Victron energy BMV-700 Manual page 35

5.2.5 What to do in case of an alarm during discharging
The individual batteries or cells of a battery bank are not identical, and
when fully discharging a battery bank the voltage of some cells will start
dropping earlier than others. The midpoint alarm will therefore nearly
always trip at the end of a deep discharge.
If the midpoint alarm trips much earlier (and does not trip during
charging), some batteries or cells may have lost capacity or may have
developed a higher internal resistance than others. The battery bank may
have reached the end of service life, or one of more cells or batteries
have developed a fault:
a) In case of series-parallel connection, disconnect the midpoint parallel
connection wiring and measure the individual midpoint voltages
during discharging to isolate faulty batteries or cells.
b) Charge and then test all batteries or cells individually.
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