M
AVTM246004 BITE 2/2P Rev 4 July 2011
2
How the BITE 2/2P Works
Average impedance values for
different types of batteries are
available from Megger.
The operator connects the
current source leads
from the
BITE 2/2P
transmitter
to a battery string so that an ac test
current is capacitively coupled through the battery. It is best
to test the battery string when it is operating at full float, that
is, a constant charge level.
Then the operator uses the
receiver
to measure the voltage
drop across the cell terminals. When the voltage drop across
the cell is divided by the total ac current passing through the
battery, the calculated value is impedance according to Ohm's
Law. This impedance value gives the operator an indication of
the overall condition of the cell, with high impedance typically
indicating an unhealthy cell.
Several factors influence an impedance value, for instance,
the size and type of cell, ambient and electrolyte temperature,
and state of charge. Therefore, to determine the impedance of
a healthy cell, the operator should measure a large number of
similar cells under similar conditions and then calculate the
average value. Deteriorating cells are easily identified by their
higher-than-average impedance.
The BITE 2/2P also automatically measures and records the
cell voltage and the time and date of the test. This voltage
represents individual cell float voltage while measuring an
operational string of cells.
The BITE 2/2P also measures intercell or strap connections
and stores them with the cell impedance values. The BITE
2/2P can measure and record all aspects of the electrical path
of the battery, including:
•
location ID
•
user ID
•
test current
•
total current
•
internal cell impedance
•
dc voltage
•
intercell connector resistance
•
specfic gravity
•
time and date
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