Manual

Introduction
1–4 975-0560-01-01 Revision B
Charge Controlling
The charge controller can regulate PV array current at an appropriate level for
24 or 48 V batteries. It produces up to 80 amps of charging current for both
battery voltages up to 2560 watts (24 V) or 4800 watts (48 V).
The charge controller controls how the batteries are charged by the PV array. It
can be configured to use a two-stage (no float) or three-stage charging process
to maintain battery voltage at bulk, absorption, or float levels. When charging, the
charge controller regulates the battery voltage and the output current based on
the amount of DC power available from the PV array and the state of charge of
the battery.
Three-Stage Battery Charging
The three-stage battery charging process results in more efficient charging
compared to on-off relay type or constant voltage solid-state regulators. The final
float stage reduces battery gassing, minimizes electrolyte loss, and ensures
complete battery recharging. Battery voltage and current vary during the
three-stage charging process as shown in Figure 1-2 on page 1–5.
Bulk Stage
During the bulk stage, the charge controller operates in constant current mode,
delivering the maximum current to the batteries (or the maximum current
available if the PV does not have enough power to provide maximum current).
Once the battery voltage reaches the absorption voltage setting, the charge
controller transitions to the absorption stage.
Absorption Stage
During the absorption stage, the charge controller begins operating in constant
voltage mode and the current falls gradually as the amp hours are returned to the
battery. The voltage limit used for the first 60 minutes of this stage is the bulk
voltage setting. The voltage limit used for the remaining time in this stage is the
absorption voltage setting. By default, the bulk voltage setting and the
absorption voltage setting are the same for all battery types.
The default voltage limit settings (bulk and absorption) can be adjusted if the
battery type is set to Custom (see “Setting a Custom Battery Type” on page 2–6).
For flooded lead acid batteries only, you can use a custom charging scheme
which sets the bulk voltage higher than the absorption voltage. The result of this
is a boost voltage charge level that has been found to be beneficial for ensuring
enough amp hours are returned to the battery bank for off-grid installations. For
detailed information on how boost charging works and when it is recommended,
see Appendix C, “Boost Charging”.