Victron energy BMV-600S Manuel page 13

2.3.4 Synchronising the BMV
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 BMV 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 100.0 %. By precisely adjusting the charged-
parameters in the BMV, the battery monitor can automatically
synchronise with the charger when the 'float' stage is reached. The
range of the charged parameters is wide enough to adjust the BMV to
most battery charging methods.
The BMV can also be synchronised manually if required. This can be
achieved in normal mode by holding the + and – buttons
simultaneously for 3 seconds, or in setup mode by using the SYNC
option.
Ensure that the battery is fully charged before manually
synchronising the BMV.
If the BMV does not synchronise automatically, check that the
values for the charged voltage, tail current, and charged time have
been configured correctly. See paragraph 2.3.3
When the voltage supply to the BMV 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 BMV, but also prevents
substantial capacity loss of your battery which limits its lifetime.
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