Calibration pro-
cess (Fronius
Solar Battery)
1. The start conditions must be fulfilled
2. The battery is charged to 100% with a minimum current of 6.5 A or the total PV
power.
3. So that a SOC of 100% can be reached for each battery module, one of the follow-
ing two conditions must be fulfilled for at least 2 minutes (for each cell in every bat-
tery module):
3. Minimum cell voltage ³ 3.45 V and current < 100 mA
3. Minimum cell voltage > 3.5 V independent of current
4. When a battery module reaches one of these conditions, the current is limited to pre-
vent an overload. A current in the two-digit mA range flows over a bypass resistor
5. Unneeded PV power is reused directly
6. Once all cells in all battery modules have fulfilled one of the two conditions, the SOC
is set to 100% and calibration charging is complete.
Duration of calib-
ration charging
(Fronius Solar
Battery)
Due to tolerances in the cells, they are not always charged and discharged at the same
rate. As cells and battery modules are connected in series and the slowest cell determ-
ines the charging and discharging duration, some calibration charges need more or less
time.
In rare cases, calibration charges or full charge cycles (depending on the time of year,
e.g. in the winter months) can lead to large variations in the cell voltages in the battery
modules. In calibration mode, one cell charges more quickly than the others. This cell
then begins redistribution. The other cells can then only be charged with a reduced char-
ging current. It takes longer for these cells to reach the target value.
If the battery is regularly charged completely, calibration charges are rarely required. The
cells are calibrated during every charge with 100% SOC.
In the winter months. where there are few full charges and a lower energy throughput,
calibration charges can take longer, as higher variations between the battery modules
must be redistributed.
Limitations dur-
ing calibration
(Fronius Solar
Battery)
- Drawing energy from the battery (discharging) is not possible
- Self-consumption optimisation is disabled while calibration charging is in progress
- Charging from the grid can still occur if the "Battery charging from DNO grid" func-
tion is not activated, as this process concerns system-relevant service charging
- Zero feed-in continues according to the standard and service charging can even be
started if you wish to expand or replace battery modules during calibration
- Emergency power mode can be started – calibration charging is interrupted
Display during
calibration
charge (Fronius
Solar Battery)
As soon as calibration charging starts, it becomes visible in Fronius Solar.web (current
and energy balance view) or on the web interface of the Fronius Symo Hybrid inverter.
In Fronius Solar.web or on the web interface of the inverter, the cal-
ibration charge information is displayed in the overview. Clicking on
the battery symbol (see the image on the left) displays the informa-
tion "The battery is in calibration mode"
In the energy balance display in Solar.web, both the start and end of the calibration
charge is displayed by changing the battery status ("Battery Mode: Normal → Calibrate"
and "Battery Mode: Calibrate → Normal")
The following graphic shows calibration charging of the Fronius Solar Battery in the
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