Inverter programming
The simplest off-grid inverters rely upon factory settings and do not permit any programming. The function of many standard off-grid inverters is to simply convert between DC and AC - there is not much adjustability that is required. As inverters become more complicated and begin to incorporate charging capability for use a generator and monitoring/communications platforms for improved system management the programming options quickly become complicated.
To program an inverter it is necessary to have manuals for the inverter any other major components (communications/monitoring, generator) on hand.
Basic settings
- Low voltage disconnect: An inverter can be set to automatically cease inverting if the battery bank voltage reaches a certain minimum value in order to protect the it from deep discharges that can greatly reduce cycle life. Typically set at around 20% state of charge (SOC). It may be also possible to set the value at which the inverter begins inverting again to give the battery bank sufficient time to recharge - a higher value than 20% SOC is recommended.
Inverter/charger settings
An inverter/charger that will use a generator as a charging source requires far more programming as it is operating as a charge controller. This means that it must be setup to properly charge the specific battery bank to which it will be connected. Additionally, many inverter/chargers will offer Automatic Generator State (AGS) capability start the generator as programmed.
- Inverter battery charging set points: These are the set points that will control how the charger moves between different charging phases. The same values that were used for charge controller programming can be used here. These values are found in the battery manual.
- Maximum charge rate: This is the maximum amount of current that the charger will supply to charge the battery bank. The same value that was used for charge controller programming can be used. This value is found in the battery manual.
- Maximum AC input current: This is the maximum amount of current that the inverter will use from a generator to supply loads and charge the battery bank. This value is determined by choosing the smaller of the two following variables:
- The overcurrent current protection device (OCPD) rating.
- The maximum continuous duty current rating of the generator.
Auto start settings
Every inverter/charger will have specific programming and setup that is required. This will be detailed in the manual. There are various important parameters that are common to many different inverter chargers that require careful consideration to ensure a system that functions harmoniously.
- Auto-start voltage: A charger can be set to start the generator automatically when the voltage of the battery bank reaches a certain point for a certain period of time. The period of time is important to avoid the generator automatically starting as battery voltage dips due to large loads and to allow the [[PV module|PV source to perform its role. The appropriate time and voltage values for a system depends upon the loads that the system supplies, the size of the PV source, the size of the Energy storage system and the size of the generator. The goal is to choose values that minimize generator run-time, but prolong battery bank longevity by reducing deep discharges.
- Auto state of charge start: A charger can be set to start the generator when the state of charge reaches a certain value. The system must have a shunt integrated for this to work. Starting a generator based upon the state of charge rather than voltage or current demand can have advantages as the generator will not be started if the battery bank voltage drops temporarily for a brief period due to large loads.
- Auto-load start: A charger can be set to start the generator automatically when the current required by loads exceeds a certain value to protect the battery bank from deep discharges. If this setting is to be used, it is important to make sure that a value is chosen that will not lead to the generator starting needlessly for brief periods of high current demand. It can be useful to automatically start the generator to run period large loads like well-pumps.
- Total run time: A charger can be set to automatically turn off the generator after a certain amount of time. This can be important to protect the generator from damage or excessive consumption of fuel. If the battery bank suffers a failure that leads to a chronically low voltage reading, a charger that does not have a run-time limit will keep the generator running indefinitely.
- Generator exercise schedule: A charger can be set to automatically start the generator and run it for a set period of time on a programmed schedule as a form of maintenance. Periodically running a generator is good to ensure that it has a long life.
