Atec Megger-BITE Series - Manual (Page 3)

BITE ® 2 and BITE 2P
Battery Impedance Test Equipment
Test Procedure
The BITE 2 and BITE 2P work by applying a capacitively
coupled ac test signal across the battery string while on-
line. The receiver and potential probe are placed at the cell
terminals to measure the signal and resulting voltage drop
for each cell/jar. During each measurement, impedance is
calculated following Ohm’s Law, displayed on the LCD and
stored. The instruments also measure, display and record
dc voltage and interconnection (strap) resistance to help
determine the overall condition of the entire battery string’s
electrical path from terminal plate to terminal plate. The
also measure ac ripple current, a charger parameter.
The BITE 2 and BITE 2P receiver stores the readings in
its internal memory. These measurements, along with
other maintenance data such as ambient and pilot cell
temperatures and ac ripple current, assist in determining
the overall condition of battery systems. Figure 3 shows a
typical test setup.
Interpretation of Readings
Data produced by the BITE 2 and BITE 2P can be
interpreted in several modes: instantaneous, short-term and
long-term time frames. An impedance distribution plot, as
shown in Figure 4, assists in the analysis.
Instantaneous Interpretation
The operator can enter a baseline value from either the
impedance measurements obtained at commissioning
or from the Megger website. The percent changes from
baseline for warning and fail levels are entered, but 20
percent and 40 percent are the default settings. The LCD
on the receiver will display the status of the cell for a few
seconds before proceeding to the next cell. The status of
each cell/jar will be printed on the Battery Analysis Report.
Short-Term Interpretation
Impedance readings for individual cells can be used in
the short term to compare with the average impedance
readings for the entire battery string. Individual cell values
with deviations of more than ±15% for flooded lead-acid,
±35% for VRLA, and 50% for NiCd cells from the battery
string average typically indicate a problem with that cell.
Megger recommends additional investigation of such cells
including a verification of intercell connections and a single
cell load-cycle test.
Long-Term Interpretation
Impedance readings for the entire battery can be used in
the long term to determine replacement criteria. Battery
cell impedance values should be recorded and compared
to previous readings to determine the position of the cell
on the curve of impedance versus cell life as shown in
Figure 2. Based on experience, a variation of ±20% from
baseline for flooded lead-acid, ±40% for VRLA and 50%
for NiCd cells indicate significant change in the electrical
path to warrant serious evaluation of the condition of the
battery system. Megger maintains a database of impedance
values by some manufacturers and battery size/type. For
comparison purposes, this information is available upon
request.
Figure 4. Ascending impedance compared to load test
Figure 3. A typical test setup
Figure 2. Impedance increases with battery age (and weakness)
“CT”
Located
in Battery
Circuit
STRAP
CELL
TRANSMITTER LINE
VOLTAGE
CURRENT SOURCE
LEAD
CURRENT SOURCE
LEAD
BLACK
RED
SPECIFICATIONS
Application
The BITE 2 and BITE 2P test lead-acid and nickel-cadmium cells
up to 7000 Ah.
Maximum Total Voltage at Current Source Leads
275 V dc (larger battery systems can be sectioned to accommodate
this specification)
Transmitter
Supply Voltage
100 to 130 V, 50/60 Hz, 200 VA max
210 to 250 V, 50/60 Hz, 200 VA max
Source Output Current
10 A nominal, 50/60 Hz operation