Victron energy LiFePO4 Manuel page 7

3.2 Charging batteries before use
The batteries are aproximately 50% charged when shipped.
When charging series connected batteries, the voltage of the batteries or cells
with the highest initial state of charge will increase when reaching the fully
charged state, while other batteries or cells may lag behind. This may result in
over voltage on the batteries or cells with the highest initial state of charge,
and the charge process will be interrupted by the BMS.
Therefore, new batteries must be fully charged before using them in a
series or series-parallel configuration.
This can best be done by individually charging the batteries at a low rate (C/20
or less) with a charger or power supply set at 14,2V resp. 28,4V. An
absorption period of several hours at 14,2V resp. 28,4V is recommended to
fully balance the cells.
If no BMS is used, charge only when a supervisor is present to stop the
charging process in case of malfunction of a battery.
Parallel connecting the batteries and simultaneous charging is also possible.
In this case every battery must be protected by a fuse and the recommended
charge rate is again C/20 or less, with C being the capacity of one of the
paralleled batteries.
4 Operation
4.1 Cell balancing and alarms
Each 12,8V battery consists of four series connected cells, and the internal
cell balancing system will:
a) Measure the voltage of each cell and move Ah from cells with the
highest voltage to cells with a lower voltage until the voltage
difference between cells is less than 10mV (active balancing).
b) Give an over voltage (cell voltage > 3,75V) or under voltage (cell
voltage < 2,80V) alarm to be processed by the BMS (See 4.3).
c) Give an over temperature (T > 75°C) alarm to be processed by the
BMS.
d) Give a low temperature (T < 5°C) alarm to be processed by the
BMS (See 4.4).
Note:
The cells within a battery or series connected batteries may become
unbalanced due to high discharge currents and short float charge periods.
The available battery capacity will be reduced, and a cell overvoltage alarm
may occur.
Apply the procedures as described in section 3.2 to fully charge and balance
the batteries.
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