SMA S Technical Description page 126

Battery Management
For this charging phase, the Sunny Backup 2200 automatically selects one of the three possible
charging processes (boost, full, equalizing) that are described in more depth between sections
16.4.1 „Boost Charge" (127) and 16.4.3 „Equalization Charge" (127). The remaining charging
time (display value "120.04 AptTmRmg") of this phase and the current process (display value
"120.05 BatChrgOp") can be read on the display.
The following figure displays the relationship and the process diagram of the charging phases and
charging processes.
Once this constant voltage phase is finished, the Sunny Backup 2200 switches to float charge which
again carries out constant voltage charging but at a greatly reduced charging voltage
("222.10 ChrgVtgFlo" parameter). The purpose of the float charge is to keep the battery in a fully
charged state without causing premature aging through overcharging. The Sunny Backup 2200
remains in this phase until either more than 30 % of the nominal capacity (all discharges are added
together) has been used or the charge state is less than 70 %. When the Sunny Backup 2200 is
operating on the public grid, it can also switch from the float charge into silent mode.
Changing the charging voltage
The charging voltage does not rapidly change, but is slowly adjusted to the new nominal
value by approx. 0.5 mV/cell*s as the constant voltage phase changes to the float charge.
This also takes place if the nominal value is changed manually.
The charging capability of batteries is heavily dependent on the battery temperature. For
temperatures <20 °C, the charging voltage must be slightly increased, and for temperatures >20 °C
it must be slightly decreased. This is necessary to prevent overcharging and insufficient charging
reliably at any battery temperature.
126 SBU2200-TEN083320
SMA Solar Technology AG
Technical Description