Installation and Operation
8
900-00264-01-001 Rev A
State of Charge
The NorthStar NSB BLUE+
®
state of
charge (SoC) can be determined by
two methods. One is to measure its
voltage. This method is typically used
when batteries are in storage. This is
accurate only if the batteries are left at
rest (no charging or loads) for 12 hours
at room temperature (77°F or 25°C).
If
these conditions are not met, then
voltage checks may not yield
accurate results.
If they are met, then
on average, a battery at 13.0 Vdc will
be at 100% SoC. A rest voltage of
12.2 Vdc represents roughly 50% SoC.
The second method is when batteries
are in use, the most accurate method
to measure SoC is to use a battery monitor such as the OutBack FLEXnet DC. Using a sensor
known as a shunt, the monitor observes the current through the battery. It keeps a total of
amp-hours lost or gained by the battery and can give accurate SoC readings.
The NorthStar NSB BLUE+
®
can be discharged and recharged (cycled) regularly to a level
as low as 50% depth of discharge (DoD). This is common in a cycling application such as an
off-grid system. However, for optimal life, the best practice is to avoid ever discharging below
50%. Lower DoD levels can shorten the cycle life.
If operated in a range with consistent charge and discharge to no more than 50% DoD, the
NorthStar NSB BLUE+
®
will typically have a life of 2,050 cycles. With consistently lighter
discharge (10 to 30% DoD with proper recharge), the battery may have significantly
more cycles.
System Layout
CAUTION: Fire Hazard
Failure to ventilate the battery compartment can result in the buildup of hydrogen
gas, which is explosive.
o The battery enclosure or room must be well-ventilated. This ventilation protects against accidental
gas buildup. All NorthStar NSB BLUE+
®
batteries are valve-regulated and do not normally emit
noticeable amounts of gas. However, in the event of accidental leakage, the enclosure must not
allow the leaked gas to become concentrated.
o The battery enclosure or room must have adequate lighting. This is necessary to read terminal
polarity, identify cable color, and view the physical state of the battery as required.
o The battery should be installed with a minimum 2" for airflow and 36” (91.4 cm) clearance in front of
batteries or cabinet. This allows access for testing, maintenance, and any other reasons.
o Multiple batteries should have a minimum of ¼” (12.7 mm) clearance on either side (½" recommended).
Figure 5
State of Charge vs.
Open Circuit Voltage (OCV)