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SMA Solar Technology AG
4.2 Stand-Alone Operation
During stand-alone operation or during operation with the 3324/4248 Sunny Island inverters, the
charge controller automatically controls the charging voltage of the battery, depending on the battery
type set and current charging phase, according to the "four-phase charging process" (MPP, boost,
continuous, float). During the first phase, charging is carried out using the maximum power provided
by the PV array. During the second phase, the charging current is reduced and the battery voltage is
regulated to the charging voltage set for the boost phase. This phase is only completed if the battery
voltage ever drops below 2.08 V/cell during the preceding discharging phase. Otherwise, the
charging process is immediately continued with the third phase, "continuous". The continuous and the
boost charging phases are identical, except that the continuous phase has a slightly lower charging
voltage. Once continuous charging is completed, the charge controller switches to float charging until
the next complete discharge.
If a battery temperature sensor is connected, the charging voltage is adjusted to the temperature using
-4 mV/°C and cell.
Working principle of the charge controller in stand-alone operation
Battery
Installation Guide
PC
Battery Management and Charge Control
SIC50-IA-en-11
Charge
controller
13
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