no surprise the P–1188 VRLA proposed
Standard recommends internal measurements be taken quarterly. On the other hand, the standard for
vented batteries, 4501, doesn't specify this type of check. However, it does call for annual connection
resistance readings and you would want to take the internal resistances at the same time.
That's the nicest part of the Cellcorder...its "multimeter" functions measure and record both the internal
and connection resistances at the same time! It saves you time and you don't even move the test leads
for single post cells. For detailed information, request Cellcorder Application Note CC002, Intercell
Resistance Measurement Procedures which covers single and multiple–post cells measurements.
Managing the Cellcorder's Data Files
As a testing program progresses, the number of computer data files will increase rapidly... as many as
four yearly per battery string if the P–1188 guidelines are followed. To quickly identify these type files
and manage them with minimum errors through DOS or through Windows File Manager, a file naming
system can be important. Try to include in the filenames' eight characters as many descriptors as
possible to reflect the data's date, location and battery. Thus, filename 941WPB1A.DAT would describe
the first test data, in 1994, for location WPB's battery 1, string A.
590-2099-501A/SL-29414/4200-070 19- 10 Revision 4