NorthStar NSB BLUE+
Batteries
900-00264-01-001 Rev A
15
Charging
NorthStar NSB BLUE+
®
batteries are usually charged using a “three-stage” charging cycle: bulk
stage, absorption stage, and float stage. However, not all chargers are designed or
programmed the same way. The settings should be checked and changed to match the
recommendations below if necessary.
Charging Voltages
o
Absorb Charging Voltage
: 14.1 Vdc
o
Equalize Charging Voltage
: 14.4 Vdc (4 hours every 12 months)
o
Float Voltage
: 13.6 Vdc
Bulk Stage
The bulk stage is a constant-current stage. The charge current is maintained at a constant high
level. The battery voltage will rise as long as the current flows. This battery has a minimum
recommended charge current of (2 × I10-hour) with no maximum limit (per battery).
The charge rate (amps) is expressed as I10, where I10 is the current for a 10-hour discharge to
100% depth-of-discharge (DoD). For example:
o
The 10-hour discharge capacity for the NSB190FT = 184.2 Ah (1.75 VpC@25ºC)
o
I10, the 10-hour discharge rate = 184.2 Ah ÷ 10 hours = 18.4 Adc
o
2 x I10 = 2 x 18.4 Adc = 36.8 Adc
Absorption Stage
Absorption is a constant-voltage stage.
It is established upon reaching the Absorb
voltage setting. The charger limits the
current flow to only what is necessary to
maintain this voltage. A high current is
required to raise the voltage to the
absorption level, but less is required to
maintain it there. As long as the absorption
level is maintained, the requirement tends
to decrease, causing a tapering current.
The amount of absorption current will vary
with conditions, but will typically decrease to
a very low number. This “tops off the tank”,
leaving the battery at 100% SoC.
The battery is considered full when the
charge current tapers down to 0.5 to 1% of
the C20 rate (unlike traditional batteries,
which are considered full when charge
current reaches 2 to 3%, the BLUE+®
charge current will drop even lower
because of the purity of metals used). This
represents 100% SoC. The charger can
then exit the absorption stage.
Figure 11 Three-stage Charging