Freedom Lite Installation Manual Revision 12
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of the incoming grid supply. An average recommended charge current is one third of the
continuous rating of the battery. This will usually ensure that the combination of the mains
charger and the Solar Charge Controller (SCC) does not exceed the maximum continuous
charge current, although this must be specifically checked.
The voltage settings for the Freedom Lite range of nominally 52V batteries when operating
in a system where the BMS can control the external devices as explained above are as
follows:
Minimum (cut off) – 47V (the Lite should never reach this low voltage but is it good
to have this set as a redundancy protection measure.
Low Battery Voltage Warning (if applicable, often used to revert back to grid power
in increased self-consumption applications because it approximates 30% SoC) – 51V
Max Charge Voltage – 55,8V (Bulk, Absorption and Float are all set to this value)
If the BMS is not able to control the external devices
with remote enable functions, then
the voltages must be set at slightly conservative values. This is to reduce the likelihood that
an outlying cell will reach its voltage limit ahead of the pack, which the external devices
would not be aware of because they can only monitor the total pack voltage. Using a lower
pack voltage to monitor and control charging and a higher voltage for discharge will allow a
greater spread in cell voltage values without any of them reaching their limits. The BMS
inside the Freedom Lite will deal with an excessive spread of cell voltages by balancing them
out using the cell tap wires attached to each cell and its internal circuitry. If a cell voltage
does reach its limit the BMS will be forced to intervene. This would be either by:
switching off a contactor on the AC in, AC out, or PV DC input as mentioned earlier
in this manual,
or if the relevant one of these functions does not exist in a particular system,
the BMS shutting down the main breaker on the battery
Frequent occurrences of these two situations is not desirable so the voltages should be set
to the following to reduce this occurrence to abnormal circumstances:
Minimum (cut off) – 49V
Low Battery Voltage Warning (if applicable) – 51V
Max Charge Voltage – 55.5V
A voltage can also be set according to user requirements on the inverter depending on how
much battery power may be used before grid power will take over from the battery (if it is
available). It should be determined based on how much battery SoC is desired at all times as
a minimum to ensure adequate capacity to handle a grid outage or load shedding. The daily
cycling depth is also a consideration for the user in terms of battery service life.
The recommended voltage for forcing the inverter back to grid power in a self-consumption
setup is:
