Victron energy VBC 12-24-48V Manuel page 15

4.1.3 Synchronising the battery monitor
For a reliable readout of the state of charge of your battery, the battery
monitor has to be synchronised regularly with the battery and charger.
This is accomplished by fully charging the battery. When the charger is
operating in the 'float' stage, the charger considers the battery full. At
this moment the VBC must also determine that the battery is full. Now
the Amp hour count can be reset to zero and the state of charge
reading can be set to 100 %.
When the voltage supply to the VBC has been interrupted, the
battery monitor must be resynchronised before it can operate
correctly.
Please note that regularly (at least once per month) fully charging your
battery not only keeps it in sync with the VBC, but also prevents
substantial capacity loss of your battery which limits its lifetime.
4.1.4 Synchronisation parameters
Based on increasing charge voltage and decreasing charge current, a
decision can be made whether the battery is fully charged or not. When
the battery voltage is above a certain level during a predefined period
while the charge current is below a certain level for the same period, the
battery can be considered fully charged. These values are called
synchronisation parameters. In general for a 12 V lead acid battery, the
synchronisation voltage is 13.2 V and the synchronisation current is
4.0 % of the total battery capacity (e.g. 8 A with a 200 Ah battery). A
synchronisation time of 4 minutes is sufficient for most battery systems.
Please note that these parameters are very important for correct
operation of your VBC, and must be set appropriately in the
corresponding menu items.
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