Outback FM80 User Manual

Applications
900-0009-01-00 Rev D 99
ABSORBING
This is the second stage of charging. It is a constant-voltage stage. Current varies as needed
to maintain the Absorbing voltage setting. However, it will typically decrease to a very low
number over time. This “tops off the tank”, leaving the batteries at essentially 100% of capacity.
The duration of the Absorbing stage is the user-defined Absorb Time Limit. The ChgT timer is
preset to zero following the previous charge cycle. Once in Absorbing, ChgT will count until it
reaches this limit. (See pages 22, 47, and 51.) The charger will then exit Absorbing and enter
the Float stage. The charger will also also exit Absorbing if the Absorb End Amps setting is
reached, regardless of the timer. This resets the timer to zero. (See page 47.) This stage is
temperature compensated. (See page 99.)
FLOAT
When the charger enters this stage, it reduces the voltage to prevent battery overcharging. The
batteries are maintained at the Float set point. Floating is displayed on the screen. This stage
is not timed. The FLEXmax will continue to maintain Float as long as PV energy is available.
If the PV cannot supply enough power to maintain the Float set point, the FLEXmax will not
immediately initiate a new charge cycle. It will attempt to draw more PV energy and recharge
the battery until the Float voltage set point is reached. When this occurs, MPPT Float is
displayed (see page 25). This stage is temperature compensated. (See page 99.)
A new cycle can be initiated if the voltage falls below the ReBulk set point (see page 53).
Battery Temperature Compensation
Battery performance changes when the temperature varies above or below room temperature
(77°F or 25°C). Compensation is a process that adjusts charging to correct for these changes.
When a battery is cooler than room temperature, its internal resistance goes up and the voltage
changes more quickly. This makes it easier for the charger to reach its voltage set points.
However, while accomplishing this process, it will not deliver all the current that the battery
requires. As a result, the battery will tend to be undercharged.
Conversely, when a battery is warmer than room temperature, its internal resistance goes down
and the voltage changes more slowly. This makes it harder for the charger to reach its voltage
set points. It will deliver energy as time passes until the set points are reached. However, this
tends to be more than the battery requires, meaning it will tend to be overcharged.
The FLEXmax controller, when equipped with the Remote Temperature Sensor (RTS) will
compensate for temperature. The RTS is attached to a single battery near the center of the
bank. When charging, the RTS will increase or decrease the charge voltage by 5 mV per
degree Celsius per battery cell. This setting affects the Absorbing and Float set points.
Equalization is not compensated in the FLEXmax.
o
In a 12 Vdc system (6 cells, 2 volts each), this means 0.03 volts per degree Celsius above or below 25°C.
Maximum compensation is ± 0.6 Vdc.
o
In a 24 Vdc system (12 cells, 2 volts each), this means 0.06 volts per degree Celsius above or below 25°C.
Maximum compensation is ± 1.2 Vdc.
o
In a 48 Vdc system (24 cells, 2 volts each), this means 0.12 volts per degree Celsius above or below 25°C.
Maximum compensation is ± 2.4 Vdc.
Examples:
o
A 12 Vdc system with 10°C batteries will compensate its charging to 0.45 Vdc
higher
than the set points.
o
A 24 Vdc system with 35°C batteries will compensate its charging to 0.6 Vdc
lower
than the set points.
o
A 48 Vdc system with 15°C batteries will compensate its charging to 1.2 Vdc
higher
than the set points.