Page 63
©
2017 Sensata Technologies
Operation
4.4 Charger Control Operation
As a charge controller, the PT-100’s primary function is to monitor and charge the batteries
appropriately when PV power is available, and to prevent the batteries from being overcharged.
When PV power is connected to the PV input, the charge controller begins monitoring for acceptable
PV power and begins charging the batteries once it has accepted the PV input. The PT controller
uses up to four different charging stages to help monitor and keep the batteries healthy. The four
stages include an automatic 3-stage charging process: Bulk, Absorb, and Float (see Figure 4-9);
and a manual Equalization (EQ) charge stage. The automatic 3-stage charge process provides
complete recharging and monitoring of the batteries without damage due to overcharging. The
EQ stage (requires a two pushbutton press to enable) is used to stir up strati
fi
ed electrolyte and
to reverse any battery plate sulfation that may have occurred.
Bulk Charging:
This is the initial stage of charging. While bulk charging, the charger supplies the
battery with controlled constant current (up to 100 amps). The charger will remain in bulk charge
until the absorption charge voltage (determined by the Battery Type selection) is achieved. The
BULK (blue) LED comes ON to indicate the PT controller is in the Bulk charge stage. The controller
begins each new day (new day = 2 hours without sun) in the Bulk charge stage.
Absorb Charging:
This is the second charging stage and begins after the absorb voltage has
been reached. Absorb charging provides the batteries with a constant voltage (determined by the
Battery Type setting) and reduces the charging current in order to maintain the Absorb Voltage
setting. The controller’s ABSORB (yellow) LED comes on to indicate it is in the Absorb charge
stage for a time period (determined by the Absorb Time setting), then switches to
fl
oat charging.
Info:
While absorb charging, the timer inside the PT controller that is used to determine
how long to stay in the Absorb charge stage, only counts when the battery voltage is
at the Absorb Voltage setting. This means the PT controller will be in the Absorb charge
mode longer than the Absorb Time setting if conditions prevent the PV array from
producing enough power to maintain the batteries at the absorb voltage level.
Float Charging:
The third charging stage occurs at the end of the absorb charge time. While
fl
oat charging, the charge voltage is reduced to the
fl
oat charge voltage (determined by the
Battery Type setting). In this stage, the batteries are kept fully charged and ready if needed. The
charge controller’s FLOAT (green) LED comes on to indicate
fl
oat charging. The Float charge stage
reduces battery gassing, minimizes watering requirements (for
fl
ooded batteries), and ensures
the batteries are maintained at optimum capacity.
Note:
If the battery voltage falls
≤
12.2 VDC
(12-volt system),
≤
24.4 VDC (24-volt system), or
≤
48.8 VDC (48-volt system) for more than 1
minute, the controller will re-initiate bulk charging.
Bulk Charging
Absorb Charging
Float Charging
Voltage
Current
Max Charge
Amps
Absorb Done Time
CURRENT & VOLTAGE
TIME
Absorb
Volts
Float
Volts
First Stage
Second Stage
Third Stage
Figure 4-9, Automatic 3-Stage Charging Graph