A BMS is therefore essential to avoid damaging the lithium batteries. When the system is
not in use, damage due to deep discharge can occur when small loads (such as alarm
systems, relays, standby current of certain loads, reverse current flow from chargers of
battery or charge controllers) slowly discharge the battery. If you are unsure of a residual
current draw, disconnect the battery by opening the battery disconnect switch, remov-
ing the fuse (s), or disconnecting the positive terminal on the battery when the system is
not in use.
A discharge current is particularly dangerous if the system has been completely discharged
and shut down due to a low cell voltage. After a cut-off due to a low cell voltage, a reserve
capacity of approximately �Ah per ���Ah of battery capacity remains in the battery. The
battery will be damaged if the remaining reserve capacity is removed from the battery. A
residual current of ��mA, for example, can damage a ���Ah battery if the system is left in
the discharged state for a long period.
Protection of the cell against overvoltages by reducing the charging current or by stopping
the charging process.
System shutdown in case of overheating.
Battery charging is stopped at low temperature.
The additional functions of a BMS are:
Protection of the cell against undervoltage by cutting the load over time.
A LiFePO� cell will fail if the voltage across the cell exceeds �.��V.
The cells of LiFePO� battery do not automatically compensate each other at the end of
the charge cycle.
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