OPERATION | SP PRO Operation
Doc #OI0003 Part #004122 Rev19 2014
|
59
Battery Management
Please refer to the battery manufacturer’s documentation for recommendations regarding
settings for the particular battery. Inappropriate settings may have a detrimental affect on the
battery life and performance.
The SP PRO provides comprehensive battery management settings and control to allow a
charge regime to achieve optimal battery life.
SP PRO battery management features include:
•
State of Charge monitoring and control.
•
Battery terminal voltage monitoring (Battery Sense / pre-charge) and control.
•
Charging initiated by battery state of charge and/or battery voltage.
•
Five stage charge cycle: Initial, Bulk, Absorption, Float (short term and long term) and Equalise.
•
Shutdown on low battery voltage, battery state of charge, or both.
•
Two stage Battery Temperature compensation of charging voltage based on battery temperature.
The SP PRO may be configured to use the Grid power or to automatically start a backup generator (with
Grid Fail - Generator Backup Option) when a battery charge cycle is required during a prolonged grid
outage.
Battery State of Charge (SoC) monitoring and control
For SoC control to function correctly all DC battery currents, other than the inverter current, must be
monitored on either or both of the two current shunt inputs to the SP PRO. No current shunt is required to
read the SP PROs current or any AC Coupled supply as this is read internally. The resultant battery current
is monitored to track the battery SoC which is expressed as a percentage of the battery size set in the
SP PRO (Battery Capacity).
The accuracy of the battery SoC is limited by a number of factors including the charge and discharge
efficiency of the battery bank. To improve the accuracy of the battery SoC calculation, the SP PRO employs
an adaptive algorithm to constantly update a “charge efficiency index” which is used during recharge.
In an Off Grid system where a Generator is installed, the state of charge is used to automatically start
the generator as required. The generator will then supply the load while any excess available generator
capacity will charge the batteries.
In a Solar Hybrid system, the state of charge along with time of day and load demand is used to vary the
priority and direct the renewable energy to either power the AC load, recharge the battery bank and/or
export to the grid. This allows for the maximum use of the renewable energy (such as PV solar) whilst taking
advantage of variable electricity tariffs
Battery Voltage monitoring and control
The SP PRO measures the battery voltage both at the inverter and also directly at the battery bank using the
Battery Sense / pre-charge wiring (if installed). Sensing the actual battery terminal voltage (using Battery
Sense / pre-charge wiring) compensates for the effect of cable losses which, irrespective of charge or
discharge currents, keeps the battery terminal voltage within set limits.
Battery voltage is used to protect the system by shutting the unit down should the battery voltage go above
or below set limits. The shutdown limits must be set to higher than the maximum charge voltage. For the low
voltage shutdown limits the SP PRO employs different levels depending on system load. The system will
always attempt to reconnect to the grid or start the backup generator (when installed) before shutting the
inverter down due to low battery voltage or SoC.
