11
3.4
THREE STEP PLUS CHARGE ALGORITHM
See Figure 3. Battery charging is accomplished in three
automatic stages: BULK, ABSORPTION and FLOAT.
The first step of the three step plus charge system is the
BULK phase, in which the output current of the charger is
100%, and the greater part of the capacity of the battery is
rapidly charged. The current charges the batteries and
gradually the voltage rises to the BULK voltage 14.4V
(MLi:14.25V) resp. 28.8V (MLi: 28.5V) at 25°C / 77°F.
The duration of this phase depends on the ratio of battery
to charger capacity, and the battery state of charge.
Figure 3: Three step charge algorithm
The bulk phase is followed by the ABSORPTION phase.
Absorption charging starts when the voltage on the
batteries has reached the BULK voltage, and ends when
the battery is completely full. Battery voltage remains
constant at 14.25V / 28.5V at 25°C / 77°F throughout this
stage, and the charge current depends on the degree to
which the battery was initially discharged, the battery type,
the ambient temperature, and so on. With a flooded
battery this stage lasts approx. 4h, with gel and AGM
around 3h. Once the battery is 100% full, the
ChargeMaster Plus automatically switches over to the float
phase. At FLOAT (for Gel/AGM, flooded batteries) the
ChargeMaster Plus switches to a stabilised 13.25V (MLi:
13.5V) or 26.5V (MLi: 27.0V) at 25°C / 77°F.
Connected DC-loads are powered directly by the charger.
If the load is higher than charger capacity, the required
additional power comes from the battery, which will be
progressively discharged until the charger automatically
switches back to the bulk phase. Once consumption
decreases, the charger goes back to normal operation of
the three-step charge system.
As the ChargeMaster Plus is equipped with a three-step
plus charge system, the batteries can also remain
connected to the ChargeMaster Plus during winter. One
hour every 12 days the charger automatically switches to
absorption to keep the battery running properly and
prolong its life span. The three-step plus charge system is
also safe for all the connected equipment.
3.4.1
Pre-float
The ChargeMaster Plus has the ability to individually move
each battery from absorption to pre-float stage. In pre-float
stage, the charge voltage is lower than in absorption
stage. Pre-float ensures batteries that are nearly full
don’t
receive the higher charge voltage needed in the
absorption stage. This prevents over-charging, extending
the lifespan of the batteries
.
3.4.2
Temperature compensated charging
By installing the battery temperature sensor the charge
voltages
are
automatically
adapted
for
deviating
temperatures.
Figure 4:
Temperature compensated charging
See figure 4. When the battery temperature is low, the
charge voltage increases. On the other hand, when the
battery temperature is high, the charge voltage is
decreased. Over charge and gassing are prevented this
way. This will extend the life of your batteries.
3.4.3
Flat battery support
The ChargeMaster Plus automatically detects a flat
battery, and will initiate the flat battery charge curve
described in the table below.
UBat
Voltage
Output power
12V
0.00V - 2.50V
15%-30% of Imax
2.50V
– 8.00V
25% of Imax
8.00V
– 10.00V
linear from 25% - 100% of
Imax
10.00V
– 14.25V
100% of Imax
>14.25
Limited by Pmax
UBat
Voltage
Output power
24V
0.00V
– 5.00V
15%-30% of Imax
5.00V
– 16.00V
25% of Imax
16.00V
– 20.00V
linear from 25% - 100% of
Imax
20.00V
– 28.50V
100% of Imax
>28.50
Limited by Pmax
