Interpreting Test Results; Overview - Megger BITE 2 Instruction Manual

7

INTERPRETING TEST RESULTS

Overview

AVTM246004 BITE 2/2P Rev 4 July 2011
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This chapter discusses various factors to consider when
interpreting results of tests obtained with the BITE 2/BITE 2P.
Megger maintains a database of impedance values. Megger
will provide approximate baseline values if specific information
is received from the user. The list of required information
needed from the user is found on our website,
Impedance measurements with the BITE 2/2P should be made
part of a battery maintenance program with readings taken
and recorded semiannually for flooded lead-acid and nickel-
cadmium cells and quarterly for VRLA.
Increases in impedance are caused by numerous factors.
Some of the failure modes that can be detected by impedance
are:
•
plate sulphation
•
dry-out
•
soft shorts (dendritic shorts)
•
hard shorts (due to sediment build-up or paste lumps)
•
intercell and intertier connections (due to loose
hardware or corrosion)
•
internal corrosion
However, there are other factors that can change the
impedance value of a cell. Impedance shifts can be caused by:
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