12
Charge mode
The three-stage charging mode is the default setting and is
recommended for most operations. The battery is charged in
three stages, which is a quick method of charging (when solar
power is available we want the system to store it rather than feed
it into the grid). The three stages are:
1.
Bulk stage – charges the battery to 70-80% of its capacity at
maximum charging current and with increasing voltage.
2.
Absorption stage – charges the battery to 85-90% of its
capacity at the absorption voltage.
3.
Float stage – tops off the charge to 100% of the battery
capacity, with low current and float voltage.
The current and voltage values you should enter here can be
found on the battery data sheet. For proper operation it is
essential that these values are set correctly. Incorrect settings can
damage the batteries!
At fixed float, the batteries are charged with a constant voltage.
This can be used in a backup application where batteries may be
charged over a long period of time.
Maintenance
During every charge/discharge cycle the SOC value (state of
charge) of a battery becomes less accurate. For good battery
management the system needs to calibrate 100% SOC with the
batteries fully charged on a regular basis. To optimize their service
life, batteries should also be protected against operation that
prevents them from becoming fully charged. During maintenance
charge the system will give priority to charging the batteries
with the solar power, and it can take a maximum three days to
fully charge the batteries. When an SOC of 100% is reached
the system will go in normal mode again. During winter mode,
maintenance charging will be performed. The default setting is
once every four weeks.
Figure 26: Charge mode
Figure 27: Maintenance
