Cellwatch Frontier - Page 44

Cellwatch Frontier System Installation & User Manual
Section I – Installation Guide-44
Standard maintenance around the DCM (i.e. replacing a cell)
When replacing a cell, the DCM connected to or across the cell that is being replaced should be removed
entirely. Document the location of the wires and the directional path of the fiber optics. Using colored
tape can help ensure that the fiber optics are connected properly.
There is always a risk of circuit completion (i.e. a short) on a battery that can result in the whole battery
voltage or partial battery voltage being placed across a single DCM if a battery or inter-tier link is
removed.
Damaged DCM units should not be reconnected to the battery for any reason. Always replace a DCM
with same model or compatible DCM.
Note: DCM specifications may change with each generation and may not be compatible replacements
for older models on the same string due to differences in current draw.
DCM location
The grounded chassis of battery cabinets or steel battery racks can radiate large amounts of high
frequency electrical noise. The DCM is carefully “hardened” against EMC radiation but cannot withstand
all radiation. In 1% of cases or less, fixing the DCM directly to a grounded steel cabinet or rack may cause
a degradation in data measurements, variability in ohmic readings, or in rare cases data corruption. It is
for this reason that NDSL recommends that the DCM be affixed to the battery (or Panduit/DIN rail) with
the 3M™ Dual Lock™ strips provided. Stick the DCM to the front of the front most block or container,
ensuring no safety or other labels are being covered. Dress all DCM cables using the cable ties provided,
making sticks and not loops with excess cable.
Note: We always recommend fixing the DCMs to the insulated battery cases that are being monitored
as opposed to the steel cabinets or racks. This is to avoid electrical interference from “Ground”, as the
noise radiated from the metal work is unknown.
Other considerations when placing DCMs
Other considerations should be evaluated when installing the DCMs on the battery system. These
include but are not limited to:
 Monitoring inter-tier links
 Monitoring all inter-cell straps
 Monitoring DC bus cables
 Monitoring cell temperatures
 Strings not divisible by four
 VLA cells with dry cells
 16V VRLA configurations